[fs/lustre-release.git] / lustre / llite / rw.c

/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
 * vim:expandtab:shiftwidth=8:tabstop=8:
 *
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see [sun.com URL with a
 * copy of GPLv2].
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright  2008 Sun Microsystems, Inc. All rights reserved
 * Use is subject to license terms.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/llite/rw.c
 *
 * Lustre Lite I/O page cache routines shared by different kernel revs
 */

#include <linux/autoconf.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/smp_lock.h>
#include <linux/unistd.h>
#include <linux/version.h>
#include <asm/system.h>
#include <asm/uaccess.h>

#include <linux/fs.h>
#include <linux/stat.h>
#include <asm/uaccess.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>

#define DEBUG_SUBSYSTEM S_LLITE

//#include <lustre_mdc.h>
#include <lustre_lite.h>
#include <obd_cksum.h>
#include "llite_internal.h"
#include <linux/lustre_compat25.h>

#ifndef list_for_each_prev_safe
#define list_for_each_prev_safe(pos, n, head) \
        for (pos = (head)->prev, n = pos->prev; pos != (head); \
                pos = n, n = pos->prev )
#endif

cfs_mem_cache_t *ll_async_page_slab = NULL;
size_t ll_async_page_slab_size = 0;

/* SYNCHRONOUS I/O to object storage for an inode */
static int ll_brw(int cmd, struct inode *inode, struct obdo *oa,
                  struct page *page, int flags)
{
        struct ll_inode_info *lli = ll_i2info(inode);
        struct lov_stripe_md *lsm = lli->lli_smd;
        struct obd_info oinfo = { { { 0 } } };
        struct brw_page pg;
        int opc, rc;
        ENTRY;

        pg.pg = page;
        pg.off = ((obd_off)page->index) << CFS_PAGE_SHIFT;

        if ((cmd & OBD_BRW_WRITE) && (pg.off+CFS_PAGE_SIZE>i_size_read(inode)))
                pg.count = i_size_read(inode) % CFS_PAGE_SIZE;
        else
                pg.count = CFS_PAGE_SIZE;

        LL_CDEBUG_PAGE(D_PAGE, page, "%s %d bytes ino %lu at "LPU64"/"LPX64"\n",
                       cmd & OBD_BRW_WRITE ? "write" : "read", pg.count,
                       inode->i_ino, pg.off, pg.off);
        if (pg.count == 0) {
                CERROR("ZERO COUNT: ino %lu: size %p:%Lu(%p:%Lu) idx %lu off "
                       LPU64"\n", inode->i_ino, inode, i_size_read(inode),
                       page->mapping->host, i_size_read(page->mapping->host),
                       page->index, pg.off);
        }

        pg.flag = flags;

        if (cmd & OBD_BRW_WRITE)
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_BRW_WRITE,
                                   pg.count);
        else
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_BRW_READ,
                                   pg.count);
        oinfo.oi_oa = oa;
        oinfo.oi_md = lsm;
        /* NB partial write, so we might not have CAPA_OPC_OSS_READ capa */
        opc = cmd & OBD_BRW_WRITE ? CAPA_OPC_OSS_WRITE : CAPA_OPC_OSS_RW;
        oinfo.oi_capa = ll_osscapa_get(inode, opc);
        rc = obd_brw(cmd, ll_i2dtexp(inode), &oinfo, 1, &pg, NULL);
        capa_put(oinfo.oi_capa);
        if (rc == 0)
                obdo_to_inode(inode, oa, OBD_MD_FLBLOCKS);
        else if (rc != -EIO)
                CERROR("error from obd_brw: rc = %d\n", rc);
        RETURN(rc);
}

int ll_file_punch(struct inode * inode, loff_t new_size, int srvlock)
{
        struct ll_inode_info *lli = ll_i2info(inode);
        struct obd_info oinfo = { { { 0 } } };
        struct obdo oa;
        int rc;

        ENTRY;
        CDEBUG(D_INFO, "calling punch for "LPX64" (new size %Lu=%#Lx)\n",
               lli->lli_smd->lsm_object_id, i_size_read(inode), i_size_read(inode));

        oinfo.oi_md = lli->lli_smd;
        oinfo.oi_policy.l_extent.start = new_size;
        oinfo.oi_policy.l_extent.end = OBD_OBJECT_EOF;
        oinfo.oi_oa = &oa;
        oa.o_id = lli->lli_smd->lsm_object_id;
        oa.o_gr = lli->lli_smd->lsm_object_gr;
        oa.o_valid = OBD_MD_FLID | OBD_MD_FLGROUP;
        if (srvlock) {
                /* set OBD_MD_FLFLAGS in o_valid, only if we
                 * set OBD_FL_TRUNCLOCK, otherwise ost_punch
                 * and filter_setattr get confused, see the comment
                 * in ost_punch */
                oa.o_flags = OBD_FL_TRUNCLOCK;
                oa.o_valid |= OBD_MD_FLFLAGS;
        }
        obdo_from_inode(&oa, inode, OBD_MD_FLTYPE | OBD_MD_FLMODE |
                        OBD_MD_FLATIME | OBD_MD_FLMTIME | OBD_MD_FLCTIME |
                        OBD_MD_FLFID | OBD_MD_FLGENER);

        oinfo.oi_capa = ll_osscapa_get(inode, CAPA_OPC_OSS_TRUNC);
        rc = obd_punch_rqset(ll_i2dtexp(inode), &oinfo, NULL);
        ll_truncate_free_capa(oinfo.oi_capa);
        if (rc)
                CERROR("obd_truncate fails (%d) ino %lu\n", rc, inode->i_ino);
        else
                obdo_to_inode(inode, &oa, OBD_MD_FLSIZE | OBD_MD_FLBLOCKS |
                              OBD_MD_FLATIME | OBD_MD_FLMTIME | OBD_MD_FLCTIME);
        RETURN(rc);
}

/* this isn't where truncate starts.   roughly:
 * sys_truncate->ll_setattr_raw->vmtruncate->ll_truncate. setattr_raw grabs
 * DLM lock on [size, EOF], i_mutex, ->lli_size_sem, and WRITE_I_ALLOC_SEM to
 * avoid races.
 *
 * must be called under ->lli_size_sem */
void ll_truncate(struct inode *inode)
{
        struct ll_inode_info *lli = ll_i2info(inode);
        int srvlock = !!(lli->lli_flags & LLIF_SRVLOCK);
        loff_t new_size;
        ENTRY;
        CDEBUG(D_VFSTRACE, "VFS Op:inode=%lu/%u(%p) to %Lu=%#Lx\n",inode->i_ino,
               inode->i_generation, inode, i_size_read(inode),
               i_size_read(inode));

        ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_TRUNC, 1);
        if (lli->lli_size_sem_owner != current) {
                EXIT;
                return;
        }

        if (!lli->lli_smd) {
                CDEBUG(D_INODE, "truncate on inode %lu with no objects\n",
                       inode->i_ino);
                GOTO(out_unlock, 0);
        }

        LASSERT(atomic_read(&lli->lli_size_sem.count) <= 0);

        if (!srvlock) {
                struct ost_lvb lvb;
                int rc;

                /* XXX I'm pretty sure this is a hack to paper
                 * over a more fundamental race condition. */
                lov_stripe_lock(lli->lli_smd);
                inode_init_lvb(inode, &lvb);
                rc = obd_merge_lvb(ll_i2dtexp(inode), lli->lli_smd, &lvb, 0);
                if (lvb.lvb_size == i_size_read(inode) && rc == 0) {
                        CDEBUG(D_VFSTRACE, "skipping punch for obj "LPX64
                               ",%Lu=%#Lx\n", lli->lli_smd->lsm_object_id,
                               i_size_read(inode), i_size_read(inode));
                        lov_stripe_unlock(lli->lli_smd);
                        GOTO(out_unlock, 0);
                }
                obd_adjust_kms(ll_i2dtexp(inode), lli->lli_smd,
                               i_size_read(inode), 1);
                lov_stripe_unlock(lli->lli_smd);
        }

        if (unlikely((ll_i2sbi(inode)->ll_flags & LL_SBI_CHECKSUM) &&
                     (i_size_read(inode) & ~CFS_PAGE_MASK))) {
                /* If the truncate leaves behind a partial page, update its
                 * checksum. */
                struct page *page = find_get_page(inode->i_mapping,
                                                  i_size_read(inode) >>
                                                  CFS_PAGE_SHIFT);
                if (page != NULL) {
                        struct ll_async_page *llap = llap_cast_private(page);
                        if (llap != NULL) {
                                char *kaddr = kmap_atomic(page, KM_USER0);
                                llap->llap_checksum =
                                        init_checksum(OSC_DEFAULT_CKSUM);
                                llap->llap_checksum =
                                        compute_checksum(llap->llap_checksum,
                                                         kaddr, CFS_PAGE_SIZE,
                                                         OSC_DEFAULT_CKSUM);
                                kunmap_atomic(kaddr, KM_USER0);
                        }
                        page_cache_release(page);
                }
        }

        new_size = i_size_read(inode);
        ll_inode_size_unlock(inode, 0);
        if (!srvlock)
                ll_file_punch(inode, new_size, 0);
        else
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_LOCKLESS_TRUNC, 1);

        EXIT;
        return;

 out_unlock:
        ll_inode_size_unlock(inode, 0);
} /* ll_truncate */

int ll_prepare_write(struct file *file, struct page *page, unsigned from,
                     unsigned to)
{
        struct inode *inode = page->mapping->host;
        struct ll_inode_info *lli = ll_i2info(inode);
        struct lov_stripe_md *lsm = lli->lli_smd;
        obd_off offset = ((obd_off)page->index) << CFS_PAGE_SHIFT;
        struct obd_info oinfo = { { { 0 } } };
        struct brw_page pga;
        struct obdo oa;
        struct ost_lvb lvb;
        int rc = 0;
        ENTRY;

        LASSERT(PageLocked(page));
        (void)llap_cast_private(page); /* assertion */

        /* Check to see if we should return -EIO right away */
        pga.pg = page;
        pga.off = offset;
        pga.count = CFS_PAGE_SIZE;
        pga.flag = 0;

        oa.o_mode = inode->i_mode;
        oa.o_id = lsm->lsm_object_id;
        oa.o_gr = lsm->lsm_object_gr;
        oa.o_valid = OBD_MD_FLID | OBD_MD_FLMODE |
                     OBD_MD_FLTYPE | OBD_MD_FLGROUP;
        obdo_from_inode(&oa, inode, OBD_MD_FLFID | OBD_MD_FLGENER);

        oinfo.oi_oa = &oa;
        oinfo.oi_md = lsm;
        rc = obd_brw(OBD_BRW_CHECK, ll_i2dtexp(inode), &oinfo, 1, &pga, NULL);
        if (rc)
                RETURN(rc);

        if (PageUptodate(page)) {
                LL_CDEBUG_PAGE(D_PAGE, page, "uptodate\n");
                RETURN(0);
        }

        /* We're completely overwriting an existing page, so _don't_ set it up
         * to date until commit_write */
        if (from == 0 && to == CFS_PAGE_SIZE) {
                LL_CDEBUG_PAGE(D_PAGE, page, "full page write\n");
                POISON_PAGE(page, 0x11);
                RETURN(0);
        }

        /* If are writing to a new page, no need to read old data.  The extent
         * locking will have updated the KMS, and for our purposes here we can
         * treat it like i_size. */
        lov_stripe_lock(lsm);
        inode_init_lvb(inode, &lvb);
        obd_merge_lvb(ll_i2dtexp(inode), lsm, &lvb, 1);
        lov_stripe_unlock(lsm);
        if (lvb.lvb_size <= offset) {
                char *kaddr = kmap_atomic(page, KM_USER0);
                LL_CDEBUG_PAGE(D_PAGE, page, "kms "LPU64" <= offset "LPU64"\n",
                               lvb.lvb_size, offset);
                memset(kaddr, 0, CFS_PAGE_SIZE);
                kunmap_atomic(kaddr, KM_USER0);
                GOTO(prepare_done, rc = 0);
        }

        /* XXX could be an async ocp read.. read-ahead? */
        rc = ll_brw(OBD_BRW_READ, inode, &oa, page, 0);
        if (rc == 0) {
                /* bug 1598: don't clobber blksize */
                oa.o_valid &= ~(OBD_MD_FLSIZE | OBD_MD_FLBLKSZ);
                obdo_refresh_inode(inode, &oa, oa.o_valid);
        }

        EXIT;
 prepare_done:
        if (rc == 0)
                SetPageUptodate(page);

        return rc;
}

/**
 * make page ready for ASYNC write
 * \param data - pointer to llap cookie
 * \param cmd - is OBD_BRW_* macroses
 *
 * \retval 0 is page successfully prepared to send
 * \retval -EAGAIN is page not need to send
 */
static int ll_ap_make_ready(void *data, int cmd)
{
        struct ll_async_page *llap;
        struct page *page;
        ENTRY;

        llap = LLAP_FROM_COOKIE(data);
        page = llap->llap_page;

        /* we're trying to write, but the page is locked.. come back later */
        if (TryLockPage(page))
                RETURN(-EAGAIN);

        LASSERTF(!(cmd & OBD_BRW_READ) || !PageWriteback(page),
                "cmd %x page %p ino %lu index %lu fl %lx\n", cmd, page,
                 page->mapping->host->i_ino, page->index, page->flags);

        /* if we left PageDirty we might get another writepage call
         * in the future.  list walkers are bright enough
         * to check page dirty so we can leave it on whatever list
         * its on.  XXX also, we're called with the cli list so if
         * we got the page cache list we'd create a lock inversion
         * with the removepage path which gets the page lock then the
         * cli lock */
        LASSERTF(!PageWriteback(page),"cmd %x page %p ino %lu index %lu\n", cmd, page,
                 page->mapping->host->i_ino, page->index);
        if(!clear_page_dirty_for_io(page)) {
                unlock_page(page);
                RETURN(-EAGAIN);
        }

        /* This actually clears the dirty bit in the radix tree.*/
        set_page_writeback(page);

        LL_CDEBUG_PAGE(D_PAGE, page, "made ready\n");
        page_cache_get(page);

        RETURN(0);
}

/* We have two reasons for giving llite the opportunity to change the
 * write length of a given queued page as it builds the RPC containing
 * the page:
 *
 * 1) Further extending writes may have landed in the page cache
 *    since a partial write first queued this page requiring us
 *    to write more from the page cache.  (No further races are possible, since
 *    by the time this is called, the page is locked.)
 * 2) We might have raced with truncate and want to avoid performing
 *    write RPCs that are just going to be thrown away by the
 *    truncate's punch on the storage targets.
 *
 * The kms serves these purposes as it is set at both truncate and extending
 * writes.
 */
static int ll_ap_refresh_count(void *data, int cmd)
{
        struct ll_inode_info *lli;
        struct ll_async_page *llap;
        struct lov_stripe_md *lsm;
        struct page *page;
        struct inode *inode;
        struct ost_lvb lvb;
        __u64 kms;
        ENTRY;

        /* readpage queues with _COUNT_STABLE, shouldn't get here. */
        LASSERT(cmd != OBD_BRW_READ);

        llap = LLAP_FROM_COOKIE(data);
        page = llap->llap_page;
        inode = page->mapping->host;
        lli = ll_i2info(inode);
        lsm = lli->lli_smd;

        lov_stripe_lock(lsm);
        inode_init_lvb(inode, &lvb);
        obd_merge_lvb(ll_i2dtexp(inode), lsm, &lvb, 1);
        kms = lvb.lvb_size;
        lov_stripe_unlock(lsm);

        /* catch race with truncate */
        if (((__u64)page->index << CFS_PAGE_SHIFT) >= kms)
                return 0;

        /* catch sub-page write at end of file */
        if (((__u64)page->index << CFS_PAGE_SHIFT) + CFS_PAGE_SIZE > kms)
                return kms % CFS_PAGE_SIZE;

        return CFS_PAGE_SIZE;
}

void ll_inode_fill_obdo(struct inode *inode, int cmd, struct obdo *oa)
{
        struct lov_stripe_md *lsm;
        obd_flag valid_flags;

        lsm = ll_i2info(inode)->lli_smd;

        oa->o_id = lsm->lsm_object_id;
        oa->o_gr = lsm->lsm_object_gr;
        oa->o_valid = OBD_MD_FLID | OBD_MD_FLGROUP;
        valid_flags = OBD_MD_FLTYPE | OBD_MD_FLATIME;
        if (cmd & OBD_BRW_WRITE) {
                oa->o_valid |= OBD_MD_FLEPOCH;
                oa->o_easize = ll_i2info(inode)->lli_ioepoch;

                valid_flags |= OBD_MD_FLMTIME | OBD_MD_FLCTIME |
                        OBD_MD_FLUID | OBD_MD_FLGID |
                        OBD_MD_FLFID | OBD_MD_FLGENER;
        }

        obdo_from_inode(oa, inode, valid_flags);
}

static void ll_ap_fill_obdo(void *data, int cmd, struct obdo *oa)
{
        struct ll_async_page *llap;
        ENTRY;

        llap = LLAP_FROM_COOKIE(data);
        ll_inode_fill_obdo(llap->llap_page->mapping->host, cmd, oa);

        EXIT;
}

static void ll_ap_update_obdo(void *data, int cmd, struct obdo *oa,
                              obd_valid valid)
{
        struct ll_async_page *llap;
        ENTRY;

        llap = LLAP_FROM_COOKIE(data);
        obdo_from_inode(oa, llap->llap_page->mapping->host, valid);

        EXIT;
}

static struct obd_capa *ll_ap_lookup_capa(void *data, int cmd)
{
        struct ll_async_page *llap = LLAP_FROM_COOKIE(data);
        int opc = cmd & OBD_BRW_WRITE ? CAPA_OPC_OSS_WRITE : CAPA_OPC_OSS_RW;

        return ll_osscapa_get(llap->llap_page->mapping->host, opc);
}

static struct obd_async_page_ops ll_async_page_ops = {
        .ap_make_ready =        ll_ap_make_ready,
        .ap_refresh_count =     ll_ap_refresh_count,
        .ap_fill_obdo =         ll_ap_fill_obdo,
        .ap_update_obdo =       ll_ap_update_obdo,
        .ap_completion =        ll_ap_completion,
        .ap_lookup_capa =       ll_ap_lookup_capa,
};

struct ll_async_page *llap_cast_private(struct page *page)
{
        struct ll_async_page *llap = (struct ll_async_page *)page_private(page);

        LASSERTF(llap == NULL || llap->llap_magic == LLAP_MAGIC,
                 "page %p private %lu gave magic %d which != %d\n",
                 page, page_private(page), llap->llap_magic, LLAP_MAGIC);

        return llap;
}

/* Try to shrink the page cache for the @sbi filesystem by 1/@shrink_fraction.
 *
 * There is an llap attached onto every page in lustre, linked off @sbi.
 * We add an llap to the list so we don't lose our place during list walking.
 * If llaps in the list are being moved they will only move to the end
 * of the LRU, and we aren't terribly interested in those pages here (we
 * start at the beginning of the list where the least-used llaps are.
 */
int llap_shrink_cache(struct ll_sb_info *sbi, int shrink_fraction)
{
        struct ll_async_page *llap, dummy_llap = { .llap_magic = 0xd11ad11a };
        unsigned long total, want, count = 0;

        total = sbi->ll_async_page_count;

        /* There can be a large number of llaps (600k or more in a large
         * memory machine) so the VM 1/6 shrink ratio is likely too much.
         * Since we are freeing pages also, we don't necessarily want to
         * shrink so much.  Limit to 40MB of pages + llaps per call. */
        if (shrink_fraction == 0)
                want = sbi->ll_async_page_count - sbi->ll_async_page_max + 32;
        else
                want = (total + shrink_fraction - 1) / shrink_fraction;

        if (want > 40 << (20 - CFS_PAGE_SHIFT))
                want = 40 << (20 - CFS_PAGE_SHIFT);

        CDEBUG(D_CACHE, "shrinking %lu of %lu pages (1/%d)\n",
               want, total, shrink_fraction);

        spin_lock(&sbi->ll_lock);
        list_add(&dummy_llap.llap_pglist_item, &sbi->ll_pglist);

        while (--total >= 0 && count < want) {
                struct page *page;
                int keep;

                if (unlikely(need_resched())) {
                        spin_unlock(&sbi->ll_lock);
                        cond_resched();
                        spin_lock(&sbi->ll_lock);
                }

                llap = llite_pglist_next_llap(sbi,&dummy_llap.llap_pglist_item);
                list_del_init(&dummy_llap.llap_pglist_item);
                if (llap == NULL)
                        break;

                page = llap->llap_page;
                LASSERT(page != NULL);

                list_add(&dummy_llap.llap_pglist_item, &llap->llap_pglist_item);

                /* Page needs/undergoing IO */
                if (TryLockPage(page)) {
                        LL_CDEBUG_PAGE(D_PAGE, page, "can't lock\n");
                        continue;
                }

               keep = (llap->llap_write_queued || PageDirty(page) ||
                      PageWriteback(page) || (!PageUptodate(page) &&
                      llap->llap_origin != LLAP_ORIGIN_READAHEAD));

                LL_CDEBUG_PAGE(D_PAGE, page,"%s LRU page: %s%s%s%s%s origin %s\n",
                               keep ? "keep" : "drop",
                               llap->llap_write_queued ? "wq " : "",
                               PageDirty(page) ? "pd " : "",
                               PageUptodate(page) ? "" : "!pu ",
                               PageWriteback(page) ? "wb" : "",
                               llap->llap_defer_uptodate ? "" : "!du",
                               llap_origins[llap->llap_origin]);

                /* If page is dirty or undergoing IO don't discard it */
                if (keep) {
                        unlock_page(page);
                        continue;
                }

                page_cache_get(page);
                spin_unlock(&sbi->ll_lock);

                if (page->mapping != NULL) {
                        ll_teardown_mmaps(page->mapping,
                                         (__u64)page->index << CFS_PAGE_SHIFT,
                                         ((__u64)page->index << CFS_PAGE_SHIFT)|
                                          ~CFS_PAGE_MASK);
                        if (!PageDirty(page) && !page_mapped(page)) {
                                ll_ra_accounting(llap, page->mapping);
                                ll_truncate_complete_page(page);
                                ++count;
                        } else {
                                LL_CDEBUG_PAGE(D_PAGE, page, "Not dropping page"
                                                             " because it is "
                                                             "%s\n",
                                                              PageDirty(page)?
                                                              "dirty":"mapped");
                        }
                }
                unlock_page(page);
                page_cache_release(page);

                spin_lock(&sbi->ll_lock);
        }
        list_del(&dummy_llap.llap_pglist_item);
        spin_unlock(&sbi->ll_lock);

        CDEBUG(D_CACHE, "shrank %lu/%lu and left %lu unscanned\n",
               count, want, total);

        return count;
}

static struct ll_async_page *llap_from_page_with_lockh(struct page *page,
                                                       unsigned origin,
                                                       struct lustre_handle *lockh)
{
        struct ll_async_page *llap;
        struct obd_export *exp;
        struct inode *inode = page->mapping->host;
        struct ll_sb_info *sbi;
        int rc;
        ENTRY;

        if (!inode) {
                static int triggered;

                if (!triggered) {
                        LL_CDEBUG_PAGE(D_ERROR, page, "Bug 10047. Wrong anon "
                                       "page received\n");
                        libcfs_debug_dumpstack(NULL);
                        triggered = 1;
                }
                RETURN(ERR_PTR(-EINVAL));
        }
        sbi = ll_i2sbi(inode);
        LASSERT(ll_async_page_slab);
        LASSERTF(origin < LLAP__ORIGIN_MAX, "%u\n", origin);

        llap = llap_cast_private(page);
        if (llap != NULL) {
                /* move to end of LRU list, except when page is just about to
                 * die */
                if (origin != LLAP_ORIGIN_REMOVEPAGE) {
                        spin_lock(&sbi->ll_lock);
                        sbi->ll_pglist_gen++;
                        list_del_init(&llap->llap_pglist_item);
                        list_add_tail(&llap->llap_pglist_item, &sbi->ll_pglist);
                        spin_unlock(&sbi->ll_lock);
                }
                GOTO(out, llap);
        }

        exp = ll_i2dtexp(page->mapping->host);
        if (exp == NULL)
                RETURN(ERR_PTR(-EINVAL));

        /* limit the number of lustre-cached pages */
        if (sbi->ll_async_page_count >= sbi->ll_async_page_max)
                llap_shrink_cache(sbi, 0);

        OBD_SLAB_ALLOC(llap, ll_async_page_slab, CFS_ALLOC_STD,
                       ll_async_page_slab_size);
        if (llap == NULL)
                RETURN(ERR_PTR(-ENOMEM));
        llap->llap_magic = LLAP_MAGIC;
        llap->llap_cookie = (void *)llap + size_round(sizeof(*llap));

        /* XXX: for bug 11270 - check for lockless origin here! */
        if (origin == LLAP_ORIGIN_LOCKLESS_IO)
                llap->llap_nocache = 1;

        rc = obd_prep_async_page(exp, ll_i2info(inode)->lli_smd, NULL, page,
                                 (obd_off)page->index << CFS_PAGE_SHIFT,
                                 &ll_async_page_ops, llap, &llap->llap_cookie,
                                 llap->llap_nocache, lockh);
        if (rc) {
                OBD_SLAB_FREE(llap, ll_async_page_slab,
                              ll_async_page_slab_size);
                RETURN(ERR_PTR(rc));
        }

        CDEBUG(D_CACHE, "llap %p page %p cookie %p obj off "LPU64"\n", llap,
               page, llap->llap_cookie, (obd_off)page->index << CFS_PAGE_SHIFT);
        /* also zeroing the PRIVBITS low order bitflags */
        __set_page_ll_data(page, llap);
        llap->llap_page = page;
        spin_lock(&sbi->ll_lock);
        sbi->ll_pglist_gen++;
        sbi->ll_async_page_count++;
        list_add_tail(&llap->llap_pglist_item, &sbi->ll_pglist);
        INIT_LIST_HEAD(&llap->llap_pending_write);
        spin_unlock(&sbi->ll_lock);

 out:
        if (unlikely(sbi->ll_flags & LL_SBI_CHECKSUM)) {
                __u32 csum;
                char *kaddr = kmap_atomic(page, KM_USER0);
                csum = init_checksum(OSC_DEFAULT_CKSUM);
                csum = compute_checksum(csum, kaddr, CFS_PAGE_SIZE,
                                        OSC_DEFAULT_CKSUM);
                kunmap_atomic(kaddr, KM_USER0);
                if (origin == LLAP_ORIGIN_READAHEAD ||
                    origin == LLAP_ORIGIN_READPAGE ||
                    origin == LLAP_ORIGIN_LOCKLESS_IO) {
                        llap->llap_checksum = 0;
                } else if (origin == LLAP_ORIGIN_COMMIT_WRITE ||
                           llap->llap_checksum == 0) {
                        llap->llap_checksum = csum;
                        CDEBUG(D_PAGE, "page %p cksum %x\n", page, csum);
                } else if (llap->llap_checksum == csum) {
                        /* origin == LLAP_ORIGIN_WRITEPAGE */
                        CDEBUG(D_PAGE, "page %p cksum %x confirmed\n",
                               page, csum);
                } else {
                        /* origin == LLAP_ORIGIN_WRITEPAGE */
                        LL_CDEBUG_PAGE(D_ERROR, page, "old cksum %x != new "
                                       "%x!\n", llap->llap_checksum, csum);
                }
        }

        llap->llap_origin = origin;
        RETURN(llap);
}

struct ll_async_page *llap_from_page(struct page *page,
                                     unsigned origin)
{
        return llap_from_page_with_lockh(page, origin, NULL);
}

static int queue_or_sync_write(struct obd_export *exp, struct inode *inode,
                               struct ll_async_page *llap,
                               unsigned to, obd_flag async_flags)
{
        unsigned long size_index = i_size_read(inode) >> CFS_PAGE_SHIFT;
        struct obd_io_group *oig;
        struct ll_sb_info *sbi = ll_i2sbi(inode);
        int rc, noquot = llap->llap_ignore_quota ? OBD_BRW_NOQUOTA : 0;
        ENTRY;

        /* _make_ready only sees llap once we've unlocked the page */
        llap->llap_write_queued = 1;
        rc = obd_queue_async_io(exp, ll_i2info(inode)->lli_smd, NULL,
                                llap->llap_cookie, OBD_BRW_WRITE | noquot,
                                0, 0, 0, async_flags);
        if (rc == 0) {
                LL_CDEBUG_PAGE(D_PAGE, llap->llap_page, "write queued\n");
                GOTO(out, 0);
        }

        llap->llap_write_queued = 0;
        /* Do not pass llap here as it is sync write. */
        llap_write_pending(inode, NULL);

        rc = oig_init(&oig);
        if (rc)
                GOTO(out, rc);

        /* make full-page requests if we are not at EOF (bug 4410) */
        if (to != CFS_PAGE_SIZE && llap->llap_page->index < size_index) {
                LL_CDEBUG_PAGE(D_PAGE, llap->llap_page,
                               "sync write before EOF: size_index %lu, to %d\n",
                               size_index, to);
                to = CFS_PAGE_SIZE;
        } else if (to != CFS_PAGE_SIZE && llap->llap_page->index == size_index) {
                int size_to = i_size_read(inode) & ~CFS_PAGE_MASK;
                LL_CDEBUG_PAGE(D_PAGE, llap->llap_page,
                               "sync write at EOF: size_index %lu, to %d/%d\n",
                               size_index, to, size_to);
                if (to < size_to)
                        to = size_to;
        }

        /* compare the checksum once before the page leaves llite */
        if (unlikely((sbi->ll_flags & LL_SBI_CHECKSUM) &&
                     llap->llap_checksum != 0)) {
                __u32 csum;
                struct page *page = llap->llap_page;
                char *kaddr = kmap_atomic(page, KM_USER0);
                csum = init_checksum(OSC_DEFAULT_CKSUM);
                csum = compute_checksum(csum, kaddr, CFS_PAGE_SIZE,
                                        OSC_DEFAULT_CKSUM);
                kunmap_atomic(kaddr, KM_USER0);
                if (llap->llap_checksum == csum) {
                        CDEBUG(D_PAGE, "page %p cksum %x confirmed\n",
                               page, csum);
                } else {
                        CERROR("page %p old cksum %x != new cksum %x!\n",
                               page, llap->llap_checksum, csum);
                }
        }

        rc = obd_queue_group_io(exp, ll_i2info(inode)->lli_smd, NULL, oig,
                                llap->llap_cookie, OBD_BRW_WRITE | noquot,
                                0, to, 0, ASYNC_READY | ASYNC_URGENT |
                                ASYNC_COUNT_STABLE | ASYNC_GROUP_SYNC);
        if (rc)
                GOTO(free_oig, rc);

        rc = obd_trigger_group_io(exp, ll_i2info(inode)->lli_smd, NULL, oig);
        if (rc)
                GOTO(free_oig, rc);

        rc = oig_wait(oig);

        if (!rc && async_flags & ASYNC_READY) {
                unlock_page(llap->llap_page);
                if (PageWriteback(llap->llap_page))
                        end_page_writeback(llap->llap_page);
        }

        if (rc == 0 && llap_write_complete(inode, llap))
                ll_queue_done_writing(inode, 0);

        LL_CDEBUG_PAGE(D_PAGE, llap->llap_page, "sync write returned %d\n", rc);

free_oig:
        oig_release(oig);
out:
        RETURN(rc);
}

/* update our write count to account for i_size increases that may have
 * happened since we've queued the page for io. */

/* be careful not to return success without setting the page Uptodate or
 * the next pass through prepare_write will read in stale data from disk. */
int ll_commit_write(struct file *file, struct page *page, unsigned from,
                    unsigned to)
{
        struct ll_file_data *fd = LUSTRE_FPRIVATE(file);
        struct inode *inode = page->mapping->host;
        struct ll_inode_info *lli = ll_i2info(inode);
        struct lov_stripe_md *lsm = lli->lli_smd;
        struct obd_export *exp;
        struct ll_async_page *llap;
        loff_t size;
        struct lustre_handle *lockh = NULL;
        int rc = 0;
        ENTRY;

        SIGNAL_MASK_ASSERT(); /* XXX BUG 1511 */
        LASSERT(inode == file->f_dentry->d_inode);
        LASSERT(PageLocked(page));

        CDEBUG(D_INODE, "inode %p is writing page %p from %d to %d at %lu\n",
               inode, page, from, to, page->index);

        if (fd->fd_flags & LL_FILE_GROUP_LOCKED)
                lockh = &fd->fd_cwlockh;

        llap = llap_from_page_with_lockh(page, LLAP_ORIGIN_COMMIT_WRITE, lockh);
        if (IS_ERR(llap))
                RETURN(PTR_ERR(llap));

        exp = ll_i2dtexp(inode);
        if (exp == NULL)
                RETURN(-EINVAL);

        llap->llap_ignore_quota = capable(CAP_SYS_RESOURCE);

        /*
         * queue a write for some time in the future the first time we
         * dirty the page.
         *
         * This is different from what other file systems do: they usually
         * just mark page (and some of its buffers) dirty and rely on
         * balance_dirty_pages() to start a write-back. Lustre wants write-back
         * to be started earlier for the following reasons:
         *
         *     (1) with a large number of clients we need to limit the amount
         *     of cached data on the clients a lot;
         *
         *     (2) large compute jobs generally want compute-only then io-only
         *     and the IO should complete as quickly as possible;
         *
         *     (3) IO is batched up to the RPC size and is async until the
         *     client max cache is hit
         *     (/proc/fs/lustre/osc/OSC.../max_dirty_mb)
         *
         */
        if (!PageDirty(page)) {
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_DIRTY_MISSES, 1);

                rc = queue_or_sync_write(exp, inode, llap, to, 0);
                if (rc)
                        GOTO(out, rc);
        } else {
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_DIRTY_HITS, 1);
        }

        /* put the page in the page cache, from now on ll_removepage is
         * responsible for cleaning up the llap.
         * only set page dirty when it's queued to be write out */
        if (llap->llap_write_queued)
                set_page_dirty(page);

out:
        size = (((obd_off)page->index) << CFS_PAGE_SHIFT) + to;
        ll_inode_size_lock(inode, 0);
        if (rc == 0) {
                lov_stripe_lock(lsm);
                obd_adjust_kms(exp, lsm, size, 0);
                lov_stripe_unlock(lsm);
                if (size > i_size_read(inode))
                        i_size_write(inode, size);
                SetPageUptodate(page);
        } else if (size > i_size_read(inode)) {
                /* this page beyond the pales of i_size, so it can't be
                 * truncated in ll_p_r_e during lock revoking. we must
                 * teardown our book-keeping here. */
                ll_removepage(page);
        }
        ll_inode_size_unlock(inode, 0);
        RETURN(rc);
}

static unsigned long ll_ra_count_get(struct ll_sb_info *sbi, unsigned long len)
{
        struct ll_ra_info *ra = &sbi->ll_ra_info;
        unsigned long ret;
        ENTRY;

        spin_lock(&sbi->ll_lock);
        ret = min(ra->ra_max_pages - ra->ra_cur_pages, len);
        ra->ra_cur_pages += ret;
        spin_unlock(&sbi->ll_lock);

        RETURN(ret);
}

static void ll_ra_count_put(struct ll_sb_info *sbi, unsigned long len)
{
        struct ll_ra_info *ra = &sbi->ll_ra_info;
        spin_lock(&sbi->ll_lock);
        LASSERTF(ra->ra_cur_pages >= len, "r_c_p %lu len %lu\n",
                 ra->ra_cur_pages, len);
        ra->ra_cur_pages -= len;
        spin_unlock(&sbi->ll_lock);
}

/* called for each page in a completed rpc.*/
int ll_ap_completion(void *data, int cmd, struct obdo *oa, int rc)
{
        struct ll_async_page *llap;
        struct page *page;
        int ret = 0;
        ENTRY;

        llap = LLAP_FROM_COOKIE(data);
        page = llap->llap_page;
        LASSERT(PageLocked(page));
        LASSERT(CheckWriteback(page,cmd));

        LL_CDEBUG_PAGE(D_PAGE, page, "completing cmd %d with %d\n", cmd, rc);

        if (cmd & OBD_BRW_READ && llap->llap_defer_uptodate)
                ll_ra_count_put(ll_i2sbi(page->mapping->host), 1);

        if (rc == 0)  {
                if (cmd & OBD_BRW_READ) {
                        if (!llap->llap_defer_uptodate)
                                SetPageUptodate(page);
                } else {
                        llap->llap_write_queued = 0;
                }
                ClearPageError(page);
        } else {
                if (cmd & OBD_BRW_READ) {
                        llap->llap_defer_uptodate = 0;
                }
                SetPageError(page);
                if (rc == -ENOSPC)
                        set_bit(AS_ENOSPC, &page->mapping->flags);
                else
                        set_bit(AS_EIO, &page->mapping->flags);
        }

        /* be carefull about clear WB.
         * if WB will cleared after page lock is released - paralel IO can be
         * started before ap_make_ready is finished - so we will be have page
         * with PG_Writeback set from ->writepage() and completed READ which
         * clear this flag */
        if ((cmd & OBD_BRW_WRITE) && PageWriteback(page))
                end_page_writeback(page);

        unlock_page(page);

        if (cmd & OBD_BRW_WRITE) {
                /* Only rc == 0, write succeed, then this page could be deleted
                 * from the pending_writing list
                 */
                if (rc == 0 && llap_write_complete(page->mapping->host, llap))
                        ll_queue_done_writing(page->mapping->host, 0);
        }

        page_cache_release(page);

        RETURN(ret);
}

static void __ll_put_llap(struct page *page)
{
        struct inode *inode = page->mapping->host;
        struct obd_export *exp;
        struct ll_async_page *llap;
        struct ll_sb_info *sbi = ll_i2sbi(inode);
        int rc;
        ENTRY;

        exp = ll_i2dtexp(inode);
        if (exp == NULL) {
                CERROR("page %p ind %lu gave null export\n", page, page->index);
                EXIT;
                return;
        }

        llap = llap_from_page(page, LLAP_ORIGIN_REMOVEPAGE);
        if (IS_ERR(llap)) {
                CERROR("page %p ind %lu couldn't find llap: %ld\n", page,
                       page->index, PTR_ERR(llap));
                EXIT;
                return;
        }

        if (llap_write_complete(inode, llap))
                ll_queue_done_writing(inode, 0);

        rc = obd_teardown_async_page(exp, ll_i2info(inode)->lli_smd, NULL,
                                     llap->llap_cookie);
        if (rc != 0)
                CERROR("page %p ind %lu failed: %d\n", page, page->index, rc);

        /* this unconditional free is only safe because the page lock
         * is providing exclusivity to memory pressure/truncate/writeback..*/
        __clear_page_ll_data(page);

        spin_lock(&sbi->ll_lock);
        if (!list_empty(&llap->llap_pglist_item))
                list_del_init(&llap->llap_pglist_item);
        sbi->ll_pglist_gen++;
        sbi->ll_async_page_count--;
        spin_unlock(&sbi->ll_lock);
        OBD_SLAB_FREE(llap, ll_async_page_slab, ll_async_page_slab_size);
        EXIT;
}

/* the kernel calls us here when a page is unhashed from the page cache.
 * the page will be locked and the kernel is holding a spinlock, so
 * we need to be careful.  we're just tearing down our book-keeping
 * here. */
void ll_removepage(struct page *page)
{
        struct ll_async_page *llap = llap_cast_private(page);
        ENTRY;

        LASSERT(!in_interrupt());

        /* sync pages or failed read pages can leave pages in the page
         * cache that don't have our data associated with them anymore */
        if (page_private(page) == 0) {
                EXIT;
                return;
        }

        LASSERT(!llap->llap_lockless_io_page);
        LASSERT(!llap->llap_nocache);
        LL_CDEBUG_PAGE(D_PAGE, page, "being evicted\n");
        __ll_put_llap(page);
        EXIT;
}

static int ll_issue_page_read(struct obd_export *exp,
                              struct ll_async_page *llap,
                              struct obd_io_group *oig, int defer)
{
        struct page *page = llap->llap_page;
        int rc;

        page_cache_get(page);
        llap->llap_defer_uptodate = defer;
        llap->llap_ra_used = 0;
        rc = obd_queue_group_io(exp, ll_i2info(page->mapping->host)->lli_smd,
                                NULL, oig, llap->llap_cookie, OBD_BRW_READ, 0,
                                CFS_PAGE_SIZE, 0, ASYNC_COUNT_STABLE |
                                                  ASYNC_READY | ASYNC_URGENT);
        if (rc) {
                LL_CDEBUG_PAGE(D_ERROR, page, "read queue failed: rc %d\n", rc);
                page_cache_release(page);
        }
        RETURN(rc);
}

static void ll_ra_stats_inc_unlocked(struct ll_ra_info *ra, enum ra_stat which)
{
        LASSERTF(which >= 0 && which < _NR_RA_STAT, "which: %u\n", which);
        ra->ra_stats[which]++;
}

static void ll_ra_stats_inc(struct address_space *mapping, enum ra_stat which)
{
        struct ll_sb_info *sbi = ll_i2sbi(mapping->host);
        struct ll_ra_info *ra = &ll_i2sbi(mapping->host)->ll_ra_info;

        spin_lock(&sbi->ll_lock);
        ll_ra_stats_inc_unlocked(ra, which);
        spin_unlock(&sbi->ll_lock);
}

void ll_ra_accounting(struct ll_async_page *llap, struct address_space *mapping)
{
        if (!llap->llap_defer_uptodate || llap->llap_ra_used)
                return;

        ll_ra_stats_inc(mapping, RA_STAT_DISCARDED);
}

#define RAS_CDEBUG(ras) \
        CDEBUG(D_READA,                                                      \
               "lrp %lu cr %lu cp %lu ws %lu wl %lu nra %lu r %lu ri %lu"    \
               "csr %lu sf %lu sp %lu sl %lu \n",                            \
               ras->ras_last_readpage, ras->ras_consecutive_requests,        \
               ras->ras_consecutive_pages, ras->ras_window_start,            \
               ras->ras_window_len, ras->ras_next_readahead,                 \
               ras->ras_requests, ras->ras_request_index,                    \
               ras->ras_consecutive_stride_requests, ras->ras_stride_offset, \
               ras->ras_stride_pages, ras->ras_stride_length)

static int index_in_window(unsigned long index, unsigned long point,
                           unsigned long before, unsigned long after)
{
        unsigned long start = point - before, end = point + after;

        if (start > point)
               start = 0;
        if (end < point)
               end = ~0;

        return start <= index && index <= end;
}

static struct ll_readahead_state *ll_ras_get(struct file *f)
{
        struct ll_file_data       *fd;

        fd = LUSTRE_FPRIVATE(f);
        return &fd->fd_ras;
}

void ll_ra_read_in(struct file *f, struct ll_ra_read *rar)
{
        struct ll_readahead_state *ras;

        ras = ll_ras_get(f);

        spin_lock(&ras->ras_lock);
        ras->ras_requests++;
        ras->ras_request_index = 0;
        ras->ras_consecutive_requests++;
        rar->lrr_reader = current;

        list_add(&rar->lrr_linkage, &ras->ras_read_beads);
        spin_unlock(&ras->ras_lock);
}

void ll_ra_read_ex(struct file *f, struct ll_ra_read *rar)
{
        struct ll_readahead_state *ras;

        ras = ll_ras_get(f);

        spin_lock(&ras->ras_lock);
        list_del_init(&rar->lrr_linkage);
        spin_unlock(&ras->ras_lock);
}

static struct ll_ra_read *ll_ra_read_get_locked(struct ll_readahead_state *ras)
{
        struct ll_ra_read *scan;

        list_for_each_entry(scan, &ras->ras_read_beads, lrr_linkage) {
                if (scan->lrr_reader == current)
                        return scan;
        }
        return NULL;
}

struct ll_ra_read *ll_ra_read_get(struct file *f)
{
        struct ll_readahead_state *ras;
        struct ll_ra_read         *bead;

        ras = ll_ras_get(f);

        spin_lock(&ras->ras_lock);
        bead = ll_ra_read_get_locked(ras);
        spin_unlock(&ras->ras_lock);
        return bead;
}

static int ll_read_ahead_page(struct obd_export *exp, struct obd_io_group *oig,
                              int index, struct address_space *mapping)
{
        struct ll_async_page *llap;
        struct page *page;
        unsigned int gfp_mask = 0;
        int rc = 0;

        gfp_mask = GFP_HIGHUSER & ~__GFP_WAIT;
#ifdef __GFP_NOWARN
        gfp_mask |= __GFP_NOWARN;
#endif
        page = grab_cache_page_nowait_gfp(mapping, index, gfp_mask);
        if (page == NULL) {
                ll_ra_stats_inc(mapping, RA_STAT_FAILED_GRAB_PAGE);
                CDEBUG(D_READA, "g_c_p_n failed\n");
                return 0;
        }

        /* Check if page was truncated or reclaimed */
        if (page->mapping != mapping) {
                ll_ra_stats_inc(mapping, RA_STAT_WRONG_GRAB_PAGE);
                CDEBUG(D_READA, "g_c_p_n returned invalid page\n");
                GOTO(unlock_page, rc = 0);      
        }

        /* we do this first so that we can see the page in the /proc
         * accounting */
        llap = llap_from_page(page, LLAP_ORIGIN_READAHEAD);
        if (IS_ERR(llap) || llap->llap_defer_uptodate) {
                if (PTR_ERR(llap) == -ENOLCK) {
                        ll_ra_stats_inc(mapping, RA_STAT_FAILED_MATCH);
                        CDEBUG(D_READA | D_PAGE,
                               "Adding page to cache failed index "
                                "%d\n", index);
                                CDEBUG(D_READA, "nolock page\n");
                                GOTO(unlock_page, rc = -ENOLCK);
                }
                CDEBUG(D_READA, "read-ahead page\n");
                GOTO(unlock_page, rc = 0);      
        }

        /* skip completed pages */
        if (Page_Uptodate(page))
                GOTO(unlock_page, rc = 0);      

        /* bail out when we hit the end of the lock. */
        rc = ll_issue_page_read(exp, llap, oig, 1);
        if (rc == 0) {
                LL_CDEBUG_PAGE(D_READA | D_PAGE, page, "started read-ahead\n");
                rc = 1;
        } else {
unlock_page:    
                unlock_page(page);
                LL_CDEBUG_PAGE(D_READA | D_PAGE, page, "skipping read-ahead\n");
        }
        page_cache_release(page);
        return rc;
}

/* ra_io_arg will be filled in the beginning of ll_readahead with
 * ras_lock, then the following ll_read_ahead_pages will read RA
 * pages according to this arg, all the items in this structure are
 * counted by page index.
 */
struct ra_io_arg {
        unsigned long ria_start;  /* start offset of read-ahead*/
        unsigned long ria_end;    /* end offset of read-ahead*/
        /* If stride read pattern is detected, ria_stoff means where
         * stride read is started. Note: for normal read-ahead, the
         * value here is meaningless, and also it will not be accessed*/
        pgoff_t ria_stoff;
        /* ria_length and ria_pages are the length and pages length in the
         * stride I/O mode. And they will also be used to check whether
         * it is stride I/O read-ahead in the read-ahead pages*/
        unsigned long ria_length;
        unsigned long ria_pages;
};

#define RIA_DEBUG(ria)                                                \
        CDEBUG(D_READA, "rs %lu re %lu ro %lu rl %lu rp %lu\n",       \
        ria->ria_start, ria->ria_end, ria->ria_stoff, ria->ria_length,\
        ria->ria_pages)

#define RAS_INCREASE_STEP (1024 * 1024 >> CFS_PAGE_SHIFT)

static inline int stride_io_mode(struct ll_readahead_state *ras)
{
        return ras->ras_consecutive_stride_requests > 1;
}

/* The function calculates how much pages will be read in
 * [off, off + length], which will be read by stride I/O mode,
 * stride_offset = st_off, stride_lengh = st_len,
 * stride_pages = st_pgs
 */
static unsigned long
stride_pg_count(pgoff_t st_off, unsigned long st_len, unsigned long st_pgs,
                unsigned long off, unsigned length)
{
        unsigned long cont_len = st_off > off ?  st_off - off : 0;
        __u64 stride_len = length + off > st_off ?
                           length + off + 1 - st_off : 0;
        unsigned long left, pg_count;

        if (st_len == 0 || length == 0)
                return length;

        left = do_div(stride_len, st_len);
        left = min(left, st_pgs);

        pg_count = left + stride_len * st_pgs + cont_len;

        LASSERT(pg_count >= left);

        CDEBUG(D_READA, "st_off %lu, st_len %lu st_pgs %lu off %lu length %u"
               "pgcount %lu\n", st_off, st_len, st_pgs, off, length, pg_count);

        return pg_count;
}

static int ria_page_count(struct ra_io_arg *ria)
{
        __u64 length = ria->ria_end >= ria->ria_start ?
                       ria->ria_end - ria->ria_start + 1 : 0;

        return stride_pg_count(ria->ria_stoff, ria->ria_length,
                               ria->ria_pages, ria->ria_start,
                               length);
}

/*Check whether the index is in the defined ra-window */
static int ras_inside_ra_window(unsigned long idx, struct ra_io_arg *ria)
{
        /* If ria_length == ria_pages, it means non-stride I/O mode,
         * idx should always inside read-ahead window in this case
         * For stride I/O mode, just check whether the idx is inside
         * the ria_pages. */
        return ria->ria_length == 0 || ria->ria_length == ria->ria_pages ||
               (idx - ria->ria_stoff) % ria->ria_length < ria->ria_pages;
}

static int ll_read_ahead_pages(struct obd_export *exp,
                               struct obd_io_group *oig,
                               struct ra_io_arg *ria,   
                               unsigned long *reserved_pages,
                               struct address_space *mapping,
                               unsigned long *ra_end)
{
        int rc, count = 0, stride_ria;
        unsigned long page_idx;

        LASSERT(ria != NULL);
        RIA_DEBUG(ria);

        stride_ria = ria->ria_length > ria->ria_pages && ria->ria_pages > 0;
        for (page_idx = ria->ria_start; page_idx <= ria->ria_end &&
                        *reserved_pages > 0; page_idx++) {
                if (ras_inside_ra_window(page_idx, ria)) {
                        /* If the page is inside the read-ahead window*/
                        rc = ll_read_ahead_page(exp, oig, page_idx, mapping);
                        if (rc == 1) {
                                (*reserved_pages)--;
                                count ++;
                        } else if (rc == -ENOLCK)
                                break;
                } else if (stride_ria) {
                        /* If it is not in the read-ahead window, and it is
                         * read-ahead mode, then check whether it should skip
                         * the stride gap */
                        pgoff_t offset;
                        /* FIXME: This assertion only is valid when it is for
                         * forward read-ahead, it will be fixed when backward
                         * read-ahead is implemented */
                        LASSERTF(page_idx > ria->ria_stoff, "since %lu in the"
                                " gap of ra window,it should bigger than stride"
                                " offset %lu \n", page_idx, ria->ria_stoff);

                        offset = page_idx - ria->ria_stoff;
                        offset = offset % (ria->ria_length);
                        if (offset > ria->ria_pages) {
                                page_idx += ria->ria_length - offset;
                                CDEBUG(D_READA, "i %lu skip %lu \n", page_idx,
                                       ria->ria_length - offset);
                                continue;
                        }
                }
        }
        *ra_end = page_idx;
        return count;
}

static int ll_readahead(struct ll_readahead_state *ras,
                         struct obd_export *exp, struct address_space *mapping,
                         struct obd_io_group *oig, int flags)
{
        unsigned long start = 0, end = 0, reserved;
        unsigned long ra_end, len;
        struct inode *inode;
        struct lov_stripe_md *lsm;
        struct ll_ra_read *bead;
        struct ost_lvb lvb;
        struct ra_io_arg ria = { 0 };
        int ret = 0;
        __u64 kms;
        ENTRY;

        inode = mapping->host;
        lsm = ll_i2info(inode)->lli_smd;

        lov_stripe_lock(lsm);
        inode_init_lvb(inode, &lvb);
        obd_merge_lvb(ll_i2dtexp(inode), lsm, &lvb, 1);
        kms = lvb.lvb_size;
        lov_stripe_unlock(lsm);
        if (kms == 0) {
                ll_ra_stats_inc(mapping, RA_STAT_ZERO_LEN);
                RETURN(0);
        }

        spin_lock(&ras->ras_lock);
        bead = ll_ra_read_get_locked(ras);
        /* Enlarge the RA window to encompass the full read */
        if (bead != NULL && ras->ras_window_start + ras->ras_window_len <
            bead->lrr_start + bead->lrr_count) {
                ras->ras_window_len = bead->lrr_start + bead->lrr_count -
                                      ras->ras_window_start;
        }
        /* Reserve a part of the read-ahead window that we'll be issuing */
        if (ras->ras_window_len) {
                start = ras->ras_next_readahead;
                end = ras->ras_window_start + ras->ras_window_len - 1;
        }
        if (end != 0) {
                /* Truncate RA window to end of file */
                end = min(end, (unsigned long)((kms - 1) >> CFS_PAGE_SHIFT));
                ras->ras_next_readahead = max(end, end + 1);
                RAS_CDEBUG(ras);
        }
        ria.ria_start = start;
        ria.ria_end = end;
        /* If stride I/O mode is detected, get stride window*/
        if (stride_io_mode(ras)) {
                ria.ria_stoff = ras->ras_stride_offset;
                ria.ria_length = ras->ras_stride_length;
                ria.ria_pages = ras->ras_stride_pages;
        }
        spin_unlock(&ras->ras_lock);

        if (end == 0) {
                ll_ra_stats_inc(mapping, RA_STAT_ZERO_WINDOW);
                RETURN(0);
        }
        len = ria_page_count(&ria);
        if (len == 0)
                RETURN(0);

        reserved = ll_ra_count_get(ll_i2sbi(inode), len);

        if (reserved < len)
                ll_ra_stats_inc(mapping, RA_STAT_MAX_IN_FLIGHT);

        CDEBUG(D_READA, "reserved page %lu \n", reserved);
        
        ret = ll_read_ahead_pages(exp, oig, &ria, &reserved, mapping, &ra_end);

        LASSERTF(reserved >= 0, "reserved %lu\n", reserved);
        if (reserved != 0)
                ll_ra_count_put(ll_i2sbi(inode), reserved);

        if (ra_end == end + 1 && ra_end == (kms >> CFS_PAGE_SHIFT))
                ll_ra_stats_inc(mapping, RA_STAT_EOF);

        /* if we didn't get to the end of the region we reserved from
         * the ras we need to go back and update the ras so that the
         * next read-ahead tries from where we left off.  we only do so
         * if the region we failed to issue read-ahead on is still ahead
         * of the app and behind the next index to start read-ahead from */
        CDEBUG(D_READA, "ra_end %lu end %lu stride end %lu \n",
               ra_end, end, ria.ria_end);

        if (ra_end != (end + 1)) {
                spin_lock(&ras->ras_lock);
                if (ra_end < ras->ras_next_readahead &&
                    index_in_window(ra_end, ras->ras_window_start, 0,
                                    ras->ras_window_len)) {
                        ras->ras_next_readahead = ra_end;
                        RAS_CDEBUG(ras);
                }
                spin_unlock(&ras->ras_lock);
        }

        RETURN(ret);
}

static void ras_set_start(struct ll_readahead_state *ras, unsigned long index)
{
        ras->ras_window_start = index & (~(RAS_INCREASE_STEP - 1));
}

/* called with the ras_lock held or from places where it doesn't matter */
static void ras_reset(struct ll_readahead_state *ras, unsigned long index)
{
        ras->ras_last_readpage = index;
        ras->ras_consecutive_requests = 0;
        ras->ras_consecutive_pages = 0;
        ras->ras_window_len = 0;
        ras_set_start(ras, index);
        ras->ras_next_readahead = max(ras->ras_window_start, index);

        RAS_CDEBUG(ras);
}

/* called with the ras_lock held or from places where it doesn't matter */
static void ras_stride_reset(struct ll_readahead_state *ras)
{
        ras->ras_consecutive_stride_requests = 0;
        RAS_CDEBUG(ras);
}

void ll_readahead_init(struct inode *inode, struct ll_readahead_state *ras)
{
        spin_lock_init(&ras->ras_lock);
        ras_reset(ras, 0);
        ras->ras_requests = 0;
        INIT_LIST_HEAD(&ras->ras_read_beads);
}

/* Check whether the read request is in the stride window.
 * If it is in the stride window, return 1, otherwise return 0.
 * and also update stride_gap and stride_pages.
 */
static int index_in_stride_window(unsigned long index,
                                  struct ll_readahead_state *ras,
                                  struct inode *inode)
{
        int stride_gap = index - ras->ras_last_readpage - 1;

        LASSERT(stride_gap != 0);

        if (ras->ras_consecutive_pages == 0)
                return 0;

        /*Otherwise check the stride by itself */
        if ((ras->ras_stride_length - ras->ras_stride_pages) == stride_gap &&
            ras->ras_consecutive_pages == ras->ras_stride_pages)
                return 1;

        if (stride_gap >= 0) {
                /*
                 * only set stride_pages, stride_length if
                 * it is forward reading ( stride_gap > 0)
                 */
                ras->ras_stride_pages = ras->ras_consecutive_pages;
                ras->ras_stride_length = stride_gap + ras->ras_consecutive_pages;
        } else {
                /*
                 * If stride_gap < 0,(back_forward reading),
                 * reset the stride_pages/length.
                 * FIXME:back_ward stride I/O read.
                 *
                 */
                ras->ras_stride_pages = 0;
                ras->ras_stride_length = 0;
        }
        RAS_CDEBUG(ras);

        return 0;
}

static unsigned long
stride_page_count(struct ll_readahead_state *ras, unsigned long len)
{
        return stride_pg_count(ras->ras_stride_offset, ras->ras_stride_length,
                               ras->ras_stride_pages, ras->ras_stride_offset,
                               len);
}

/* Stride Read-ahead window will be increased inc_len according to
 * stride I/O pattern */
static void ras_stride_increase_window(struct ll_readahead_state *ras,
                                       struct ll_ra_info *ra,
                                       unsigned long inc_len)
{
        unsigned long left, step, window_len;
        unsigned long stride_len;

        LASSERT(ras->ras_stride_length > 0);

        stride_len = ras->ras_window_start + ras->ras_window_len -
                     ras->ras_stride_offset;

        LASSERTF(stride_len >= 0, "window_start %lu, window_len %lu"
                 " stride_offset %lu\n", ras->ras_window_start,
                 ras->ras_window_len, ras->ras_stride_offset);

        left = stride_len % ras->ras_stride_length;

        window_len = ras->ras_window_len - left;

        if (left < ras->ras_stride_pages)
                left += inc_len;
        else
                left = ras->ras_stride_pages + inc_len;

        LASSERT(ras->ras_stride_pages != 0);

        step = left / ras->ras_stride_pages;
        left %= ras->ras_stride_pages;

        window_len += step * ras->ras_stride_length + left;

        if (stride_page_count(ras, window_len) <= ra->ra_max_pages)
                ras->ras_window_len = window_len;

        RAS_CDEBUG(ras);
}

/* Set stride I/O read-ahead window start offset */
static void ras_set_stride_offset(struct ll_readahead_state *ras)
{
        unsigned long window_len = ras->ras_next_readahead -
                                   ras->ras_window_start;
        unsigned long left;

        LASSERT(ras->ras_stride_length != 0);

        left = window_len % ras->ras_stride_length;

        ras->ras_stride_offset = ras->ras_next_readahead - left;

        RAS_CDEBUG(ras);
}

static void ras_update(struct ll_sb_info *sbi, struct inode *inode,
                       struct ll_readahead_state *ras, unsigned long index,
                       unsigned hit)
{
        struct ll_ra_info *ra = &sbi->ll_ra_info;
        int zero = 0, stride_zero = 0, stride_detect = 0, ra_miss = 0;
        ENTRY;

        spin_lock(&sbi->ll_lock);
        spin_lock(&ras->ras_lock);

        ll_ra_stats_inc_unlocked(ra, hit ? RA_STAT_HIT : RA_STAT_MISS);

        /* reset the read-ahead window in two cases.  First when the app seeks
         * or reads to some other part of the file.  Secondly if we get a
         * read-ahead miss that we think we've previously issued.  This can
         * be a symptom of there being so many read-ahead pages that the VM is
         * reclaiming it before we get to it. */
        if (!index_in_window(index, ras->ras_last_readpage, 8, 8)) {
                zero = 1;
                ll_ra_stats_inc_unlocked(ra, RA_STAT_DISTANT_READPAGE);
                /* check whether it is in stride I/O mode*/
                if (!index_in_stride_window(index, ras, inode))
                        stride_zero = 1;
        } else if (!hit && ras->ras_window_len &&
                   index < ras->ras_next_readahead &&
                   index_in_window(index, ras->ras_window_start, 0,
                                   ras->ras_window_len)) {
                zero = 1;
                ra_miss = 1;
                /* If it hits read-ahead miss and the stride I/O is still
                 * not detected, reset stride stuff to re-detect the whole
                 * stride I/O mode to avoid complication */
                if (!stride_io_mode(ras))
                        stride_zero = 1;
                ll_ra_stats_inc_unlocked(ra, RA_STAT_MISS_IN_WINDOW);
        }

        /* On the second access to a file smaller than the tunable
         * ra_max_read_ahead_whole_pages trigger RA on all pages in the
         * file up to ra_max_pages.  This is simply a best effort and
         * only occurs once per open file.  Normal RA behavior is reverted
         * to for subsequent IO.  The mmap case does not increment
         * ras_requests and thus can never trigger this behavior. */
        if (ras->ras_requests == 2 && !ras->ras_request_index) {
                __u64 kms_pages;

                kms_pages = (i_size_read(inode) + CFS_PAGE_SIZE - 1) >>
                            CFS_PAGE_SHIFT;

                CDEBUG(D_READA, "kmsp "LPU64" mwp %lu mp %lu\n", kms_pages,
                       ra->ra_max_read_ahead_whole_pages, ra->ra_max_pages);

                if (kms_pages &&
                    kms_pages <= ra->ra_max_read_ahead_whole_pages) {
                        ras->ras_window_start = 0;
                        ras->ras_last_readpage = 0;
                        ras->ras_next_readahead = 0;
                        ras->ras_window_len = min(ra->ra_max_pages,
                                ra->ra_max_read_ahead_whole_pages);
                        GOTO(out_unlock, 0);
                }
        }

        if (zero) {
                /* If it is discontinuous read, check
                 * whether it is stride I/O mode*/
                if (stride_zero) {
                        ras_reset(ras, index);
                        ras->ras_consecutive_pages++;
                        ras_stride_reset(ras);
                        RAS_CDEBUG(ras);
                        GOTO(out_unlock, 0);
                } else {
                        /* The read is still in stride window or
                         * it hits read-ahead miss */

                        /* If ra-window miss is hitted, which probably means VM
                         * pressure, and some read-ahead pages were reclaimed.So
                         * the length of ra-window will not increased, but also
                         * not reset to avoid redetecting the stride I/O mode.*/
                        ras->ras_consecutive_requests = 0;
                        if (!ra_miss) {
                                ras->ras_consecutive_pages = 0;
                                if (++ras->ras_consecutive_stride_requests > 1)
                                        stride_detect = 1;
                        }
                        RAS_CDEBUG(ras);
                }
        } else if (ras->ras_consecutive_stride_requests > 1) {
                /* If this is contiguous read but in stride I/O mode
                 * currently, check whether stride step still is valid,
                 * if invalid, it will reset the stride ra window*/     
                if (ras->ras_consecutive_pages + 1 > ras->ras_stride_pages)
                        ras_stride_reset(ras);
        }

        ras->ras_last_readpage = index;
        ras->ras_consecutive_pages++;
        ras_set_start(ras, index);
        ras->ras_next_readahead = max(ras->ras_window_start,
                                      ras->ras_next_readahead);
        RAS_CDEBUG(ras);

        /* Trigger RA in the mmap case where ras_consecutive_requests
         * is not incremented and thus can't be used to trigger RA */
        if (!ras->ras_window_len && ras->ras_consecutive_pages == 4) {
                ras->ras_window_len = RAS_INCREASE_STEP;
                GOTO(out_unlock, 0);
        }

        /* Initially reset the stride window offset to next_readahead*/
        if (ras->ras_consecutive_stride_requests == 2 && stride_detect)
                ras_set_stride_offset(ras);

        /* The initial ras_window_len is set to the request size.  To avoid
         * uselessly reading and discarding pages for random IO the window is
         * only increased once per consecutive request received. */
        if ((ras->ras_consecutive_requests > 1 &&
            !ras->ras_request_index) || stride_detect) {
                if (stride_io_mode(ras))
                        ras_stride_increase_window(ras, ra, RAS_INCREASE_STEP);
                else
                        ras->ras_window_len = min(ras->ras_window_len +
                                                  RAS_INCREASE_STEP,
                                                  ra->ra_max_pages);
        }
        EXIT;
out_unlock:
        RAS_CDEBUG(ras);
        ras->ras_request_index++;
        spin_unlock(&ras->ras_lock);
        spin_unlock(&sbi->ll_lock);
        return;
}

int ll_writepage(struct page *page)
{
        struct inode *inode = page->mapping->host;
        struct ll_inode_info *lli = ll_i2info(inode);
        struct obd_export *exp;
        struct ll_async_page *llap;
        int rc = 0;
        ENTRY;

        LASSERT(PageLocked(page));

        exp = ll_i2dtexp(inode);
        if (exp == NULL)
                GOTO(out, rc = -EINVAL);

        llap = llap_from_page(page, LLAP_ORIGIN_WRITEPAGE);
        if (IS_ERR(llap))
                GOTO(out, rc = PTR_ERR(llap));

        LASSERT(!llap->llap_nocache);
        LASSERT(!PageWriteback(page));
        set_page_writeback(page);

        page_cache_get(page);
        if (llap->llap_write_queued) {
                LL_CDEBUG_PAGE(D_PAGE, page, "marking urgent\n");
                rc = obd_set_async_flags(exp, lli->lli_smd, NULL,
                                         llap->llap_cookie,
                                         ASYNC_READY | ASYNC_URGENT);
        } else {
                rc = queue_or_sync_write(exp, inode, llap, CFS_PAGE_SIZE,
                                         ASYNC_READY | ASYNC_URGENT);
        }
        if (rc) {
                /* re-dirty page on error so it retries write */
                if (PageWriteback(page))
                        end_page_writeback(page);

                /* resend page only for not started IO*/
                if (!PageError(page))
                        ll_redirty_page(page);

                page_cache_release(page);
        }
out:
        if (rc) {
                if (!lli->lli_async_rc)
                        lli->lli_async_rc = rc;
                /* resend page only for not started IO*/
                unlock_page(page);
        }
        RETURN(rc);
}

/*
 * for now we do our readpage the same on both 2.4 and 2.5.  The kernel's
 * read-ahead assumes it is valid to issue readpage all the way up to
 * i_size, but our dlm locks make that not the case.  We disable the
 * kernel's read-ahead and do our own by walking ahead in the page cache
 * checking for dlm lock coverage.  the main difference between 2.4 and
 * 2.6 is how read-ahead gets batched and issued, but we're using our own,
 * so they look the same.
 */
int ll_readpage(struct file *filp, struct page *page)
{
        struct ll_file_data *fd = LUSTRE_FPRIVATE(filp);
        struct inode *inode = page->mapping->host;
        struct obd_export *exp;
        struct ll_async_page *llap;
        struct obd_io_group *oig = NULL;
        struct lustre_handle *lockh = NULL;
        int rc;
        ENTRY;

        LASSERT(PageLocked(page));
        LASSERT(!PageUptodate(page));
        CDEBUG(D_VFSTRACE, "VFS Op:inode=%lu/%u(%p),offset=%Lu=%#Lx\n",
               inode->i_ino, inode->i_generation, inode,
               (((loff_t)page->index) << CFS_PAGE_SHIFT),
               (((loff_t)page->index) << CFS_PAGE_SHIFT));
        LASSERT(atomic_read(&filp->f_dentry->d_inode->i_count) > 0);

        if (!ll_i2info(inode)->lli_smd) {
                /* File with no objects - one big hole */
                /* We use this just for remove_from_page_cache that is not
                 * exported, we'd make page back up to date. */
                ll_truncate_complete_page(page);
                clear_page(kmap(page));
                kunmap(page);
                SetPageUptodate(page);
                unlock_page(page);
                RETURN(0);
        }

        rc = oig_init(&oig);
        if (rc < 0)
                GOTO(out, rc);

        exp = ll_i2dtexp(inode);
        if (exp == NULL)
                GOTO(out, rc = -EINVAL);

        if (fd->fd_flags & LL_FILE_GROUP_LOCKED)
                lockh = &fd->fd_cwlockh;

        llap = llap_from_page_with_lockh(page, LLAP_ORIGIN_READPAGE, lockh);
        if (IS_ERR(llap)) {
                if (PTR_ERR(llap) == -ENOLCK) {
                        CWARN("ino %lu page %lu (%llu) not covered by "
                              "a lock (mmap?).  check debug logs.\n",
                              inode->i_ino, page->index,
                              (long long)page->index << PAGE_CACHE_SHIFT);
                }
                GOTO(out, rc = PTR_ERR(llap));
        }

        if (ll_i2sbi(inode)->ll_ra_info.ra_max_pages)
                ras_update(ll_i2sbi(inode), inode, &fd->fd_ras, page->index,
                           llap->llap_defer_uptodate);


        if (llap->llap_defer_uptodate) {
                /* This is the callpath if we got the page from a readahead */
                llap->llap_ra_used = 1;
                rc = ll_readahead(&fd->fd_ras, exp, page->mapping, oig,
                                  fd->fd_flags);
                if (rc > 0)
                        obd_trigger_group_io(exp, ll_i2info(inode)->lli_smd,
                                             NULL, oig);
                LL_CDEBUG_PAGE(D_PAGE, page, "marking uptodate from defer\n");
                SetPageUptodate(page);
                unlock_page(page);
                GOTO(out_oig, rc = 0);
        }

        rc = ll_issue_page_read(exp, llap, oig, 0);
        if (rc)
                GOTO(out, rc);

        LL_CDEBUG_PAGE(D_PAGE, page, "queued readpage\n");
        /* We have just requested the actual page we want, see if we can tack
         * on some readahead to that page's RPC before it is sent. */
        if (ll_i2sbi(inode)->ll_ra_info.ra_max_pages)
                ll_readahead(&fd->fd_ras, exp, page->mapping, oig,
                             fd->fd_flags);

        rc = obd_trigger_group_io(exp, ll_i2info(inode)->lli_smd, NULL, oig);

out:
        if (rc)
                unlock_page(page);
out_oig:
        if (oig != NULL)
                oig_release(oig);
        RETURN(rc);
}

static void ll_file_put_pages(struct page **pages, int numpages)
{
        int i;
        struct page **pp;
        ENTRY;

        for (i = 0, pp = pages; i < numpages; i++, pp++) {
                if (*pp) {
                        LL_CDEBUG_PAGE(D_PAGE, (*pp), "free\n");
                        __ll_put_llap(*pp);
                        if (page_private(*pp))
                                CERROR("the llap wasn't freed\n");
                        (*pp)->mapping = NULL;
                        if (page_count(*pp) != 1)
                                CERROR("page %p, flags %#lx, count %i, private %p\n",
                                (*pp), (unsigned long)(*pp)->flags, page_count(*pp),
                                (void*)page_private(*pp));
                        __free_pages(*pp, 0);
                }
        }
        OBD_FREE(pages, numpages * sizeof(struct page*));
        EXIT;
}

static struct page **ll_file_prepare_pages(int numpages, struct inode *inode,
                                           unsigned long first)
{
        struct page **pages;
        int i;
        int rc = 0;
        ENTRY;

        OBD_ALLOC(pages, sizeof(struct page *) * numpages);
        if (pages == NULL)
                RETURN(ERR_PTR(-ENOMEM));
        for (i = 0; i < numpages; i++) {
                struct page *page;
                struct ll_async_page *llap;

                page = alloc_pages(GFP_HIGHUSER, 0);
                if (page == NULL)
                        GOTO(err, rc = -ENOMEM);
                pages[i] = page;
                /* llap_from_page needs page index and mapping to be set */
                page->index = first++;
                page->mapping = inode->i_mapping;
                llap = llap_from_page(page, LLAP_ORIGIN_LOCKLESS_IO);
                if (IS_ERR(llap))
                        GOTO(err, rc = PTR_ERR(llap));
                llap->llap_lockless_io_page = 1;
        }
        RETURN(pages);
err:
        ll_file_put_pages(pages, numpages);
        RETURN(ERR_PTR(rc));
 }

static ssize_t ll_file_copy_pages(struct page **pages, int numpages,
                                  char *buf, loff_t pos, size_t count, int rw)
{
        ssize_t amount = 0;
        int i;
        int updatechecksum = ll_i2sbi(pages[0]->mapping->host)->ll_flags &
                             LL_SBI_CHECKSUM;
        ENTRY;

        for (i = 0; i < numpages; i++) {
                unsigned offset, bytes, left;
                char *vaddr;

                vaddr = kmap(pages[i]);
                offset = pos & (CFS_PAGE_SIZE - 1);
                bytes = min_t(unsigned, CFS_PAGE_SIZE - offset, count);
                LL_CDEBUG_PAGE(D_PAGE, pages[i], "op = %s, addr = %p, "
                               "buf = %p, bytes = %u\n",
                               (rw == WRITE) ? "CFU" : "CTU",
                               vaddr + offset, buf, bytes);
                if (rw == WRITE) {
                        left = copy_from_user(vaddr + offset, buf, bytes);
                        if (updatechecksum) {
                                struct ll_async_page *llap;

                                llap = llap_cast_private(pages[i]);
                                llap->llap_checksum = crc32_le(0, vaddr,
                                                               CFS_PAGE_SIZE);
                        }
                } else {
                        left = copy_to_user(buf, vaddr + offset, bytes);
                }
                kunmap(pages[i]);
                amount += bytes;
                if (left) {
                        amount -= left;
                        break;
                }
                buf += bytes;
                count -= bytes;
                pos += bytes;
        }
        if (amount == 0)
                RETURN(-EFAULT);
        RETURN(amount);
}

static int ll_file_oig_pages(struct inode * inode, struct page **pages,
                             int numpages, loff_t pos, size_t count, int rw)
{
        struct obd_io_group *oig;
        struct ll_inode_info *lli = ll_i2info(inode);
        struct obd_export *exp;
        loff_t org_pos = pos;
        obd_flag brw_flags;
        int rc;
        int i;
        ENTRY;

        exp = ll_i2dtexp(inode);
        if (exp == NULL)
                RETURN(-EINVAL);
        rc = oig_init(&oig);
        if (rc)
                RETURN(rc);
        brw_flags = OBD_BRW_SRVLOCK;
        if (capable(CAP_SYS_RESOURCE))
                brw_flags |= OBD_BRW_NOQUOTA;

        for (i = 0; i < numpages; i++) {
                struct ll_async_page *llap;
                unsigned from, bytes;

                from = pos & (CFS_PAGE_SIZE - 1);
                bytes = min_t(unsigned, CFS_PAGE_SIZE - from,
                              count - pos + org_pos);
                llap = llap_cast_private(pages[i]);
                LASSERT(llap);

                lock_page(pages[i]);

                LL_CDEBUG_PAGE(D_PAGE, pages[i], "offset "LPU64","
                               " from %u, bytes = %u\n",
                               pos, from, bytes);
                LASSERTF(pos >> CFS_PAGE_SHIFT == pages[i]->index,
                         "wrong page index %lu (%lu)\n",
                         pages[i]->index,
                         (unsigned long)(pos >> CFS_PAGE_SHIFT));
                rc = obd_queue_group_io(exp, lli->lli_smd, NULL, oig,
                                        llap->llap_cookie,
                                        (rw == WRITE) ?
                                        OBD_BRW_WRITE:OBD_BRW_READ,
                                        from, bytes, brw_flags,
                                        ASYNC_READY | ASYNC_URGENT |
                                        ASYNC_COUNT_STABLE | ASYNC_GROUP_SYNC);
                if (rc) {
                        i++;
                        GOTO(out, rc);
                }
                pos += bytes;
        }
        rc = obd_trigger_group_io(exp, lli->lli_smd, NULL, oig);
        if (rc)
                GOTO(out, rc);
        rc = oig_wait(oig);
out:
        while(--i >= 0)
                unlock_page(pages[i]);
        oig_release(oig);
        RETURN(rc);
}

ssize_t ll_file_lockless_io(struct file *file, char *buf, size_t count,
                                   loff_t *ppos, int rw)
{
        loff_t pos;
        struct inode *inode = file->f_dentry->d_inode;
        ssize_t rc = 0;
        int max_pages;
        size_t amount = 0;
        unsigned long first, last;
        ENTRY;

        if (rw == READ) {
                loff_t isize;

                ll_inode_size_lock(inode, 0);
                isize = i_size_read(inode);
                ll_inode_size_unlock(inode, 0);
                if (*ppos >= isize)
                        GOTO(out, rc = 0);
                if (*ppos + count >= isize)
                        count -= *ppos + count - isize;
                if (count == 0)
                        GOTO(out, rc);
        } else {
                rc = generic_write_checks(file, ppos, &count, 0);
                if (rc)
                        GOTO(out, rc);
                rc = remove_suid(file->f_dentry);
                if (rc)
                        GOTO(out, rc);
        }
        pos = *ppos;
        first = pos >> CFS_PAGE_SHIFT;
        last = (pos + count - 1) >> CFS_PAGE_SHIFT;
        max_pages = PTLRPC_MAX_BRW_PAGES *
                ll_i2info(inode)->lli_smd->lsm_stripe_count;
        CDEBUG(D_INFO, "%u, stripe_count = %u\n",
               PTLRPC_MAX_BRW_PAGES /* max_pages_per_rpc */,
               ll_i2info(inode)->lli_smd->lsm_stripe_count);

        while (first <= last && rc >= 0) {
                int pages_for_io;
                struct page **pages;
                size_t bytes = count - amount;

                pages_for_io = min_t(int, last - first + 1, max_pages);
                pages = ll_file_prepare_pages(pages_for_io, inode, first);
                if (IS_ERR(pages)) {
                        rc = PTR_ERR(pages);
                        break;
                }
                if (rw == WRITE) {
                        rc = ll_file_copy_pages(pages, pages_for_io, buf,
                                                pos + amount, bytes, rw);
                        if (rc < 0)
                                GOTO(put_pages, rc);
                        bytes = rc;
                }
                rc = ll_file_oig_pages(inode, pages, pages_for_io,
                                       pos + amount, bytes, rw);
                if (rc)
                        GOTO(put_pages, rc);
                if (rw == READ) {
                        rc = ll_file_copy_pages(pages, pages_for_io, buf,
                                                pos + amount, bytes, rw);
                        if (rc < 0)
                                GOTO(put_pages, rc);
                        bytes = rc;
                }
                amount += bytes;
                buf += bytes;
put_pages:
                ll_file_put_pages(pages, pages_for_io);
                first += pages_for_io;
                /* a short read/write check */
                if (pos + amount < ((loff_t)first << CFS_PAGE_SHIFT))
                        break;
        }
        /* NOTE: don't update i_size and KMS in absence of LDLM locks even
         * write makes the file large */
        file_accessed(file);
        if (rw == READ && amount < count && rc == 0) {
                unsigned long not_cleared;

                not_cleared = clear_user(buf, count - amount);
                amount = count - not_cleared;
                if (not_cleared)
                        rc = -EFAULT;
        }
        if (amount > 0) {
                lprocfs_counter_add(ll_i2sbi(inode)->ll_stats,
                                    (rw == WRITE) ?
                                    LPROC_LL_LOCKLESS_WRITE :
                                    LPROC_LL_LOCKLESS_READ,
                                    (long)amount);
                *ppos += amount;
                RETURN(amount);
        }
out:
        RETURN(rc);
}