/*
 * 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
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * 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 (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2013, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * Implementation of cl_io for OSC layer.
 *
 *   Author: Nikita Danilov <nikita.danilov@sun.com>
 *   Author: Jinshan Xiong <jinshan.xiong@whamcloud.com>
 */

#define DEBUG_SUBSYSTEM S_OSC

#include "osc_cl_internal.h"

/** \addtogroup osc 
 *  @{ 
 */

/*****************************************************************************
 *
 * Type conversions.
 *
 */

static struct osc_req *cl2osc_req(const struct cl_req_slice *slice)
{
        LINVRNT(slice->crs_dev->cd_lu_dev.ld_type == &osc_device_type);
        return container_of0(slice, struct osc_req, or_cl);
}

static struct osc_io *cl2osc_io(const struct lu_env *env,
                                const struct cl_io_slice *slice)
{
        struct osc_io *oio = container_of0(slice, struct osc_io, oi_cl);
        LINVRNT(oio == osc_env_io(env));
        return oio;
}

static struct osc_page *osc_cl_page_osc(struct cl_page *page)
{
        const struct cl_page_slice *slice;

        slice = cl_page_at(page, &osc_device_type);
        LASSERT(slice != NULL);

        return cl2osc_page(slice);
}


/*****************************************************************************
 *
 * io operations.
 *
 */

static void osc_io_fini(const struct lu_env *env, const struct cl_io_slice *io)
{
}

/**
 * An implementation of cl_io_operations::cio_io_submit() method for osc
 * layer. Iterates over pages in the in-queue, prepares each for io by calling
 * cl_page_prep() and then either submits them through osc_io_submit_page()
 * or, if page is already submitted, changes osc flags through
 * osc_set_async_flags().
 */
static int osc_io_submit(const struct lu_env *env,
                         const struct cl_io_slice *ios,
			 enum cl_req_type crt, struct cl_2queue *queue)
{
        struct cl_page    *page;
        struct cl_page    *tmp;
        struct client_obd *cli  = NULL;
        struct osc_object *osc  = NULL; /* to keep gcc happy */
        struct osc_page   *opg;
        struct cl_io      *io;
	CFS_LIST_HEAD     (list);

	struct cl_page_list *qin      = &queue->c2_qin;
	struct cl_page_list *qout     = &queue->c2_qout;
	int queued = 0;
	int result = 0;
	int cmd;
	int brw_flags;
	int max_pages;

	LASSERT(qin->pl_nr > 0);

	CDEBUG(D_CACHE, "%d %d\n", qin->pl_nr, crt);

	osc = cl2osc(ios->cis_obj);
	cli = osc_cli(osc);
	max_pages = cli->cl_max_pages_per_rpc;

	cmd = crt == CRT_WRITE ? OBD_BRW_WRITE : OBD_BRW_READ;
	brw_flags = osc_io_srvlock(cl2osc_io(env, ios)) ? OBD_BRW_SRVLOCK : 0;

        /*
         * NOTE: here @page is a top-level page. This is done to avoid
         *       creation of sub-page-list.
         */
        cl_page_list_for_each_safe(page, tmp, qin) {
                struct osc_async_page *oap;

                /* Top level IO. */
                io = page->cp_owner;
                LASSERT(io != NULL);

                opg = osc_cl_page_osc(page);
                oap = &opg->ops_oap;
		LASSERT(osc == oap->oap_obj);

		if (!cfs_list_empty(&oap->oap_pending_item) ||
		    !cfs_list_empty(&oap->oap_rpc_item)) {
			CDEBUG(D_CACHE, "Busy oap %p page %p for submit.\n",
			       oap, opg);
                        result = -EBUSY;
                        break;
                }

                result = cl_page_prep(env, io, page, crt);
		if (result != 0) {
                        LASSERT(result < 0);
                        if (result != -EALREADY)
                                break;
                        /*
                         * Handle -EALREADY error: for read case, the page is
                         * already in UPTODATE state; for write, the page
                         * is not dirty.
                         */
                        result = 0;
			continue;
                }

		cl_page_list_move(qout, qin, page);
		spin_lock(&oap->oap_lock);
		oap->oap_async_flags = ASYNC_URGENT|ASYNC_READY;
		oap->oap_async_flags |= ASYNC_COUNT_STABLE;
		spin_unlock(&oap->oap_lock);

		osc_page_submit(env, opg, crt, brw_flags);
		cfs_list_add_tail(&oap->oap_pending_item, &list);
		if (++queued == max_pages) {
			queued = 0;
			result = osc_queue_sync_pages(env, osc, &list, cmd,
						      brw_flags);
			if (result < 0)
				break;
		}
	}

	if (queued > 0)
		result = osc_queue_sync_pages(env, osc, &list, cmd, brw_flags);

	CDEBUG(D_INFO, "%d/%d %d\n", qin->pl_nr, qout->pl_nr, result);
	return qout->pl_nr > 0 ? 0 : result;
}

static void osc_page_touch_at(const struct lu_env *env,
                              struct cl_object *obj, pgoff_t idx, unsigned to)
{
        struct lov_oinfo  *loi  = cl2osc(obj)->oo_oinfo;
        struct cl_attr    *attr = &osc_env_info(env)->oti_attr;
        int valid;
        __u64 kms;

        /* offset within stripe */
        kms = cl_offset(obj, idx) + to;

        cl_object_attr_lock(obj);
        /*
         * XXX old code used
         *
         *         ll_inode_size_lock(inode, 0); lov_stripe_lock(lsm);
         *
         * here
         */
        CDEBUG(D_INODE, "stripe KMS %sincreasing "LPU64"->"LPU64" "LPU64"\n",
               kms > loi->loi_kms ? "" : "not ", loi->loi_kms, kms,
               loi->loi_lvb.lvb_size);

        valid = 0;
        if (kms > loi->loi_kms) {
                attr->cat_kms = kms;
                valid |= CAT_KMS;
        }
        if (kms > loi->loi_lvb.lvb_size) {
                attr->cat_size = kms;
                valid |= CAT_SIZE;
        }
        cl_object_attr_set(env, obj, attr, valid);
        cl_object_attr_unlock(obj);
}

/**
 * This is called when a page is accessed within file in a way that creates
 * new page, if one were missing (i.e., if there were a hole at that place in
 * the file, or accessed page is beyond the current file size). Examples:
 * ->commit_write() and ->nopage() methods.
 *
 * Expand stripe KMS if necessary.
 */
static void osc_page_touch(const struct lu_env *env,
                           struct osc_page *opage, unsigned to)
{
        struct cl_page    *page = opage->ops_cl.cpl_page;
        struct cl_object  *obj  = opage->ops_cl.cpl_obj;

        osc_page_touch_at(env, obj, page->cp_index, to);
}

/**
 * Implements cl_io_operations::cio_prepare_write() method for osc layer.
 *
 * \retval -EIO transfer initiated against this osc will most likely fail
 * \retval 0    transfer initiated against this osc will most likely succeed.
 *
 * The reason for this check is to immediately return an error to the caller
 * in the case of a deactivated import. Note, that import can be deactivated
 * later, while pages, dirtied by this IO, are still in the cache, but this is
 * irrelevant, because that would still return an error to the application (if
 * it does fsync), but many applications don't do fsync because of performance
 * issues, and we wanted to return an -EIO at write time to notify the
 * application.
 */
static int osc_io_prepare_write(const struct lu_env *env,
                                const struct cl_io_slice *ios,
                                const struct cl_page_slice *slice,
                                unsigned from, unsigned to)
{
        struct osc_device *dev = lu2osc_dev(slice->cpl_obj->co_lu.lo_dev);
        struct obd_import *imp = class_exp2cliimp(dev->od_exp);
        struct osc_io     *oio = cl2osc_io(env, ios);
        int result = 0;
        ENTRY;

        /*
         * This implements OBD_BRW_CHECK logic from old client.
         */

        if (imp == NULL || imp->imp_invalid)
                result = -EIO;
        if (result == 0 && oio->oi_lockless)
                /* this page contains `invalid' data, but who cares?
                 * nobody can access the invalid data.
                 * in osc_io_commit_write(), we're going to write exact
                 * [from, to) bytes of this page to OST. -jay */
                cl_page_export(env, slice->cpl_page, 1);

        RETURN(result);
}

static int osc_io_commit_write(const struct lu_env *env,
                               const struct cl_io_slice *ios,
                               const struct cl_page_slice *slice,
                               unsigned from, unsigned to)
{
        struct osc_io         *oio = cl2osc_io(env, ios);
        struct osc_page       *opg = cl2osc_page(slice);
        struct osc_object     *obj = cl2osc(opg->ops_cl.cpl_obj);
        struct osc_async_page *oap = &opg->ops_oap;
        ENTRY;

        LASSERT(to > 0);
        /*
         * XXX instead of calling osc_page_touch() here and in
         * osc_io_fault_start() it might be more logical to introduce
         * cl_page_touch() method, that generic cl_io_commit_write() and page
         * fault code calls.
         */
        osc_page_touch(env, cl2osc_page(slice), to);
        if (!client_is_remote(osc_export(obj)) &&
            cfs_capable(CFS_CAP_SYS_RESOURCE))
                oap->oap_brw_flags |= OBD_BRW_NOQUOTA;

        if (oio->oi_lockless)
                /* see osc_io_prepare_write() for lockless io handling. */
                cl_page_clip(env, slice->cpl_page, from, to);

        RETURN(0);
}

static int osc_io_fault_start(const struct lu_env *env,
                              const struct cl_io_slice *ios)
{
        struct cl_io       *io;
        struct cl_fault_io *fio;

        ENTRY;

        io  = ios->cis_io;
        fio = &io->u.ci_fault;
        CDEBUG(D_INFO, "%lu %d %d\n",
               fio->ft_index, fio->ft_writable, fio->ft_nob);
        /*
         * If mapping is writeable, adjust kms to cover this page,
         * but do not extend kms beyond actual file size.
         * See bug 10919.
         */
        if (fio->ft_writable)
                osc_page_touch_at(env, ios->cis_obj,
                                  fio->ft_index, fio->ft_nob);
        RETURN(0);
}

static int osc_async_upcall(void *a, int rc)
{
	struct osc_async_cbargs *args = a;

        args->opc_rc = rc;
	complete(&args->opc_sync);
        return 0;
}

#if defined(__KERNEL__)
/**
 * Checks that there are no pages being written in the extent being truncated.
 */
static int trunc_check_cb(const struct lu_env *env, struct cl_io *io,
			  struct cl_page *page, void *cbdata)
{
	const struct cl_page_slice *slice;
	struct osc_page *ops;
	struct osc_async_page *oap;
	__u64 start = *(__u64 *)cbdata;

	slice = cl_page_at(page, &osc_device_type);
	LASSERT(slice != NULL);
	ops = cl2osc_page(slice);
	oap = &ops->ops_oap;

	if (oap->oap_cmd & OBD_BRW_WRITE &&
	    !cfs_list_empty(&oap->oap_pending_item))
		CL_PAGE_DEBUG(D_ERROR, env, page, "exists " LPU64 "/%s.\n",
				start, current->comm);

#ifdef __linux__
	{
		struct page *vmpage = cl_page_vmpage(env, page);
		if (PageLocked(vmpage))
			CDEBUG(D_CACHE, "page %p index %lu locked for %d.\n",
			       ops, page->cp_index,
			       (oap->oap_cmd & OBD_BRW_RWMASK));
	}
#endif

	return CLP_GANG_OKAY;
}

static void osc_trunc_check(const struct lu_env *env, struct cl_io *io,
			    struct osc_io *oio, __u64 size)
{
	struct cl_object *clob;
	int     partial;
	pgoff_t start;

        clob    = oio->oi_cl.cis_obj;
        start   = cl_index(clob, size);
        partial = cl_offset(clob, start) < size;

        /*
         * Complain if there are pages in the truncated region.
         */
	cl_page_gang_lookup(env, clob, io, start + partial, CL_PAGE_EOF,
			    trunc_check_cb, (void *)&size);
}
#else /* __KERNEL__ */
static void osc_trunc_check(const struct lu_env *env, struct cl_io *io,
			    struct osc_io *oio, __u64 size)
{
	return;
}
#endif

static int osc_io_setattr_start(const struct lu_env *env,
                                const struct cl_io_slice *slice)
{
        struct cl_io            *io     = slice->cis_io;
        struct osc_io           *oio    = cl2osc_io(env, slice);
        struct cl_object        *obj    = slice->cis_obj;
        struct lov_oinfo        *loi    = cl2osc(obj)->oo_oinfo;
        struct cl_attr          *attr   = &osc_env_info(env)->oti_attr;
        struct obdo             *oa     = &oio->oi_oa;
	struct osc_async_cbargs *cbargs = &oio->oi_cbarg;
	__u64                    size   = io->u.ci_setattr.sa_attr.lvb_size;
	unsigned int             ia_valid = io->u.ci_setattr.sa_valid;
	int                      result = 0;
	struct obd_info          oinfo = { { { 0 } } };

	/* truncate cache dirty pages first */
	if (cl_io_is_trunc(io))
		result = osc_cache_truncate_start(env, oio, cl2osc(obj), size);

	if (result == 0 && oio->oi_lockless == 0) {
		cl_object_attr_lock(obj);
		result = cl_object_attr_get(env, obj, attr);
		if (result == 0) {
			struct ost_lvb *lvb = &io->u.ci_setattr.sa_attr;
			unsigned int cl_valid = 0;

			if (ia_valid & ATTR_SIZE) {
				attr->cat_size = attr->cat_kms = size;
				cl_valid = (CAT_SIZE | CAT_KMS);
			}
			if (ia_valid & ATTR_MTIME_SET) {
				attr->cat_mtime = lvb->lvb_mtime;
				cl_valid |= CAT_MTIME;
			}
			if (ia_valid & ATTR_ATIME_SET) {
				attr->cat_atime = lvb->lvb_atime;
				cl_valid |= CAT_ATIME;
			}
			if (ia_valid & ATTR_CTIME_SET) {
				attr->cat_ctime = lvb->lvb_ctime;
                                cl_valid |= CAT_CTIME;
                        }
                        result = cl_object_attr_set(env, obj, attr, cl_valid);
                }
                cl_object_attr_unlock(obj);
        }
        memset(oa, 0, sizeof(*oa));
        if (result == 0) {
		oa->o_oi = loi->loi_oi;
		oa->o_mtime = attr->cat_mtime;
		oa->o_atime = attr->cat_atime;
		oa->o_ctime = attr->cat_ctime;
		oa->o_valid = OBD_MD_FLID | OBD_MD_FLGROUP | OBD_MD_FLATIME |
			OBD_MD_FLCTIME | OBD_MD_FLMTIME;
                if (ia_valid & ATTR_SIZE) {
                        oa->o_size = size;
                        oa->o_blocks = OBD_OBJECT_EOF;
                        oa->o_valid |= OBD_MD_FLSIZE | OBD_MD_FLBLOCKS;

                        if (oio->oi_lockless) {
                                oa->o_flags = OBD_FL_SRVLOCK;
                                oa->o_valid |= OBD_MD_FLFLAGS;
                        }
                } else {
                        LASSERT(oio->oi_lockless == 0);
                }

                oinfo.oi_oa = oa;
                oinfo.oi_capa = io->u.ci_setattr.sa_capa;
		init_completion(&cbargs->opc_sync);

                if (ia_valid & ATTR_SIZE)
                        result = osc_punch_base(osc_export(cl2osc(obj)),
						&oinfo, osc_async_upcall,
                                                cbargs, PTLRPCD_SET);
                else
                        result = osc_setattr_async_base(osc_export(cl2osc(obj)),
                                                        &oinfo, NULL,
							osc_async_upcall,
                                                        cbargs, PTLRPCD_SET);
		cbargs->opc_rpc_sent = result == 0;
        }
        return result;
}

static void osc_io_setattr_end(const struct lu_env *env,
                               const struct cl_io_slice *slice)
{
	struct cl_io     *io  = slice->cis_io;
	struct osc_io    *oio = cl2osc_io(env, slice);
	struct cl_object *obj = slice->cis_obj;
	struct osc_async_cbargs *cbargs = &oio->oi_cbarg;
        int result = 0;

	if (cbargs->opc_rpc_sent) {
		wait_for_completion(&cbargs->opc_sync);
		result = io->ci_result = cbargs->opc_rc;
	}
        if (result == 0) {
                if (oio->oi_lockless) {
                        /* lockless truncate */
                        struct osc_device *osd = lu2osc_dev(obj->co_lu.lo_dev);

                        LASSERT(cl_io_is_trunc(io));
                        /* XXX: Need a lock. */
                        osd->od_stats.os_lockless_truncates++;
                }
        }

	if (cl_io_is_trunc(io)) {
		__u64 size = io->u.ci_setattr.sa_attr.lvb_size;
		osc_trunc_check(env, io, oio, size);
		if (oio->oi_trunc != NULL) {
			osc_cache_truncate_end(env, oio, cl2osc(obj));
			oio->oi_trunc = NULL;
		}
	}
}

static int osc_io_read_start(const struct lu_env *env,
                             const struct cl_io_slice *slice)
{
	struct osc_io	 *oio  = cl2osc_io(env, slice);
	struct cl_object *obj  = slice->cis_obj;
	struct cl_attr	 *attr = &osc_env_info(env)->oti_attr;
	int rc = 0;
	ENTRY;

	if (oio->oi_lockless == 0 && !slice->cis_io->ci_noatime) {
		cl_object_attr_lock(obj);
		attr->cat_atime = LTIME_S(CFS_CURRENT_TIME);
		rc = cl_object_attr_set(env, obj, attr, CAT_ATIME);
		cl_object_attr_unlock(obj);
	}

	RETURN(rc);
}

static int osc_io_write_start(const struct lu_env *env,
                              const struct cl_io_slice *slice)
{
        struct osc_io    *oio   = cl2osc_io(env, slice);
        struct cl_object *obj   = slice->cis_obj;
        struct cl_attr   *attr  = &osc_env_info(env)->oti_attr;
        int              result = 0;
        ENTRY;

        if (oio->oi_lockless == 0) {
		OBD_FAIL_TIMEOUT(OBD_FAIL_OSC_DELAY_SETTIME, 1);
                cl_object_attr_lock(obj);
                result = cl_object_attr_get(env, obj, attr);
                if (result == 0) {
                        attr->cat_mtime = attr->cat_ctime =
                                LTIME_S(CFS_CURRENT_TIME);
                        result = cl_object_attr_set(env, obj, attr,
                                                    CAT_MTIME | CAT_CTIME);
                }
                cl_object_attr_unlock(obj);
        }
        RETURN(result);
}

static int osc_fsync_ost(const struct lu_env *env, struct osc_object *obj,
			 struct cl_fsync_io *fio)
{
	struct osc_io    *oio   = osc_env_io(env);
	struct obdo      *oa    = &oio->oi_oa;
	struct obd_info  *oinfo = &oio->oi_info;
	struct lov_oinfo *loi   = obj->oo_oinfo;
	struct osc_async_cbargs *cbargs = &oio->oi_cbarg;
	int rc = 0;
	ENTRY;

	memset(oa, 0, sizeof(*oa));
	oa->o_oi = loi->loi_oi;
	oa->o_valid = OBD_MD_FLID | OBD_MD_FLGROUP;

	/* reload size abd blocks for start and end of sync range */
	oa->o_size = fio->fi_start;
	oa->o_blocks = fio->fi_end;
	oa->o_valid |= OBD_MD_FLSIZE | OBD_MD_FLBLOCKS;

	obdo_set_parent_fid(oa, fio->fi_fid);

	memset(oinfo, 0, sizeof(*oinfo));
	oinfo->oi_oa = oa;
	oinfo->oi_capa = fio->fi_capa;
	init_completion(&cbargs->opc_sync);

	rc = osc_sync_base(osc_export(obj), oinfo, osc_async_upcall, cbargs,
			   PTLRPCD_SET);
	RETURN(rc);
}

static int osc_io_fsync_start(const struct lu_env *env,
			      const struct cl_io_slice *slice)
{
	struct cl_io       *io  = slice->cis_io;
	struct cl_fsync_io *fio = &io->u.ci_fsync;
	struct cl_object   *obj = slice->cis_obj;
	struct osc_object  *osc = cl2osc(obj);
	pgoff_t start  = cl_index(obj, fio->fi_start);
	pgoff_t end    = cl_index(obj, fio->fi_end);
	int     result = 0;
	ENTRY;

	if (fio->fi_end == OBD_OBJECT_EOF)
		end = CL_PAGE_EOF;

	result = osc_cache_writeback_range(env, osc, start, end, 0,
					   fio->fi_mode == CL_FSYNC_DISCARD);
	if (result > 0) {
		fio->fi_nr_written += result;
		result = 0;
	}
	if (fio->fi_mode == CL_FSYNC_ALL) {
		int rc;

		/* we have to wait for writeback to finish before we can
		 * send OST_SYNC RPC. This is bad because it causes extents
		 * to be written osc by osc. However, we usually start
		 * writeback before CL_FSYNC_ALL so this won't have any real
		 * problem. */
		rc = osc_cache_wait_range(env, osc, start, end);
		if (result == 0)
			result = rc;
		rc = osc_fsync_ost(env, osc, fio);
		if (result == 0)
			result = rc;
	}

	RETURN(result);
}

static void osc_io_fsync_end(const struct lu_env *env,
			     const struct cl_io_slice *slice)
{
	struct cl_fsync_io *fio = &slice->cis_io->u.ci_fsync;
	struct cl_object   *obj = slice->cis_obj;
	pgoff_t start = cl_index(obj, fio->fi_start);
	pgoff_t end   = cl_index(obj, fio->fi_end);
	int result = 0;

	if (fio->fi_mode == CL_FSYNC_LOCAL) {
		result = osc_cache_wait_range(env, cl2osc(obj), start, end);
	} else if (fio->fi_mode == CL_FSYNC_ALL) {
		struct osc_io           *oio    = cl2osc_io(env, slice);
		struct osc_async_cbargs *cbargs = &oio->oi_cbarg;

		wait_for_completion(&cbargs->opc_sync);
		if (result == 0)
			result = cbargs->opc_rc;
	}
	slice->cis_io->ci_result = result;
}

static void osc_io_end(const struct lu_env *env,
		       const struct cl_io_slice *slice)
{
	struct osc_io *oio = cl2osc_io(env, slice);

	if (oio->oi_active) {
		osc_extent_release(env, oio->oi_active);
		oio->oi_active = NULL;
	}
}

static const struct cl_io_operations osc_io_ops = {
        .op = {
                [CIT_READ] = {
                        .cio_start  = osc_io_read_start,
                        .cio_fini   = osc_io_fini
                },
                [CIT_WRITE] = {
                        .cio_start  = osc_io_write_start,
			.cio_end    = osc_io_end,
                        .cio_fini   = osc_io_fini
                },
                [CIT_SETATTR] = {
                        .cio_start  = osc_io_setattr_start,
                        .cio_end    = osc_io_setattr_end
                },
                [CIT_FAULT] = {
			.cio_start  = osc_io_fault_start,
			.cio_end    = osc_io_end,
			.cio_fini   = osc_io_fini
		},
		[CIT_FSYNC] = {
			.cio_start  = osc_io_fsync_start,
			.cio_end    = osc_io_fsync_end,
			.cio_fini   = osc_io_fini
		},
                [CIT_MISC] = {
                        .cio_fini   = osc_io_fini
                }
        },
        .req_op = {
                 [CRT_READ] = {
                         .cio_submit    = osc_io_submit
                 },
                 [CRT_WRITE] = {
                         .cio_submit    = osc_io_submit
                 }
         },
        .cio_prepare_write = osc_io_prepare_write,
        .cio_commit_write  = osc_io_commit_write
};

/*****************************************************************************
 *
 * Transfer operations.
 *
 */

static int osc_req_prep(const struct lu_env *env,
                        const struct cl_req_slice *slice)
{
        return 0;
}

static void osc_req_completion(const struct lu_env *env,
                               const struct cl_req_slice *slice, int ioret)
{
        struct osc_req *or;

        or = cl2osc_req(slice);
        OBD_SLAB_FREE_PTR(or, osc_req_kmem);
}

/**
 * Implementation of struct cl_req_operations::cro_attr_set() for osc
 * layer. osc is responsible for struct obdo::o_id and struct obdo::o_seq
 * fields.
 */
static void osc_req_attr_set(const struct lu_env *env,
			     const struct cl_req_slice *slice,
			     const struct cl_object *obj,
			     struct cl_req_attr *attr, obd_valid flags)
{
	struct lov_oinfo *oinfo;
	struct cl_req    *clerq;
	struct cl_page   *apage; /* _some_ page in @clerq */
	struct cl_lock   *lock;  /* _some_ lock protecting @apage */
	struct osc_lock  *olck;
	struct osc_page  *opg;
	struct obdo      *oa;
	struct ost_lvb   *lvb;

	oinfo	= cl2osc(obj)->oo_oinfo;
	lvb	= &oinfo->loi_lvb;
	oa	= attr->cra_oa;

	if ((flags & OBD_MD_FLMTIME) != 0) {
		oa->o_mtime = lvb->lvb_mtime;
		oa->o_valid |= OBD_MD_FLMTIME;
	}
	if ((flags & OBD_MD_FLATIME) != 0) {
		oa->o_atime = lvb->lvb_atime;
		oa->o_valid |= OBD_MD_FLATIME;
	}
	if ((flags & OBD_MD_FLCTIME) != 0) {
		oa->o_ctime = lvb->lvb_ctime;
		oa->o_valid |= OBD_MD_FLCTIME;
	}
	if (flags & OBD_MD_FLGROUP) {
		ostid_set_seq(&oa->o_oi, ostid_seq(&oinfo->loi_oi));
		oa->o_valid |= OBD_MD_FLGROUP;
	}
	if (flags & OBD_MD_FLID) {
		ostid_set_id(&oa->o_oi, ostid_id(&oinfo->loi_oi));
		oa->o_valid |= OBD_MD_FLID;
	}
	if (flags & OBD_MD_FLHANDLE) {
                clerq = slice->crs_req;
                LASSERT(!cfs_list_empty(&clerq->crq_pages));
                apage = container_of(clerq->crq_pages.next,
                                     struct cl_page, cp_flight);
                opg = osc_cl_page_osc(apage);
                apage = opg->ops_cl.cpl_page; /* now apage is a sub-page */
                lock = cl_lock_at_page(env, apage->cp_obj, apage, NULL, 1, 1);
                if (lock == NULL) {
                        struct cl_object_header *head;
                        struct cl_lock          *scan;

                        head = cl_object_header(apage->cp_obj);
                        cfs_list_for_each_entry(scan, &head->coh_locks,
                                                cll_linkage)
                                CL_LOCK_DEBUG(D_ERROR, env, scan,
                                              "no cover page!\n");
                        CL_PAGE_DEBUG(D_ERROR, env, apage,
                                      "dump uncover page!\n");
                        libcfs_debug_dumpstack(NULL);
                        LBUG();
                }

                olck = osc_lock_at(lock);
                LASSERT(olck != NULL);
                LASSERT(ergo(opg->ops_srvlock, olck->ols_lock == NULL));
                /* check for lockless io. */
                if (olck->ols_lock != NULL) {
                        oa->o_handle = olck->ols_lock->l_remote_handle;
                        oa->o_valid |= OBD_MD_FLHANDLE;
                }
                cl_lock_put(env, lock);
        }
}

static const struct cl_req_operations osc_req_ops = {
        .cro_prep       = osc_req_prep,
        .cro_attr_set   = osc_req_attr_set,
        .cro_completion = osc_req_completion
};


int osc_io_init(const struct lu_env *env,
                struct cl_object *obj, struct cl_io *io)
{
        struct osc_io *oio = osc_env_io(env);

        CL_IO_SLICE_CLEAN(oio, oi_cl);
        cl_io_slice_add(io, &oio->oi_cl, obj, &osc_io_ops);
        return 0;
}

int osc_req_init(const struct lu_env *env, struct cl_device *dev,
                 struct cl_req *req)
{
        struct osc_req *or;
        int result;

	OBD_SLAB_ALLOC_PTR_GFP(or, osc_req_kmem, __GFP_IO);
        if (or != NULL) {
                cl_req_slice_add(req, &or->or_cl, dev, &osc_req_ops);
                result = 0;
        } else
                result = -ENOMEM;
        return result;
}

/** @} osc */