/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
 * vim:expandtab:shiftwidth=8:tabstop=8:
 *
 * Lustre virtual block device emulator.
 *
 *  Copyright (c) 2001-2003 Cluster File Systems, Inc.
 *
 *   This file is part of Lustre, http://www.lustre.org.
 *
 *   Lustre is free software; you can redistribute it and/or
 *   modify it under the terms of version 2 of the GNU General Public
 *   License as published by the Free Software Foundation.
 *
 *   Lustre 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 for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with Lustre; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *  linux/drivers/block/loop.c
 *
 *  Written by Theodore Ts'o, 3/29/93
 *
 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
 * permitted under the GNU General Public License.
 *
 * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
 * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
 *
 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
 *
 * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
 *
 * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
 *
 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
 *
 * Loadable modules and other fixes by AK, 1998
 *
 * Make real block number available to downstream transfer functions, enables
 * CBC (and relatives) mode encryption requiring unique IVs per data block.
 * Reed H. Petty, rhp@draper.net
 *
 * Maximum number of loop devices now dynamic via max_loop module parameter.
 * Russell Kroll <rkroll@exploits.org> 19990701
 *
 * Maximum number of loop devices when compiled-in now selectable by passing
 * max_loop=<1-255> to the kernel on boot.
 * Erik I. Bols?, <eriki@himolde.no>, Oct 31, 1999
 *
 * Completely rewrite request handling to be make_request_fn style and
 * non blocking, pushing work to a helper thread. Lots of fixes from
 * Al Viro too.
 * Jens Axboe <axboe@suse.de>, Nov 2000
 *
 * Support up to 256 loop devices
 * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
 *
 * Support for falling back on the write file operation when the address space
 * operations prepare_write and/or commit_write are not available on the
 * backing filesystem.
 * Anton Altaparmakov, 16 Feb 2005
 *
 * Still To Fix:
 * - Advisory locking is ignored here.
 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
 *
 */

#ifndef AUTOCONF_INCLUDED
#include <linux/config.h>
#endif
#include <linux/module.h>

#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/major.h>
#include <linux/wait.h>
#include <linux/blkdev.h>
#include <linux/blkpg.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h>                /* for invalidate_bdev() */
#include <linux/completion.h>
#include <linux/highmem.h>
#include <linux/gfp.h>
#include <linux/swap.h>
#include <linux/pagevec.h>

#include <asm/uaccess.h>

#include <lustre_lib.h>
#include <lustre_lite.h>
#include "llite_internal.h"

#define LLOOP_MAX_SEGMENTS        PTLRPC_MAX_BRW_PAGES

/* Possible states of device */
enum {
        LLOOP_UNBOUND,
        LLOOP_BOUND,
        LLOOP_RUNDOWN,
};

struct lloop_device {
        int                lo_number;
        int                lo_refcnt;
        loff_t             lo_offset;
        loff_t             lo_sizelimit;
        int                lo_flags;
        int                (*ioctl)(struct lloop_device *, int cmd, 
                                 unsigned long arg); 

        struct file *      lo_backing_file;
        struct block_device *lo_device;
        unsigned           lo_blocksize;

        int                old_gfp_mask;

        spinlock_t         lo_lock;
        struct bio         *lo_bio;
        struct bio         *lo_biotail;
        int                lo_state;
        struct semaphore   lo_sem;
        struct semaphore   lo_ctl_mutex;
        struct semaphore   lo_bh_mutex;
        atomic_t           lo_pending;

        request_queue_t    *lo_queue;

        /* data to handle bio for lustre. */
        struct lo_request_data {
                struct brw_page    lrd_pages[LLOOP_MAX_SEGMENTS];
                struct obdo        lrd_oa;
        } lo_requests[1];

};

/*
 * Loop flags
 */
enum {
        LO_FLAGS_READ_ONLY       = 1,
};

static int lloop_major;
static int max_loop = 8;
static struct lloop_device *loop_dev;
static struct gendisk **disks;
static struct semaphore lloop_mutex;
static void *ll_iocontrol_magic = NULL;

static loff_t get_loop_size(struct lloop_device *lo, struct file *file)
{
        loff_t size, offset, loopsize;

        /* Compute loopsize in bytes */
        size = i_size_read(file->f_mapping->host);
        offset = lo->lo_offset;
        loopsize = size - offset;
        if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
                loopsize = lo->lo_sizelimit;

        /*
         * Unfortunately, if we want to do I/O on the device,
         * the number of 512-byte sectors has to fit into a sector_t.
         */
        return loopsize >> 9;
}

static int do_bio_filebacked(struct lloop_device *lo, struct bio *bio)
{
        struct inode *inode = lo->lo_backing_file->f_dentry->d_inode;
        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 = lo->lo_requests[0].lrd_pages;
        struct obdo *oa = &lo->lo_requests[0].lrd_oa;
        pgoff_t offset;
        int ret, cmd, i, opc;
        struct bio_vec *bvec;

        BUG_ON(bio->bi_hw_segments > LLOOP_MAX_SEGMENTS);

        offset = (pgoff_t)(bio->bi_sector << 9) + lo->lo_offset;
        bio_for_each_segment(bvec, bio, i) {
                BUG_ON(bvec->bv_offset != 0);
                BUG_ON(bvec->bv_len != CFS_PAGE_SIZE);

                pg->pg = bvec->bv_page;
                pg->off = offset;
                pg->count = bvec->bv_len;
                pg->flag = OBD_BRW_SRVLOCK;

                pg++;
                offset += bvec->bv_len;
        }

        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);

        cmd = OBD_BRW_READ;
        if (bio_rw(bio) == WRITE)
                cmd = OBD_BRW_WRITE;

        if (cmd == OBD_BRW_WRITE)
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_BRW_WRITE, bio->bi_size);
        else
                ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_BRW_READ, bio->bi_size);
        oinfo.oi_oa = oa;
        oinfo.oi_md = lsm;
        opc = cmd & OBD_BRW_WRITE ? CAPA_OPC_OSS_WRITE : CAPA_OPC_OSS_RW;
        oinfo.oi_capa = ll_osscapa_get(inode, opc);
        ret = obd_brw(cmd, ll_i2dtexp(inode), &oinfo, 
                      (obd_count)(i - bio->bi_idx), 
                      lo->lo_requests[0].lrd_pages, NULL);
        capa_put(oinfo.oi_capa);
        if (ret == 0)
                obdo_to_inode(inode, oa, OBD_MD_FLBLOCKS);
        return ret;
}


/*
 * Add bio to back of pending list
 */
static void loop_add_bio(struct lloop_device *lo, struct bio *bio)
{
        unsigned long flags;

        spin_lock_irqsave(&lo->lo_lock, flags);
        if (lo->lo_biotail) {
                lo->lo_biotail->bi_next = bio;
                lo->lo_biotail = bio;
        } else
                lo->lo_bio = lo->lo_biotail = bio;
        spin_unlock_irqrestore(&lo->lo_lock, flags);

        up(&lo->lo_bh_mutex);
}

/*
 * Grab first pending buffer
 */
static struct bio *loop_get_bio(struct lloop_device *lo)
{
        struct bio *bio;

        spin_lock_irq(&lo->lo_lock);
        if ((bio = lo->lo_bio)) {
                if (bio == lo->lo_biotail)
                        lo->lo_biotail = NULL;
                lo->lo_bio = bio->bi_next;
                bio->bi_next = NULL;
        }
        spin_unlock_irq(&lo->lo_lock);

        return bio;
}

static int loop_make_request(request_queue_t *q, struct bio *old_bio)
{
        struct lloop_device *lo = q->queuedata;
        int rw = bio_rw(old_bio);

        if (!lo)
                goto out;

        spin_lock_irq(&lo->lo_lock);
        if (lo->lo_state != LLOOP_BOUND)
                goto inactive;
        atomic_inc(&lo->lo_pending);
        spin_unlock_irq(&lo->lo_lock);

        if (rw == WRITE) {
                if (lo->lo_flags & LO_FLAGS_READ_ONLY)
                        goto err;
        } else if (rw == READA) {
                rw = READ;
        } else if (rw != READ) {
                CERROR("lloop: unknown command (%x)\n", rw);
                goto err;
        }
        loop_add_bio(lo, old_bio);
        return 0;
err:
        if (atomic_dec_and_test(&lo->lo_pending))
                up(&lo->lo_bh_mutex);
out:
        bio_io_error(old_bio, old_bio->bi_size);
        return 0;
inactive:
        spin_unlock_irq(&lo->lo_lock);
        goto out;
}

/*
 * kick off io on the underlying address space
 */
static void loop_unplug(request_queue_t *q)
{
        struct lloop_device *lo = q->queuedata;

        clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
        blk_run_address_space(lo->lo_backing_file->f_mapping);
}

static inline void loop_handle_bio(struct lloop_device *lo, struct bio *bio)
{
        int ret;
        ret = do_bio_filebacked(lo, bio);
        bio_endio(bio, bio->bi_size, ret);
}

/*
 * worker thread that handles reads/writes to file backed loop devices,
 * to avoid blocking in our make_request_fn. it also does loop decrypting
 * on reads for block backed loop, as that is too heavy to do from
 * b_end_io context where irqs may be disabled.
 */
static int loop_thread(void *data)
{
        struct lloop_device *lo = data;
        struct bio *bio;

        daemonize("lloop%d", lo->lo_number);

        set_user_nice(current, -20);

        lo->lo_state = LLOOP_BOUND;
        atomic_inc(&lo->lo_pending);

        /*
         * up sem, we are running
         */
        up(&lo->lo_sem);

        for (;;) {
                down_interruptible(&lo->lo_bh_mutex);
                /*
                 * could be upped because of tear-down, not because of
                 * pending work
                 */
                if (!atomic_read(&lo->lo_pending))
                        break;

                bio = loop_get_bio(lo);
                if (!bio) {
                        CWARN("lloop(minor: %d): missing bio\n", lo->lo_number);
                        continue;
                }
                loop_handle_bio(lo, bio);

                /*
                 * upped both for pending work and tear-down, lo_pending
                 * will hit zero then
                 */
                if (atomic_dec_and_test(&lo->lo_pending))
                        break;
        }

        up(&lo->lo_sem);
        return 0;
}

static int loop_set_fd(struct lloop_device *lo, struct file *unused,
                       struct block_device *bdev, struct file *file)
{
        struct inode        *inode;
        struct address_space *mapping;
        int                lo_flags = 0;
        int                error;
        loff_t                size;

        if (!try_module_get(THIS_MODULE))
                return -ENODEV;

        error = -EBUSY;
        if (lo->lo_state != LLOOP_UNBOUND)
                goto out;

        mapping = file->f_mapping;
        inode = mapping->host;

        error = -EINVAL;
        if (!S_ISREG(inode->i_mode) || inode->i_sb->s_magic != LL_SUPER_MAGIC)
                goto out;

        if (!(file->f_mode & FMODE_WRITE))
                lo_flags |= LO_FLAGS_READ_ONLY;

        size = get_loop_size(lo, file);

        if ((loff_t)(sector_t)size != size) {
                error = -EFBIG;
                goto out;
        }

        /* remove all pages in cache so as dirty pages not to be existent. */
        truncate_inode_pages(mapping, 0);

        set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);

        lo->lo_blocksize = CFS_PAGE_SIZE;
        lo->lo_device = bdev;
        lo->lo_flags = lo_flags;
        lo->lo_backing_file = file;
        lo->ioctl = NULL;
        lo->lo_sizelimit = 0;
        lo->old_gfp_mask = mapping_gfp_mask(mapping);
        mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));

        lo->lo_bio = lo->lo_biotail = NULL;

        /*
         * set queue make_request_fn, and add limits based on lower level
         * device
         */
        blk_queue_make_request(lo->lo_queue, loop_make_request);
        lo->lo_queue->queuedata = lo;
        lo->lo_queue->unplug_fn = loop_unplug;

        /* queue parameters */
        blk_queue_hardsect_size(lo->lo_queue, CFS_PAGE_SIZE);
        blk_queue_max_sectors(lo->lo_queue, LLOOP_MAX_SEGMENTS);
        blk_queue_max_phys_segments(lo->lo_queue, LLOOP_MAX_SEGMENTS);

        set_capacity(disks[lo->lo_number], size);
        bd_set_size(bdev, size << 9);

        set_blocksize(bdev, lo->lo_blocksize);

        kernel_thread(loop_thread, lo, CLONE_KERNEL);
        down(&lo->lo_sem);
        return 0;

 out:
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
        return error;
}

static int loop_clr_fd(struct lloop_device *lo, struct block_device *bdev, 
                       int count)
{
        struct file *filp = lo->lo_backing_file;
        int gfp = lo->old_gfp_mask;

        if (lo->lo_state != LLOOP_BOUND)
                return -ENXIO;

        if (lo->lo_refcnt > count)        /* we needed one fd for the ioctl */
                return -EBUSY;

        if (filp == NULL)
                return -EINVAL;

        spin_lock_irq(&lo->lo_lock);
        lo->lo_state = LLOOP_RUNDOWN;
        if (atomic_dec_and_test(&lo->lo_pending))
                up(&lo->lo_bh_mutex);
        spin_unlock_irq(&lo->lo_lock);

        down(&lo->lo_sem);
        lo->lo_backing_file = NULL;
        lo->ioctl = NULL;
        lo->lo_device = NULL;
        lo->lo_offset = 0;
        lo->lo_sizelimit = 0;
        lo->lo_flags = 0;
        ll_invalidate_bdev(bdev, 0);
        set_capacity(disks[lo->lo_number], 0);
        bd_set_size(bdev, 0);
        mapping_set_gfp_mask(filp->f_mapping, gfp);
        lo->lo_state = LLOOP_UNBOUND;
        fput(filp);
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
        return 0;
}

static int lo_open(struct inode *inode, struct file *file)
{
        struct lloop_device *lo = inode->i_bdev->bd_disk->private_data;

        down(&lo->lo_ctl_mutex);
        lo->lo_refcnt++;
        up(&lo->lo_ctl_mutex);

        return 0;
}

static int lo_release(struct inode *inode, struct file *file)
{
        struct lloop_device *lo = inode->i_bdev->bd_disk->private_data;

        down(&lo->lo_ctl_mutex);
        --lo->lo_refcnt;
        up(&lo->lo_ctl_mutex);

        return 0;
}

/* lloop device node's ioctl function. */
static int lo_ioctl(struct inode *inode, struct file *unused, 
        unsigned int cmd, unsigned long arg)
{
        struct lloop_device *lo = inode->i_bdev->bd_disk->private_data;
        struct block_device *bdev = inode->i_bdev;
        int err = 0;

        down(&lloop_mutex);
        switch (cmd) {
        case LL_IOC_LLOOP_DETACH: {
                err = loop_clr_fd(lo, bdev, 2);
                if (err == 0)
                        blkdev_put(bdev); /* grabbed in LLOOP_ATTACH */
                break;
        }

        case LL_IOC_LLOOP_INFO: {
                __u64 ino = 0;

                if (lo->lo_state == LLOOP_BOUND)
                        ino = lo->lo_backing_file->f_dentry->d_inode->i_ino;

                if (put_user(ino, (__u64 *)arg))
                        err = -EFAULT;
                break; 
        }

        default:
                err = -EINVAL;
                break;
        }
        up(&lloop_mutex);

        return err;
}

static struct block_device_operations lo_fops = {
        .owner =        THIS_MODULE,
        .open =         lo_open,
        .release =      lo_release,
        .ioctl =        lo_ioctl,
};

/* dynamic iocontrol callback. 
 * This callback is registered in lloop_init and will be called by 
 * ll_iocontrol_call. 
 * This is a llite regular file ioctl function. It takes the responsibility 
 * of attaching a file, and detaching a file by a lloop's device numner. 
 */
static enum llioc_iter lloop_ioctl(struct inode *unused, struct file *file, 
                unsigned int cmd, unsigned long arg,
                void *magic, int *rcp)
{
        struct lloop_device *lo = NULL;
        struct block_device *bdev = NULL;
        int err = 0;
        dev_t dev;

        if (magic != ll_iocontrol_magic)
                return LLIOC_CONT;

        if (disks == NULL)
                GOTO(out1, err = -ENODEV);

        CWARN("Enter llop_ioctl\n");

        down(&lloop_mutex);
        switch (cmd) {
        case LL_IOC_LLOOP_ATTACH: {
                struct lloop_device *lo_free = NULL;
                int i;

                for (i = 0; i < max_loop; i++, lo = NULL) {
                        lo = &loop_dev[i];
                        if (lo->lo_state == LLOOP_UNBOUND) {
                                if (!lo_free)
                                        lo_free = lo;
                                continue;
                        }
                        if (lo->lo_backing_file->f_dentry->d_inode == 
                            file->f_dentry->d_inode)
                                break;
                }
                if (lo || !lo_free)
                        GOTO(out, err = -EBUSY);

                lo = lo_free;
                dev = MKDEV(lloop_major, lo->lo_number);

                /* quit if the used pointer is writable */
                if (put_user((long)old_encode_dev(dev), (long*)arg))
                        GOTO(out, err = -EFAULT);

                bdev = open_by_devnum(dev, file->f_mode);
                if (IS_ERR(bdev))
                        GOTO(out, err = PTR_ERR(bdev));

                get_file(file);
                err = loop_set_fd(lo, NULL, bdev, file);
                if (err) {
                        fput(file);
                        blkdev_put(bdev);
                }

                break;
        }

        case LL_IOC_LLOOP_DETACH_BYDEV: {
                int minor;
                
                dev = old_decode_dev(arg);
                if (MAJOR(dev) != lloop_major)
                        GOTO(out, err = -EINVAL);

                minor = MINOR(dev);
                if (minor > max_loop - 1)
                        GOTO(out, err = -EINVAL);

                lo = &loop_dev[minor];
                if (lo->lo_state != LLOOP_BOUND)
                        GOTO(out, err = -EINVAL);

                bdev = lo->lo_device;
                err = loop_clr_fd(lo, bdev, 1);
                if (err == 0)
                        blkdev_put(bdev); /* grabbed in LLOOP_ATTACH */

                break;
        }

        default:
                err = -EINVAL;
                break;
        }

out:
        up(&lloop_mutex);
out1:
        if (rcp)
                *rcp = err;
        return LLIOC_STOP;
}

static int __init lloop_init(void)
{
        int        i;
        unsigned int cmdlist[] = {
                LL_IOC_LLOOP_ATTACH,
                LL_IOC_LLOOP_DETACH_BYDEV,
        };

        if (max_loop < 1 || max_loop > 256) {
                CWARN("lloop: invalid max_loop (must be between"
                      " 1 and 256), using default (8)\n");
                max_loop = 8;
        }

        lloop_major = register_blkdev(0, "lloop");
        if (lloop_major < 0)
                return -EIO;

        ll_iocontrol_magic = ll_iocontrol_register(lloop_ioctl, 2, cmdlist);
        if (ll_iocontrol_magic == NULL)
                goto out_mem1;

        loop_dev = kmalloc(max_loop * sizeof(struct lloop_device), GFP_KERNEL);
        if (!loop_dev)
                goto out_mem1;
        memset(loop_dev, 0, max_loop * sizeof(struct lloop_device));

        disks = kmalloc(max_loop * sizeof(struct gendisk *), GFP_KERNEL);
        if (!disks)
                goto out_mem2;

        for (i = 0; i < max_loop; i++) {
                disks[i] = alloc_disk(1);
                if (!disks[i])
                        goto out_mem3;
        }

        init_MUTEX(&lloop_mutex);

        for (i = 0; i < max_loop; i++) {
                struct lloop_device *lo = &loop_dev[i];
                struct gendisk *disk = disks[i];

                memset(lo, 0, sizeof(*lo));
                lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
                if (!lo->lo_queue)
                        goto out_mem4;

                init_MUTEX(&lo->lo_ctl_mutex);
                init_MUTEX_LOCKED(&lo->lo_sem);
                init_MUTEX_LOCKED(&lo->lo_bh_mutex);
                lo->lo_number = i;
                spin_lock_init(&lo->lo_lock);
                disk->major = lloop_major;
                disk->first_minor = i;
                disk->fops = &lo_fops;
                sprintf(disk->disk_name, "lloop%d", i);
                disk->private_data = lo;
                disk->queue = lo->lo_queue;
        }

        /* We cannot fail after we call this, so another loop!*/
        for (i = 0; i < max_loop; i++)
                add_disk(disks[i]);
        return 0;

out_mem4:
        while (i--)
                blk_put_queue(loop_dev[i].lo_queue);
        i = max_loop;
out_mem3:
        while (i--)
                put_disk(disks[i]);
        kfree(disks);
out_mem2:
        kfree(loop_dev);
out_mem1:
        unregister_blkdev(lloop_major, "lloop");
        ll_iocontrol_unregister(ll_iocontrol_magic);
        CERROR("lloop: ran out of memory\n");
        return -ENOMEM;
}

static void lloop_exit(void)
{
        int i;

        ll_iocontrol_unregister(ll_iocontrol_magic);
        for (i = 0; i < max_loop; i++) {
                del_gendisk(disks[i]);
                blk_put_queue(loop_dev[i].lo_queue);
                put_disk(disks[i]);
        }
        if (ll_unregister_blkdev(lloop_major, "lloop"))
                CWARN("lloop: cannot unregister blkdev\n");

        kfree(disks);
        kfree(loop_dev);
}

module_init(lloop_init);
module_exit(lloop_exit);

CFS_MODULE_PARM(max_loop, "i", int, 0444, "maximum of lloop_device");