/*
 * 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) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 */

/*
 *  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.
 *
 * 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
 *
 * 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
 *
 */

#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/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      LNET_MAX_IOV

/* 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 mutex            lo_ctl_mutex;
        atomic_t         lo_pending;
        wait_queue_head_t         lo_bh_wait;

        struct request_queue *lo_queue;

        const struct lu_env *lo_env;
        struct cl_io     lo_io;
        struct ll_dio_pages  lo_pvec;

        /* data to handle bio for lustre. */
        struct lo_request_data {
                struct page *lrd_pages[LLOOP_MAX_SEGMENTS];
                loff_t       lrd_offsets[LLOOP_MAX_SEGMENTS];
        } lo_requests[1];
};

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

static int lloop_major;
#define MAX_LOOP_DEFAULT  16
static int max_loop = MAX_LOOP_DEFAULT;
static struct lloop_device *loop_dev;
static struct gendisk **disks;
static struct mutex 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_lustrebacked(struct lloop_device *lo, struct bio *head)
{
        const struct lu_env  *env   = lo->lo_env;
        struct cl_io     *io    = &lo->lo_io;
        struct inode     *inode = lo->lo_backing_file->f_dentry->d_inode;
        struct cl_object     *obj = ll_i2info(inode)->lli_clob;
        pgoff_t        offset;
        int                ret;
        int                i;
        int                rw;
        obd_count            page_count = 0;
        struct bio_vec       *bvec;
        struct bio         *bio;
        ssize_t        bytes;

        struct ll_dio_pages  *pvec = &lo->lo_pvec;
        struct page      **pages = pvec->ldp_pages;
        loff_t         *offsets = pvec->ldp_offsets;

        truncate_inode_pages(inode->i_mapping, 0);

        /* initialize the IO */
        memset(io, 0, sizeof(*io));
        io->ci_obj = obj;
        ret = cl_io_init(env, io, CIT_MISC, obj);
        if (ret)
                return io->ci_result;
        io->ci_lockreq = CILR_NEVER;

        LASSERT(head != NULL);
        rw = head->bi_rw;
        for (bio = head; bio != NULL; bio = bio->bi_next) {
                LASSERT(rw == bio->bi_rw);

                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 != PAGE_CACHE_SIZE);

                        pages[page_count] = bvec->bv_page;
                        offsets[page_count] = offset;
                        page_count++;
                        offset += bvec->bv_len;
                }
                LASSERT(page_count <= LLOOP_MAX_SEGMENTS);
        }

        ll_stats_ops_tally(ll_i2sbi(inode),
                        (rw == WRITE) ? LPROC_LL_BRW_WRITE : LPROC_LL_BRW_READ,
                        page_count);

        pvec->ldp_size = page_count << PAGE_CACHE_SHIFT;
        pvec->ldp_nr = page_count;

        /* FIXME: in ll_direct_rw_pages, it has to allocate many cl_page{}s to
         * write those pages into OST. Even worse case is that more pages
         * would be asked to write out to swap space, and then finally get here
         * again.
         * Unfortunately this is NOT easy to fix.
         * Thoughts on solution:
         * 0. Define a reserved pool for cl_pages, which could be a list of
         *    pre-allocated cl_pages;
         * 1. Define a new operation in cl_object_operations{}, says clo_depth,
         *    which measures how many layers for this lustre object. Generally
         *    speaking, the depth would be 2, one for llite, and one for lovsub.
         *    However, for SNS, there will be more since we need additional page
         *    to store parity;
         * 2. Reserve the # of (page_count * depth) cl_pages from the reserved
         *    pool. Afterwards, the clio would allocate the pages from reserved
         *    pool, this guarantees we neeedn't allocate the cl_pages from
         *    generic cl_page slab cache.
         *    Of course, if there is NOT enough pages in the pool, we might
         *    be asked to write less pages once, this purely depends on
         *    implementation. Anyway, we should be careful to avoid deadlocking.
         */
        mutex_lock(&inode->i_mutex);
        bytes = ll_direct_rw_pages(env, io, rw, inode, pvec);
        mutex_unlock(&inode->i_mutex);
        cl_io_fini(env, io);
        return (bytes == pvec->ldp_size) ? 0 : (int)bytes;
}

/*
 * 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);

        atomic_inc(&lo->lo_pending);
        if (waitqueue_active(&lo->lo_bh_wait))
                wake_up(&lo->lo_bh_wait);
}

/*
 * Grab first pending buffer
 */
static unsigned int loop_get_bio(struct lloop_device *lo, struct bio **req)
{
        struct bio *first;
        struct bio **bio;
        unsigned int count = 0;
        unsigned int page_count = 0;
        int rw;

        spin_lock_irq(&lo->lo_lock);
        first = lo->lo_bio;
        if (unlikely(first == NULL)) {
                spin_unlock_irq(&lo->lo_lock);
                return 0;
        }

        /* TODO: need to split the bio, too bad. */
        LASSERT(first->bi_vcnt <= LLOOP_MAX_SEGMENTS);

        rw = first->bi_rw;
        bio = &lo->lo_bio;
        while (*bio && (*bio)->bi_rw == rw) {
                CDEBUG(D_INFO, "bio sector %llu size %u count %u vcnt%u \n",
                       (unsigned long long)(*bio)->bi_sector, (*bio)->bi_size,
                       page_count, (*bio)->bi_vcnt);
                if (page_count + (*bio)->bi_vcnt > LLOOP_MAX_SEGMENTS)
                        break;


                page_count += (*bio)->bi_vcnt;
                count++;
                bio = &(*bio)->bi_next;
        }
        if (*bio) {
                /* Some of bios can't be mergable. */
                lo->lo_bio = *bio;
                *bio = NULL;
        } else {
                /* Hit the end of queue */
                lo->lo_biotail = NULL;
                lo->lo_bio = NULL;
        }
        *req = first;
        spin_unlock_irq(&lo->lo_lock);
        return count;
}

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

        if (!lo)
                goto err;

        CDEBUG(D_INFO, "submit bio sector %llu size %u\n",
               (unsigned long long)old_bio->bi_sector, old_bio->bi_size);

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

        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);
        LL_MRF_RETURN(0);
err:
        cfs_bio_io_error(old_bio, old_bio->bi_size);
        LL_MRF_RETURN(0);
}


static inline void loop_handle_bio(struct lloop_device *lo, struct bio *bio)
{
        int ret;
        ret = do_bio_lustrebacked(lo, bio);
        while (bio) {
                struct bio *tmp = bio->bi_next;
                bio->bi_next = NULL;
                cfs_bio_endio(bio, bio->bi_size, ret);
                bio = tmp;
        }
}

static inline int loop_active(struct lloop_device *lo)
{
        return atomic_read(&lo->lo_pending) ||
                (lo->lo_state == LLOOP_RUNDOWN);
}

/*
 * worker thread that handles reads/writes to file backed loop devices,
 * to avoid blocking in our make_request_fn.
 */
static int loop_thread(void *data)
{
        struct lloop_device *lo = data;
        struct bio *bio;
        unsigned int count;
        unsigned long times = 0;
        unsigned long total_count = 0;

        struct lu_env *env;
        int refcheck;
        int ret = 0;

        set_user_nice(current, -20);

        lo->lo_state = LLOOP_BOUND;

        env = cl_env_get(&refcheck);
        if (IS_ERR(env))
                GOTO(out, ret = PTR_ERR(env));

        lo->lo_env = env;
        memset(&lo->lo_pvec, 0, sizeof(lo->lo_pvec));
        lo->lo_pvec.ldp_pages   = lo->lo_requests[0].lrd_pages;
        lo->lo_pvec.ldp_offsets = lo->lo_requests[0].lrd_offsets;

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

        for (;;) {
                wait_event(lo->lo_bh_wait, loop_active(lo));
                if (!atomic_read(&lo->lo_pending)) {
                        int exiting = 0;
                        spin_lock_irq(&lo->lo_lock);
                        exiting = (lo->lo_state == LLOOP_RUNDOWN);
                        spin_unlock_irq(&lo->lo_lock);
                        if (exiting)
                                break;
                }

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

                total_count += count;
                if (total_count < count) {     /* overflow */
                        total_count = count;
                        times = 1;
                } else {
                        times++;
                }
                if ((times & 127) == 0) {
                        CDEBUG(D_INFO, "total: %lu, count: %lu, avg: %lu\n",
                               total_count, times, total_count / times);
                }

                LASSERT(bio != NULL);
                LASSERT(count <= atomic_read(&lo->lo_pending));
                loop_handle_bio(lo, bio);
                atomic_sub(count, &lo->lo_pending);
        }
        cl_env_put(env, &refcheck);

out:
        up(&lo->lo_sem);
        return ret;
}

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 = PAGE_CACHE_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;

        /* queue parameters */
        CLASSERT(PAGE_CACHE_SIZE < (1 << (sizeof(unsigned short) * 8)));
        blk_queue_logical_block_size(lo->lo_queue,
                                     (unsigned short)PAGE_CACHE_SIZE);
        blk_queue_max_hw_sectors(lo->lo_queue,
                                 LLOOP_MAX_SEGMENTS << (PAGE_CACHE_SHIFT - 9));
        blk_queue_max_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);

        kthread_run(loop_thread, lo, "lloop%d", lo->lo_number);
        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;
        spin_unlock_irq(&lo->lo_lock);
        wake_up(&lo->lo_bh_wait);

        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 block_device *bdev, fmode_t mode)
{
        struct lloop_device *lo = bdev->bd_disk->private_data;

        mutex_lock(&lo->lo_ctl_mutex);
        lo->lo_refcnt++;
        mutex_unlock(&lo->lo_ctl_mutex);

        return 0;
}

static void lo_release(struct gendisk *disk, fmode_t mode)
{
        struct lloop_device *lo = disk->private_data;

        mutex_lock(&lo->lo_ctl_mutex);
        --lo->lo_refcnt;
        mutex_unlock(&lo->lo_ctl_mutex);
}

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

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

        case LL_IOC_LLOOP_INFO: {
                struct lu_fid fid;

                LASSERT(lo->lo_backing_file != NULL);
                if (inode == NULL)
                        inode = lo->lo_backing_file->f_dentry->d_inode;
                if (lo->lo_state == LLOOP_BOUND)
                        fid = ll_i2info(inode)->lli_fid;
                else
                        fid_zero(&fid);

                if (copy_to_user((struct lu_fid *)arg, &fid, sizeof(fid)))
                        err = -EFAULT;
                break;
        }

        default:
                err = -EINVAL;
                break;
        }
        mutex_unlock(&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 or 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");

        mutex_lock(&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 = blkdev_get_by_dev(dev, file->f_mode, NULL);
                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);
                        ll_blkdev_put(bdev, 0);
                }

                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)
                        ll_blkdev_put(bdev, 0); /* grabbed in LLOOP_ATTACH */

                break;
        }

        default:
                err = -EINVAL;
                break;
        }

out:
        mutex_unlock(&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) {
                max_loop = MAX_LOOP_DEFAULT;
                CWARN("lloop: invalid max_loop (must be between"
                      " 1 and 256), using default (%u)\n", max_loop);
        }

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

        CDEBUG(D_CONFIG, "registered lloop major %d with %u minors\n",
               lloop_major, max_loop);

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

        OBD_ALLOC_WAIT(loop_dev, max_loop * sizeof(*loop_dev));
        if (!loop_dev)
                goto out_mem1;

        OBD_ALLOC_WAIT(disks, max_loop * sizeof(*disks));
        if (!disks)
                goto out_mem2;

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

        mutex_init(&lloop_mutex);

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

                lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
                if (!lo->lo_queue)
                        goto out_mem4;

                mutex_init(&lo->lo_ctl_mutex);
                sema_init(&lo->lo_sem, 0);
                init_waitqueue_head(&lo->lo_bh_wait);
                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_cleanup_queue(loop_dev[i].lo_queue);
        i = max_loop;
out_mem3:
        while (i--)
                put_disk(disks[i]);
        OBD_FREE(disks, max_loop * sizeof(*disks));
out_mem2:
        OBD_FREE(loop_dev, max_loop * sizeof(*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_cleanup_queue(loop_dev[i].lo_queue);
                put_disk(disks[i]);
        }
        if (ll_unregister_blkdev(lloop_major, "lloop"))
                CWARN("lloop: cannot unregister blkdev\n");
        else
                CDEBUG(D_CONFIG, "unregistered lloop major %d\n", lloop_major);

        OBD_FREE(disks, max_loop * sizeof(*disks));
        OBD_FREE(loop_dev, max_loop * sizeof(*loop_dev));
}

module_init(lloop_init);
module_exit(lloop_exit);

CFS_MODULE_PARM(max_loop, "i", int, 0444, "maximum of lloop_device");
MODULE_AUTHOR("Sun Microsystems, Inc. <http://www.lustre.org/>");
MODULE_DESCRIPTION("Lustre virtual block device");
MODULE_LICENSE("GPL");