4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 only,
8 * as published by the Free Software Foundation.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License version 2 for more details (a copy is included
14 * in the LICENSE file that accompanied this code).
16 * You should have received a copy of the GNU General Public License
17 * version 2 along with this program; If not, see
18 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
20 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
21 * CA 95054 USA or visit www.sun.com if you need additional information or
27 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
28 * Use is subject to license terms.
30 * Copyright (c) 2011, 2012, Intel Corporation.
33 * This file is part of Lustre, http://www.lustre.org/
34 * Lustre is a trademark of Sun Microsystems, Inc.
38 * linux/drivers/block/loop.c
40 * Written by Theodore Ts'o, 3/29/93
42 * Copyright 1993 by Theodore Ts'o. Redistribution of this file is
43 * permitted under the GNU General Public License.
45 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
46 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
48 * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
50 * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
52 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
54 * Loadable modules and other fixes by AK, 1998
56 * Maximum number of loop devices now dynamic via max_loop module parameter.
57 * Russell Kroll <rkroll@exploits.org> 19990701
59 * Maximum number of loop devices when compiled-in now selectable by passing
60 * max_loop=<1-255> to the kernel on boot.
61 * Erik I. Bols?, <eriki@himolde.no>, Oct 31, 1999
63 * Completely rewrite request handling to be make_request_fn style and
64 * non blocking, pushing work to a helper thread. Lots of fixes from
66 * Jens Axboe <axboe@suse.de>, Nov 2000
68 * Support up to 256 loop devices
69 * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
71 * Support for falling back on the write file operation when the address space
72 * operations prepare_write and/or commit_write are not available on the
74 * Anton Altaparmakov, 16 Feb 2005
77 * - Advisory locking is ignored here.
78 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
82 #include <linux/module.h>
84 #include <linux/sched.h>
86 #include <linux/file.h>
87 #include <linux/stat.h>
88 #include <linux/errno.h>
89 #include <linux/major.h>
90 #include <linux/wait.h>
91 #include <linux/blkdev.h>
92 #include <linux/blkpg.h>
93 #include <linux/init.h>
94 #include <linux/swap.h>
95 #include <linux/slab.h>
96 #include <linux/suspend.h>
97 #include <linux/writeback.h>
98 #include <linux/buffer_head.h> /* for invalidate_bdev() */
99 #include <linux/completion.h>
100 #include <linux/highmem.h>
101 #include <linux/gfp.h>
102 #include <linux/pagevec.h>
104 #include <asm/uaccess.h>
106 #include "../include/lustre_lib.h"
107 #include "../include/lustre_lite.h"
108 #include "llite_internal.h"
110 #define LLOOP_MAX_SEGMENTS LNET_MAX_IOV
112 /* Possible states of device */
119 struct lloop_device
{
125 struct file
*lo_backing_file
;
126 struct block_device
*lo_device
;
127 unsigned lo_blocksize
;
133 struct bio
*lo_biotail
;
135 struct semaphore lo_sem
;
136 struct mutex lo_ctl_mutex
;
138 wait_queue_head_t lo_bh_wait
;
140 struct request_queue
*lo_queue
;
142 const struct lu_env
*lo_env
;
144 struct ll_dio_pages lo_pvec
;
146 /* data to handle bio for lustre. */
147 struct lo_request_data
{
148 struct page
*lrd_pages
[LLOOP_MAX_SEGMENTS
];
149 loff_t lrd_offsets
[LLOOP_MAX_SEGMENTS
];
157 LO_FLAGS_READ_ONLY
= 1,
160 static int lloop_major
;
161 #define MAX_LOOP_DEFAULT 16
162 static int max_loop
= MAX_LOOP_DEFAULT
;
163 static struct lloop_device
*loop_dev
;
164 static struct gendisk
**disks
;
165 static struct mutex lloop_mutex
;
166 static void *ll_iocontrol_magic
= NULL
;
168 static loff_t
get_loop_size(struct lloop_device
*lo
, struct file
*file
)
170 loff_t size
, offset
, loopsize
;
172 /* Compute loopsize in bytes */
173 size
= i_size_read(file
->f_mapping
->host
);
174 offset
= lo
->lo_offset
;
175 loopsize
= size
- offset
;
176 if (lo
->lo_sizelimit
> 0 && lo
->lo_sizelimit
< loopsize
)
177 loopsize
= lo
->lo_sizelimit
;
180 * Unfortunately, if we want to do I/O on the device,
181 * the number of 512-byte sectors has to fit into a sector_t.
183 return loopsize
>> 9;
186 static int do_bio_lustrebacked(struct lloop_device
*lo
, struct bio
*head
)
188 const struct lu_env
*env
= lo
->lo_env
;
189 struct cl_io
*io
= &lo
->lo_io
;
190 struct inode
*inode
= lo
->lo_backing_file
->f_dentry
->d_inode
;
191 struct cl_object
*obj
= ll_i2info(inode
)->lli_clob
;
197 struct bvec_iter iter
;
201 struct ll_dio_pages
*pvec
= &lo
->lo_pvec
;
202 struct page
**pages
= pvec
->ldp_pages
;
203 loff_t
*offsets
= pvec
->ldp_offsets
;
205 truncate_inode_pages(inode
->i_mapping
, 0);
207 /* initialize the IO */
208 memset(io
, 0, sizeof(*io
));
210 ret
= cl_io_init(env
, io
, CIT_MISC
, obj
);
212 return io
->ci_result
;
213 io
->ci_lockreq
= CILR_NEVER
;
215 LASSERT(head
!= NULL
);
217 for (bio
= head
; bio
!= NULL
; bio
= bio
->bi_next
) {
218 LASSERT(rw
== bio
->bi_rw
);
220 offset
= (pgoff_t
)(bio
->bi_iter
.bi_sector
<< 9) + lo
->lo_offset
;
221 bio_for_each_segment(bvec
, bio
, iter
) {
222 BUG_ON(bvec
.bv_offset
!= 0);
223 BUG_ON(bvec
.bv_len
!= PAGE_CACHE_SIZE
);
225 pages
[page_count
] = bvec
.bv_page
;
226 offsets
[page_count
] = offset
;
228 offset
+= bvec
.bv_len
;
230 LASSERT(page_count
<= LLOOP_MAX_SEGMENTS
);
233 ll_stats_ops_tally(ll_i2sbi(inode
),
234 (rw
== WRITE
) ? LPROC_LL_BRW_WRITE
: LPROC_LL_BRW_READ
,
237 pvec
->ldp_size
= page_count
<< PAGE_CACHE_SHIFT
;
238 pvec
->ldp_nr
= page_count
;
240 /* FIXME: in ll_direct_rw_pages, it has to allocate many cl_page{}s to
241 * write those pages into OST. Even worse case is that more pages
242 * would be asked to write out to swap space, and then finally get here
244 * Unfortunately this is NOT easy to fix.
245 * Thoughts on solution:
246 * 0. Define a reserved pool for cl_pages, which could be a list of
247 * pre-allocated cl_pages;
248 * 1. Define a new operation in cl_object_operations{}, says clo_depth,
249 * which measures how many layers for this lustre object. Generally
250 * speaking, the depth would be 2, one for llite, and one for lovsub.
251 * However, for SNS, there will be more since we need additional page
253 * 2. Reserve the # of (page_count * depth) cl_pages from the reserved
254 * pool. Afterwards, the clio would allocate the pages from reserved
255 * pool, this guarantees we needn't allocate the cl_pages from
256 * generic cl_page slab cache.
257 * Of course, if there is NOT enough pages in the pool, we might
258 * be asked to write less pages once, this purely depends on
259 * implementation. Anyway, we should be careful to avoid deadlocking.
261 mutex_lock(&inode
->i_mutex
);
262 bytes
= ll_direct_rw_pages(env
, io
, rw
, inode
, pvec
);
263 mutex_unlock(&inode
->i_mutex
);
265 return (bytes
== pvec
->ldp_size
) ? 0 : (int)bytes
;
269 * Add bio to back of pending list
271 static void loop_add_bio(struct lloop_device
*lo
, struct bio
*bio
)
275 spin_lock_irqsave(&lo
->lo_lock
, flags
);
276 if (lo
->lo_biotail
) {
277 lo
->lo_biotail
->bi_next
= bio
;
278 lo
->lo_biotail
= bio
;
280 lo
->lo_bio
= lo
->lo_biotail
= bio
;
281 spin_unlock_irqrestore(&lo
->lo_lock
, flags
);
283 atomic_inc(&lo
->lo_pending
);
284 if (waitqueue_active(&lo
->lo_bh_wait
))
285 wake_up(&lo
->lo_bh_wait
);
289 * Grab first pending buffer
291 static unsigned int loop_get_bio(struct lloop_device
*lo
, struct bio
**req
)
295 unsigned int count
= 0;
296 unsigned int page_count
= 0;
299 spin_lock_irq(&lo
->lo_lock
);
301 if (unlikely(first
== NULL
)) {
302 spin_unlock_irq(&lo
->lo_lock
);
306 /* TODO: need to split the bio, too bad. */
307 LASSERT(first
->bi_vcnt
<= LLOOP_MAX_SEGMENTS
);
311 while (*bio
&& (*bio
)->bi_rw
== rw
) {
312 CDEBUG(D_INFO
, "bio sector %llu size %u count %u vcnt%u \n",
313 (unsigned long long)(*bio
)->bi_iter
.bi_sector
,
314 (*bio
)->bi_iter
.bi_size
,
315 page_count
, (*bio
)->bi_vcnt
);
316 if (page_count
+ (*bio
)->bi_vcnt
> LLOOP_MAX_SEGMENTS
)
320 page_count
+= (*bio
)->bi_vcnt
;
322 bio
= &(*bio
)->bi_next
;
325 /* Some of bios can't be mergeable. */
329 /* Hit the end of queue */
330 lo
->lo_biotail
= NULL
;
334 spin_unlock_irq(&lo
->lo_lock
);
338 static void loop_make_request(struct request_queue
*q
, struct bio
*old_bio
)
340 struct lloop_device
*lo
= q
->queuedata
;
341 int rw
= bio_rw(old_bio
);
347 CDEBUG(D_INFO
, "submit bio sector %llu size %u\n",
348 (unsigned long long)old_bio
->bi_iter
.bi_sector
,
349 old_bio
->bi_iter
.bi_size
);
351 spin_lock_irq(&lo
->lo_lock
);
352 inactive
= (lo
->lo_state
!= LLOOP_BOUND
);
353 spin_unlock_irq(&lo
->lo_lock
);
358 if (lo
->lo_flags
& LO_FLAGS_READ_ONLY
)
360 } else if (rw
== READA
) {
362 } else if (rw
!= READ
) {
363 CERROR("lloop: unknown command (%x)\n", rw
);
366 loop_add_bio(lo
, old_bio
);
369 cfs_bio_io_error(old_bio
, old_bio
->bi_iter
.bi_size
);
373 static inline void loop_handle_bio(struct lloop_device
*lo
, struct bio
*bio
)
376 ret
= do_bio_lustrebacked(lo
, bio
);
378 struct bio
*tmp
= bio
->bi_next
;
380 cfs_bio_endio(bio
, bio
->bi_iter
.bi_size
, ret
);
385 static inline int loop_active(struct lloop_device
*lo
)
387 return atomic_read(&lo
->lo_pending
) ||
388 (lo
->lo_state
== LLOOP_RUNDOWN
);
392 * worker thread that handles reads/writes to file backed loop devices,
393 * to avoid blocking in our make_request_fn.
395 static int loop_thread(void *data
)
397 struct lloop_device
*lo
= data
;
400 unsigned long times
= 0;
401 unsigned long total_count
= 0;
407 set_user_nice(current
, MIN_NICE
);
409 lo
->lo_state
= LLOOP_BOUND
;
411 env
= cl_env_get(&refcheck
);
418 memset(&lo
->lo_pvec
, 0, sizeof(lo
->lo_pvec
));
419 lo
->lo_pvec
.ldp_pages
= lo
->lo_requests
[0].lrd_pages
;
420 lo
->lo_pvec
.ldp_offsets
= lo
->lo_requests
[0].lrd_offsets
;
423 * up sem, we are running
428 wait_event(lo
->lo_bh_wait
, loop_active(lo
));
429 if (!atomic_read(&lo
->lo_pending
)) {
431 spin_lock_irq(&lo
->lo_lock
);
432 exiting
= (lo
->lo_state
== LLOOP_RUNDOWN
);
433 spin_unlock_irq(&lo
->lo_lock
);
439 count
= loop_get_bio(lo
, &bio
);
441 CWARN("lloop(minor: %d): missing bio\n", lo
->lo_number
);
445 total_count
+= count
;
446 if (total_count
< count
) { /* overflow */
452 if ((times
& 127) == 0) {
453 CDEBUG(D_INFO
, "total: %lu, count: %lu, avg: %lu\n",
454 total_count
, times
, total_count
/ times
);
457 LASSERT(bio
!= NULL
);
458 LASSERT(count
<= atomic_read(&lo
->lo_pending
));
459 loop_handle_bio(lo
, bio
);
460 atomic_sub(count
, &lo
->lo_pending
);
462 cl_env_put(env
, &refcheck
);
469 static int loop_set_fd(struct lloop_device
*lo
, struct file
*unused
,
470 struct block_device
*bdev
, struct file
*file
)
473 struct address_space
*mapping
;
478 if (!try_module_get(THIS_MODULE
))
482 if (lo
->lo_state
!= LLOOP_UNBOUND
)
485 mapping
= file
->f_mapping
;
486 inode
= mapping
->host
;
489 if (!S_ISREG(inode
->i_mode
) || inode
->i_sb
->s_magic
!= LL_SUPER_MAGIC
)
492 if (!(file
->f_mode
& FMODE_WRITE
))
493 lo_flags
|= LO_FLAGS_READ_ONLY
;
495 size
= get_loop_size(lo
, file
);
497 if ((loff_t
)(sector_t
)size
!= size
) {
502 /* remove all pages in cache so as dirty pages not to be existent. */
503 truncate_inode_pages(mapping
, 0);
505 set_device_ro(bdev
, (lo_flags
& LO_FLAGS_READ_ONLY
) != 0);
507 lo
->lo_blocksize
= PAGE_CACHE_SIZE
;
508 lo
->lo_device
= bdev
;
509 lo
->lo_flags
= lo_flags
;
510 lo
->lo_backing_file
= file
;
511 lo
->lo_sizelimit
= 0;
512 lo
->old_gfp_mask
= mapping_gfp_mask(mapping
);
513 mapping_set_gfp_mask(mapping
, lo
->old_gfp_mask
& ~(__GFP_IO
|__GFP_FS
));
515 lo
->lo_bio
= lo
->lo_biotail
= NULL
;
518 * set queue make_request_fn, and add limits based on lower level
521 blk_queue_make_request(lo
->lo_queue
, loop_make_request
);
522 lo
->lo_queue
->queuedata
= lo
;
524 /* queue parameters */
525 CLASSERT(PAGE_CACHE_SIZE
< (1 << (sizeof(unsigned short) * 8)));
526 blk_queue_logical_block_size(lo
->lo_queue
,
527 (unsigned short)PAGE_CACHE_SIZE
);
528 blk_queue_max_hw_sectors(lo
->lo_queue
,
529 LLOOP_MAX_SEGMENTS
<< (PAGE_CACHE_SHIFT
- 9));
530 blk_queue_max_segments(lo
->lo_queue
, LLOOP_MAX_SEGMENTS
);
532 set_capacity(disks
[lo
->lo_number
], size
);
533 bd_set_size(bdev
, size
<< 9);
535 set_blocksize(bdev
, lo
->lo_blocksize
);
537 kthread_run(loop_thread
, lo
, "lloop%d", lo
->lo_number
);
542 /* This is safe: open() is still holding a reference. */
543 module_put(THIS_MODULE
);
547 static int loop_clr_fd(struct lloop_device
*lo
, struct block_device
*bdev
,
550 struct file
*filp
= lo
->lo_backing_file
;
551 gfp_t gfp
= lo
->old_gfp_mask
;
553 if (lo
->lo_state
!= LLOOP_BOUND
)
556 if (lo
->lo_refcnt
> count
) /* we needed one fd for the ioctl */
562 spin_lock_irq(&lo
->lo_lock
);
563 lo
->lo_state
= LLOOP_RUNDOWN
;
564 spin_unlock_irq(&lo
->lo_lock
);
565 wake_up(&lo
->lo_bh_wait
);
568 lo
->lo_backing_file
= NULL
;
569 lo
->lo_device
= NULL
;
571 lo
->lo_sizelimit
= 0;
573 invalidate_bdev(bdev
);
574 set_capacity(disks
[lo
->lo_number
], 0);
575 bd_set_size(bdev
, 0);
576 mapping_set_gfp_mask(filp
->f_mapping
, gfp
);
577 lo
->lo_state
= LLOOP_UNBOUND
;
579 /* This is safe: open() is still holding a reference. */
580 module_put(THIS_MODULE
);
584 static int lo_open(struct block_device
*bdev
, fmode_t mode
)
586 struct lloop_device
*lo
= bdev
->bd_disk
->private_data
;
588 mutex_lock(&lo
->lo_ctl_mutex
);
590 mutex_unlock(&lo
->lo_ctl_mutex
);
595 static void lo_release(struct gendisk
*disk
, fmode_t mode
)
597 struct lloop_device
*lo
= disk
->private_data
;
599 mutex_lock(&lo
->lo_ctl_mutex
);
601 mutex_unlock(&lo
->lo_ctl_mutex
);
604 /* lloop device node's ioctl function. */
605 static int lo_ioctl(struct block_device
*bdev
, fmode_t mode
,
606 unsigned int cmd
, unsigned long arg
)
608 struct lloop_device
*lo
= bdev
->bd_disk
->private_data
;
609 struct inode
*inode
= NULL
;
612 mutex_lock(&lloop_mutex
);
614 case LL_IOC_LLOOP_DETACH
: {
615 err
= loop_clr_fd(lo
, bdev
, 2);
617 blkdev_put(bdev
, 0); /* grabbed in LLOOP_ATTACH */
621 case LL_IOC_LLOOP_INFO
: {
624 if (lo
->lo_backing_file
== NULL
) {
629 inode
= lo
->lo_backing_file
->f_dentry
->d_inode
;
630 if (lo
->lo_state
== LLOOP_BOUND
)
631 fid
= ll_i2info(inode
)->lli_fid
;
635 if (copy_to_user((struct lu_fid
*)arg
, &fid
, sizeof(fid
)))
644 mutex_unlock(&lloop_mutex
);
649 static struct block_device_operations lo_fops
= {
650 .owner
= THIS_MODULE
,
652 .release
= lo_release
,
656 /* dynamic iocontrol callback.
657 * This callback is registered in lloop_init and will be called by
660 * This is a llite regular file ioctl function. It takes the responsibility
661 * of attaching or detaching a file by a lloop's device number.
663 static enum llioc_iter
lloop_ioctl(struct inode
*unused
, struct file
*file
,
664 unsigned int cmd
, unsigned long arg
,
665 void *magic
, int *rcp
)
667 struct lloop_device
*lo
= NULL
;
668 struct block_device
*bdev
= NULL
;
672 if (magic
!= ll_iocontrol_magic
)
680 CWARN("Enter llop_ioctl\n");
682 mutex_lock(&lloop_mutex
);
684 case LL_IOC_LLOOP_ATTACH
: {
685 struct lloop_device
*lo_free
= NULL
;
688 for (i
= 0; i
< max_loop
; i
++, lo
= NULL
) {
690 if (lo
->lo_state
== LLOOP_UNBOUND
) {
695 if (lo
->lo_backing_file
->f_dentry
->d_inode
==
696 file
->f_dentry
->d_inode
)
699 if (lo
|| !lo_free
) {
705 dev
= MKDEV(lloop_major
, lo
->lo_number
);
707 /* quit if the used pointer is writable */
708 if (put_user((long)old_encode_dev(dev
), (long *)arg
)) {
713 bdev
= blkdev_get_by_dev(dev
, file
->f_mode
, NULL
);
720 err
= loop_set_fd(lo
, NULL
, bdev
, file
);
729 case LL_IOC_LLOOP_DETACH_BYDEV
: {
732 dev
= old_decode_dev(arg
);
733 if (MAJOR(dev
) != lloop_major
) {
739 if (minor
> max_loop
- 1) {
744 lo
= &loop_dev
[minor
];
745 if (lo
->lo_state
!= LLOOP_BOUND
) {
750 bdev
= lo
->lo_device
;
751 err
= loop_clr_fd(lo
, bdev
, 1);
753 blkdev_put(bdev
, 0); /* grabbed in LLOOP_ATTACH */
764 mutex_unlock(&lloop_mutex
);
771 static int __init
lloop_init(void)
774 unsigned int cmdlist
[] = {
776 LL_IOC_LLOOP_DETACH_BYDEV
,
779 if (max_loop
< 1 || max_loop
> 256) {
780 max_loop
= MAX_LOOP_DEFAULT
;
781 CWARN("lloop: invalid max_loop (must be between"
782 " 1 and 256), using default (%u)\n", max_loop
);
785 lloop_major
= register_blkdev(0, "lloop");
789 CDEBUG(D_CONFIG
, "registered lloop major %d with %u minors\n",
790 lloop_major
, max_loop
);
792 ll_iocontrol_magic
= ll_iocontrol_register(lloop_ioctl
, 2, cmdlist
);
793 if (ll_iocontrol_magic
== NULL
)
796 loop_dev
= kzalloc(max_loop
* sizeof(*loop_dev
), GFP_KERNEL
);
800 disks
= kzalloc(max_loop
* sizeof(*disks
), GFP_KERNEL
);
804 for (i
= 0; i
< max_loop
; i
++) {
805 disks
[i
] = alloc_disk(1);
810 mutex_init(&lloop_mutex
);
812 for (i
= 0; i
< max_loop
; i
++) {
813 struct lloop_device
*lo
= &loop_dev
[i
];
814 struct gendisk
*disk
= disks
[i
];
816 lo
->lo_queue
= blk_alloc_queue(GFP_KERNEL
);
820 mutex_init(&lo
->lo_ctl_mutex
);
821 sema_init(&lo
->lo_sem
, 0);
822 init_waitqueue_head(&lo
->lo_bh_wait
);
824 spin_lock_init(&lo
->lo_lock
);
825 disk
->major
= lloop_major
;
826 disk
->first_minor
= i
;
827 disk
->fops
= &lo_fops
;
828 sprintf(disk
->disk_name
, "lloop%d", i
);
829 disk
->private_data
= lo
;
830 disk
->queue
= lo
->lo_queue
;
833 /* We cannot fail after we call this, so another loop!*/
834 for (i
= 0; i
< max_loop
; i
++)
840 blk_cleanup_queue(loop_dev
[i
].lo_queue
);
845 OBD_FREE(disks
, max_loop
* sizeof(*disks
));
847 OBD_FREE(loop_dev
, max_loop
* sizeof(*loop_dev
));
849 unregister_blkdev(lloop_major
, "lloop");
850 ll_iocontrol_unregister(ll_iocontrol_magic
);
851 CERROR("lloop: ran out of memory\n");
855 static void lloop_exit(void)
859 ll_iocontrol_unregister(ll_iocontrol_magic
);
860 for (i
= 0; i
< max_loop
; i
++) {
861 del_gendisk(disks
[i
]);
862 blk_cleanup_queue(loop_dev
[i
].lo_queue
);
866 unregister_blkdev(lloop_major
, "lloop");
868 OBD_FREE(disks
, max_loop
* sizeof(*disks
));
869 OBD_FREE(loop_dev
, max_loop
* sizeof(*loop_dev
));
872 module_init(lloop_init
);
873 module_exit(lloop_exit
);
875 module_param(max_loop
, int, 0444);
876 MODULE_PARM_DESC(max_loop
, "maximum of lloop_device");
877 MODULE_AUTHOR("Sun Microsystems, Inc. <http://www.lustre.org/>");
878 MODULE_DESCRIPTION("Lustre virtual block device");
879 MODULE_LICENSE("GPL");