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>
103 #include <linux/uaccess.h>
105 #include "../include/lustre_lib.h"
106 #include "../include/lustre_lite.h"
107 #include "llite_internal.h"
109 #define LLOOP_MAX_SEGMENTS LNET_MAX_IOV
111 /* Possible states of device */
118 struct lloop_device
{
124 struct file
*lo_backing_file
;
125 struct block_device
*lo_device
;
126 unsigned lo_blocksize
;
132 struct bio
*lo_biotail
;
134 struct semaphore lo_sem
;
135 struct mutex lo_ctl_mutex
;
137 wait_queue_head_t lo_bh_wait
;
139 struct request_queue
*lo_queue
;
141 const struct lu_env
*lo_env
;
143 struct ll_dio_pages lo_pvec
;
145 /* data to handle bio for lustre. */
146 struct lo_request_data
{
147 struct page
*lrd_pages
[LLOOP_MAX_SEGMENTS
];
148 loff_t lrd_offsets
[LLOOP_MAX_SEGMENTS
];
156 LO_FLAGS_READ_ONLY
= 1,
159 static int lloop_major
;
160 #define MAX_LOOP_DEFAULT 16
161 static int max_loop
= MAX_LOOP_DEFAULT
;
162 static struct lloop_device
*loop_dev
;
163 static struct gendisk
**disks
;
164 static struct mutex lloop_mutex
;
165 static void *ll_iocontrol_magic
= NULL
;
167 static loff_t
get_loop_size(struct lloop_device
*lo
, struct file
*file
)
169 loff_t size
, offset
, loopsize
;
171 /* Compute loopsize in bytes */
172 size
= i_size_read(file
->f_mapping
->host
);
173 offset
= lo
->lo_offset
;
174 loopsize
= size
- offset
;
175 if (lo
->lo_sizelimit
> 0 && lo
->lo_sizelimit
< loopsize
)
176 loopsize
= lo
->lo_sizelimit
;
179 * Unfortunately, if we want to do I/O on the device,
180 * the number of 512-byte sectors has to fit into a sector_t.
182 return loopsize
>> 9;
185 static int do_bio_lustrebacked(struct lloop_device
*lo
, struct bio
*head
)
187 const struct lu_env
*env
= lo
->lo_env
;
188 struct cl_io
*io
= &lo
->lo_io
;
189 struct inode
*inode
= file_inode(lo
->lo_backing_file
);
190 struct cl_object
*obj
= ll_i2info(inode
)->lli_clob
;
196 struct bvec_iter iter
;
200 struct ll_dio_pages
*pvec
= &lo
->lo_pvec
;
201 struct page
**pages
= pvec
->ldp_pages
;
202 loff_t
*offsets
= pvec
->ldp_offsets
;
204 truncate_inode_pages(inode
->i_mapping
, 0);
206 /* initialize the IO */
207 memset(io
, 0, sizeof(*io
));
209 ret
= cl_io_init(env
, io
, CIT_MISC
, obj
);
211 return io
->ci_result
;
212 io
->ci_lockreq
= CILR_NEVER
;
214 LASSERT(head
!= NULL
);
216 for (bio
= head
; bio
!= NULL
; bio
= bio
->bi_next
) {
217 LASSERT(rw
== bio
->bi_rw
);
219 offset
= (pgoff_t
)(bio
->bi_iter
.bi_sector
<< 9) + lo
->lo_offset
;
220 bio_for_each_segment(bvec
, bio
, iter
) {
221 BUG_ON(bvec
.bv_offset
!= 0);
222 BUG_ON(bvec
.bv_len
!= PAGE_CACHE_SIZE
);
224 pages
[page_count
] = bvec
.bv_page
;
225 offsets
[page_count
] = offset
;
227 offset
+= bvec
.bv_len
;
229 LASSERT(page_count
<= LLOOP_MAX_SEGMENTS
);
232 ll_stats_ops_tally(ll_i2sbi(inode
),
233 (rw
== WRITE
) ? LPROC_LL_BRW_WRITE
: LPROC_LL_BRW_READ
,
236 pvec
->ldp_size
= page_count
<< PAGE_CACHE_SHIFT
;
237 pvec
->ldp_nr
= page_count
;
239 /* FIXME: in ll_direct_rw_pages, it has to allocate many cl_page{}s to
240 * write those pages into OST. Even worse case is that more pages
241 * would be asked to write out to swap space, and then finally get here
243 * Unfortunately this is NOT easy to fix.
244 * Thoughts on solution:
245 * 0. Define a reserved pool for cl_pages, which could be a list of
246 * pre-allocated cl_pages;
247 * 1. Define a new operation in cl_object_operations{}, says clo_depth,
248 * which measures how many layers for this lustre object. Generally
249 * speaking, the depth would be 2, one for llite, and one for lovsub.
250 * However, for SNS, there will be more since we need additional page
252 * 2. Reserve the # of (page_count * depth) cl_pages from the reserved
253 * pool. Afterwards, the clio would allocate the pages from reserved
254 * pool, this guarantees we needn't allocate the cl_pages from
255 * generic cl_page slab cache.
256 * Of course, if there is NOT enough pages in the pool, we might
257 * be asked to write less pages once, this purely depends on
258 * implementation. Anyway, we should be careful to avoid deadlocking.
260 mutex_lock(&inode
->i_mutex
);
261 bytes
= ll_direct_rw_pages(env
, io
, rw
, inode
, pvec
);
262 mutex_unlock(&inode
->i_mutex
);
264 return (bytes
== pvec
->ldp_size
) ? 0 : (int)bytes
;
268 * Add bio to back of pending list
270 static void loop_add_bio(struct lloop_device
*lo
, struct bio
*bio
)
274 spin_lock_irqsave(&lo
->lo_lock
, flags
);
275 if (lo
->lo_biotail
) {
276 lo
->lo_biotail
->bi_next
= bio
;
277 lo
->lo_biotail
= bio
;
279 lo
->lo_bio
= lo
->lo_biotail
= bio
;
280 spin_unlock_irqrestore(&lo
->lo_lock
, flags
);
282 atomic_inc(&lo
->lo_pending
);
283 if (waitqueue_active(&lo
->lo_bh_wait
))
284 wake_up(&lo
->lo_bh_wait
);
288 * Grab first pending buffer
290 static unsigned int loop_get_bio(struct lloop_device
*lo
, struct bio
**req
)
294 unsigned int count
= 0;
295 unsigned int page_count
= 0;
298 spin_lock_irq(&lo
->lo_lock
);
300 if (unlikely(first
== NULL
)) {
301 spin_unlock_irq(&lo
->lo_lock
);
305 /* TODO: need to split the bio, too bad. */
306 LASSERT(first
->bi_vcnt
<= LLOOP_MAX_SEGMENTS
);
310 while (*bio
&& (*bio
)->bi_rw
== rw
) {
311 CDEBUG(D_INFO
, "bio sector %llu size %u count %u vcnt%u \n",
312 (unsigned long long)(*bio
)->bi_iter
.bi_sector
,
313 (*bio
)->bi_iter
.bi_size
,
314 page_count
, (*bio
)->bi_vcnt
);
315 if (page_count
+ (*bio
)->bi_vcnt
> LLOOP_MAX_SEGMENTS
)
319 page_count
+= (*bio
)->bi_vcnt
;
321 bio
= &(*bio
)->bi_next
;
324 /* Some of bios can't be mergeable. */
328 /* Hit the end of queue */
329 lo
->lo_biotail
= NULL
;
333 spin_unlock_irq(&lo
->lo_lock
);
337 static void loop_make_request(struct request_queue
*q
, struct bio
*old_bio
)
339 struct lloop_device
*lo
= q
->queuedata
;
340 int rw
= bio_rw(old_bio
);
346 CDEBUG(D_INFO
, "submit bio sector %llu size %u\n",
347 (unsigned long long)old_bio
->bi_iter
.bi_sector
,
348 old_bio
->bi_iter
.bi_size
);
350 spin_lock_irq(&lo
->lo_lock
);
351 inactive
= lo
->lo_state
!= LLOOP_BOUND
;
352 spin_unlock_irq(&lo
->lo_lock
);
357 if (lo
->lo_flags
& LO_FLAGS_READ_ONLY
)
359 } else if (rw
== READA
) {
361 } else if (rw
!= READ
) {
362 CERROR("lloop: unknown command (%x)\n", rw
);
365 loop_add_bio(lo
, old_bio
);
368 cfs_bio_io_error(old_bio
, old_bio
->bi_iter
.bi_size
);
372 static inline void loop_handle_bio(struct lloop_device
*lo
, struct bio
*bio
)
375 ret
= do_bio_lustrebacked(lo
, bio
);
377 struct bio
*tmp
= bio
->bi_next
;
379 cfs_bio_endio(bio
, bio
->bi_iter
.bi_size
, ret
);
384 static inline int loop_active(struct lloop_device
*lo
)
386 return atomic_read(&lo
->lo_pending
) ||
387 (lo
->lo_state
== LLOOP_RUNDOWN
);
391 * worker thread that handles reads/writes to file backed loop devices,
392 * to avoid blocking in our make_request_fn.
394 static int loop_thread(void *data
)
396 struct lloop_device
*lo
= data
;
399 unsigned long times
= 0;
400 unsigned long total_count
= 0;
406 set_user_nice(current
, MIN_NICE
);
408 lo
->lo_state
= LLOOP_BOUND
;
410 env
= cl_env_get(&refcheck
);
417 memset(&lo
->lo_pvec
, 0, sizeof(lo
->lo_pvec
));
418 lo
->lo_pvec
.ldp_pages
= lo
->lo_requests
[0].lrd_pages
;
419 lo
->lo_pvec
.ldp_offsets
= lo
->lo_requests
[0].lrd_offsets
;
422 * up sem, we are running
427 wait_event(lo
->lo_bh_wait
, loop_active(lo
));
428 if (!atomic_read(&lo
->lo_pending
)) {
430 spin_lock_irq(&lo
->lo_lock
);
431 exiting
= (lo
->lo_state
== LLOOP_RUNDOWN
);
432 spin_unlock_irq(&lo
->lo_lock
);
438 count
= loop_get_bio(lo
, &bio
);
440 CWARN("lloop(minor: %d): missing bio\n", lo
->lo_number
);
444 total_count
+= count
;
445 if (total_count
< count
) { /* overflow */
451 if ((times
& 127) == 0) {
452 CDEBUG(D_INFO
, "total: %lu, count: %lu, avg: %lu\n",
453 total_count
, times
, total_count
/ times
);
456 LASSERT(bio
!= NULL
);
457 LASSERT(count
<= atomic_read(&lo
->lo_pending
));
458 loop_handle_bio(lo
, bio
);
459 atomic_sub(count
, &lo
->lo_pending
);
461 cl_env_put(env
, &refcheck
);
468 static int loop_set_fd(struct lloop_device
*lo
, struct file
*unused
,
469 struct block_device
*bdev
, struct file
*file
)
472 struct address_space
*mapping
;
477 if (!try_module_get(THIS_MODULE
))
481 if (lo
->lo_state
!= LLOOP_UNBOUND
)
484 mapping
= file
->f_mapping
;
485 inode
= mapping
->host
;
488 if (!S_ISREG(inode
->i_mode
) || inode
->i_sb
->s_magic
!= LL_SUPER_MAGIC
)
491 if (!(file
->f_mode
& FMODE_WRITE
))
492 lo_flags
|= LO_FLAGS_READ_ONLY
;
494 size
= get_loop_size(lo
, file
);
496 if ((loff_t
)(sector_t
)size
!= size
) {
501 /* remove all pages in cache so as dirty pages not to be existent. */
502 truncate_inode_pages(mapping
, 0);
504 set_device_ro(bdev
, (lo_flags
& LO_FLAGS_READ_ONLY
) != 0);
506 lo
->lo_blocksize
= PAGE_CACHE_SIZE
;
507 lo
->lo_device
= bdev
;
508 lo
->lo_flags
= lo_flags
;
509 lo
->lo_backing_file
= file
;
510 lo
->lo_sizelimit
= 0;
511 lo
->old_gfp_mask
= mapping_gfp_mask(mapping
);
512 mapping_set_gfp_mask(mapping
, lo
->old_gfp_mask
& ~(__GFP_IO
|__GFP_FS
));
514 lo
->lo_bio
= lo
->lo_biotail
= NULL
;
517 * set queue make_request_fn, and add limits based on lower level
520 blk_queue_make_request(lo
->lo_queue
, loop_make_request
);
521 lo
->lo_queue
->queuedata
= lo
;
523 /* queue parameters */
524 CLASSERT(PAGE_CACHE_SIZE
< (1 << (sizeof(unsigned short) * 8)));
525 blk_queue_logical_block_size(lo
->lo_queue
,
526 (unsigned short)PAGE_CACHE_SIZE
);
527 blk_queue_max_hw_sectors(lo
->lo_queue
,
528 LLOOP_MAX_SEGMENTS
<< (PAGE_CACHE_SHIFT
- 9));
529 blk_queue_max_segments(lo
->lo_queue
, LLOOP_MAX_SEGMENTS
);
531 set_capacity(disks
[lo
->lo_number
], size
);
532 bd_set_size(bdev
, size
<< 9);
534 set_blocksize(bdev
, lo
->lo_blocksize
);
536 kthread_run(loop_thread
, lo
, "lloop%d", lo
->lo_number
);
541 /* This is safe: open() is still holding a reference. */
542 module_put(THIS_MODULE
);
546 static int loop_clr_fd(struct lloop_device
*lo
, struct block_device
*bdev
,
549 struct file
*filp
= lo
->lo_backing_file
;
550 gfp_t gfp
= lo
->old_gfp_mask
;
552 if (lo
->lo_state
!= LLOOP_BOUND
)
555 if (lo
->lo_refcnt
> count
) /* we needed one fd for the ioctl */
561 spin_lock_irq(&lo
->lo_lock
);
562 lo
->lo_state
= LLOOP_RUNDOWN
;
563 spin_unlock_irq(&lo
->lo_lock
);
564 wake_up(&lo
->lo_bh_wait
);
567 lo
->lo_backing_file
= NULL
;
568 lo
->lo_device
= NULL
;
570 lo
->lo_sizelimit
= 0;
572 invalidate_bdev(bdev
);
573 set_capacity(disks
[lo
->lo_number
], 0);
574 bd_set_size(bdev
, 0);
575 mapping_set_gfp_mask(filp
->f_mapping
, gfp
);
576 lo
->lo_state
= LLOOP_UNBOUND
;
578 /* This is safe: open() is still holding a reference. */
579 module_put(THIS_MODULE
);
583 static int lo_open(struct block_device
*bdev
, fmode_t mode
)
585 struct lloop_device
*lo
= bdev
->bd_disk
->private_data
;
587 mutex_lock(&lo
->lo_ctl_mutex
);
589 mutex_unlock(&lo
->lo_ctl_mutex
);
594 static void lo_release(struct gendisk
*disk
, fmode_t mode
)
596 struct lloop_device
*lo
= disk
->private_data
;
598 mutex_lock(&lo
->lo_ctl_mutex
);
600 mutex_unlock(&lo
->lo_ctl_mutex
);
603 /* lloop device node's ioctl function. */
604 static int lo_ioctl(struct block_device
*bdev
, fmode_t mode
,
605 unsigned int cmd
, unsigned long arg
)
607 struct lloop_device
*lo
= bdev
->bd_disk
->private_data
;
608 struct inode
*inode
= NULL
;
611 mutex_lock(&lloop_mutex
);
613 case LL_IOC_LLOOP_DETACH
: {
614 err
= loop_clr_fd(lo
, bdev
, 2);
616 blkdev_put(bdev
, 0); /* grabbed in LLOOP_ATTACH */
620 case LL_IOC_LLOOP_INFO
: {
623 if (lo
->lo_backing_file
== NULL
) {
628 inode
= file_inode(lo
->lo_backing_file
);
629 if (lo
->lo_state
== LLOOP_BOUND
)
630 fid
= ll_i2info(inode
)->lli_fid
;
634 if (copy_to_user((struct lu_fid
*)arg
, &fid
, sizeof(fid
)))
643 mutex_unlock(&lloop_mutex
);
648 static struct block_device_operations lo_fops
= {
649 .owner
= THIS_MODULE
,
651 .release
= lo_release
,
655 /* dynamic iocontrol callback.
656 * This callback is registered in lloop_init and will be called by
659 * This is a llite regular file ioctl function. It takes the responsibility
660 * of attaching or detaching a file by a lloop's device number.
662 static enum llioc_iter
lloop_ioctl(struct inode
*unused
, struct file
*file
,
663 unsigned int cmd
, unsigned long arg
,
664 void *magic
, int *rcp
)
666 struct lloop_device
*lo
= NULL
;
667 struct block_device
*bdev
= NULL
;
671 if (magic
!= ll_iocontrol_magic
)
679 CWARN("Enter llop_ioctl\n");
681 mutex_lock(&lloop_mutex
);
683 case LL_IOC_LLOOP_ATTACH
: {
684 struct lloop_device
*lo_free
= NULL
;
687 for (i
= 0; i
< max_loop
; i
++, lo
= NULL
) {
689 if (lo
->lo_state
== LLOOP_UNBOUND
) {
694 if (file_inode(lo
->lo_backing_file
) == file_inode(file
))
697 if (lo
|| !lo_free
) {
703 dev
= MKDEV(lloop_major
, lo
->lo_number
);
705 /* quit if the used pointer is writable */
706 if (put_user((long)old_encode_dev(dev
), (long *)arg
)) {
711 bdev
= blkdev_get_by_dev(dev
, file
->f_mode
, NULL
);
718 err
= loop_set_fd(lo
, NULL
, bdev
, file
);
727 case LL_IOC_LLOOP_DETACH_BYDEV
: {
730 dev
= old_decode_dev(arg
);
731 if (MAJOR(dev
) != lloop_major
) {
737 if (minor
> max_loop
- 1) {
742 lo
= &loop_dev
[minor
];
743 if (lo
->lo_state
!= LLOOP_BOUND
) {
748 bdev
= lo
->lo_device
;
749 err
= loop_clr_fd(lo
, bdev
, 1);
751 blkdev_put(bdev
, 0); /* grabbed in LLOOP_ATTACH */
762 mutex_unlock(&lloop_mutex
);
769 static int __init
lloop_init(void)
772 unsigned int cmdlist
[] = {
774 LL_IOC_LLOOP_DETACH_BYDEV
,
777 if (max_loop
< 1 || max_loop
> 256) {
778 max_loop
= MAX_LOOP_DEFAULT
;
779 CWARN("lloop: invalid max_loop (must be between 1 and 256), using default (%u)\n",
783 lloop_major
= register_blkdev(0, "lloop");
787 CDEBUG(D_CONFIG
, "registered lloop major %d with %u minors\n",
788 lloop_major
, max_loop
);
790 ll_iocontrol_magic
= ll_iocontrol_register(lloop_ioctl
, 2, cmdlist
);
791 if (ll_iocontrol_magic
== NULL
)
794 loop_dev
= kcalloc(max_loop
, sizeof(*loop_dev
), GFP_KERNEL
);
798 disks
= kcalloc(max_loop
, sizeof(*disks
), GFP_KERNEL
);
802 for (i
= 0; i
< max_loop
; i
++) {
803 disks
[i
] = alloc_disk(1);
808 mutex_init(&lloop_mutex
);
810 for (i
= 0; i
< max_loop
; i
++) {
811 struct lloop_device
*lo
= &loop_dev
[i
];
812 struct gendisk
*disk
= disks
[i
];
814 lo
->lo_queue
= blk_alloc_queue(GFP_KERNEL
);
818 mutex_init(&lo
->lo_ctl_mutex
);
819 sema_init(&lo
->lo_sem
, 0);
820 init_waitqueue_head(&lo
->lo_bh_wait
);
822 spin_lock_init(&lo
->lo_lock
);
823 disk
->major
= lloop_major
;
824 disk
->first_minor
= i
;
825 disk
->fops
= &lo_fops
;
826 sprintf(disk
->disk_name
, "lloop%d", i
);
827 disk
->private_data
= lo
;
828 disk
->queue
= lo
->lo_queue
;
831 /* We cannot fail after we call this, so another loop!*/
832 for (i
= 0; i
< max_loop
; i
++)
838 blk_cleanup_queue(loop_dev
[i
].lo_queue
);
843 OBD_FREE(disks
, max_loop
* sizeof(*disks
));
845 OBD_FREE(loop_dev
, max_loop
* sizeof(*loop_dev
));
847 unregister_blkdev(lloop_major
, "lloop");
848 ll_iocontrol_unregister(ll_iocontrol_magic
);
849 CERROR("lloop: ran out of memory\n");
853 static void lloop_exit(void)
857 ll_iocontrol_unregister(ll_iocontrol_magic
);
858 for (i
= 0; i
< max_loop
; i
++) {
859 del_gendisk(disks
[i
]);
860 blk_cleanup_queue(loop_dev
[i
].lo_queue
);
864 unregister_blkdev(lloop_major
, "lloop");
866 OBD_FREE(disks
, max_loop
* sizeof(*disks
));
867 OBD_FREE(loop_dev
, max_loop
* sizeof(*loop_dev
));
870 module_init(lloop_init
);
871 module_exit(lloop_exit
);
873 module_param(max_loop
, int, 0444);
874 MODULE_PARM_DESC(max_loop
, "maximum of lloop_device");
875 MODULE_AUTHOR("Sun Microsystems, Inc. <http://www.lustre.org/>");
876 MODULE_DESCRIPTION("Lustre virtual block device");
877 MODULE_LICENSE("GPL");