2 * linux/drivers/block/loop.c
4 * Written by Theodore Ts'o, 3/29/93
6 * Copyright 1993 by Theodore Ts'o. Redistribution of this file is
7 * permitted under the GNU General Public License.
9 * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
10 * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
12 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
13 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
15 * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
17 * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
19 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
21 * Loadable modules and other fixes by AK, 1998
23 * Make real block number available to downstream transfer functions, enables
24 * CBC (and relatives) mode encryption requiring unique IVs per data block.
25 * Reed H. Petty, rhp@draper.net
27 * Maximum number of loop devices now dynamic via max_loop module parameter.
28 * Russell Kroll <rkroll@exploits.org> 19990701
30 * Maximum number of loop devices when compiled-in now selectable by passing
31 * max_loop=<1-255> to the kernel on boot.
32 * Erik I. Bolsø, <eriki@himolde.no>, Oct 31, 1999
34 * Completely rewrite request handling to be make_request_fn style and
35 * non blocking, pushing work to a helper thread. Lots of fixes from
37 * Jens Axboe <axboe@suse.de>, Nov 2000
39 * Support up to 256 loop devices
40 * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
42 * Support for falling back on the write file operation when the address space
43 * operations write_begin is not available on the backing filesystem.
44 * Anton Altaparmakov, 16 Feb 2005
47 * - Advisory locking is ignored here.
48 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
52 #include <linux/module.h>
53 #include <linux/moduleparam.h>
54 #include <linux/sched.h>
56 #include <linux/file.h>
57 #include <linux/stat.h>
58 #include <linux/errno.h>
59 #include <linux/major.h>
60 #include <linux/wait.h>
61 #include <linux/blkdev.h>
62 #include <linux/blkpg.h>
63 #include <linux/init.h>
64 #include <linux/swap.h>
65 #include <linux/slab.h>
66 #include <linux/loop.h>
67 #include <linux/compat.h>
68 #include <linux/suspend.h>
69 #include <linux/freezer.h>
70 #include <linux/mutex.h>
71 #include <linux/writeback.h>
72 #include <linux/buffer_head.h> /* for invalidate_bdev() */
73 #include <linux/completion.h>
74 #include <linux/highmem.h>
75 #include <linux/kthread.h>
76 #include <linux/splice.h>
77 #include <linux/sysfs.h>
78 #include <linux/miscdevice.h>
79 #include <asm/uaccess.h>
81 static DEFINE_IDR(loop_index_idr);
82 static DEFINE_MUTEX(loop_index_mutex);
85 static int part_shift;
90 static int transfer_none(struct loop_device *lo, int cmd,
91 struct page *raw_page, unsigned raw_off,
92 struct page *loop_page, unsigned loop_off,
93 int size, sector_t real_block)
95 char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
96 char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
99 memcpy(loop_buf, raw_buf, size);
101 memcpy(raw_buf, loop_buf, size);
103 kunmap_atomic(loop_buf, KM_USER1);
104 kunmap_atomic(raw_buf, KM_USER0);
109 static int transfer_xor(struct loop_device *lo, int cmd,
110 struct page *raw_page, unsigned raw_off,
111 struct page *loop_page, unsigned loop_off,
112 int size, sector_t real_block)
114 char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
115 char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
116 char *in, *out, *key;
127 key = lo->lo_encrypt_key;
128 keysize = lo->lo_encrypt_key_size;
129 for (i = 0; i < size; i++)
130 *out++ = *in++ ^ key[(i & 511) % keysize];
132 kunmap_atomic(loop_buf, KM_USER1);
133 kunmap_atomic(raw_buf, KM_USER0);
138 static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
140 if (unlikely(info->lo_encrypt_key_size <= 0))
145 static struct loop_func_table none_funcs = {
146 .number = LO_CRYPT_NONE,
147 .transfer = transfer_none,
150 static struct loop_func_table xor_funcs = {
151 .number = LO_CRYPT_XOR,
152 .transfer = transfer_xor,
156 /* xfer_funcs[0] is special - its release function is never called */
157 static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
162 static loff_t get_loop_size(struct loop_device *lo, struct file *file)
164 loff_t size, offset, loopsize;
166 /* Compute loopsize in bytes */
167 size = i_size_read(file->f_mapping->host);
168 offset = lo->lo_offset;
169 loopsize = size - offset;
170 if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
171 loopsize = lo->lo_sizelimit;
174 * Unfortunately, if we want to do I/O on the device,
175 * the number of 512-byte sectors has to fit into a sector_t.
177 return loopsize >> 9;
181 figure_loop_size(struct loop_device *lo)
183 loff_t size = get_loop_size(lo, lo->lo_backing_file);
184 sector_t x = (sector_t)size;
186 if (unlikely((loff_t)x != size))
189 set_capacity(lo->lo_disk, x);
194 lo_do_transfer(struct loop_device *lo, int cmd,
195 struct page *rpage, unsigned roffs,
196 struct page *lpage, unsigned loffs,
197 int size, sector_t rblock)
199 if (unlikely(!lo->transfer))
202 return lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
206 * do_lo_send_aops - helper for writing data to a loop device
208 * This is the fast version for backing filesystems which implement the address
209 * space operations write_begin and write_end.
211 static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
212 loff_t pos, struct page *unused)
214 struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */
215 struct address_space *mapping = file->f_mapping;
217 unsigned offset, bv_offs;
220 mutex_lock(&mapping->host->i_mutex);
221 index = pos >> PAGE_CACHE_SHIFT;
222 offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1);
223 bv_offs = bvec->bv_offset;
227 unsigned size, copied;
232 IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
233 size = PAGE_CACHE_SIZE - offset;
237 ret = pagecache_write_begin(file, mapping, pos, size, 0,
242 file_update_time(file);
244 transfer_result = lo_do_transfer(lo, WRITE, page, offset,
245 bvec->bv_page, bv_offs, size, IV);
247 if (unlikely(transfer_result))
250 ret = pagecache_write_end(file, mapping, pos, size, copied,
252 if (ret < 0 || ret != copied)
255 if (unlikely(transfer_result))
266 mutex_unlock(&mapping->host->i_mutex);
274 * __do_lo_send_write - helper for writing data to a loop device
276 * This helper just factors out common code between do_lo_send_direct_write()
277 * and do_lo_send_write().
279 static int __do_lo_send_write(struct file *file,
280 u8 *buf, const int len, loff_t pos)
283 mm_segment_t old_fs = get_fs();
286 bw = file->f_op->write(file, buf, len, &pos);
288 if (likely(bw == len))
290 printk(KERN_ERR "loop: Write error at byte offset %llu, length %i.\n",
291 (unsigned long long)pos, len);
298 * do_lo_send_direct_write - helper for writing data to a loop device
300 * This is the fast, non-transforming version for backing filesystems which do
301 * not implement the address space operations write_begin and write_end.
302 * It uses the write file operation which should be present on all writeable
305 static int do_lo_send_direct_write(struct loop_device *lo,
306 struct bio_vec *bvec, loff_t pos, struct page *page)
308 ssize_t bw = __do_lo_send_write(lo->lo_backing_file,
309 kmap(bvec->bv_page) + bvec->bv_offset,
311 kunmap(bvec->bv_page);
317 * do_lo_send_write - helper for writing data to a loop device
319 * This is the slow, transforming version for filesystems which do not
320 * implement the address space operations write_begin and write_end. It
321 * uses the write file operation which should be present on all writeable
324 * Using fops->write is slower than using aops->{prepare,commit}_write in the
325 * transforming case because we need to double buffer the data as we cannot do
326 * the transformations in place as we do not have direct access to the
327 * destination pages of the backing file.
329 static int do_lo_send_write(struct loop_device *lo, struct bio_vec *bvec,
330 loff_t pos, struct page *page)
332 int ret = lo_do_transfer(lo, WRITE, page, 0, bvec->bv_page,
333 bvec->bv_offset, bvec->bv_len, pos >> 9);
335 return __do_lo_send_write(lo->lo_backing_file,
336 page_address(page), bvec->bv_len,
338 printk(KERN_ERR "loop: Transfer error at byte offset %llu, "
339 "length %i.\n", (unsigned long long)pos, bvec->bv_len);
345 static int lo_send(struct loop_device *lo, struct bio *bio, loff_t pos)
347 int (*do_lo_send)(struct loop_device *, struct bio_vec *, loff_t,
349 struct bio_vec *bvec;
350 struct page *page = NULL;
353 do_lo_send = do_lo_send_aops;
354 if (!(lo->lo_flags & LO_FLAGS_USE_AOPS)) {
355 do_lo_send = do_lo_send_direct_write;
356 if (lo->transfer != transfer_none) {
357 page = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
361 do_lo_send = do_lo_send_write;
364 bio_for_each_segment(bvec, bio, i) {
365 ret = do_lo_send(lo, bvec, pos, page);
377 printk(KERN_ERR "loop: Failed to allocate temporary page for write.\n");
382 struct lo_read_data {
383 struct loop_device *lo;
390 lo_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
391 struct splice_desc *sd)
393 struct lo_read_data *p = sd->u.data;
394 struct loop_device *lo = p->lo;
395 struct page *page = buf->page;
399 IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9)) +
405 if (lo_do_transfer(lo, READ, page, buf->offset, p->page, p->offset, size, IV)) {
406 printk(KERN_ERR "loop: transfer error block %ld\n",
411 flush_dcache_page(p->page);
420 lo_direct_splice_actor(struct pipe_inode_info *pipe, struct splice_desc *sd)
422 return __splice_from_pipe(pipe, sd, lo_splice_actor);
426 do_lo_receive(struct loop_device *lo,
427 struct bio_vec *bvec, int bsize, loff_t pos)
429 struct lo_read_data cookie;
430 struct splice_desc sd;
435 cookie.page = bvec->bv_page;
436 cookie.offset = bvec->bv_offset;
437 cookie.bsize = bsize;
440 sd.total_len = bvec->bv_len;
445 file = lo->lo_backing_file;
446 retval = splice_direct_to_actor(file, &sd, lo_direct_splice_actor);
455 lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
457 struct bio_vec *bvec;
460 bio_for_each_segment(bvec, bio, i) {
461 ret = do_lo_receive(lo, bvec, bsize, pos);
469 static int do_bio_filebacked(struct loop_device *lo, struct bio *bio)
474 pos = ((loff_t) bio->bi_sector << 9) + lo->lo_offset;
476 if (bio_rw(bio) == WRITE) {
477 struct file *file = lo->lo_backing_file;
479 if (bio->bi_rw & REQ_FLUSH) {
480 ret = vfs_fsync(file, 0);
481 if (unlikely(ret && ret != -EINVAL)) {
487 ret = lo_send(lo, bio, pos);
489 if ((bio->bi_rw & REQ_FUA) && !ret) {
490 ret = vfs_fsync(file, 0);
491 if (unlikely(ret && ret != -EINVAL))
495 ret = lo_receive(lo, bio, lo->lo_blocksize, pos);
502 * Add bio to back of pending list
504 static void loop_add_bio(struct loop_device *lo, struct bio *bio)
506 bio_list_add(&lo->lo_bio_list, bio);
510 * Grab first pending buffer
512 static struct bio *loop_get_bio(struct loop_device *lo)
514 return bio_list_pop(&lo->lo_bio_list);
517 static int loop_make_request(struct request_queue *q, struct bio *old_bio)
519 struct loop_device *lo = q->queuedata;
520 int rw = bio_rw(old_bio);
525 BUG_ON(!lo || (rw != READ && rw != WRITE));
527 spin_lock_irq(&lo->lo_lock);
528 if (lo->lo_state != Lo_bound)
530 if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
532 loop_add_bio(lo, old_bio);
533 wake_up(&lo->lo_event);
534 spin_unlock_irq(&lo->lo_lock);
538 spin_unlock_irq(&lo->lo_lock);
539 bio_io_error(old_bio);
543 struct switch_request {
545 struct completion wait;
548 static void do_loop_switch(struct loop_device *, struct switch_request *);
550 static inline void loop_handle_bio(struct loop_device *lo, struct bio *bio)
552 if (unlikely(!bio->bi_bdev)) {
553 do_loop_switch(lo, bio->bi_private);
556 int ret = do_bio_filebacked(lo, bio);
562 * worker thread that handles reads/writes to file backed loop devices,
563 * to avoid blocking in our make_request_fn. it also does loop decrypting
564 * on reads for block backed loop, as that is too heavy to do from
565 * b_end_io context where irqs may be disabled.
567 * Loop explanation: loop_clr_fd() sets lo_state to Lo_rundown before
568 * calling kthread_stop(). Therefore once kthread_should_stop() is
569 * true, make_request will not place any more requests. Therefore
570 * once kthread_should_stop() is true and lo_bio is NULL, we are
571 * done with the loop.
573 static int loop_thread(void *data)
575 struct loop_device *lo = data;
578 set_user_nice(current, -20);
580 while (!kthread_should_stop() || !bio_list_empty(&lo->lo_bio_list)) {
582 wait_event_interruptible(lo->lo_event,
583 !bio_list_empty(&lo->lo_bio_list) ||
584 kthread_should_stop());
586 if (bio_list_empty(&lo->lo_bio_list))
588 spin_lock_irq(&lo->lo_lock);
589 bio = loop_get_bio(lo);
590 spin_unlock_irq(&lo->lo_lock);
593 loop_handle_bio(lo, bio);
600 * loop_switch performs the hard work of switching a backing store.
601 * First it needs to flush existing IO, it does this by sending a magic
602 * BIO down the pipe. The completion of this BIO does the actual switch.
604 static int loop_switch(struct loop_device *lo, struct file *file)
606 struct switch_request w;
607 struct bio *bio = bio_alloc(GFP_KERNEL, 0);
610 init_completion(&w.wait);
612 bio->bi_private = &w;
614 loop_make_request(lo->lo_queue, bio);
615 wait_for_completion(&w.wait);
620 * Helper to flush the IOs in loop, but keeping loop thread running
622 static int loop_flush(struct loop_device *lo)
624 /* loop not yet configured, no running thread, nothing to flush */
628 return loop_switch(lo, NULL);
632 * Do the actual switch; called from the BIO completion routine
634 static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
636 struct file *file = p->file;
637 struct file *old_file = lo->lo_backing_file;
638 struct address_space *mapping;
640 /* if no new file, only flush of queued bios requested */
644 mapping = file->f_mapping;
645 mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
646 lo->lo_backing_file = file;
647 lo->lo_blocksize = S_ISBLK(mapping->host->i_mode) ?
648 mapping->host->i_bdev->bd_block_size : PAGE_SIZE;
649 lo->old_gfp_mask = mapping_gfp_mask(mapping);
650 mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
657 * loop_change_fd switched the backing store of a loopback device to
658 * a new file. This is useful for operating system installers to free up
659 * the original file and in High Availability environments to switch to
660 * an alternative location for the content in case of server meltdown.
661 * This can only work if the loop device is used read-only, and if the
662 * new backing store is the same size and type as the old backing store.
664 static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
667 struct file *file, *old_file;
672 if (lo->lo_state != Lo_bound)
675 /* the loop device has to be read-only */
677 if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
685 inode = file->f_mapping->host;
686 old_file = lo->lo_backing_file;
690 if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
693 /* size of the new backing store needs to be the same */
694 if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
698 error = loop_switch(lo, file);
704 ioctl_by_bdev(bdev, BLKRRPART, 0);
713 static inline int is_loop_device(struct file *file)
715 struct inode *i = file->f_mapping->host;
717 return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
720 /* loop sysfs attributes */
722 static ssize_t loop_attr_show(struct device *dev, char *page,
723 ssize_t (*callback)(struct loop_device *, char *))
725 struct gendisk *disk = dev_to_disk(dev);
726 struct loop_device *lo = disk->private_data;
728 return callback(lo, page);
731 #define LOOP_ATTR_RO(_name) \
732 static ssize_t loop_attr_##_name##_show(struct loop_device *, char *); \
733 static ssize_t loop_attr_do_show_##_name(struct device *d, \
734 struct device_attribute *attr, char *b) \
736 return loop_attr_show(d, b, loop_attr_##_name##_show); \
738 static struct device_attribute loop_attr_##_name = \
739 __ATTR(_name, S_IRUGO, loop_attr_do_show_##_name, NULL);
741 static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
746 mutex_lock(&lo->lo_ctl_mutex);
747 if (lo->lo_backing_file)
748 p = d_path(&lo->lo_backing_file->f_path, buf, PAGE_SIZE - 1);
749 mutex_unlock(&lo->lo_ctl_mutex);
751 if (IS_ERR_OR_NULL(p))
755 memmove(buf, p, ret);
763 static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
765 return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
768 static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
770 return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
773 static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
775 int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);
777 return sprintf(buf, "%s\n", autoclear ? "1" : "0");
780 LOOP_ATTR_RO(backing_file);
781 LOOP_ATTR_RO(offset);
782 LOOP_ATTR_RO(sizelimit);
783 LOOP_ATTR_RO(autoclear);
785 static struct attribute *loop_attrs[] = {
786 &loop_attr_backing_file.attr,
787 &loop_attr_offset.attr,
788 &loop_attr_sizelimit.attr,
789 &loop_attr_autoclear.attr,
793 static struct attribute_group loop_attribute_group = {
798 static int loop_sysfs_init(struct loop_device *lo)
800 return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
801 &loop_attribute_group);
804 static void loop_sysfs_exit(struct loop_device *lo)
806 sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
807 &loop_attribute_group);
810 static int loop_set_fd(struct loop_device *lo, fmode_t mode,
811 struct block_device *bdev, unsigned int arg)
813 struct file *file, *f;
815 struct address_space *mapping;
816 unsigned lo_blocksize;
821 /* This is safe, since we have a reference from open(). */
822 __module_get(THIS_MODULE);
830 if (lo->lo_state != Lo_unbound)
833 /* Avoid recursion */
835 while (is_loop_device(f)) {
836 struct loop_device *l;
838 if (f->f_mapping->host->i_bdev == bdev)
841 l = f->f_mapping->host->i_bdev->bd_disk->private_data;
842 if (l->lo_state == Lo_unbound) {
846 f = l->lo_backing_file;
849 mapping = file->f_mapping;
850 inode = mapping->host;
852 if (!(file->f_mode & FMODE_WRITE))
853 lo_flags |= LO_FLAGS_READ_ONLY;
856 if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) {
857 const struct address_space_operations *aops = mapping->a_ops;
859 if (aops->write_begin)
860 lo_flags |= LO_FLAGS_USE_AOPS;
861 if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
862 lo_flags |= LO_FLAGS_READ_ONLY;
864 lo_blocksize = S_ISBLK(inode->i_mode) ?
865 inode->i_bdev->bd_block_size : PAGE_SIZE;
872 size = get_loop_size(lo, file);
874 if ((loff_t)(sector_t)size != size) {
879 if (!(mode & FMODE_WRITE))
880 lo_flags |= LO_FLAGS_READ_ONLY;
882 set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
884 lo->lo_blocksize = lo_blocksize;
885 lo->lo_device = bdev;
886 lo->lo_flags = lo_flags;
887 lo->lo_backing_file = file;
888 lo->transfer = transfer_none;
890 lo->lo_sizelimit = 0;
891 lo->old_gfp_mask = mapping_gfp_mask(mapping);
892 mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
894 bio_list_init(&lo->lo_bio_list);
897 * set queue make_request_fn, and add limits based on lower level
900 blk_queue_make_request(lo->lo_queue, loop_make_request);
901 lo->lo_queue->queuedata = lo;
903 if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
904 blk_queue_flush(lo->lo_queue, REQ_FLUSH);
906 set_capacity(lo->lo_disk, size);
907 bd_set_size(bdev, size << 9);
909 /* let user-space know about the new size */
910 kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
912 set_blocksize(bdev, lo_blocksize);
914 lo->lo_thread = kthread_create(loop_thread, lo, "loop%d",
916 if (IS_ERR(lo->lo_thread)) {
917 error = PTR_ERR(lo->lo_thread);
920 lo->lo_state = Lo_bound;
921 wake_up_process(lo->lo_thread);
923 ioctl_by_bdev(bdev, BLKRRPART, 0);
928 lo->lo_thread = NULL;
929 lo->lo_device = NULL;
930 lo->lo_backing_file = NULL;
932 set_capacity(lo->lo_disk, 0);
933 invalidate_bdev(bdev);
934 bd_set_size(bdev, 0);
935 kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
936 mapping_set_gfp_mask(mapping, lo->old_gfp_mask);
937 lo->lo_state = Lo_unbound;
941 /* This is safe: open() is still holding a reference. */
942 module_put(THIS_MODULE);
947 loop_release_xfer(struct loop_device *lo)
950 struct loop_func_table *xfer = lo->lo_encryption;
954 err = xfer->release(lo);
956 lo->lo_encryption = NULL;
957 module_put(xfer->owner);
963 loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
964 const struct loop_info64 *i)
969 struct module *owner = xfer->owner;
971 if (!try_module_get(owner))
974 err = xfer->init(lo, i);
978 lo->lo_encryption = xfer;
983 static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
985 struct file *filp = lo->lo_backing_file;
986 gfp_t gfp = lo->old_gfp_mask;
988 if (lo->lo_state != Lo_bound)
991 if (lo->lo_refcnt > 1) /* we needed one fd for the ioctl */
997 spin_lock_irq(&lo->lo_lock);
998 lo->lo_state = Lo_rundown;
999 spin_unlock_irq(&lo->lo_lock);
1001 kthread_stop(lo->lo_thread);
1003 lo->lo_backing_file = NULL;
1005 loop_release_xfer(lo);
1006 lo->transfer = NULL;
1008 lo->lo_device = NULL;
1009 lo->lo_encryption = NULL;
1011 lo->lo_sizelimit = 0;
1012 lo->lo_encrypt_key_size = 0;
1014 lo->lo_thread = NULL;
1015 memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
1016 memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
1017 memset(lo->lo_file_name, 0, LO_NAME_SIZE);
1019 invalidate_bdev(bdev);
1020 set_capacity(lo->lo_disk, 0);
1021 loop_sysfs_exit(lo);
1023 bd_set_size(bdev, 0);
1024 /* let user-space know about this change */
1025 kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
1027 mapping_set_gfp_mask(filp->f_mapping, gfp);
1028 lo->lo_state = Lo_unbound;
1029 /* This is safe: open() is still holding a reference. */
1030 module_put(THIS_MODULE);
1031 if (max_part > 0 && bdev)
1032 ioctl_by_bdev(bdev, BLKRRPART, 0);
1033 mutex_unlock(&lo->lo_ctl_mutex);
1035 * Need not hold lo_ctl_mutex to fput backing file.
1036 * Calling fput holding lo_ctl_mutex triggers a circular
1037 * lock dependency possibility warning as fput can take
1038 * bd_mutex which is usually taken before lo_ctl_mutex.
1045 loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
1048 struct loop_func_table *xfer;
1049 uid_t uid = current_uid();
1051 if (lo->lo_encrypt_key_size &&
1052 lo->lo_key_owner != uid &&
1053 !capable(CAP_SYS_ADMIN))
1055 if (lo->lo_state != Lo_bound)
1057 if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
1060 err = loop_release_xfer(lo);
1064 if (info->lo_encrypt_type) {
1065 unsigned int type = info->lo_encrypt_type;
1067 if (type >= MAX_LO_CRYPT)
1069 xfer = xfer_funcs[type];
1075 err = loop_init_xfer(lo, xfer, info);
1079 if (lo->lo_offset != info->lo_offset ||
1080 lo->lo_sizelimit != info->lo_sizelimit) {
1081 lo->lo_offset = info->lo_offset;
1082 lo->lo_sizelimit = info->lo_sizelimit;
1083 if (figure_loop_size(lo))
1087 memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
1088 memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
1089 lo->lo_file_name[LO_NAME_SIZE-1] = 0;
1090 lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
1094 lo->transfer = xfer->transfer;
1095 lo->ioctl = xfer->ioctl;
1097 if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) !=
1098 (info->lo_flags & LO_FLAGS_AUTOCLEAR))
1099 lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
1101 lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
1102 lo->lo_init[0] = info->lo_init[0];
1103 lo->lo_init[1] = info->lo_init[1];
1104 if (info->lo_encrypt_key_size) {
1105 memcpy(lo->lo_encrypt_key, info->lo_encrypt_key,
1106 info->lo_encrypt_key_size);
1107 lo->lo_key_owner = uid;
1114 loop_get_status(struct loop_device *lo, struct loop_info64 *info)
1116 struct file *file = lo->lo_backing_file;
1120 if (lo->lo_state != Lo_bound)
1122 error = vfs_getattr(file->f_path.mnt, file->f_path.dentry, &stat);
1125 memset(info, 0, sizeof(*info));
1126 info->lo_number = lo->lo_number;
1127 info->lo_device = huge_encode_dev(stat.dev);
1128 info->lo_inode = stat.ino;
1129 info->lo_rdevice = huge_encode_dev(lo->lo_device ? stat.rdev : stat.dev);
1130 info->lo_offset = lo->lo_offset;
1131 info->lo_sizelimit = lo->lo_sizelimit;
1132 info->lo_flags = lo->lo_flags;
1133 memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
1134 memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
1135 info->lo_encrypt_type =
1136 lo->lo_encryption ? lo->lo_encryption->number : 0;
1137 if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
1138 info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
1139 memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
1140 lo->lo_encrypt_key_size);
1146 loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
1148 memset(info64, 0, sizeof(*info64));
1149 info64->lo_number = info->lo_number;
1150 info64->lo_device = info->lo_device;
1151 info64->lo_inode = info->lo_inode;
1152 info64->lo_rdevice = info->lo_rdevice;
1153 info64->lo_offset = info->lo_offset;
1154 info64->lo_sizelimit = 0;
1155 info64->lo_encrypt_type = info->lo_encrypt_type;
1156 info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
1157 info64->lo_flags = info->lo_flags;
1158 info64->lo_init[0] = info->lo_init[0];
1159 info64->lo_init[1] = info->lo_init[1];
1160 if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1161 memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
1163 memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
1164 memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
1168 loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
1170 memset(info, 0, sizeof(*info));
1171 info->lo_number = info64->lo_number;
1172 info->lo_device = info64->lo_device;
1173 info->lo_inode = info64->lo_inode;
1174 info->lo_rdevice = info64->lo_rdevice;
1175 info->lo_offset = info64->lo_offset;
1176 info->lo_encrypt_type = info64->lo_encrypt_type;
1177 info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
1178 info->lo_flags = info64->lo_flags;
1179 info->lo_init[0] = info64->lo_init[0];
1180 info->lo_init[1] = info64->lo_init[1];
1181 if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1182 memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
1184 memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
1185 memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
1187 /* error in case values were truncated */
1188 if (info->lo_device != info64->lo_device ||
1189 info->lo_rdevice != info64->lo_rdevice ||
1190 info->lo_inode != info64->lo_inode ||
1191 info->lo_offset != info64->lo_offset)
1198 loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
1200 struct loop_info info;
1201 struct loop_info64 info64;
1203 if (copy_from_user(&info, arg, sizeof (struct loop_info)))
1205 loop_info64_from_old(&info, &info64);
1206 return loop_set_status(lo, &info64);
1210 loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
1212 struct loop_info64 info64;
1214 if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
1216 return loop_set_status(lo, &info64);
1220 loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
1221 struct loop_info info;
1222 struct loop_info64 info64;
1228 err = loop_get_status(lo, &info64);
1230 err = loop_info64_to_old(&info64, &info);
1231 if (!err && copy_to_user(arg, &info, sizeof(info)))
1238 loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
1239 struct loop_info64 info64;
1245 err = loop_get_status(lo, &info64);
1246 if (!err && copy_to_user(arg, &info64, sizeof(info64)))
1252 static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
1259 if (unlikely(lo->lo_state != Lo_bound))
1261 err = figure_loop_size(lo);
1264 sec = get_capacity(lo->lo_disk);
1265 /* the width of sector_t may be narrow for bit-shift */
1268 mutex_lock(&bdev->bd_mutex);
1269 bd_set_size(bdev, sz);
1270 /* let user-space know about the new size */
1271 kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
1272 mutex_unlock(&bdev->bd_mutex);
1278 static int lo_ioctl(struct block_device *bdev, fmode_t mode,
1279 unsigned int cmd, unsigned long arg)
1281 struct loop_device *lo = bdev->bd_disk->private_data;
1284 mutex_lock_nested(&lo->lo_ctl_mutex, 1);
1287 err = loop_set_fd(lo, mode, bdev, arg);
1289 case LOOP_CHANGE_FD:
1290 err = loop_change_fd(lo, bdev, arg);
1293 /* loop_clr_fd would have unlocked lo_ctl_mutex on success */
1294 err = loop_clr_fd(lo, bdev);
1298 case LOOP_SET_STATUS:
1299 err = loop_set_status_old(lo, (struct loop_info __user *) arg);
1301 case LOOP_GET_STATUS:
1302 err = loop_get_status_old(lo, (struct loop_info __user *) arg);
1304 case LOOP_SET_STATUS64:
1305 err = loop_set_status64(lo, (struct loop_info64 __user *) arg);
1307 case LOOP_GET_STATUS64:
1308 err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
1310 case LOOP_SET_CAPACITY:
1312 if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
1313 err = loop_set_capacity(lo, bdev);
1316 err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
1318 mutex_unlock(&lo->lo_ctl_mutex);
1324 #ifdef CONFIG_COMPAT
1325 struct compat_loop_info {
1326 compat_int_t lo_number; /* ioctl r/o */
1327 compat_dev_t lo_device; /* ioctl r/o */
1328 compat_ulong_t lo_inode; /* ioctl r/o */
1329 compat_dev_t lo_rdevice; /* ioctl r/o */
1330 compat_int_t lo_offset;
1331 compat_int_t lo_encrypt_type;
1332 compat_int_t lo_encrypt_key_size; /* ioctl w/o */
1333 compat_int_t lo_flags; /* ioctl r/o */
1334 char lo_name[LO_NAME_SIZE];
1335 unsigned char lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
1336 compat_ulong_t lo_init[2];
1341 * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
1342 * - noinlined to reduce stack space usage in main part of driver
1345 loop_info64_from_compat(const struct compat_loop_info __user *arg,
1346 struct loop_info64 *info64)
1348 struct compat_loop_info info;
1350 if (copy_from_user(&info, arg, sizeof(info)))
1353 memset(info64, 0, sizeof(*info64));
1354 info64->lo_number = info.lo_number;
1355 info64->lo_device = info.lo_device;
1356 info64->lo_inode = info.lo_inode;
1357 info64->lo_rdevice = info.lo_rdevice;
1358 info64->lo_offset = info.lo_offset;
1359 info64->lo_sizelimit = 0;
1360 info64->lo_encrypt_type = info.lo_encrypt_type;
1361 info64->lo_encrypt_key_size = info.lo_encrypt_key_size;
1362 info64->lo_flags = info.lo_flags;
1363 info64->lo_init[0] = info.lo_init[0];
1364 info64->lo_init[1] = info.lo_init[1];
1365 if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1366 memcpy(info64->lo_crypt_name, info.lo_name, LO_NAME_SIZE);
1368 memcpy(info64->lo_file_name, info.lo_name, LO_NAME_SIZE);
1369 memcpy(info64->lo_encrypt_key, info.lo_encrypt_key, LO_KEY_SIZE);
1374 * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
1375 * - noinlined to reduce stack space usage in main part of driver
1378 loop_info64_to_compat(const struct loop_info64 *info64,
1379 struct compat_loop_info __user *arg)
1381 struct compat_loop_info info;
1383 memset(&info, 0, sizeof(info));
1384 info.lo_number = info64->lo_number;
1385 info.lo_device = info64->lo_device;
1386 info.lo_inode = info64->lo_inode;
1387 info.lo_rdevice = info64->lo_rdevice;
1388 info.lo_offset = info64->lo_offset;
1389 info.lo_encrypt_type = info64->lo_encrypt_type;
1390 info.lo_encrypt_key_size = info64->lo_encrypt_key_size;
1391 info.lo_flags = info64->lo_flags;
1392 info.lo_init[0] = info64->lo_init[0];
1393 info.lo_init[1] = info64->lo_init[1];
1394 if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1395 memcpy(info.lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
1397 memcpy(info.lo_name, info64->lo_file_name, LO_NAME_SIZE);
1398 memcpy(info.lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
1400 /* error in case values were truncated */
1401 if (info.lo_device != info64->lo_device ||
1402 info.lo_rdevice != info64->lo_rdevice ||
1403 info.lo_inode != info64->lo_inode ||
1404 info.lo_offset != info64->lo_offset ||
1405 info.lo_init[0] != info64->lo_init[0] ||
1406 info.lo_init[1] != info64->lo_init[1])
1409 if (copy_to_user(arg, &info, sizeof(info)))
1415 loop_set_status_compat(struct loop_device *lo,
1416 const struct compat_loop_info __user *arg)
1418 struct loop_info64 info64;
1421 ret = loop_info64_from_compat(arg, &info64);
1424 return loop_set_status(lo, &info64);
1428 loop_get_status_compat(struct loop_device *lo,
1429 struct compat_loop_info __user *arg)
1431 struct loop_info64 info64;
1437 err = loop_get_status(lo, &info64);
1439 err = loop_info64_to_compat(&info64, arg);
1443 static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
1444 unsigned int cmd, unsigned long arg)
1446 struct loop_device *lo = bdev->bd_disk->private_data;
1450 case LOOP_SET_STATUS:
1451 mutex_lock(&lo->lo_ctl_mutex);
1452 err = loop_set_status_compat(
1453 lo, (const struct compat_loop_info __user *) arg);
1454 mutex_unlock(&lo->lo_ctl_mutex);
1456 case LOOP_GET_STATUS:
1457 mutex_lock(&lo->lo_ctl_mutex);
1458 err = loop_get_status_compat(
1459 lo, (struct compat_loop_info __user *) arg);
1460 mutex_unlock(&lo->lo_ctl_mutex);
1462 case LOOP_SET_CAPACITY:
1464 case LOOP_GET_STATUS64:
1465 case LOOP_SET_STATUS64:
1466 arg = (unsigned long) compat_ptr(arg);
1468 case LOOP_CHANGE_FD:
1469 err = lo_ioctl(bdev, mode, cmd, arg);
1479 static int lo_open(struct block_device *bdev, fmode_t mode)
1481 struct loop_device *lo;
1484 mutex_lock(&loop_index_mutex);
1485 lo = bdev->bd_disk->private_data;
1491 mutex_lock(&lo->lo_ctl_mutex);
1493 mutex_unlock(&lo->lo_ctl_mutex);
1495 mutex_unlock(&loop_index_mutex);
1499 static int lo_release(struct gendisk *disk, fmode_t mode)
1501 struct loop_device *lo = disk->private_data;
1504 mutex_lock(&lo->lo_ctl_mutex);
1506 if (--lo->lo_refcnt)
1509 if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
1511 * In autoclear mode, stop the loop thread
1512 * and remove configuration after last close.
1514 err = loop_clr_fd(lo, NULL);
1519 * Otherwise keep thread (if running) and config,
1520 * but flush possible ongoing bios in thread.
1526 mutex_unlock(&lo->lo_ctl_mutex);
1531 static const struct block_device_operations lo_fops = {
1532 .owner = THIS_MODULE,
1534 .release = lo_release,
1536 #ifdef CONFIG_COMPAT
1537 .compat_ioctl = lo_compat_ioctl,
1542 * And now the modules code and kernel interface.
1544 static int max_loop;
1545 module_param(max_loop, int, S_IRUGO);
1546 MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
1547 module_param(max_part, int, S_IRUGO);
1548 MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
1549 MODULE_LICENSE("GPL");
1550 MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
1552 int loop_register_transfer(struct loop_func_table *funcs)
1554 unsigned int n = funcs->number;
1556 if (n >= MAX_LO_CRYPT || xfer_funcs[n])
1558 xfer_funcs[n] = funcs;
1562 static int unregister_transfer_cb(int id, void *ptr, void *data)
1564 struct loop_device *lo = ptr;
1565 struct loop_func_table *xfer = data;
1567 mutex_lock(&lo->lo_ctl_mutex);
1568 if (lo->lo_encryption == xfer)
1569 loop_release_xfer(lo);
1570 mutex_unlock(&lo->lo_ctl_mutex);
1574 int loop_unregister_transfer(int number)
1576 unsigned int n = number;
1577 struct loop_func_table *xfer;
1579 if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
1582 xfer_funcs[n] = NULL;
1583 idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
1587 EXPORT_SYMBOL(loop_register_transfer);
1588 EXPORT_SYMBOL(loop_unregister_transfer);
1590 static int loop_add(struct loop_device **l, int i)
1592 struct loop_device *lo;
1593 struct gendisk *disk;
1596 lo = kzalloc(sizeof(*lo), GFP_KERNEL);
1602 err = idr_pre_get(&loop_index_idr, GFP_KERNEL);
1609 /* create specific i in the index */
1610 err = idr_get_new_above(&loop_index_idr, lo, i, &m);
1611 if (err >= 0 && i != m) {
1612 idr_remove(&loop_index_idr, m);
1615 } else if (i == -1) {
1618 /* get next free nr */
1619 err = idr_get_new(&loop_index_idr, lo, &m);
1628 lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
1632 disk = lo->lo_disk = alloc_disk(1 << part_shift);
1634 goto out_free_queue;
1636 mutex_init(&lo->lo_ctl_mutex);
1638 lo->lo_thread = NULL;
1639 init_waitqueue_head(&lo->lo_event);
1640 spin_lock_init(&lo->lo_lock);
1641 disk->major = LOOP_MAJOR;
1642 disk->first_minor = i << part_shift;
1643 disk->fops = &lo_fops;
1644 disk->private_data = lo;
1645 disk->queue = lo->lo_queue;
1646 sprintf(disk->disk_name, "loop%d", i);
1649 return lo->lo_number;
1652 blk_cleanup_queue(lo->lo_queue);
1659 static void loop_remove(struct loop_device *lo)
1661 del_gendisk(lo->lo_disk);
1662 blk_cleanup_queue(lo->lo_queue);
1663 put_disk(lo->lo_disk);
1667 static int find_free_cb(int id, void *ptr, void *data)
1669 struct loop_device *lo = ptr;
1670 struct loop_device **l = data;
1672 if (lo->lo_state == Lo_unbound) {
1679 static int loop_lookup(struct loop_device **l, int i)
1681 struct loop_device *lo;
1687 err = idr_for_each(&loop_index_idr, &find_free_cb, &lo);
1690 ret = lo->lo_number;
1695 /* lookup and return a specific i */
1696 lo = idr_find(&loop_index_idr, i);
1699 ret = lo->lo_number;
1705 static struct kobject *loop_probe(dev_t dev, int *part, void *data)
1707 struct loop_device *lo;
1708 struct kobject *kobj;
1711 mutex_lock(&loop_index_mutex);
1712 err = loop_lookup(&lo, MINOR(dev) >> part_shift);
1714 err = loop_add(&lo, MINOR(dev) >> part_shift);
1716 kobj = ERR_PTR(err);
1718 kobj = get_disk(lo->lo_disk);
1719 mutex_unlock(&loop_index_mutex);
1725 static long loop_control_ioctl(struct file *file, unsigned int cmd,
1728 struct loop_device *lo;
1731 mutex_lock(&loop_index_mutex);
1734 ret = loop_lookup(&lo, parm);
1739 ret = loop_add(&lo, parm);
1741 case LOOP_CTL_REMOVE:
1742 ret = loop_lookup(&lo, parm);
1745 mutex_lock(&lo->lo_ctl_mutex);
1746 if (lo->lo_state != Lo_unbound) {
1748 mutex_unlock(&lo->lo_ctl_mutex);
1751 if (lo->lo_refcnt > 0) {
1753 mutex_unlock(&lo->lo_ctl_mutex);
1756 lo->lo_disk->private_data = NULL;
1757 mutex_unlock(&lo->lo_ctl_mutex);
1758 idr_remove(&loop_index_idr, lo->lo_number);
1761 case LOOP_CTL_GET_FREE:
1762 ret = loop_lookup(&lo, -1);
1765 ret = loop_add(&lo, -1);
1767 mutex_unlock(&loop_index_mutex);
1772 static const struct file_operations loop_ctl_fops = {
1773 .open = nonseekable_open,
1774 .unlocked_ioctl = loop_control_ioctl,
1775 .compat_ioctl = loop_control_ioctl,
1776 .owner = THIS_MODULE,
1777 .llseek = noop_llseek,
1780 static struct miscdevice loop_misc = {
1781 .minor = LOOP_CTRL_MINOR,
1782 .name = "loop-control",
1783 .fops = &loop_ctl_fops,
1786 MODULE_ALIAS_MISCDEV(LOOP_CTRL_MINOR);
1787 MODULE_ALIAS("devname:loop-control");
1789 static int __init loop_init(void)
1792 unsigned long range;
1793 struct loop_device *lo;
1797 * loop module now has a feature to instantiate underlying device
1798 * structure on-demand, provided that there is an access dev node.
1799 * However, this will not work well with user space tool that doesn't
1800 * know about such "feature". In order to not break any existing
1801 * tool, we do the following:
1803 * (1) if max_loop is specified, create that many upfront, and this
1804 * also becomes a hard limit.
1805 * (2) if max_loop is not specified, create 8 loop device on module
1806 * load, user can further extend loop device by create dev node
1807 * themselves and have kernel automatically instantiate actual
1811 err = misc_register(&loop_misc);
1817 part_shift = fls(max_part);
1820 * Adjust max_part according to part_shift as it is exported
1821 * to user space so that user can decide correct minor number
1822 * if [s]he want to create more devices.
1824 * Note that -1 is required because partition 0 is reserved
1825 * for the whole disk.
1827 max_part = (1UL << part_shift) - 1;
1830 if ((1UL << part_shift) > DISK_MAX_PARTS)
1833 if (max_loop > 1UL << (MINORBITS - part_shift))
1838 range = max_loop << part_shift;
1841 range = 1UL << MINORBITS;
1844 if (register_blkdev(LOOP_MAJOR, "loop"))
1847 blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
1848 THIS_MODULE, loop_probe, NULL, NULL);
1850 /* pre-create number devices of devices given by config or max_loop */
1851 mutex_lock(&loop_index_mutex);
1852 for (i = 0; i < nr; i++)
1854 mutex_unlock(&loop_index_mutex);
1856 printk(KERN_INFO "loop: module loaded\n");
1860 static int loop_exit_cb(int id, void *ptr, void *data)
1862 struct loop_device *lo = ptr;
1868 static void __exit loop_exit(void)
1870 unsigned long range;
1872 range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
1874 idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
1875 idr_remove_all(&loop_index_idr);
1876 idr_destroy(&loop_index_idr);
1878 blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
1879 unregister_blkdev(LOOP_MAJOR, "loop");
1881 misc_deregister(&loop_misc);
1884 module_init(loop_init);
1885 module_exit(loop_exit);
1888 static int __init max_loop_setup(char *str)
1890 max_loop = simple_strtol(str, NULL, 0);
1894 __setup("max_loop=", max_loop_setup);