linux.git/drivers/block/loop.c, branch v5.2-rc2

block: loop: mark bvec as ITER_BVEC_FLAG_NO_REF

2019-04-01T18:11:48+00:00

loop is one block device, for any bio submitted to this device,
the upper layer does guarantee that pages added to loop's bio won't
go away when the bio is in-flight.

So mark loop's bvec as ITER_BVEC_FLAG_NO_REF then get_page/put_page
can be saved for serving loop's IO.

Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe

loop: properly observe rotational flag of underlying device

2019-04-01T14:15:40+00:00

The loop driver always declares the rotational flag of its device as
rotational, even when the device of the mapped file is nonrotational,
as is the case with SSDs or on tmpfs. This can confuse filesystem tools
which are SSD-aware; in my case I frequently forget to tell mkfs.btrfs
that my loop device on tmpfs is nonrotational, and that I really don't
need any automatic metadata redundancy.

The attached patch fixes this by introspecting the rotational flag of the
mapped file's underlying block device, if it exists. If the mapped file's
filesystem has no associated block device - as is the case on e.g. tmpfs -
we assume nonrotational storage. If there is a better way to identify such
non-devices I'd love to hear them.

Cc: Jens Axboe 
Cc: linux-block@vger.kernel.org
Cc: holger@applied-asynchrony.com
Signed-off-by: Holger Hoffstätte 
Signed-off-by: Gwendal Grignou 
Signed-off-by: Benjamin Gordon 
Reviewed-by: Guenter Roeck 
Signed-off-by: Jens Axboe

loop: access lo_backing_file only when the loop device is Lo_bound

2019-03-18T14:20:53+00:00

Commit 758a58d0bc67 ("loop: set GENHD_FL_NO_PART_SCAN after
blkdev_reread_part()") separates "lo->lo_backing_file = NULL" and
"lo->lo_state = Lo_unbound" into different critical regions protected by
loop_ctl_mutex.

However, there is below race that the NULL lo->lo_backing_file would be
accessed when the backend of a loop is another loop device, e.g., loop0's
backend is a file, while loop1's backend is loop0.

loop0's backend is file            loop1's backend is loop0

__loop_clr_fd()
  mutex_lock(&loop_ctl_mutex);
  lo->lo_backing_file = NULL; --> set to NULL
  mutex_unlock(&loop_ctl_mutex);
                                   loop_set_fd()
                                     mutex_lock_killable(&loop_ctl_mutex);
                                     loop_validate_file()
                                       f = l->lo_backing_file; --> NULL
                                         access if loop0 is not Lo_unbound
  mutex_lock(&loop_ctl_mutex);
  lo->lo_state = Lo_unbound;
  mutex_unlock(&loop_ctl_mutex);

lo->lo_backing_file should be accessed only when the loop device is
Lo_bound.

In fact, the problem has been introduced already in commit 7ccd0791d985
("loop: Push loop_ctl_mutex down into loop_clr_fd()") after which
loop_validate_file() could see devices in Lo_rundown state with which it
did not count. It was harmless at that point but still.

Fixes: 7ccd0791d985 ("loop: Push loop_ctl_mutex down into loop_clr_fd()")
Reported-by: syzbot+9bdc1adc1c55e7fe765b@syzkaller.appspotmail.com
Signed-off-by: Dongli Zhang 
Reviewed-by: Jan Kara 
Signed-off-by: Jens Axboe

loop: set GENHD_FL_NO_PART_SCAN after blkdev_reread_part()

2019-02-22T22:51:22+00:00

Commit 0da03cab87e6
("loop: Fix deadlock when calling blkdev_reread_part()") moves
blkdev_reread_part() out of the loop_ctl_mutex. However,
GENHD_FL_NO_PART_SCAN is set before __blkdev_reread_part(). As a result,
__blkdev_reread_part() will fail the check of GENHD_FL_NO_PART_SCAN and
will not rescan the loop device to delete all partitions.

Below are steps to reproduce the issue:

step1 # dd if=/dev/zero of=tmp.raw bs=1M count=100
step2 # losetup -P /dev/loop0 tmp.raw
step3 # parted /dev/loop0 mklabel gpt
step4 # parted -a none -s /dev/loop0 mkpart primary 64s 1
step5 # losetup -d /dev/loop0

Step5 will not be able to delete /dev/loop0p1 (introduced by step4) and
there is below kernel warning message:

[  464.414043] __loop_clr_fd: partition scan of loop0 failed (rc=-22)

This patch sets GENHD_FL_NO_PART_SCAN after blkdev_reread_part().

Fixes: 0da03cab87e6 ("loop: Fix deadlock when calling blkdev_reread_part()")
Signed-off-by: Dongli Zhang 
Reviewed-by: Jan Kara 
Signed-off-by: Jens Axboe

loop: do not print warn message if partition scan is successful

2019-02-22T22:51:21+00:00

Do not print warn message when the partition scan returns 0.

Fixes: d57f3374ba48 ("loop: Move special partition reread handling in loop_clr_fd()")
Signed-off-by: Dongli Zhang 
Reviewed-by: Jan Kara 
Signed-off-by: Jens Axboe

block: kill BLK_MQ_F_SG_MERGE

2019-02-15T15:40:12+00:00

QUEUE_FLAG_NO_SG_MERGE has been killed, so kill BLK_MQ_F_SG_MERGE too.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Omar Sandoval 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe

block: loop: pass multi-page bvec to iov_iter

2019-02-15T15:40:11+00:00

iov_iter is implemented on bvec itererator helpers, so it is safe to pass
multi-page bvec to it, and this way is much more efficient than passing one
page in each bvec.

Reviewed-by: Christoph Hellwig 
Reviewed-by: Omar Sandoval 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe

loop: drop caches if offset or block_size are changed

2019-01-10T03:51:44+00:00

If we don't drop caches used in old offset or block_size, we can get old data
from new offset/block_size, which gives unexpected data to user.

For example, Martijn found a loopback bug in the below scenario.
1) LOOP_SET_FD loads first two pages on loop file
2) LOOP_SET_STATUS64 changes the offset on the loop file
3) mount is failed due to the cached pages having wrong superblock

Cc: Jens Axboe 
Cc: linux-block@vger.kernel.org
Reported-by: Martijn Coenen 
Reviewed-by: Bart Van Assche 
Signed-off-by: Jaegeuk Kim 
Signed-off-by: Jens Axboe

block: loop: remove redundant code

2018-12-22T21:45:31+00:00

Code cleanup for removing redundant break in switch case.

Signed-off-by: Chengguang Xu 
Signed-off-by: Jens Axboe

block: loop: check error using IS_ERR instead of IS_ERR_OR_NULL in loop_add()

2018-12-16T16:01:38+00:00

blk_mq_init_queue() will not return NULL pointer to its caller,
so it's better to replace IS_ERR_OR_NULL using IS_ERR in loop_add().

If in the future things change to check NULL pointer inside loop_add(),
we should return -ENOMEM as return code instead of PTR_ERR(NULL).

Signed-off-by: Chengguang Xu 
Signed-off-by: Jens Axboe