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loop: Move special partition reread handling in loop_clr_fd()

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The call of __blkdev_reread_part() from loop_reread_partition() happens
only when we need to invalidate partitions from loop_release(). Thus
move a detection for this into loop_clr_fd() and simplify
loop_reread_partition().

This makes loop_reread_partition() safe to use without loop_ctl_mutex
because we use only lo->lo_number and lo->lo_file_name in case of error
for reporting purposes (thus possibly reporting outdate information is
not a big deal) and we are safe from 'lo' going away under us by
elevated lo->lo_refcnt.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jan Kara 2018-11-08 14:01:12 +01:00 committed by Jens Axboe
parent c371077000
commit d57f3374ba
1 changed files with 19 additions and 14 deletions
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33
drivers/block/loop.c
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@ -630,18 +630,7 @@ static void loop_reread_partitions(struct loop_device *lo,
{
int rc;
/*
* bd_mutex has been held already in release path, so don't
* acquire it if this function is called in such case.
*
* If the reread partition isn't from release path, lo_refcnt
* must be at least one and it can only become zero when the
* current holder is released.
*/
if (!atomic_read(&lo->lo_refcnt))
rc = __blkdev_reread_part(bdev);
else
rc = blkdev_reread_part(bdev);
rc = blkdev_reread_part(bdev);
if (rc)
pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
__func__, lo->lo_number, lo->lo_file_name, rc);
@ -1095,8 +1084,24 @@ static int __loop_clr_fd(struct loop_device *lo)
module_put(THIS_MODULE);
blk_mq_unfreeze_queue(lo->lo_queue);
if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
loop_reread_partitions(lo, bdev);
if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev) {
/*
* bd_mutex has been held already in release path, so don't
* acquire it if this function is called in such case.
*
* If the reread partition isn't from release path, lo_refcnt
* must be at least one and it can only become zero when the
* current holder is released.
*/
if (!atomic_read(&lo->lo_refcnt))
err = __blkdev_reread_part(bdev);
else
err = blkdev_reread_part(bdev);
pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
__func__, lo->lo_number, err);
/* Device is gone, no point in returning error */
err = 0;
}
lo->lo_flags = 0;
if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;