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block: loop:use kstatfs.f_bsize of backing file to set discard granularity

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If backing file's filesystem has implemented ->fallocate(), we think the
loop device can support discard, then pass sb->s_blocksize as
discard_granularity. However, some underlying FS, such as overlayfs,
doesn't set sb->s_blocksize, and causes discard_granularity to be set as
zero, then the warning in __blkdev_issue_discard() is triggered.

Christoph suggested to pass kstatfs.f_bsize as discard granularity, and
this way is fine because kstatfs.f_bsize means 'Optimal transfer block
size', which still matches with definition of discard granularity.

So fix the issue by setting discard_granularity as kstatfs.f_bsize if it
is available, otherwise claims discard isn't supported.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Reported-by: Pei Zhang <pezhang@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220126035830.296465-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2022-01-26 11:58:30 +08:00 committed by Jens Axboe
parent a12821d5e0
commit 06582bc86d
1 changed files with 7 additions and 1 deletions
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8
drivers/block/loop.c
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@ -79,6 +79,7 @@
#include <linux/ioprio.h>
#include <linux/blk-cgroup.h>
#include <linux/sched/mm.h>
#include <linux/statfs.h>
#include "loop.h"
@ -774,8 +775,13 @@ static void loop_config_discard(struct loop_device *lo)
granularity = 0;
} else {
struct kstatfs sbuf;
max_discard_sectors = UINT_MAX >> 9;
granularity = inode->i_sb->s_blocksize;
if (!vfs_statfs(&file->f_path, &sbuf))
granularity = sbuf.f_bsize;
else
max_discard_sectors = 0;
}
if (max_discard_sectors) {