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@xxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Reported-by: Pei Zhang <pezhang@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
V3:
- following Christoph's suggestion to not claim discard support if
vfs_statfs() fails
V2:
- take Christoph's suggestion to use kstatfs.f_bsize
drivers/block/loop.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b1b05c45c07c..8b56eeb7e144 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -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) {
--
2.31.1
