From: Ming Lei ming.lei@redhat.com
[ Upstream commit 06582bc86d7f48d35cd044098ca1e246e8c7c52e ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c00ae30fde89e..92f9d32bfae5e 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"
@@ -939,8 +940,13 @@ 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) {