From 06582bc86d7f48d35cd044098ca1e246e8c7c52e Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Wed, 26 Jan 2022 11:58:30 +0800
Subject: [PATCH] block: loop:use kstatfs.f_bsize of backing file to set
discard granularity
Git-commit: 06582bc86d7f48d35cd044098ca1e246e8c7c52e
Patch-mainline: v5.17-rc5
References: git-fixes
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: Coly Li <colyli@suse.de>
---
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 150012ffb387..19fe19eaa50e 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) {
--
2.35.3