Hi Greg,
On Fri, Apr 06, 2018 at 09:12:17AM +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.9-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
The attached patch should now apply to v4.9-stable tree.
--
Regards
Sudip
>From 898c00a307fb80cf2b18a5c84dd3c6ee61f037af Mon Sep 17 00:00:00 2001
From: Liu Bo <bo.li.liu@xxxxxxxxxx>
Date: Wed, 31 Jan 2018 17:09:13 -0700
Subject: [PATCH] Btrfs: fix unexpected cow in run_delalloc_nocow
commit 5811375325420052fcadd944792a416a43072b7f upstream
Fstests generic/475 provides a way to fail metadata reads while
checking if checksum exists for the inode inside run_delalloc_nocow(),
and csum_exist_in_range() interprets error (-EIO) as inode having
checksum and makes its caller enter the cow path.
In case of free space inode, this ends up with a warning in
cow_file_range().
The same problem applies to btrfs_cross_ref_exist() since it may also
read metadata in between.
With this, run_delalloc_nocow() bails out when errors occur at the two
places.
cc: <stable@xxxxxxxxxxxxxxx> v2.6.28+
Fixes: 17d217fe970d ("Btrfs: fix nodatasum handling in balancing code")
Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
---
fs/btrfs/inode.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f073de65e818..e67c7da54604 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1230,6 +1230,8 @@ static noinline int csum_exist_in_range(struct btrfs_root *root,
list_del(&sums->list);
kfree(sums);
}
+ if (ret < 0)
+ return ret;
return 1;
}
@@ -1381,10 +1383,23 @@ static noinline int run_delalloc_nocow(struct inode *inode,
goto out_check;
if (btrfs_extent_readonly(root, disk_bytenr))
goto out_check;
- if (btrfs_cross_ref_exist(trans, root, ino,
+ ret = btrfs_cross_ref_exist(trans, root, ino,
found_key.offset -
- extent_offset, disk_bytenr))
+ extent_offset, disk_bytenr);
+ if (ret) {
+ /*
+ * ret could be -EIO if the above fails to read
+ * metadata.
+ */
+ if (ret < 0) {
+ if (cow_start != (u64)-1)
+ cur_offset = cow_start;
+ goto error;
+ }
+
+ WARN_ON_ONCE(nolock);
goto out_check;
+ }
disk_bytenr += extent_offset;
disk_bytenr += cur_offset - found_key.offset;
num_bytes = min(end + 1, extent_end) - cur_offset;
@@ -1402,8 +1417,20 @@ static noinline int run_delalloc_nocow(struct inode *inode,
* this ensure that csum for a given extent are
* either valid or do not exist.
*/
- if (csum_exist_in_range(root, disk_bytenr, num_bytes))
+ ret = csum_exist_in_range(root, disk_bytenr, num_bytes);
+ if (ret) {
+ /*
+ * ret could be -EIO if the above fails to read
+ * metadata.
+ */
+ if (ret < 0) {
+ if (cow_start != (u64)-1)
+ cur_offset = cow_start;
+ goto error;
+ }
+ WARN_ON_ONCE(nolock);
goto out_check;
+ }
if (!btrfs_inc_nocow_writers(root->fs_info,
disk_bytenr))
goto out_check;
--
2.11.0
