On Thu, Mar 25, 2021 at 07:33:39PM +0530, Chandan Babu R wrote:
> With dax enabled filesystems, a direct write operation into an existing
> unwritten extent results in xfs_iomap_write_direct() zero-ing and converting
> the extent into a normal extent before the actual data is copied from the
> userspace buffer.
>
> The inode extent count can increase by 2 if the extent range being written to
> maps to the middle of the existing unwritten extent range. Hence this commit
> uses XFS_IEXT_WRITE_UNWRITTEN_CNT as the extent count delta when such a write
> operation is being performed.
>
> Fixes: 727e1acd297c ("xfs: Check for extent overflow when trivally adding a new extent")
> Reported-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> Signed-off-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
Pretty much what I was expecting,
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_iomap.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index e17ab7f42928..8b27c10a3d08 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -198,6 +198,7 @@ xfs_iomap_write_direct(
> bool force = false;
> int error;
> int bmapi_flags = XFS_BMAPI_PREALLOC;
> + int nr_exts = XFS_IEXT_ADD_NOSPLIT_CNT;
>
> ASSERT(count_fsb > 0);
>
> @@ -232,6 +233,7 @@ xfs_iomap_write_direct(
> bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
> if (imap->br_state == XFS_EXT_UNWRITTEN) {
> force = true;
> + nr_exts = XFS_IEXT_WRITE_UNWRITTEN_CNT;
> dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
> }
> }
> @@ -241,8 +243,7 @@ xfs_iomap_write_direct(
> if (error)
> return error;
>
> - error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
> - XFS_IEXT_ADD_NOSPLIT_CNT);
> + error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, nr_exts);
> if (error)
> goto out_trans_cancel;
>
> --
> 2.29.2
>
