xfs: do not allocate the entire delalloc extent in xfs_bmapi_write

Source kernel commit: 21255afdd7296f57dd65f815301426bcf911c82d

While trying to convert the entire delalloc extent is a good decision
for regular writeback as it leads to larger contigous on-disk extents,
but for other callers of xfs_bmapi_write is is rather questionable as
it forced them to loop creating new transactions just in case there
is no large enough contiguous extent to cover the whole delalloc
reservation.

Change xfs_bmapi_write to only allocate the passed in range instead,
whіle the writeback path through xfs_bmapi_convert_delalloc and
xfs_bmapi_allocate still always converts the full extents.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index 9af65a182791ff0a213ca988d40f035a5388d64b..e6d70013895b7bb9910e6a58fb0cc5be91a716d5 100644 (file)
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -4518,8 +4518,9 @@ xfs_bmapi_write(
                        bma.length = XFS_FILBLKS_MIN(len, XFS_MAX_BMBT_EXTLEN);
 
                        if (wasdelay) {
-                               bma.offset = bma.got.br_startoff;
-                               bma.length = bma.got.br_blockcount;
+                               bma.length = XFS_FILBLKS_MIN(bma.length,
+                                       bma.got.br_blockcount -
+                                       (bno - bma.got.br_startoff));
                        } else {
                                if (!eof)
                                        bma.length = XFS_FILBLKS_MIN(bma.length,