xfs: allow block allocator to take an alignment hint

Add a BMAPI flag to provide a hint to the block allocator to align extents
according to the extszhint.

This will be useful for atomic writes to ensure that we are not being
allocated extents which are not suitable (for atomic writes).

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 63255820b58ac868f3deb9d0dfeb6ae1032f9591..d954f9b8071f4b8e28e8083d71bcf403da7d2c61 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3312,6 +3312,11 @@ xfs_bmap_compute_alignments(
                align = xfs_get_cowextsz_hint(ap->ip);
        else if (ap->datatype & XFS_ALLOC_USERDATA)
                align = xfs_get_extsz_hint(ap->ip);
+
+       /* Try to align start block to any minimum allocation alignment */
+       if (align > 1 && (ap->flags & XFS_BMAPI_EXTSZALIGN))
+               args->alignment = align;
+
        if (align) {
                if (xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, align, 0,
                                        ap->eof, 0, ap->conv, &ap->offset,

diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index b4d9c6e0f3f9b6dc23172901201e951ef905ee73..d5f2729305fada794f94c2c86766572f167e0dd4 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -87,6 +87,9 @@ struct xfs_bmalloca {
 /* Do not update the rmap btree.  Used for reconstructing bmbt from rmapbt. */
 #define XFS_BMAPI_NORMAP       (1u << 10)
 
+/* Try to align allocations to the extent size hint */
+#define XFS_BMAPI_EXTSZALIGN   (1u << 11)
+
 #define XFS_BMAPI_FLAGS \
        { XFS_BMAPI_ENTIRE,     "ENTIRE" }, \
        { XFS_BMAPI_METADATA,   "METADATA" }, \
@@ -98,7 +101,8 @@ struct xfs_bmalloca {
        { XFS_BMAPI_REMAP,      "REMAP" }, \
        { XFS_BMAPI_COWFORK,    "COWFORK" }, \
        { XFS_BMAPI_NODISCARD,  "NODISCARD" }, \
-       { XFS_BMAPI_NORMAP,     "NORMAP" }
+       { XFS_BMAPI_NORMAP,     "NORMAP" },\
+       { XFS_BMAPI_EXTSZALIGN, "EXTSZALIGN" }
 
 
 static inline int xfs_bmapi_aflag(int w)