On 24/02/2025 20:37, Darrick J. Wong wrote:
On Thu, Feb 13, 2025 at 01:56:19PM +0000, John Garry wrote:
When issuing an atomic write by the CoW method, give the block allocator a
hint to naturally align the data blocks.
This means that we have a better chance to issuing the atomic write via
HW offload next time.
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_bmap.c | 7 ++++++-
fs/xfs/libxfs/xfs_bmap.h | 6 +++++-
fs/xfs/xfs_reflink.c | 8 ++++++--
3 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 0ef19f1469ec..9bfdfb7cdcae 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3454,6 +3454,12 @@ 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);
+
+ if (align > 1 && ap->flags & XFS_BMAPI_EXTSZALIGN)
+ args->alignment = align;
+ else
+ args->alignment = 1;
+
if (align) {
if (xfs_bmap_extsize_align(mp, &ap->got, &ap->prev, align, 0,
ap->eof, 0, ap->conv, &ap->offset,
@@ -3782,7 +3788,6 @@ xfs_bmap_btalloc(
.wasdel = ap->wasdel,
.resv = XFS_AG_RESV_NONE,
.datatype = ap->datatype,
- .alignment = 1,
.minalignslop = 0,
};
xfs_fileoff_t orig_offset;
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index 4b721d935994..7a31697331dc 100644
--- 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 naturally align allocations to extsz hint */
+#define XFS_BMAPI_EXTSZALIGN (1u << 11)
IMO "naturally" makes things confusing here -- are we aligning to the
extent size hint, or are we aligning to the length requested? Or
whatever it is that "naturally" means.
We align to extsz hint, not length.
As for use of word "naturally", I'll try to avoid using that word.
(FWIW you and I have bumped over this repeatedly, so maybe this is
simple one of those cognitive friction things where block storage always
deals with powers of two and "naturally" means a lot, vs. filesystems
where we don't usually enforce alignment anywhere.)
I suggest "Try to align allocations to the extent size hint" for the
comment, and with that:
that's fine
Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
cheers,
John
