fs: add STATX_DIO_READ_ALIGN

Add a separate dio read align field, as many out of place write
file systems can easily do reads aligned to the device sector size,
but require bigger alignment for writes.

This is usually papered over by falling back to buffered I/O for smaller
writes and doing read-modify-write cycles, but performance for this
sucks, so applications benefit from knowing the actual write alignment.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250109083109.1441561-3-hch@lst.de
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/stat.h b/include/linux/stat.h
index 3d900c86981c..9d8382e23a9c 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -52,6 +52,7 @@ struct kstat {
 	u64		mnt_id;
 	u32		dio_mem_align;
 	u32		dio_offset_align;
+	u32		dio_read_offset_align;
 	u64		change_cookie;
 	u64		subvol;
 	u32		atomic_write_unit_min;