From 5d894321c49e61379189b0ff605f316e39cbd1e9 Mon Sep 17 00:00:00 2001 From: John Garry Date: Wed, 7 May 2025 14:18:21 -0700 Subject: fs: add atomic write unit max opt to statx XFS will be able to support large atomic writes (atomic write > 1x block) in future. This will be achieved by using different operating methods, depending on the size of the write. Specifically a new method of operation based in FS atomic extent remapping will be supported in addition to the current HW offload-based method. The FS method will generally be appreciably slower performing than the HW-offload method. However the FS method will be typically able to contribute to achieving a larger atomic write unit max limit. XFS will support a hybrid mode, where HW offload method will be used when possible, i.e. HW offload is used when the length of the write is supported, and for other times FS-based atomic writes will be used. As such, there is an atomic write length at which the user may experience appreciably slower performance. Advertise this limit in a new statx field, stx_atomic_write_unit_max_opt. When zero, it means that there is no such performance boundary. Masks STATX{_ATTR}_WRITE_ATOMIC can be used to get this new field. This is ok for older kernels which don't support this new field, as they would report 0 in this field (from zeroing in cp_statx()) already. Furthermore those older kernels don't support large atomic writes - apart from block fops, but there would be consistent performance there for atomic writes in range [unit min, unit max]. Reviewed-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Signed-off-by: Darrick J. Wong Acked-by: Darrick J. Wong Signed-off-by: John Garry --- include/linux/stat.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/stat.h') diff --git a/include/linux/stat.h b/include/linux/stat.h index be7496a6a0dd..e3d00e7bb26d 100644 --- a/include/linux/stat.h +++ b/include/linux/stat.h @@ -57,6 +57,7 @@ struct kstat { u32 dio_read_offset_align; u32 atomic_write_unit_min; u32 atomic_write_unit_max; + u32 atomic_write_unit_max_opt; u32 atomic_write_segments_max; }; -- cgit v1.2.3