[PATCH v9 01/15] fs: add atomic write unit max opt to statx
From: John Garry <john.g.garry@oracle.com>
Date: 2025-04-25 16:45:47
Also in:
linux-block, linux-ext4, linux-fsdevel, linux-xfs, lkml
Subsystem:
block layer, ext4 file system, filesystems (vfs and infrastructure), the rest, xfs filesystem · Maintainers:
Jens Axboe, "Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds, Carlos Maiolino
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].
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
block/bdev.c | 3 ++-
fs/ext4/inode.c | 2 +-
fs/stat.c | 6 +++++-
fs/xfs/xfs_iops.c | 2 +-
include/linux/fs.h | 3 ++-
include/linux/stat.h | 1 +
include/uapi/linux/stat.h | 8 ++++++--
7 files changed, 18 insertions(+), 7 deletions(-)
diff --git a/block/bdev.c b/block/bdev.c
index 4844d1e27b6f..b4afc1763e8e 100644
--- a/block/bdev.c
+++ b/block/bdev.c@@ -1301,7 +1301,8 @@ void bdev_statx(struct path *path, struct kstat *stat, generic_fill_statx_atomic_writes(stat, queue_atomic_write_unit_min_bytes(bd_queue), - queue_atomic_write_unit_max_bytes(bd_queue)); + queue_atomic_write_unit_max_bytes(bd_queue), + 0); } stat->blksize = bdev_io_min(bdev);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 94c7d2d828a6..cdf01e60fa6d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c@@ -5692,7 +5692,7 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path, awu_max = sbi->s_awu_max; } - generic_fill_statx_atomic_writes(stat, awu_min, awu_max); + generic_fill_statx_atomic_writes(stat, awu_min, awu_max, 0); } flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
diff --git a/fs/stat.c b/fs/stat.c
index f13308bfdc98..c41855f62d22 100644
--- a/fs/stat.c
+++ b/fs/stat.c@@ -136,13 +136,15 @@ EXPORT_SYMBOL(generic_fill_statx_attr); * @stat: Where to fill in the attribute flags * @unit_min: Minimum supported atomic write length in bytes * @unit_max: Maximum supported atomic write length in bytes + * @unit_max_opt: Optimised maximum supported atomic write length in bytes * * Fill in the STATX{_ATTR}_WRITE_ATOMIC flags in the kstat structure from * atomic write unit_min and unit_max values. */ void generic_fill_statx_atomic_writes(struct kstat *stat, unsigned int unit_min, - unsigned int unit_max) + unsigned int unit_max, + unsigned int unit_max_opt) { /* Confirm that the request type is known */ stat->result_mask |= STATX_WRITE_ATOMIC;
@@ -153,6 +155,7 @@ void generic_fill_statx_atomic_writes(struct kstat *stat, if (unit_min) { stat->atomic_write_unit_min = unit_min; stat->atomic_write_unit_max = unit_max; + stat->atomic_write_unit_max_opt = unit_max_opt; /* Initially only allow 1x segment */ stat->atomic_write_segments_max = 1;
@@ -732,6 +735,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min; tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max; tmp.stx_atomic_write_segments_max = stat->atomic_write_segments_max; + tmp.stx_atomic_write_unit_max_opt = stat->atomic_write_unit_max_opt; return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0; }
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 756bd3ca8e00..f0e5d83195df 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c@@ -610,7 +610,7 @@ xfs_report_atomic_write( if (xfs_inode_can_atomicwrite(ip)) unit_min = unit_max = ip->i_mount->m_sb.sb_blocksize; - generic_fill_statx_atomic_writes(stat, unit_min, unit_max); + generic_fill_statx_atomic_writes(stat, unit_min, unit_max, 0); } STATIC int
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 016b0fe1536e..7b19d8f99aff 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h@@ -3475,7 +3475,8 @@ void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *); void generic_fill_statx_attr(struct inode *inode, struct kstat *stat); void generic_fill_statx_atomic_writes(struct kstat *stat, unsigned int unit_min, - unsigned int unit_max); + unsigned int unit_max, + unsigned int unit_max_opt); extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int); extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int); void __inode_add_bytes(struct inode *inode, loff_t bytes);
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; };
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index f78ee3670dd5..1686861aae20 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h@@ -182,8 +182,12 @@ struct statx { /* File offset alignment for direct I/O reads */ __u32 stx_dio_read_offset_align; - /* 0xb8 */ - __u64 __spare3[9]; /* Spare space for future expansion */ + /* Optimised max atomic write unit in bytes */ + __u32 stx_atomic_write_unit_max_opt; + __u32 __spare2[1]; + + /* 0xc0 */ + __u64 __spare3[8]; /* Spare space for future expansion */ /* 0x100 */ };
--
2.31.1