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| author | John Garry <john.g.garry@oracle.com> | 2025-06-19 15:44:55 +0000 |
|---|---|---|
| committer | Alejandro Colomar <alx@kernel.org> | 2025-06-28 16:51:41 +0200 |
| commit | 684b9001d0cd0367daad5d7a7c9e3b7c040e0250 (patch) | |
| tree | 128fde87d752ca255d6f8e743a16af97ae0b519b | |
| parent | 2fc4bf025adba6cb7dbc0beb3ebc2a4df48854ae (diff) | |
| download | man-pages-684b9001d0cd0367daad5d7a7c9e3b7c040e0250.tar.gz | |
man/man2/statx.2: Add stx_atomic_write_unit_max_opt
XFS supports atomic writes - or untorn writes - based on two different
methods:
- HW offload in the disk
- FS method based on out-of-place writes
The value reported in stx_atomic_write_unit_max will be the max size of the
FS-based method.
The max atomic write unit size of the FS-based atomic writes will
typically be much larger than what is capable from the HW offload. However,
FS-based atomic writes will also be typically much slower.
Advertise this HW offload size limit to the user in a new statx member,
stx_atomic_write_unit_max_opt.
We want STATX_WRITE_ATOMIC to get this new member in addition to the
already-existing members, so mention that a value of 0 in
stx_atomic_write_unit_max_opt means that stx_atomic_write_unit_max holds
this optimised limit.
Linux will zero unused statx members, so stx_atomic_write_unit_max_opt
will always hold 0 for older kernel versions which do not support
this FS-based atomic write method (for XFS).
Signed-off-by: John Garry <john.g.garry@oracle.com>
Message-ID: <20250619154455.321848-3-john.g.garry@oracle.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
| -rw-r--r-- | man/man2/statx.2 | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/man/man2/statx.2 b/man/man2/statx.2 index 273d80711a..07ac60b3c5 100644 --- a/man/man2/statx.2 +++ b/man/man2/statx.2 @@ -74,6 +74,9 @@ struct statx { \& /* File offset alignment for direct I/O reads */ __u32 stx_dio_read_offset_align; +\& + /* Direct I/O atomic write max opt limit */ + __u32 stx_atomic_write_unit_max_opt; }; .EE .in @@ -266,7 +269,8 @@ STATX_SUBVOL Want stx_subvol (since Linux 6.10; support varies by filesystem) STATX_WRITE_ATOMIC Want stx_atomic_write_unit_min, stx_atomic_write_unit_max, - and stx_atomic_write_segments_max. + stx_atomic_write_segments_max, + and stx_atomic_write_unit_max_opt. (since Linux 6.11; support varies by filesystem) STATX_DIO_READ_ALIGN Want stx_dio_read_offset_align. (since Linux 6.14; support varies by filesystem) @@ -514,6 +518,21 @@ is supported on block devices since Linux 6.11. The support on regular files varies by filesystem; it is supported by xfs and ext4 since Linux 6.13. .TP +.I stx_atomic_write_unit_max_opt +The maximum size (in bytes) which is +optimised for writes issued with torn-write protection. +If non-zero, +this value will not exceed the value in +.I stx_atomic_write_unit_max +and will not be less than the value in +.IR stx_atomic_write_unit_min . +A value of zero indicates that +.I stx_atomic_write_unit_max +is the optimised limit. +Slower writes may be experienced when the size of the write exceeds +.I stx_atomic_write_unit_max_opt +(when non-zero). +.TP .I stx_atomic_write_segments_max The maximum number of elements in an array of vectors for a write with torn-write protection enabled. |