[PATCH v4 1/3] statx.2: Document STATX_WRITE_ATOMIC

John Garry
2024-07-17T09:36:51Z

From: Himanshu Madhani <himanshu.madhani@oracle.com>

Add the text to the statx man page.

Signed-off-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
man/man2/statx.2 | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)

diff --git a/man/man2/statx.2 b/man/man2/statx.2
index 3d47319c6..a7cdc0097 100644
--- a/man/man2/statx.2
+++ b/man/man2/statx.2
@@ -70,6 +70,11 @@ struct statx {
__u32 stx_dio_offset_align;
\&
__u64 stx_subvol; /* Subvolume identifier */
+\&
+ /* Direct I/O atomic write limits */
+ __u32 stx_atomic_write_unit_min;
+ __u32 stx_atomic_write_unit_max;
+ __u32 stx_atomic_write_segments_max;
};
.EE
.in
@@ -259,6 +264,9 @@ STATX_DIOALIGN Want stx_dio_mem_align and stx_dio_offset_align
STATX_MNT_ID_UNIQUE Want unique stx_mnt_id (since Linux 6.8)
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.
+ (since Linux 6.11; support varies by filesystem)
.TE
.in
.P
@@ -463,6 +471,22 @@ Subvolumes are fancy directories,
i.e. they form a tree structure that may be walked recursively.
Support varies by filesystem;
it is supported by bcachefs and btrfs since Linux 6.10.
+.TP
+.I stx_atomic_write_unit_min
+.TQ
+.I stx_atomic_write_unit_max
+The minimum and maximum sizes (in bytes) supported for direct I/O
+.RB ( O_DIRECT )
+on the file to be written with torn-write protection.
+These values are each guaranteed to be a power-of-2.
+.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.
+See
+.BR RWF_ATOMIC
+flag for
+.BR pwritev2 (2).
.P
For further information on the above fields, see
.BR inode (7).
@@ -516,6 +540,9 @@ It cannot be written to, and all reads from it will be verified
against a cryptographic hash that covers the
entire file (e.g., via a Merkle tree).
.TP
+.BR STATX_ATTR_WRITE_ATOMIC " (since Linux 6.11)"
+The file supports torn-write protection.
+.TP
.BR STATX_ATTR_DAX " (since Linux 5.8)"
The file is in the DAX (cpu direct access) state.
DAX state attempts to
--
2.31.1