[LTP] [PATCH v3] syscalls/statx13: Add basic test for STATX_WRITE_ATOMIC on regular file
Gaurav Pathak
gpathak@suse.de
Fri Sep 18 13:12:08 CEST 2026
From: Gaurav Pathak <gaurav.pathak@suse.com>
This patch adds a new test to validate these atomic write limit fields.
The test ensures the filesystem correctly advertises the STATX_ATTR_WRITE_ATOMIC
attribute when queried on a file opened with O_DIRECT. It also verifies that the
reported optimized maximum is logically consistent by falling within the
absolute minimum and maximum boundaries. Furthermore, it checks that all
reported atomic write unit sizes are valid powers of two, adhering to the strict
requirements of the kernel block layer.
If the underlying storage hardware or filesystem lacks atomic write
support, the test gracefully skips with TCONF.
Closes: #1224
Signed-off-by: Gaurav Pathak <gaurav.pathak@suse.com>
---
configure.ac | 4 +-
include/lapi/stat.h | 17 ++-
runtest/syscalls | 1 +
testcases/kernel/syscalls/statx/.gitignore | 1 +
testcases/kernel/syscalls/statx/statx13.c | 139 +++++++++++++++++++++
5 files changed, 160 insertions(+), 2 deletions(-)
create mode 100644 testcases/kernel/syscalls/statx/statx13.c
diff --git a/configure.ac b/configure.ac
index 18bfdb88c..d5a609fa7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -181,7 +181,9 @@ AC_CHECK_MEMBERS([struct iocb.aio_rw_flags],,,[#include <linux/aio_abi.h>])
AC_CHECK_MEMBERS([struct fanotify_event_info_fid.fsid.__val],,,[#include <sys/fanotify.h>])
AC_CHECK_MEMBERS([struct perf_event_mmap_page.aux_head],,,[#include <linux/perf_event.h>])
AC_CHECK_MEMBERS([struct sigaction.sa_sigaction],[],[],[#include <signal.h>])
-AC_CHECK_MEMBERS([struct statx.stx_mnt_id, struct statx.stx_dio_mem_align],,,[
+AC_CHECK_MEMBERS([struct statx.stx_mnt_id, struct statx.stx_dio_mem_align, struct statx.stx_atomic_write_unit_max_opt,
+ struct statx.stx_atomic_write_unit_min, struct statx.stx_atomic_write_unit_max,
+ struct statx.stx_atomic_write_segments_max],,,[
#define _GNU_SOURCE
#include <sys/stat.h>
])
diff --git a/include/lapi/stat.h b/include/lapi/stat.h
index 17b62ea98..859e410ab 100644
--- a/include/lapi/stat.h
+++ b/include/lapi/stat.h
@@ -93,7 +93,14 @@ struct statx_timestamp {
uint64_t stx_mnt_id; \
uint32_t stx_dio_mem_align; \
uint32_t stx_dio_offset_align; \
- uint64_t __spare3[12]; \
+ uint64_t stx_subvol; \
+ uint32_t stx_atomic_write_unit_min; \
+ uint32_t stx_atomic_write_unit_max; \
+ uint32_t stx_atomic_write_segments_max; \
+ uint32_t stx_dio_read_offset_align; \
+ uint32_t stx_atomic_write_unit_max_opt; \
+ uint32_t __spare2[1]; \
+ uint64_t __spare3[8]; \
};
LTP_DEFINE_STATX_STRUCT(statx_fallback);
@@ -197,6 +204,10 @@ static inline int statx(int dirfd, const char *pathname, unsigned int flags,
# define STATX_DIOALIGN 0x00002000U
#endif
+#ifndef STATX_WRITE_ATOMIC
+#define STATX_WRITE_ATOMIC 0x00010000U
+#endif
+
#ifndef STATX__RESERVED
# define STATX__RESERVED 0x80000000U
#endif
@@ -248,6 +259,10 @@ static inline int statx(int dirfd, const char *pathname, unsigned int flags,
# define STATX_MNT_ID_UNIQUE 0x00004000U
#endif
+#ifndef STATX_ATTR_WRITE_ATOMIC
+#define STATX_ATTR_WRITE_ATOMIC 0x00400000
+#endif
+
#define SAFE_FCHMODAT2(dfd, filename, mode, flags) \
safe_fchmodat2(__FILE__, __LINE__, (dfd), (filename), (mode), (flags))
diff --git a/runtest/syscalls b/runtest/syscalls
index d953f0558..b8c7fbb0f 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1926,6 +1926,7 @@ statx09 statx09
statx10 statx10
statx11 statx11
statx12 statx12
+statx13 statx13
membarrier01 membarrier01
diff --git a/testcases/kernel/syscalls/statx/.gitignore b/testcases/kernel/syscalls/statx/.gitignore
index f6a423eed..e601a46a3 100644
--- a/testcases/kernel/syscalls/statx/.gitignore
+++ b/testcases/kernel/syscalls/statx/.gitignore
@@ -10,3 +10,4 @@
/statx10
/statx11
/statx12
+/statx13
diff --git a/testcases/kernel/syscalls/statx/statx13.c b/testcases/kernel/syscalls/statx/statx13.c
new file mode 100644
index 000000000..cc445fa57
--- /dev/null
+++ b/testcases/kernel/syscalls/statx/statx13.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 SUSE LLC <gaurav.pathak@suse.com>
+ */
+
+/*\
+ * This test validates the STATX_WRITE_ATOMIC feature (introduced in Linux 6.13).
+ * It ensures that supported filesystems (xfs and nfs) correctly report their
+ * atomic write limits to user space when queried via statx().
+ *
+ * The test performs the following validations:
+ *
+ * - Creates a test file using O_DIRECT (a prerequisite for atomic writes).
+ * - Calls statx() with the STATX_WRITE_ATOMIC mask to retrieve the limits.
+ * - Verifies that stx_atomic_write_unit_min, stx_atomic_write_unit_max, and
+ * stx_atomic_write_unit_max_opt are logically consistent (e.g., max_opt is
+ * within the min and max bounds).
+ * - Ensures all reported atomic write unit sizes are valid powers of two.
+ */
+
+#define _GNU_SOURCE
+#include "tst_test.h"
+#include "lapi/stat.h"
+
+#define MNTPOINT "mnt_point"
+#define TESTFILE MNTPOINT "/testfile"
+#define MODE 0644
+
+#define WRITE_SIZE 4096
+#define ALIGNMENT 4096
+
+static int file_fd = -1;
+
+static void verify_statx(void)
+{
+ struct ltp_statx buff;
+
+ TST_EXP_PASS_SILENT(SAFE_STATX(AT_FDCWD, TESTFILE, 0, STATX_BASIC_STATS | STATX_WRITE_ATOMIC, &buff));
+
+ if (!TST_PASS)
+ return;
+
+ if (!(buff.data.stx_attributes & STATX_ATTR_WRITE_ATOMIC))
+ tst_brk(TCONF, "Filesystem does not support STATX_WRITE_ATOMIC");
+
+#if HAVE_STRUCT_STATX_STX_ATOMIC_WRITE_UNIT_MIN
+ if (buff.data.stx_atomic_write_unit_min <= buff.data.stx_atomic_write_unit_max)
+ tst_res(TPASS, "stx_atomic_write_unit_min(%u) <= stx_atomic_write_unit_max(%u)",
+ buff.data.stx_atomic_write_unit_min, buff.data.stx_atomic_write_unit_max);
+ else
+ tst_res(TFAIL, "stx_atomic_write_unit_min(%u) > stx_atomic_write_unit_max(%u)",
+ buff.data.stx_atomic_write_unit_min, buff.data.stx_atomic_write_unit_max);
+
+ if (buff.data.stx_atomic_write_unit_min > 0 &&
+ __builtin_popcount(buff.data.stx_atomic_write_unit_min) == 1)
+ tst_res(TPASS, "stx_atomic_write_unit_min(%u) is power of 2",
+ buff.data.stx_atomic_write_unit_min);
+ else
+ tst_res(TFAIL, "stx_atomic_write_unit_min(%u) is not a power of 2",
+ buff.data.stx_atomic_write_unit_min);
+
+ if (buff.data.stx_atomic_write_unit_max > 0 &&
+ __builtin_popcount(buff.data.stx_atomic_write_unit_max) == 1)
+ tst_res(TPASS, "stx_atomic_write_unit_max(%u) is power of 2",
+ buff.data.stx_atomic_write_unit_max);
+ else
+ tst_res(TFAIL, "stx_atomic_write_unit_max(%u) is not a power of 2",
+ buff.data.stx_atomic_write_unit_max);
+#else
+ tst_res(TCONF, "stx_atomic_write_unit_max or stx_atomic_write_unit_min is not defined in struct statx");
+#endif
+
+#if HAVE_STRUCT_STATX_STX_ATOMIC_WRITE_UNIT_MAX_OPT
+ if (buff.data.stx_atomic_write_unit_max_opt == 0) {
+ tst_res(TPASS, "stx_atomic_write_unit_max_opt is 0 (no optimized max reported)");
+ } else {
+ if (buff.data.stx_atomic_write_unit_max_opt > buff.data.stx_atomic_write_unit_max)
+ tst_res(TFAIL, "stx_atomic_write_unit_max_opt (%u) exceeds max (%u)",
+ buff.data.stx_atomic_write_unit_max_opt,
+ buff.data.stx_atomic_write_unit_max);
+
+ else if (buff.data.stx_atomic_write_unit_max_opt < buff.data.stx_atomic_write_unit_min)
+ tst_res(TFAIL, "stx_atomic_write_unit_max_opt (%u) is less than min (%u)",
+ buff.data.stx_atomic_write_unit_max_opt,
+ buff.data.stx_atomic_write_unit_min);
+ else
+ tst_res(TPASS, "stx_atomic_write_unit_max_opt (%u) is within valid range [%u, %u]",
+ buff.data.stx_atomic_write_unit_max_opt,
+ buff.data.stx_atomic_write_unit_min,
+ buff.data.stx_atomic_write_unit_max);
+
+ if (__builtin_popcount(buff.data.stx_atomic_write_unit_max_opt) != 1)
+ tst_res(TFAIL, "stx_atomic_write_unit_max_opt (%u) is not a power of 2",
+ buff.data.stx_atomic_write_unit_max_opt);
+ }
+#else
+ tst_res(TCONF, "stx_atomic_write_unit_max_opt is not defined in struct statx");
+#endif
+}
+
+static void setup(void)
+{
+ char *data_buff = SAFE_MEMALIGN(ALIGNMENT, WRITE_SIZE);
+
+ umask(0);
+ memset(data_buff, '@', WRITE_SIZE);
+
+ file_fd = SAFE_OPEN(TESTFILE, O_RDWR | O_CREAT | O_DIRECT, MODE);
+ SAFE_WRITE(SAFE_WRITE_ALL, file_fd, data_buff, WRITE_SIZE);
+
+ free(data_buff);
+}
+
+static void cleanup(void)
+{
+ if (file_fd != -1)
+ SAFE_CLOSE(file_fd);
+}
+
+static struct tst_test test = {
+ .test_all = verify_statx,
+ .setup = setup,
+ .cleanup = cleanup,
+ .min_kver = "6.11",
+ .needs_root = 1,
+ .mntpoint = MNTPOINT,
+ .mount_device = 1,
+ .filesystems = (struct tst_fs[]) {
+ {
+ .type = "xfs",
+ .mkfs_opts = (const char *const []){"-f", "-bsize=16K", NULL},
+ },
+ {
+ .type = "ext4",
+ .mkfs_opts = (const char *const []){"-O", "bigalloc", "-b", "4096", "-C", "65536", NULL},
+ },
+ {}
+ },
+};
--
2.51.0
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