Re: [LTP] syscalls/statx13: Add basic test for STATX_WRITE_ATOMIC on regular file

[linuxtestproject.agent@gmail.com]

Hi Gaurav,

On 13 Oct 2026, Gaurav Pathak wrote:
> syscalls/statx13: Add basic test for STATX_WRITE_ATOMIC on regular file

> +	struct ltp_statx buff;
> +
> +	TST_EXP_PASS(statx(AT_FDCWD, TESTFILE, 0, STATX_BASIC_STATS | STATX_WRITE_ATOMIC, &buff.buff),
> +			"statx(AT_FDCWD, %s, 0, STATX_BASIC_STATS | STATX_WRITE_ATOMIC, &buf)", TESTFILE);

TST_EXP_PASS reports failure but does not return, so a statx() error leaves
the following checks reading uninitialized output. Return immediately when
!TST_PASS before accessing buff. Allocate this syscall buffer through .bufs
rather than on the stack.

> +	.min_kver = "6.11",
> ...
> +			.type = "xfs",
> +			.mkfs_opts = (const char *const []){"-f", "-bsize=16K", NULL},

Linux 6.11 rejects XFS blocks larger than PAGE_SIZE, so this configuration
fails to mount on a 4 KiB-page system admitted by min_kver. The framework
reports TBROK before setup or feature detection, also preventing the ext4
case from running. Use a portable block size or separately gate this
large-block configuration.

> +	if (!(buff.data.stx_attributes & STATX_ATTR_WRITE_ATOMIC))
> +		tst_brk(TCONF, "STATX_WRITE_ATOMIC unsupported by block dev or filesystem: STATX_ATTR_WRITE_ATOMIC missing from stx_attributes");

A response with nonzero atomic limits but a missing support attribute is
inconsistent, not simply unsupported. This branch hides that regression as
TCONF despite the stated goal of validating the attribute. Check
attribute/limit consistency first and reserve TCONF for unsupported results
with zero limits.

> +	uint32_t	stx_atomic_write_segments_max; \

verify_statx() never checks this returned limit. A response advertising
atomic writes with segments_max = 0 passes every assertion, although it
cannot describe a nonempty atomic write. Require
stx_atomic_write_segments_max > 0 when support is advertised.

> +	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);

Use TST_EXP_EXPR for this comparison and the repeated power-of-two
assertions instead of manual TPASS/TFAIL branches.

> + * It ensures that supported filesystems (xfs and nfs) correctly report their
> + * atomic write limits to user space when queried via statx().

The filesystem list tests XFS and ext4, not NFS. Describe the actual
regular-file checks using :manpage:`statx(2)` and document that root is
required to format and mount the test filesystems.

Verdict - Needs revision

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