Re: [LTP] hugetlb/hugeshmat: Add hugeshmat06 migrated from libhugetlbfs shm-perms

[linuxtestproject.agent@gmail.com]

Hi Samir,

On Aug 20, 2026, Samir Mulani wrote:
> hugetlb/hugeshmat: Add hugeshmat06 migrated from libhugetlbfs shm-perms

> 			hugetlb_after = get_proc_hugetlb_kb(getpid());
> 			if (hugetlb_after != 0) {
> 				tst_res(TFAIL,
> 					"Child %d: HugetlbPages after detach is %ld kB (expected 0), reservation accounting leak",

Could this use an oracle tied to reservation state instead? In Linux 7.2,
HugetlbPages reports mm->hugetlb_usage, which is incremented when a huge
page is mapped and decremented when it is unmapped. The original regression
leaked hstate->resv_huge_pages, so HugetlbPages can return to zero after
shmdt() while that reservation remains leaked.

The original test exposed this by making enough read-only attachments to
exhaust the pool. Here, an eventual shmat() failure would also be handled by
SAFE_SHMAT() as TBROK rather than reported as a failure of the operation
under test. Could the original reservation-leak oracle be retained and the
regression reported as TFAIL?

> #define SEGMENT_KEY	(0x82ba15ff)
> 	shmid = SAFE_SHMGET(SEGMENT_KEY, segment_size,
> 			    IPC_CREAT | SHM_HUGETLB | 0640);

Could this segment use IPC_PRIVATE? IPC_CREAT without IPC_EXCL returns an
accessible pre-existing segment for this key when it is large enough.
setup() would then overwrite that segment, and cleanup() would remove
another process's IPC object with IPC_RMID.

> /*\
>  * [Description]

Could the deprecated [Description] header be dropped?

> static struct tst_test test = {
> 	.needs_root	 = 1,

Could the high-level description explain why root is required, namely that
the framework modifies the system huge-page pool to reserve pages?

> +/hugetlb/hugeshmat/hugeshmat06

Could this entry be placed in
testcases/kernel/mem/hugetlb/hugeshmat/.gitignore instead? New test binaries
belong in the .gitignore in their own directory.

Verdict - Needs revision

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