Re: [LTP] [PATCH] fanotify10: Calling drop_cache twice to ensure the inode is evicted

[Petr Vorel <pvorel@suse.cz>]

Hi all,

> In this test case, some scenarios are designed to verify whether the
> FANOTIFY_EVICTABLE flag takes effect: by verifying that information cannot
> be obtained from the corresponding inode after drop_cache, as this flag
> does not ping the inode.

> However, drop_cache is only performed once here, which may result in the
> inode not being released in NUMA scenarios. Suppose the inode is located
> on NUMA0 and the dentry is located on NUMA1; the first drop_cache can only
> ensure that the inode is added to the LRU list, but does not guarantee that
> evict() can been called because dispose_list does not yet include this
> inode when traversing NUMA0, which causes the testcase execution fail.

I wonder if there can be some detection that inode is evicted.
Or, can it happen that even 2x drop is not enough?

> For the single-file scenario in this testcase, executing drop_cache twice
> is necessary to ensure the inode is evicted, thus allowing the testcase to
> pass.

Acked-by: Petr Vorel <pvorel@suse.cz>

@Amir, Jan, could you please have a look?

Kind regards,
Petr

> Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
> ---
>  testcases/kernel/syscalls/fanotify/fanotify10.c | 2 ++
>  1 file changed, 2 insertions(+)

> diff --git a/testcases/kernel/syscalls/fanotify/fanotify10.c b/testcases/kernel/syscalls/fanotify/fanotify10.c
> index c6d8ec922..42018de0d 100644
> --- a/testcases/kernel/syscalls/fanotify/fanotify10.c
> +++ b/testcases/kernel/syscalls/fanotify/fanotify10.c
> @@ -515,6 +515,8 @@ static void drop_caches(void)
>  	if (syncfs(fd_syncfs) < 0)
>  		tst_brk(TBROK | TERRNO, "Unexpected error when syncing filesystem");

> +	/* Need to drop twice to ensure the inode is evicted. */
> +	SAFE_FILE_PRINTF(DROP_CACHES_FILE, "3");
>  	SAFE_FILE_PRINTF(DROP_CACHES_FILE, "3");
>  }

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