Re: [PATCH 1/7] mm: shmem: correctly pass alloced parameter to shmem_recalc_inode() to avoid WARN_ON()

[Baolin Wang]

On 2025/6/6 06:10, Kemeng Shi wrote:
> As noted in the comments, we need to release block usage for swap entry
> which was replaced with poisoned swap entry. However, no block usage is
> actually freed by calling shmem_recalc_inode(inode, -nr_pages, -nr_pages).
> Instead, call shmem_recalc_inode(inode, 0, -nr_pages) can correctly release
> the block usage.
>
> Fixes: 6cec2b95dadf7 ("mm/shmem: fix infinite loop when swap in shmem error at swapoff time")
> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
> ---
>   mm/shmem.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 4b42419ce6b2..e27d19867e03 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2145,7 +2145,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
>   	 * won't be 0 when inode is released and thus trigger WARN_ON(i_blocks)
>   	 * in shmem_evict_inode().
>   	 */
> -	shmem_recalc_inode(inode, -nr_pages, -nr_pages);
> +	shmem_recalc_inode(inode, 0, -nr_pages);
>   	swap_free_nr(swap, nr_pages);
>   }

Have you tested your patch? When I inject an error to test your patch, 
the following issue will be triggered:

[  127.173330] ------------[ cut here ]------------
[  127.173331] WARNING: CPU: 13 PID: 6860 at mm/shmem.c:1388 
shmem_evict_inode+0xf0/0x348
[  127.173920] CPU: 13 UID: 0 PID: 6860 Comm: shmem_swapin_er Kdump: 
loaded Tainted: G            E       6.15.0-rc6+ #54 VOLUNTARY
[  127.173925] pstate: 63401005 (nZCv daif +PAN -UAO +TCO +DIT +SSBS 
BTYPE=--)
[  127.173927] pc : shmem_evict_inode+0xf0/0x348
[  127.173929] lr : shmem_evict_inode+0x68/0x348
[  127.173931] sp : ffff8000895639e0
[  127.173932] x29: ffff8000895639e0 x28: 0000000000000006 x27: 
ffff00013754bfc0
[  127.173935] x26: ffff800080d8f160 x25: 0000000000000006 x24: 
ffff0000c0aab440
[  127.173937] x23: ffff00013754b780 x22: ffff00013754b780 x21: 
ffff0000cbc9c6b0
[  127.173940] x20: ffff0000c0aab440 x19: ffff0000cbc9c700 x18: 
0000000000000030
[  127.173942] x17: 0000ffffa1f4cfff x16: 0000000000000003 x15: 
0000000000001000
[  127.173945] x14: 00000000ffffffff x13: 0000000000000004 x12: 
ffff800089563108
[  127.173947] x11: 0000000000000000 x10: 0000000000000002 x9 : 
ffff800080352080
[  127.173949] x8 : fffffffffffffffe x7 : ffff800089563700 x6 : 
0000000000000001
[  127.173952] x5 : 0000000000000004 x4 : 0000000000000002 x3 : 
0000000000000002
[  127.173954] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 
ffffffffffffff80
[  127.173957] Call trace:
[  127.173958]  shmem_evict_inode+0xf0/0x348 (P)
[  127.173961]  evict+0x1c8/0x2c8
[  127.173964]  iput_final+0x84/0x1a0
[  127.173966]  iput.part.0+0xd0/0xf0
[  127.173968]  iput+0x20/0x38
[  127.173971]  dentry_unlink_inode+0xc0/0x158
[  127.173973]  __dentry_kill+0x80/0x248
[  127.173974]  dput+0xf0/0x240
[  127.173976]  __fput+0x120/0x2f0
[  127.173978]  ____fput+0x18/0x28
[  127.173980]  task_work_run+0x88/0x120
[  127.173983]  do_exit+0x198/0x3c0
[  127.173986]  do_group_exit+0x38/0xa0
[  127.173987]  get_signal+0x6ac/0x6b8
[  127.173990]  do_signal+0x100/0x208
[  127.173991]  do_notify_resume+0xc8/0x158
[  127.173994]  el0_da+0xbc/0xc0
[  127.173997]  el0t_64_sync_handler+0x70/0xc8
[  127.173999]  el0t_64_sync+0x154/0x158
[  127.174001] ---[ end trace 0000000000000000 ]---