linux-ext4 - Re: Potential Linux Crash: WARNING in ext4_dirty

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Message-ID: <CAENh_SSbkoa3srjkAMmJuf-iTFxHOtwESHoXiPAu6bO7MLOkDA@mail.gmail.com>
Date: Thu, 3 Apr 2025 13:29:44 +0100
From: Matt Fleming <matt@...dmodwrite.com>
To: willy@...radead.org
Cc: adilger.kernel@...ger.ca, akpm@...ux-foundation.org, 
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, luka.2016.cs@...il.com, 
	tytso@....edu, Barry Song <baohua@...nel.org>, kernel-team@...udflare.com, 
	Vlastimil Babka <vbabka@...e.cz>, Miklos Szeredi <miklos@...redi.hu>, Amir Goldstein <amir73il@...il.com>, 
	Dave Chinner <david@...morbit.com>, Qi Zheng <zhengqi.arch@...edance.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>
Subject: Re: Potential Linux Crash: WARNING in ext4_dirty_folio in Linux
 kernel v6.13-rc5

On Wed, Mar 26, 2025 at 10:59 AM Matt Fleming <matt@...dmodwrite.com> wrote:
>
> Hi there,
>
> I'm also seeing this PF_MEMALLOC WARN triggered from kswapd in 6.12.19.
>
> Does overlayfs need some kind of background inode reclaim support?

Hey everyone, I know there was some off-list discussion last week at
LSFMM, but I don't think a definite solution has been proposed for the
below stacktrace.

What is the shrinker API policy wrt memory allocation and I/O? Should
overlayfs do something more like XFS and background reclaim to avoid
GFP_NOFAIL
allocations when kswapd is shrinking caches?

>   Call Trace:
>    <TASK>
>    __alloc_pages_noprof+0x31c/0x330
>    alloc_pages_mpol_noprof+0xe3/0x1d0
>    folio_alloc_noprof+0x5b/0xa0
>    __filemap_get_folio+0x1f3/0x380
>    __getblk_slow+0xa3/0x1e0
>    __ext4_get_inode_loc+0x121/0x4b0
>    ext4_get_inode_loc+0x40/0xa0
>    ext4_reserve_inode_write+0x39/0xc0
>    __ext4_mark_inode_dirty+0x5b/0x220
>    ext4_evict_inode+0x26d/0x690
>    evict+0x112/0x2a0
>    __dentry_kill+0x71/0x180
>    dput+0xeb/0x1b0
>    ovl_stack_put+0x2e/0x50 [overlay]
>    ovl_destroy_inode+0x3a/0x60 [overlay]
>    destroy_inode+0x3b/0x70
>    __dentry_kill+0x71/0x180
>    shrink_dentry_list+0x6b/0xe0
>    prune_dcache_sb+0x56/0x80
>    super_cache_scan+0x12c/0x1e0
>    do_shrink_slab+0x13b/0x350
>    shrink_slab+0x278/0x3a0
>    shrink_node+0x328/0x880
>    balance_pgdat+0x36d/0x740
>    kswapd+0x1f0/0x380
>    kthread+0xd2/0x100
>    ret_from_fork+0x34/0x50
>    ret_from_fork_asm+0x1a/0x30
>    </TASK>