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

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Message-ID: <bcccb7452b6683c235452b810c964950acbb0e08.camel@HansenPartnership.com>
Date: Thu, 03 Apr 2025 15:32:45 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Matthew Wilcox <willy@...radead.org>, Matt Fleming
 <matt@...dmodwrite.com>
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 Thu, 2025-04-03 at 18:12 +0100, Matthew Wilcox wrote:
[...]
> Ideas still on the table:
> 
>  - Convert all filesystems to use the XFS inode management scheme.
>    Nobody is thrilled by this large amount of work.
>  - Find a simpler version of the XFS scheme to implement for other
>    filesystems.

What's wrong with a simpler fix: if we're in PF_MEMALLOC when we try to
run inode.c:evict(), send it through a workqueue?  It will require some
preallocation (say using a superblock based work entry ... or simply
reuse the destroy_work)  but it should be doable.  The analysis says
that evicting from reclaim is very rare because it's a deletion race,
so it shouldn't matter that it's firing once per inode with this
condition.

Regards,

James