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From: Matthew Wilcox <willy@infradead.org>
To: Pradeep P V K <ppvk@codeaurora.org>
Cc: miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
	stummala@codeaurora.org, sayalil@codeaurora.org
Subject: Re: [PATCH V1] fuse: Remove __GFP_FS flag to avoid allocator recursing
Date: Mon, 14 Sep 2020 15:07:33 +0100	[thread overview]
Message-ID: <20200914140733.GP6583@casper.infradead.org> (raw)
In-Reply-To: <1600091775-10639-1-git-send-email-ppvk@codeaurora.org>

On Mon, Sep 14, 2020 at 07:26:15PM +0530, Pradeep P V K wrote:
> Process#1(kswapd) held an inode lock and initaited a writeback to free
> the pages, as the inode superblock is fuse, process#2 forms a fuse
> request. Process#3 (Fuse daemon threads) while serving process#2 request,
> it requires memory(pages) and as the system is already running in low
> memory it ends up in calling try_to_ free_pages(), which might now call
> kswapd again, which is already stuck with an inode lock held. Thus forms
> a deadlock.
> 
> So, remove __GFP_FS flag to avoid allocator recursing into the
> filesystem that might already held locks.

This is the wrong way to fix the problem.  The fuse daemon threads should
have called memalloc_nofs_save() as this prevents them from inadvertently
tripping over other places where they forgot to use GFP_NOFS (or have
no way to pass a GFP_NOFS flags argument).


  reply	other threads:[~2020-09-14 14:08 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 13:56 [PATCH V1] fuse: Remove __GFP_FS flag to avoid allocator recursing Pradeep P V K
2020-09-14 14:07 ` Matthew Wilcox [this message]
2020-09-15 14:34   ` ppvk

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