From: Jan Kara <jack@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>, Jan Kara <jack@suse.com>,
tytso@mit.edu, Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/3] quota: Prevent memory allocation recursion while holding dq_lock
Date: Mon, 6 Jun 2022 15:08:09 +0200 [thread overview]
Message-ID: <20220606130809.6mton73yzxekjwtv@quack3.lan> (raw)
In-Reply-To: <Yp32IsyQFJXRAOtt@casper.infradead.org>
On Mon 06-06-22 13:42:10, Matthew Wilcox wrote:
> On Mon, Jun 06, 2022 at 10:03:34AM +0200, Jan Kara wrote:
> > On Sun 05-06-22 15:38:13, Matthew Wilcox (Oracle) wrote:
> > > As described in commit 02117b8ae9c0 ("f2fs: Set GF_NOFS in
> > > read_cache_page_gfp while doing f2fs_quota_read"), we must not enter
> > > filesystem reclaim while holding the dq_lock. Prevent this more generally
> > > by using memalloc_nofs_save() while holding the lock.
> > >
> > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> >
> > This is definitely a good cleanup to have and seems mostly unrelated to the
> > rest. I'll take it rightaway into my tree. Thanks for the patch!
>
> Thanks! It's really a pre-requisite for the second patch; I haven't
> seen anywhere in the current codebase that will have a problem. All
> the buffer_heads are allocated with GFP_NOFS | __GFP_NOFAIL (in
> grow_dev_page()).
Yes, I understand. But as f2fs case shows, there can be fs-local
allocations that may be impacted. And it is good to have it documented in
the code that dq_lock is not reclaim safe to avoid bugs like f2fs had in
the future.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2022-06-06 13:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-05 14:38 [PATCH 0/3] Cache quota files in the page cache Matthew Wilcox (Oracle)
2022-06-05 14:38 ` [PATCH 1/3] quota: Prevent memory allocation recursion while holding dq_lock Matthew Wilcox (Oracle)
2022-06-06 8:03 ` Jan Kara
2022-06-06 12:42 ` Matthew Wilcox
2022-06-06 13:08 ` Jan Kara [this message]
2022-06-05 14:38 ` [PATCH 2/3] quota: Support using the page cache for quota files Matthew Wilcox (Oracle)
2022-06-06 2:53 ` kernel test robot
2022-06-06 4:05 ` kernel test robot
2022-06-06 4:36 ` kernel test robot
2022-06-05 14:38 ` [PATCH 3/3] ext4: Use generic_quota_read() Matthew Wilcox (Oracle)
2022-06-06 8:38 ` Jan Kara
2022-06-08 1:42 ` Matthew Wilcox
2022-06-08 14:21 ` Jan Kara
2022-06-13 7:59 ` [ext4] fa96490369: WARNING:at_fs/ext4/inode.c:#ext4_invalidate_folio kernel test robot
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