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From: Jinchao Wang <wangjinchao600@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Christian Brauner <brauner@kernel.org>,
	Hannes Reinecke <hare@suse.de>,
	Luis Chamberlain <mcgrof@kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	syzbot+4d3cc33ef7a77041efa6@syzkaller.appspotmail.com,
	syzbot+fdba5cca73fee92c69d6@syzkaller.appspotmail.com
Subject: Re: [PATCH] mm/readahead: read min folio constraints under invalidate lock
Date: Tue, 16 Dec 2025 09:37:51 +0800	[thread overview]
Message-ID: <aUC32PJZWFayGO-X@ndev> (raw)
In-Reply-To: <aUAZn1ituYtbCEdd@casper.infradead.org>

On Mon, Dec 15, 2025 at 02:22:23PM +0000, Matthew Wilcox wrote:
> On Mon, Dec 15, 2025 at 10:19:00PM +0800, Jinchao Wang wrote:
> > page_cache_ra_order() and page_cache_ra_unbounded() read mapping minimum folio
> > constraints before taking the invalidate lock, allowing concurrent changes to
> > violate page cache invariants.
> > 
> > Move the lookups under filemap_invalidate_lock_shared() to ensure readahead
> > allocations respect the mapping constraints.
> 
> Why are the mapping folio size constraints being changed?  They're
> supposed to be set at inode instantiation and then never changed.

They can change after instantiation for block devices. In the syzbot repro:
  blkdev_ioctl() -> blkdev_bszset() -> set_blocksize() ->
  mapping_set_folio_min_order()


  reply	other threads:[~2025-12-16  1:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-15 14:19 Jinchao Wang
2025-12-15 14:22 ` Matthew Wilcox
2025-12-16  1:37   ` Jinchao Wang [this message]
2025-12-16  2:42     ` Matthew Wilcox
2025-12-16  3:12       ` Jinchao Wang
2025-12-16  3:53         ` Matthew Wilcox
2025-12-18  4:03           ` Jinchao Wang

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