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Mon, 15 Dec 2025 06:19:45 -0800 (PST) Received: from localhost ([2a12:a304:100::105b]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34abe1ffde5sm9524411a91.1.2025.12.15.06.19.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Dec 2025 06:19:44 -0800 (PST) From: Jinchao Wang To: "Matthew Wilcox (Oracle)" , Andrew Morton , Christian Brauner , Hannes Reinecke , Luis Chamberlain , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Jinchao Wang , syzbot+4d3cc33ef7a77041efa6@syzkaller.appspotmail.com, syzbot+fdba5cca73fee92c69d6@syzkaller.appspotmail.com Subject: [PATCH] mm/readahead: read min folio constraints under invalidate lock Date: Mon, 15 Dec 2025 22:19:00 +0800 Message-ID: <20251215141936.1045907-1-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" page_cache_ra_order() and page_cache_ra_unbounded() read mapping minimum fo= lio 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. Fixes: 47dd67532303 ("block/bdev: lift block size restrictions to 64k") Reported-by: syzbot+4d3cc33ef7a77041efa6@syzkaller.appspotmail.com Reported-by: syzbot+fdba5cca73fee92c69d6@syzkaller.appspotmail.com Signed-off-by: Jinchao Wang --- mm/readahead.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index b415c9969176..74acd6c4f87c 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -214,7 +214,7 @@ void page_cache_ra_unbounded(struct readahead_control *= ractl, unsigned long index =3D readahead_index(ractl); gfp_t gfp_mask =3D readahead_gfp_mask(mapping); unsigned long mark =3D ULONG_MAX, i =3D 0; - unsigned int min_nrpages =3D mapping_min_folio_nrpages(mapping); + unsigned int min_nrpages; =20 /* * Partway through the readahead operation, we will have added @@ -232,6 +232,7 @@ void page_cache_ra_unbounded(struct readahead_control *= ractl, lookahead_size); filemap_invalidate_lock_shared(mapping); index =3D mapping_align_index(mapping, index); + min_nrpages =3D mapping_min_folio_nrpages(mapping); =20 /* * As iterator `i` is aligned to min_nrpages, round_up the @@ -467,7 +468,7 @@ void page_cache_ra_order(struct readahead_control *ract= l, struct address_space *mapping =3D ractl->mapping; pgoff_t start =3D readahead_index(ractl); pgoff_t index =3D start; - unsigned int min_order =3D mapping_min_folio_order(mapping); + unsigned int min_order; pgoff_t limit =3D (i_size_read(mapping->host) - 1) >> PAGE_SHIFT; pgoff_t mark =3D index + ra->size - ra->async_size; unsigned int nofs; @@ -485,13 +486,16 @@ void page_cache_ra_order(struct readahead_control *ra= ctl, =20 new_order =3D min(mapping_max_folio_order(mapping), new_order); new_order =3D min_t(unsigned int, new_order, ilog2(ra->size)); - new_order =3D max(new_order, min_order); =20 ra->order =3D new_order; =20 /* See comment in page_cache_ra_unbounded() */ nofs =3D memalloc_nofs_save(); filemap_invalidate_lock_shared(mapping); + + min_order =3D mapping_min_folio_order(mapping); + new_order =3D max(new_order, min_order); + /* * If the new_order is greater than min_order and index is * already aligned to new_order, then this will be noop as index --=20 2.43.0