From: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
To: Tal Zussman <tz2294@columbia.edu>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
Johannes Thumshirn <johannes.thumshirn@wdc.com>,
Luis Chamberlain <mcgrof@kernel.org>,
Hannes Reinecke <hare@kernel.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
John Garry <john.g.garry@oracle.com>,
Christian Brauner <brauner@kernel.org>,
"Darrick J. Wong" <djwong@kernel.org>,
Keith Busch <kbusch@kernel.org>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/7] block: take i_rwsem for the splice read path
Date: Fri, 18 Sep 2026 11:57:22 +0900 [thread overview]
Message-ID: <aqyoQe3ZU9LPpULU@shinmob> (raw)
In-Reply-To: <20260909-blkdev-fixes-v3-3-1a5222c6e8ad@columbia.edu>
On Sep 09, 2026 / 17:59, Tal Zussman wrote:
> def_blk_fops wires ->splice_read directly to filemap_splice_read(),
> which allocates folios based on mapping_min_folio_order() without any
> lock against set_blocksize(). A splice from a block device can race
> set_blocksize() raising the minimum folio order and insert a folio that
> is too small for the mapping. blkdev_read_iter() wraps filemap_read()
> in inode_lock_shared() for this reason, but the splice path was missed.
>
> Splicing from a block device while toggling the block size between 512
> bytes and 64K with BLKBSZSET hits this within seconds on a
> CONFIG_DEBUG_VM kernel:
>
> page dumped because: VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping))
> kernel BUG at mm/filemap.c:858!
> Oops: invalid opcode: 0000 [#1] SMP NOPTI
> RIP: 0010:__filemap_add_folio+0x51c/0x570
> Call Trace:
> filemap_add_folio+0x64/0x140
> page_cache_ra_order+0x1dd/0x3d0
> filemap_get_pages+0x153/0x760
> filemap_splice_read+0x13f/0x300
> splice_file_to_pipe+0xc0/0xd0
> do_splice+0x6a8/0x890
> __do_splice+0xb0/0x210
> __x64_sys_splice+0x80/0x100
> do_syscall_64+0x10e/0x520
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Take inode_lock_shared() around filemap_splice_read(), like the read
> path does.
>
> Fixes: 3c20917120ce ("block/bdev: enable large folio support for large logical block sizes")
> Assisted-by: Claude:claude-fable-5
> Reviewed-by: Hannes Reinecke <hare@kernel.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Tal Zussman <tz2294@columbia.edu>
I confirmed that this patch avoid the hang triggered by the corresponding
blktests test case [*].
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
[*] https://lore.kernel.org/linux-block/20260909-blkdev-fixes-tests-v1-2-1f8af8665d16@columbia.edu/
next prev parent reply other threads:[~2026-09-18 2:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-09 21:59 [PATCH v3 0/7] block device fixes for large block sizes, IOCB_NOWAIT, and direct I/O Tal Zussman
2026-09-09 21:59 ` [PATCH v3 1/7] block: use iomap_dirty_folio for block devices Tal Zussman
2026-09-09 21:59 ` [PATCH v3 2/7] block: take i_rwsem for the direct I/O write fallback Tal Zussman
2026-09-18 2:55 ` Shin'ichiro Kawasaki
2026-09-09 21:59 ` [PATCH v3 3/7] block: take i_rwsem for the splice read path Tal Zussman
2026-09-18 2:57 ` Shin'ichiro Kawasaki [this message]
2026-09-18 7:25 ` Christoph Hellwig
2026-09-09 21:59 ` [PATCH v3 4/7] block: honor IOCB_NOWAIT in the block device buffered " Tal Zussman
2026-09-09 22:05 ` [PATCH v3 7/7] block: remove dead metadata handling from the async direct I/O path Tal Zussman
2026-09-10 10:40 ` Hannes Reinecke
2026-09-13 20:12 ` Tal Zussman
2026-09-09 22:05 ` [PATCH v3 5/7] block: fail atomic writes instead of falling back to buffered I/O Tal Zussman
2026-09-10 6:40 ` John Garry
2026-09-13 20:48 ` Tal Zussman
2026-09-09 22:05 ` [PATCH v3 6/7] block: unpin all pages of a bvec in bio_iov_iter_align_down() Tal Zussman
2026-09-18 3:26 ` Shin'ichiro Kawasaki
2026-09-18 8:43 ` Christoph Hellwig
2026-09-19 5:13 ` Tal Zussman
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