From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-227.mta1.migadu.com [95.215.58.227]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 701CC53163B for ; Tue, 22 Sep 2026 10:16:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.227 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790072181; cv=none; b=mU7+Cche2F1rfRXjCTE9sSNJd/5S87LDcyU5EFYTxjuo9cZHi6t/MPD9sRtrUNeCQ4/FBp5ravexDxY6ySCvNqLL/UaFgK1zv0Do3Vk/ogQ3dlgU/7VBa+omGUy/nLOY7N52qFqqQefyyXJAbQF8EcgzjgKU/5Q9udgIyrFVPvc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790072181; c=relaxed/simple; bh=5jon+ifDWFP5QwYioELCR5y1JdhGgZVy832hXqPL/DU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VIChxRDUbPORbyoYhpbsystNYygiTbnazsSN+wTXuROPsUnB+QI0Lwpv61/vY+J43KIobwY7m7VkswOSZXqGcZOnImu2StNBzVumCh2mVxwL9jUsLL/ey3xr8WyKIQ9BxC0V16KxJoACStmM9tBwdwSG1+hDXnXvzac+j52pkg8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=bExyxdh5; arc=none smtp.client-ip=95.215.58.227 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="bExyxdh5" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=5jon+ifDWFP5QwYioELCR5y1JdhGgZVy832hXqPL/DU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790072168; v=1; x=1790676968; b=bExyxdh5sDOiZYr1QNADmKoB6kGZkhKROLcRmrFJcy01VhZyyHcR9oVg3/IILTftOWSqVUqU 4sfnqqMGsjMvA9sw7dFGmNnRlOlhHO5jr83EzwXHsYhONhKVmWInKzMoS+4F9h5b3oxkAHZm1Vy dVptl4/7nSPP4KrEFTWwj4lw= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta11.migadu.com with ESMTPS id 2d792f7ed8adce60; Tue, 22 Sep 2026 10:16:07 +0000 X-Mizu-Trace-ID: 2d792f7ed8adce60 X-Migadu-Flow: FLOW_OUT Message-ID: <07aced0d-35d4-4c4f-95e4-9d3168e24617@linux.dev> Date: Tue, 22 Sep 2026 11:16:04 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/8] block: fail a short atomic pin in bio_iov_iter_get_pages() To: Tal Zussman , Jens Axboe , Christoph Hellwig , Johannes Thumshirn , Luis Chamberlain , Hannes Reinecke , "Matthew Wilcox (Oracle)" , Christian Brauner , "Darrick J. Wong" , Keith Busch , "Martin K. Petersen" Cc: Shin'ichiro Kawasaki , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260921-blkdev-fixes-v4-0-e2801f71ede9@columbia.edu> <20260921-blkdev-fixes-v4-5-e2801f71ede9@columbia.edu> Content-Language: en-US From: John Garry In-Reply-To: <20260921-blkdev-fixes-v4-5-e2801f71ede9@columbia.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/22/26 03:54, Tal Zussman wrote: > On a partial page pin, __blkdev_direct_IO_simple() and > __blkdev_direct_IO_async() submit what was pinned with REQ_ATOMIC set > and leave the rest to the buffered fallback, tearing an IOCB_ATOMIC > write. > > This can be triggered deterministically. A 16K pwritev2(RWF_ATOMIC) > whose last page is PROT_NONE, on a scsi_debug device with atomic_wr=1, > completes short with only three of the four pages written, violating > RWF_ATOMIC semantics. > > Make bio_iov_iter_get_pages() release the pins and return -EINVAL when > a REQ_ATOMIC bio doesn't cover the whole iterator, since an atomic > write is submitted as a single bio and a short one would be torn. That > covers iomap as well, where a partially unmapped buffer could trip the > WARN_ON_ONCE() in iomap_dio_bio_iter_one(). The async block device path > currently sets REQ_ATOMIC after pinning, so set it before, and move > REQ_NOWAIT along with it. > > Fixes: caf336f81b3a ("block: Add fops atomic write support") > Reported-by: Sashiko > Link: https://sashiko.dev/#/patchset/20260802-blkdev-fixes-v1-0-a82fc549fd74%40columbia.edu?part=2 > Assisted-by: Claude:claude-fable-5 > Signed-off-by: Tal Zussman > --- > block/bio.c | 29 ++++++++++++++++++++++------- > block/fops.c | 12 ++++++------ > 2 files changed, 28 insertions(+), 13 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index f95b63c0604a..14429a5d4e68 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -1285,6 +1285,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter, > unsigned mem_align_mask, unsigned len_align_mask) > { > iov_iter_extraction_t flags = 0; > + int ret; > > if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED))) > return -EIO; > @@ -1304,34 +1305,48 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter, > flags |= ITER_ALLOW_P2PDMA; > > do { > - ssize_t ret; > + ssize_t size; > > - ret = iov_iter_extract_bvecs(iter, bio->bi_io_vec, > + size = iov_iter_extract_bvecs(iter, bio->bi_io_vec, > BIO_MAX_SIZE - bio->bi_iter.bi_size, > &bio->bi_vcnt, bio->bi_max_vecs, > mem_align_mask, flags); > - if (ret <= 0) { > + if (size <= 0) { > /* > * A misaligned vector fails the whole I/O. Release any > * pages pinned by earlier iterations before returning > * since this bio won't be submitted to release them. > */ > - if (ret == -EINVAL) { > + if (size == -EINVAL) { * > bio_release_pages(bio, false); > bio_clear_flag(bio, BIO_PAGE_PINNED); > bio->bi_vcnt = 0; > } > if (!bio->bi_vcnt) > - return ret; > + return size; > break; > } > - bio->bi_iter.bi_size += ret; > + bio->bi_iter.bi_size += size; > } while (iov_iter_count(iter) && !bio_full(bio, 0)); > > if (is_pci_p2pdma_page(bio->bi_io_vec->bv_page)) > bio->bi_opf |= REQ_NOMERGE; > - return bio_iov_iter_align_down(bio, iter, > + ret = bio_iov_iter_align_down(bio, iter, > &bio->bi_io_vec[bio->bi_vcnt - 1], len_align_mask); > + if (ret) > + return ret; > + > + /* > + * An atomic write is submitted as a single bio, so it has to cover > + * the whole iterator or it would be torn. > + */ > + if ((bio->bi_opf & REQ_ATOMIC) && iov_iter_count(iter)) { > + bio_release_pages(bio, false); > + bio_clear_flag(bio, BIO_PAGE_PINNED); > + bio->bi_vcnt = 0; > + return -EINVAL; There is some commonality here with iov_iter_extract_bvecs() failing, above *. You could add an error out label for both error scenarios. If that does not work: Reviewed-by: John Garry > + } > + return 0; > } > > static struct folio *folio_alloc_greedy(gfp_t gfp, size_t *size, > diff --git a/block/fops.c b/block/fops.c > index a3a709697b40..90777e8a9a6c 100644 > --- a/block/fops.c > +++ b/block/fops.c > @@ -342,6 +342,12 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb, > bio->bi_end_io = blkdev_bio_end_io_async; > bio->bi_ioprio = iocb->ki_ioprio; > > + if (iocb->ki_flags & IOCB_ATOMIC) > + bio->bi_opf |= REQ_ATOMIC; > + > + if (iocb->ki_flags & IOCB_NOWAIT) > + bio->bi_opf |= REQ_NOWAIT; > + > /* > * Users don't rely on the iterator being in any particular > * state for async I/O returning -EIOCBQUEUED, hence we can > @@ -371,12 +377,6 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb, > goto out_bio_put; > } > > - if (iocb->ki_flags & IOCB_ATOMIC) > - bio->bi_opf |= REQ_ATOMIC; > - > - if (iocb->ki_flags & IOCB_NOWAIT) > - bio->bi_opf |= REQ_NOWAIT; > - > if (iocb->ki_flags & IOCB_HIPRI) { > bio->bi_opf |= REQ_POLLED; > submit_bio(bio); >