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[128.59.178.194]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5359b77d0eesm22234701cf.19.2026.10.09.09.50.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Oct 2026 09:50:23 -0700 (PDT) From: Tal Zussman Date: Fri, 09 Oct 2026 12:50:13 -0400 Subject: [PATCH v6 5/9] block: fail a short atomic pin in bio_iov_iter_get_pages() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261009-blkdev-fixes-v6-5-307939c387df@columbia.edu> References: <20261009-blkdev-fixes-v6-0-307939c387df@columbia.edu> In-Reply-To: <20261009-blkdev-fixes-v6-0-307939c387df@columbia.edu> To: Jens Axboe , Christoph Hellwig , Johannes Thumshirn , Luis Chamberlain , Hannes Reinecke , "Matthew Wilcox (Oracle)" , John Garry , Christian Brauner , "Darrick J. Wong" , Keith Busch , "Martin K. Petersen" Cc: Shin'ichiro Kawasaki , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Sashiko , Tal Zussman X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1791564615; l=4676; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=62IvAR081mGZwsnDCAfyOZAPUixZpTd3Wqytk+0ksZM=; b=Kow1iVWHAoTwb/DLM6HMqJjy+KZuv3Eq3m1wKfJUWyY/zkbwnQK6Ih2vZn9PJtc220b/UX/7t XKaXj92QdqTB5YQvGXM/1PyqYhzKE+Hh9olIf2fTs95pE3fiks/6c1g X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Authority-Analysis: v=2.4 cv=eaGo7LEH c=1 sm=1 tr=0 ts=6ac91b51 cx=c_pps a=EVbN6Ke/fEF3bsl7X48z0g==:117 a=u0MKzLA9JmpizDwXU9Rxjg==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=x7bEGLp0ZPQA:10 a=A0y_DWxS2BwA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=BpGzv1V74M3SfeTrGa8v:22 a=c92rfblmAAAA:8 a=VwQbUJbxAAAA:8 a=DOn4q0-T8uZzdi3JsfgA:9 a=QEXdDO2ut3YA:10 a=a_PwQJl-kcHnX1M80qC6:22 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-ORIG-GUID: _92Xm_BhdLDBZdERUMudM_MfrJNL2TLJ X-Proofpoint-GUID: _92Xm_BhdLDBZdERUMudM_MfrJNL2TLJ X-Proofpoint-Spam-Info: AW1haW4tMjYxMDA5MDA2NyBTYWx0ZWRfXyXdgEz3B3Cfy x4aOoOUFBSXcZxd7EG+jTmeceUrbGGV1ao9XmQAtey3g2r/qFXXGSuJKMnJVGH0ZG2IlQAsrKXv 9JydBQQXk7sVVPngta11wk5CU/X7VoNNYJ0Ht4K3udA2mTC8i4lN X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDA5MDA2NyBTYWx0ZWRfX6K1ryPAoVxVW Jt7HxChRLSZZzIvE8Yovolzq0EJOq41485Mkn0EiaDOJPAf86b3hcNwmjmOyWbvDwXU/qvL24Oj MNVB+H37hv6S+1UJoGWHqgjeFsIk0hTAzfuqcxtuoYk0lKJekVv6RayjaDQesdOX+1fMNtj+98r nrhIR0ecBiJL/wtBDPqxvR2+Hx2CMlfTl34MZyNv0FrSbRlhrLV9gjSvM9/7lE0RkJa1oRoG1hL Mkv/Dk85dSii+jTDqBnHEJnbY+QnnrbJX3JwOE6pDY7/6bK/vccJUw6U8U4EoFSlc/DuwqI3fLd QjZAGApfm7bG7UvpfovvAsFQX9tl/Ns/PReKv91XHh48A8TAmtneN0CDaTlq5l2E2IASV2FNQSE GeAS55P1nZRWmC53V05O7+biurps1wH0jZOXFue95nenhKzZWjZQ3XM2BlNskQfpz9+iJz98mce 85wvXI6kAbkADlxyaLw== X-Proofpoint-Virus-Version: vendor=nai engine=6900 definitions=11930 signatures=596817 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 priorityscore=1501 impostorscore=10 lowpriorityscore=10 malwarescore=0 phishscore=0 bulkscore=10 adultscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610020000 definitions=main-2610090067 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 Reviewed-by: John Garry Reviewed-by: Hannes Reinecke Signed-off-by: Tal Zussman --- block/bio.c | 46 ++++++++++++++++++++++++++++++---------------- block/fops.c | 12 ++++++------ 2 files changed, 36 insertions(+), 22 deletions(-) diff --git a/block/bio.c b/block/bio.c index 57ee335899f3..c89a0d5d6e61 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 +1305,47 @@ 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) { - /* - * 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) { - bio_release_pages(bio, false); - bio_clear_flag(bio, BIO_PAGE_PINNED); - bio->bi_vcnt = 0; - } + if (size <= 0) { + /* A misaligned vector fails the whole I/O */ + if (size == -EINVAL) + goto out_release_pages; 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)) + goto out_release_pages; + return 0; + +out_release_pages: + /* + * Release the pages pinned so far before failing, since this bio won't + * be submitted to release them. + */ + bio_release_pages(bio, false); + bio_clear_flag(bio, BIO_PAGE_PINNED); + bio->bi_vcnt = 0; + return -EINVAL; } static struct folio *folio_alloc_greedy(gfp_t gfp, size_t *size, diff --git a/block/fops.c b/block/fops.c index 2022c7cb2ee3..1ac3fa285090 100644 --- a/block/fops.c +++ b/block/fops.c @@ -357,6 +357,12 @@ 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 @@ -386,12 +392,6 @@ 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); -- 2.39.5