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Petersen" Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Sashiko , Tal Zussman X-Mailer: b4 0.17-dev-db0b7 X-Developer-Signature: v=1; a=ed25519-sha256; t=1788991197; l=1869; i=tz2294@columbia.edu; s=20250528; h=from:subject:message-id; bh=omRobIYeubqYt1ShRwO+xJfwqyahvimqDH0UuCrRjvM=; b=9Nl/nBXz4hvk3iMfr00Au+HApKUeQvDeZ6iBBKqO9QJ17SeC8ILbrAXylK0i39U56AAhdqk1p C3uCDh4Mov0C6ijIxOEQBV2lv/lFui4DUz9SbYFWmHNXQ1PAMkEJOfC X-Developer-Key: i=tz2294@columbia.edu; a=ed25519; pk=BIj5KdACscEOyAC0oIkeZqLB3L94fzBnDccEooxeM5Y= X-Authority-Analysis: v=2.4 cv=S/9MU4sP c=1 sm=1 tr=0 ts=6aa1d735 cx=c_pps a=50t2pK5VMbmlHzFWWp8p/g==:117 a=fJxgZNdXt3opHMdyAp+FXA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=x7bEGLp0ZPQA:10 a=A0y_DWxS2BwA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Da8U98TiO7q1upZEImrf:22 a=JR4YdQiviy7OQf72WyZ1:22 a=c92rfblmAAAA:8 a=VwQbUJbxAAAA:8 a=s8mzj7eOnaliLhoSWqYA:9 a=QEXdDO2ut3YA:10 a=IoWCM6iH3mJn3m4BftBB:22 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-GUID: imf63zSO2aPX3amoCYb6OwuL24qwpVlx X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA5MDI0NyBTYWx0ZWRfX+mNBKnMVliOH UoNUdgC04jQLSA8jwDm615F9AASm2ucTEQJ+rc8N9SHRHwadCaot3YVIhXnGdYWdO+9jerkImO/ IVcmSwRXKIRHReMOta+CmNn8/k8ihnnV5ZCMdsSuhXv8sdro8qikPcjBQtn4JA8qQIrtyM8JVFe B3A8dPp81p4g7TSH8LfmSmz+BaiCT13pftnL0ZzMPDo9Gy0IamxZ0nVERaH90zoKuvPIeDtdEpC /icv18tGicCSJ6qN6Xb+VwFFw3xYHHYLeIkw07y49EOmcresOlq63NEC7xGnUC5NV85RdwY2cXU qNzlD0u9Y35cjCEU/RwI1aF3xz4lLMjP/XGeT5+IOnI/zCyFtLXvw0SMCGS+GIt/KxrzPRHhyfO DobJ2jzSY+FyrzWzQvWGx2AN6KbgusxX2HbOsnECwIbVWBYSOL7s/qzGDPy9TT9DPxXH5S6zm/F h0q3MjgPhuARmSBrN0g== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA5MDI0NyBTYWx0ZWRfX3vxWvCj/UJbk pMFjDq+lLP3vp7VY2lFAvCgf3fXvgK8/Sq9r8f7BLTpUvtGtR7LMA66nHoEh1nlMxj5rXcU6cSl vYpprDgHlHgb7U6rnnCHvP/7eoutn92Vr6QMwlqw6dFECToma8ph X-Proofpoint-ORIG-GUID: imf63zSO2aPX3amoCYb6OwuL24qwpVlx X-Proofpoint-Virus-Version: vendor=nai engine=6900 definitions=11900 signatures=596817 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 lowpriorityscore=10 bulkscore=10 spamscore=0 phishscore=0 adultscore=0 clxscore=1015 impostorscore=10 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609090247 blkdev_read_iter() takes inode_lock_shared() unconditionally around filemap_read(). Unlike blkdev_write_iter(), it does not reject IOCB_NOWAIT for buffered I/O, so a non-blocking read, or the buffered tail of a short IOCB_NOWAIT direct read, blocks behind set_blocksize() holding i_rwsem across sync_blockdev(). A preadv2(RWF_NOWAIT) issued while another thread changes the block size with a dirty page cache blocks for as long as sync_blockdev() takes, 4 to 6 seconds on a scsi_debug device with delay=5. Use inode_trylock_shared() for IOCB_NOWAIT and return the bytes the direct path already read, or -EAGAIN if none, when the lock is contended, preserving NOWAIT semantics. Fixes: c0e473a0d226 ("block: fix race between set_blocksize and read paths") 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: Hannes Reinecke Reviewed-by: Christoph Hellwig Signed-off-by: Tal Zussman --- block/fops.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/block/fops.c b/block/fops.c index a51814821100..a3a709697b40 100644 --- a/block/fops.c +++ b/block/fops.c @@ -845,7 +845,15 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to) * Take i_rwsem and invalidate_lock to avoid racing with set_blocksize * changing i_blkbits/folio order and punching out the pagecache. */ - inode_lock_shared(bd_inode); + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!inode_trylock_shared(bd_inode)) { + if (!ret) + ret = -EAGAIN; + goto reexpand; + } + } else { + inode_lock_shared(bd_inode); + } ret = filemap_read(iocb, to, ret); inode_unlock_shared(bd_inode); -- 2.39.5