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2025-09-10blk-mq: cleanup shared tags case in blk_mq_update_nr_requests()Yu Kuai
For shared tags case, all hctx->sched_tags/tags are the same, it doesn't make sense to call into blk_mq_tag_update_depth() multiple times for the same tags. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-mq: convert to serialize updating nr_requests with update_nr_hwq_lockYu Kuai
request_queue->nr_requests can be changed by: a) switch elevator by updating nr_hw_queues b) switch elevator by elevator sysfs attribute c) configue queue sysfs attribute nr_requests Current lock order is: 1) update_nr_hwq_lock, case a,b 2) freeze_queue 3) elevator_lock, case a,b,c And update nr_requests is seriablized by elevator_lock() already, however, in the case c, we'll have to allocate new sched_tags if nr_requests grow, and do this with elevator_lock held and queue freezed has the risk of deadlock. Hence use update_nr_hwq_lock instead, make it possible to allocate memory if tags grow, meanwhile also prevent nr_requests to be changed concurrently. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-mq: check invalid nr_requests in queue_requests_store()Yu Kuai
queue_requests_store() is the only caller of blk_mq_update_nr_requests(), and blk_mq_update_nr_requests() is the only caller of blk_mq_tag_update_depth(), however, they all have checkings for nr_requests input by user. Make code cleaner by moving all the checkings to the top function: 1) nr_requests > reserved tags; 2) if there is elevator, 4 <= nr_requests <= 2048; 3) if elevator is none, 4 <= nr_requests <= tag_set->queue_depth; Meanwhile, case 2 is the only case tags can grow and -ENOMEM might be returned. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-mq: remove useless checkings in blk_mq_update_nr_requests()Yu Kuai
1) queue_requests_store() is the only caller of blk_mq_update_nr_requests(), where queue is already freezed, no need to check mq_freeze_depth; 2) q->tag_set must be set for request based device, and queue_is_mq() is already checked in blk_mq_queue_attr_visible(), no need to check q->tag_set. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-mq: remove useless checking in queue_requests_store()Yu Kuai
blk_mq_queue_attr_visible() already checked queue_is_mq(), no need to check this again in queue_requests_store(). Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10block: fix ordering of recursive split IOYu Kuai
Currently, split bio will be chained to original bio, and original bio will be resubmitted to the tail of current->bio_list, waiting for split bio to be issued. However, if split bio get split again, the IO order will be messed up. This problem, on the one hand, will cause performance degradation, especially for mdraid with large IO size; on the other hand, will cause write errors for zoned block devices[1]. For example, in raid456 IO will first be split by max_sector from md_submit_bio(), and then later be split again by chunksize for internal handling: For example, assume max_sectors is 1M, and chunksize is 512k 1) issue a 2M IO: bio issuing: 0+2M current->bio_list: NULL 2) md_submit_bio() split by max_sector: bio issuing: 0+1M current->bio_list: 1M+1M 3) chunk_aligned_read() split by chunksize: bio issuing: 0+512k current->bio_list: 1M+1M -> 512k+512k 4) after first bio issued, __submit_bio_noacct() will contuine issuing next bio: bio issuing: 1M+1M current->bio_list: 512k+512k bio issued: 0+512k 5) chunk_aligned_read() split by chunksize: bio issuing: 1M+512k current->bio_list: 512k+512k -> 1536k+512k bio issued: 0+512k 6) no split afterwards, finally the issue order is: 0+512k -> 1M+512k -> 512k+512k -> 1536k+512k This behaviour will cause large IO read on raid456 endup to be small discontinuous IO in underlying disks. Fix this problem by placing split bio to the head of current->bio_list. Test script: test on 8 disk raid5 with 64k chunksize dd if=/dev/md0 of=/dev/null bs=4480k iflag=direct Test results: Before this patch 1) iostat results: Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz aqu-sz %util md0 52430.00 3276.87 0.00 0.00 0.62 64.00 32.60 80.10 sd* 4487.00 409.00 2054.00 31.40 0.82 93.34 3.68 71.20 2) blktrace G stage: 8,0 0 486445 11.357392936 843 G R 14071424 + 128 [dd] 8,0 0 486451 11.357466360 843 G R 14071168 + 128 [dd] 8,0 0 486454 11.357515868 843 G R 14071296 + 128 [dd] 8,0 0 486468 11.357968099 843 G R 14072192 + 128 [dd] 8,0 0 486474 11.358031320 843 G R 14071936 + 128 [dd] 8,0 0 486480 11.358096298 843 G R 14071552 + 128 [dd] 8,0 0 486490 11.358303858 843 G R 14071808 + 128 [dd] 3) io seek for sdx: Noted io seek is the result from blktrace D stage, statistic of: ABS((offset of next IO) - (offset + len of previous IO)) Read|Write seek cnt 55175, zero cnt 25079 >=(KB) .. <(KB) : count ratio |distribution | 0 .. 1 : 25079 45.5% |########################################| 1 .. 2 : 0 0.0% | | 2 .. 4 : 0 0.0% | | 4 .. 8 : 0 0.0% | | 8 .. 16 : 0 0.0% | | 16 .. 32 : 0 0.0% | | 32 .. 64 : 12540 22.7% |##################### | 64 .. 128 : 2508 4.5% |##### | 128 .. 256 : 0 0.0% | | 256 .. 512 : 10032 18.2% |################# | 512 .. 1024 : 5016 9.1% |######### | After this patch: 1) iostat results: Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz aqu-sz %util md0 87965.00 5271.88 0.00 0.00 0.16 61.37 14.03 90.60 sd* 6020.00 658.44 5117.00 45.95 0.44 112.00 2.68 86.50 2) blktrace G stage: 8,0 0 206296 5.354894072 664 G R 7156992 + 128 [dd] 8,0 0 206305 5.355018179 664 G R 7157248 + 128 [dd] 8,0 0 206316 5.355204438 664 G R 7157504 + 128 [dd] 8,0 0 206319 5.355241048 664 G R 7157760 + 128 [dd] 8,0 0 206333 5.355500923 664 G R 7158016 + 128 [dd] 8,0 0 206344 5.355837806 664 G R 7158272 + 128 [dd] 8,0 0 206353 5.355960395 664 G R 7158528 + 128 [dd] 8,0 0 206357 5.356020772 664 G R 7158784 + 128 [dd] 3) io seek for sdx Read|Write seek cnt 28644, zero cnt 21483 >=(KB) .. <(KB) : count ratio |distribution | 0 .. 1 : 21483 75.0% |########################################| 1 .. 2 : 0 0.0% | | 2 .. 4 : 0 0.0% | | 4 .. 8 : 0 0.0% | | 8 .. 16 : 0 0.0% | | 16 .. 32 : 0 0.0% | | 32 .. 64 : 7161 25.0% |############## | BTW, this looks like a long term problem from day one, and large sequential IO read is pretty common case like video playing. And even with this patch, in this test case IO is merged to at most 128k is due to block layer plug limit BLK_PLUG_FLUSH_SIZE, increase such limit can get even better performance. However, we'll figure out how to do this properly later. [1] https://lore.kernel.org/all/e40b076d-583d-406b-b223-005910a9f46f@acm.org/ Fixes: d89d87965dcb ("When stacked block devices are in-use (e.g. md or dm), the recursive calls") Reported-by: Tie Ren <tieren@fnnas.com> Closes: https://lore.kernel.org/all/7dro5o7u5t64d6bgiansesjavxcuvkq5p2pok7dtwkav7b7ape@3isfr44b6352/ Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10block: skip unnecessary checks for split bioYu Kuai
Lots of checks are already done while submitting this bio the first time, and there is no need to check them again when this bio is resubmitted after split. Hence open code should_fail_bio() and blk_throtl_bio() that are still necessary from submit_bio_split_bioset(). Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-crypto: convert to use bio_submit_split_bioset()Yu Kuai
Unify bio split code, prepare to fix ordering of split IO. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10block: factor out a helper bio_submit_split_bioset()Yu Kuai
No functional changes are intended, some drivers like mdraid will split bio by internal processing, prepare to unify bio split codes. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-crypto: fix missing blktrace bio split eventsYu Kuai
trace_block_split() is missing, resulting in blktrace inability to catch BIO split events and making it harder to analyze the BIO sequence. Cc: stable@vger.kernel.org Fixes: 488f6682c832 ("block: blk-crypto-fallback for Inline Encryption") Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10blk-mq: add QUEUE_FLAG_BIO_ISSUE_TIMEYu Kuai
bio->issue_time_ns is initialized for every bio, however, it's only used by blk-iolatency. Add a new queue_flag and only set this flag when blk-iolatency is enabled, so that extra blk_time_get_ns() can be saved for disks that blk-iolatency is not enabled. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10block: initialize bio issue time in blk_mq_submit_bio()Yu Kuai
bio->issue_time_ns is only used by blk-iolatency, which can only be enabled for rq-based disk, hence it's not necessary to initialize the time for bio-based disk. Meanwhile, if bio is split by blk_crypto_fallback_split_bio_if_needed(), the issue time is not initialized for new split bio, this can be fixed as well. Noted the next patch will optimize better that bio issue time will only be used when blk-iolatency is really enabled by the disk. Fixes: 488f6682c832 ("block: blk-crypto-fallback for Inline Encryption") Signed-off-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-10block: cleanup bio_issueYu Kuai
Now that bio->bi_issue is only used by blk-iolatency to get bio issue time, replace bio_issue with u64 time directly and remove bio_issue to make code cleaner. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09blk-map: provide the bdev to bio if one existsKeith Busch
We can now safely provide a block device when extracting user pages for driver and user passthrough commands. Set the bdev so the caller doesn't have to do that later. This has an additional benefit of being able to extract P2P pages in the passthrough path. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09blk-mq-dma: bring back p2p request flagsKeith Busch
We only need to consider data and metadata dma mapping types separately. The request and bio integrity payload have enough flag bits to internally track the mapping type for each. Use these so the caller doesn't need to track them, and provide separete request and integrity helpers to the common code. This will make it easier to scale new mappings, like the proposed MMIO attribute, without burdening the caller to track such things. Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09blk-integrity: enable p2p source and destinationKeith Busch
Set the extraction flags to allow p2p pages for the metadata buffer if the block device allows it. Similar to data payloads, ensure the bio does not use merging if we see a p2p page. Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09blk-integrity: use simpler alignment checkKeith Busch
We're checking length and addresses against the same alignment value, so use the more simple iterator check. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09block: simplify direct io validity checkKeith Busch
The block layer checks all the segments for validity later, so no need for an early check. Just reduce it to a simple position and total length check, and defer the more invasive segment checks to the block layer. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09block: align the bio after building itKeith Busch
Instead of ensuring each vector is block size aligned while constructing the bio, just ensure the entire size is aligned after it's built. This makes getting bio pages more flexible to accepting device valid io vectors that would otherwise get rejected by alignment checks. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09block: add size alignment to bio_iov_iter_get_pagesKeith Busch
The block layer tries to align bio vectors to the block device's logical block size. Some cases don't have a block device, or we may need to align to something larger, which we can't derive it from the queue limits. Have the caller specify what they want, or allow any length alignment if nothing was specified. Since the most common use case relies on the block device's limits, a helper function is provided. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09block: check for valid bio while splittingKeith Busch
We're already iterating every segment, so check these for a valid IO lengths at the same time. Individual segment lengths will not be checked on passthrough commands. The read/write command segments must be sized to the dma alignment. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09block: remove the bi_inline_vecs variable sized array from struct bioChristoph Hellwig
Bios are embedded into other structures, and at least spare is unhappy about embedding structures with variable sized arrays. There's no real need to the array anyway, we can replace it with a helper pointing to the memory just behind the bio, and with the previous cleanups there is very few site doing anything special with it. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: John Garry <john.g.garry@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-09block: add a bio_init_inline helperChristoph Hellwig
Just a simpler wrapper around bio_init for callers that want to initialize a bio with inline bvecs. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: John Garry <john.g.garry@oracle.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08Merge tag 'vfs-6.17-rc6.fixes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs Pull vfs fixes from Christian Brauner: "fuse: - Prevent opening of non-regular backing files. Fuse doesn't support non-regular files anyway. - Check whether copy_file_range() returns a larger size than requested. - Prevent overflow in copy_file_range() as fuse currently only supports 32-bit sized copies. - Cache the blocksize value if the server returned a new value as inode->i_blkbits isn't modified directly anymore. - Fix i_blkbits handling for iomap partial writes. By default i_blkbits is set to PAGE_SIZE which causes iomap to mark the whole folio as uptodate even on a partial write. But fuseblk filesystems support choosing a blocksize smaller than PAGE_SIZE risking data corruption. Simply enforce PAGE_SIZE as blocksize for fuseblk's internal inode for now. - Prevent out-of-bounds acces in fuse_dev_write() when the number of bytes to be retrieved is truncated to the fc->max_pages limit. virtiofs: - Fix page faults for DAX page addresses. Misc: - Tighten file handle decoding from userns. Check that the decoded dentry itself has a valid idmapping in the user namespace. - Fix mount-notify selftests. - Fix some indentation errors. - Add an FMODE_ flag to indicate IOCB_HAS_METADATA availability. This will be moved to an FOP_* flag with a bit more rework needed for that to happen not suitable for a fix. - Don't silently ignore metadata for sync read/write. - Don't pointlessly log warning when reading coredump sysctls" * tag 'vfs-6.17-rc6.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: fuse: virtio_fs: fix page fault for DAX page address selftests/fs/mount-notify: Fix compilation failure. fhandle: use more consistent rules for decoding file handle from userns fuse: Block access to folio overlimit fuse: fix fuseblk i_blkbits for iomap partial writes fuse: reflect cached blocksize if blocksize was changed fuse: prevent overflow in copy_file_range return value fuse: check if copy_file_range() returns larger than requested size fuse: do not allow mapping a non-regular backing file coredump: don't pointlessly check and spew warnings fs: fix indentation style block: don't silently ignore metadata for sync read/write fs: add a FMODE_ flag to indicate IOCB_HAS_METADATA availability Please enter a commit message to explain why this merge is necessary, especially if it merges an updated upstream into a topic branch.
2025-09-08blk-throttle: fix access race during throttle policy activationHan Guangjiang
On repeated cold boots we occasionally hit a NULL pointer crash in blk_should_throtl() when throttling is consulted before the throttle policy is fully enabled for the queue. Checking only q->td != NULL is insufficient during early initialization, so blkg_to_pd() for the throttle policy can still return NULL and blkg_to_tg() becomes NULL, which later gets dereferenced. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000156 ... pc : submit_bio_noacct+0x14c/0x4c8 lr : submit_bio_noacct+0x48/0x4c8 sp : ffff800087f0b690 x29: ffff800087f0b690 x28: 0000000000005f90 x27: ffff00068af393c0 x26: 0000000000080000 x25: 000000000002fbc0 x24: ffff000684ddcc70 x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000000 x20: 0000000000080000 x19: ffff000684ddcd08 x18: ffffffffffffffff x17: 0000000000000000 x16: ffff80008132a550 x15: 0000ffff98020fff x14: 0000000000000000 x13: 1fffe000d11d7021 x12: ffff000688eb810c x11: ffff00077ec4bb80 x10: ffff000688dcb720 x9 : ffff80008068ef60 x8 : 00000a6fb8a86e85 x7 : 000000000000111e x6 : 0000000000000002 x5 : 0000000000000246 x4 : 0000000000015cff x3 : 0000000000394500 x2 : ffff000682e35e40 x1 : 0000000000364940 x0 : 000000000000001a Call trace: submit_bio_noacct+0x14c/0x4c8 verity_map+0x178/0x2c8 __map_bio+0x228/0x250 dm_submit_bio+0x1c4/0x678 __submit_bio+0x170/0x230 submit_bio_noacct_nocheck+0x16c/0x388 submit_bio_noacct+0x16c/0x4c8 submit_bio+0xb4/0x210 f2fs_submit_read_bio+0x4c/0xf0 f2fs_mpage_readpages+0x3b0/0x5f0 f2fs_readahead+0x90/0xe8 Tighten blk_throtl_activated() to also require that the throttle policy bit is set on the queue: return q->td != NULL && test_bit(blkcg_policy_throtl.plid, q->blkcg_pols); This prevents blk_should_throtl() from accessing throttle group state until policy data has been attached to blkgs. Fixes: a3166c51702b ("blk-throttle: delay initialization until configuration") Co-developed-by: Liang Jie <liangjie@lixiang.com> Signed-off-by: Liang Jie <liangjie@lixiang.com> Signed-off-by: Han Guangjiang <hanguangjiang@lixiang.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08blk-mq: Replace tags->lock with SRCU for tag iteratorsMing Lei
Replace the spinlock in blk_mq_find_and_get_req() with an SRCU read lock around the tag iterators. This is done by: - Holding the SRCU read lock in blk_mq_queue_tag_busy_iter(), blk_mq_tagset_busy_iter(), and blk_mq_hctx_has_requests(). - Removing the now-redundant tags->lock from blk_mq_find_and_get_req(). This change fixes lockup issue in scsi_host_busy() in case of shost->host_blocked. Also avoids big tags->lock when reading disk sysfs attribute `inflight`. Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08blk-mq: Defer freeing flush queue to SRCU callbackMing Lei
The freeing of the flush queue/request in blk_mq_exit_hctx() can race with tag iterators that may still be accessing it. To prevent a potential use-after-free, the deallocation should be deferred until after a grace period. With this way, we can replace the big tags->lock in tags iterator code path with srcu for solving the issue. This patch introduces an SRCU-based deferred freeing mechanism for the flush queue. The changes include: - Adding a `rcu_head` to `struct blk_flush_queue`. - Creating a new callback function, `blk_free_flush_queue_callback`, to handle the actual freeing. - Replacing the direct call to `blk_free_flush_queue()` in `blk_mq_exit_hctx()` with `call_srcu()`, using the `tags_srcu` instance to ensure synchronization with tag iterators. Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08blk-mq: Defer freeing of tags page_list to SRCU callbackMing Lei
Tag iterators can race with the freeing of the request pages(tags->page_list), potentially leading to use-after-free issues. Defer the freeing of the page list and the tags structure itself until after an SRCU grace period has passed. This ensures that any concurrent tag iterators have completed before the memory is released. With this way, we can replace the big tags->lock in tags iterator code path with srcu for solving the issue. This is achieved by: - Adding a new `srcu_struct tags_srcu` to `blk_mq_tag_set` to protect tag map iteration. - Adding an `rcu_head` to `struct blk_mq_tags` to be used with `call_srcu`. - Moving the page list freeing logic and the `kfree(tags)` call into a new callback function, `blk_mq_free_tags_callback`. - In `blk_mq_free_tags`, invoking `call_srcu` to schedule the new callback for deferred execution. The read-side protection for the tag iterators will be added in a subsequent patch. Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08blk-mq: Pass tag_set to blk_mq_free_rq_map/tagsMing Lei
To prepare for converting the tag->rqs freeing to be SRCU-based, the tag_set is needed in the freeing helper functions. This patch adds 'struct blk_mq_tag_set *' as the first parameter to blk_mq_free_rq_map() and blk_mq_free_tags(), and updates all their call sites. This allows access to the tag_set's SRCU structure in the next step, which will be used to free the tag maps after a grace period. No functional change is intended in this patch. Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08blk-mq: Move flush queue allocation into blk_mq_init_hctx()Ming Lei
Move flush queue allocation into blk_mq_init_hctx() and its release into blk_mq_exit_hctx(), and prepare for replacing tags->lock with SRCU to draining inflight request walking. blk_mq_exit_hctx() is the last chance for us to get valid `tag_set` reference, and we need to add one SRCU to `tag_set` for freeing flush request via call_srcu(). It is safe to move flush queue & request release into blk_mq_exit_hctx(), because blk_mq_clear_flush_rq_mapping() clears the flush request reference int driver tags inflight request table, meantime inflight request walking is drained. Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-05blk-mq: fix blk_mq_tags double free while nr_requests grownYu Kuai
In the case user trigger tags grow by queue sysfs attribute nr_requests, hctx->sched_tags will be freed directly and replaced with a new allocated tags, see blk_mq_tag_update_depth(). The problem is that hctx->sched_tags is from elevator->et->tags, while et->tags is still the freed tags, hence later elevator exit will try to free the tags again, causing kernel panic. Fix this problem by replacing et->tags with new allocated tags as well. Noted there are still some long term problems that will require some refactor to be fixed thoroughly[1]. [1] https://lore.kernel.org/all/20250815080216.410665-1-yukuai1@huaweicloud.com/ Fixes: f5a6604f7a44 ("block: fix lockdep warning caused by lock dependency in elv_iosched_store") Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Li Nan <linan122@huawei.com> Link: https://lore.kernel.org/r/20250821060612.1729939-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-05blk-mq: fix elevator depth_updated methodYu Kuai
Current depth_updated has some problems: 1) depth_updated() will be called for each hctx, while all elevators will update async_depth for the disk level, this is not related to hctx; 2) In blk_mq_update_nr_requests(), if previous hctx update succeed and this hctx update failed, q->nr_requests will not be updated, while async_depth is already updated with new nr_reqeuests in previous depth_updated(); 3) All elevators are using q->nr_requests to calculate async_depth now, however, q->nr_requests is still the old value when depth_updated() is called from blk_mq_update_nr_requests(); Those problems are first from error path, then mq-deadline, and recently for bfq and kyber, fix those problems by: - pass in request_queue instead of hctx; - move depth_updated() after q->nr_requests is updated in blk_mq_update_nr_requests(); - add depth_updated() call inside init_sched() method to initialize async_depth; - remove init_hctx() method for mq-deadline and bfq that is useless now; Fixes: 77f1e0a52d26 ("bfq: update internal depth state when queue depth changes") Fixes: 39823b47bbd4 ("block/mq-deadline: Fix the tag reservation code") Fixes: 42e6c6ce03fd ("lib/sbitmap: convert shallow_depth from one word to the whole sbitmap") Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Li Nan <linan122@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Link: https://lore.kernel.org/r/20250821060612.1729939-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-03Merge tag 'pull-getgeo' of ↵Jens Axboe
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs into for-6.18/block Pull struct block_device getgeo changes from Al. "switching ->getgeo() from struct block_device to struct gendisk Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>" * tag 'pull-getgeo' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: block: switch ->getgeo() to struct gendisk scsi: switch ->bios_param() to passing gendisk scsi: switch scsi_bios_ptable() and scsi_partsize() to gendisk
2025-09-02block: use int to store blk_stack_limits() return valueQianfeng Rong
Change the 'ret' variable in blk_stack_limits() from unsigned int to int, as it needs to store negative value -1. Storing the negative error codes in unsigned type, or performing equality comparisons (e.g., ret == -1), doesn't cause an issue at runtime [1] but can be confusing. Additionally, assigning negative error codes to unsigned type may trigger a GCC warning when the -Wsign-conversion flag is enabled. No effect on runtime. Link: https://lore.kernel.org/all/x3wogjf6vgpkisdhg3abzrx7v7zktmdnfmqeih5kosszmagqfs@oh3qxrgzkikf/ #1 Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com> Reviewed-by: John Garry <john.g.garry@oracle.com> Fixes: fe0b393f2c0a ("block: Correct handling of bottom device misaligment") Reviewed-by: Bart Van Assche <bvanassche@acm.org> Link: https://lore.kernel.org/r/20250902130930.68317-1-rongqianfeng@vivo.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-01copy_process: pass clone_flags as u64 across calltreeSimon Schuster
With the introduction of clone3 in commit 7f192e3cd316 ("fork: add clone3") the effective bit width of clone_flags on all architectures was increased from 32-bit to 64-bit, with a new type of u64 for the flags. However, for most consumers of clone_flags the interface was not changed from the previous type of unsigned long. While this works fine as long as none of the new 64-bit flag bits (CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still undesirable in terms of the principle of least surprise. Thus, this commit fixes all relevant interfaces of callees to sys_clone3/copy_process (excluding the architecture-specific copy_thread) to consistently pass clone_flags as u64, so that no truncation to 32-bit integers occurs on 32-bit architectures. Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com> Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-09-01Merge tag 'fuse-fixes-6.17-rc5' of ↵Christian Brauner
ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse into vfs.fixes fuse fixes for 6.17-rc5 * tag 'fuse-fixes-6.17-rc5' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (6 commits) fuse: Block access to folio overlimit fuse: fix fuseblk i_blkbits for iomap partial writes fuse: reflect cached blocksize if blocksize was changed fuse: prevent overflow in copy_file_range return value fuse: check if copy_file_range() returns larger than requested size fuse: do not allow mapping a non-regular backing file Link: https://lore.kernel.org/CAJfpeguEVMMyw_zCb+hbOuSxdE2Z3Raw=SJsq=Y56Ae6dn2W3g@mail.gmail.com Signed-off-by: Christian Brauner <brauner@kernel.org>
2025-08-28blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister_hctxLi Nan
In __blk_mq_update_nr_hw_queues() the return value of blk_mq_sysfs_register_hctxs() is not checked. If sysfs creation for hctx fails, later changing the number of hw_queues or removing disk will trigger the following warning: kernfs: can not remove 'nr_tags', no directory WARNING: CPU: 2 PID: 637 at fs/kernfs/dir.c:1707 kernfs_remove_by_name_ns+0x13f/0x160 Call Trace: remove_files.isra.1+0x38/0xb0 sysfs_remove_group+0x4d/0x100 sysfs_remove_groups+0x31/0x60 __kobject_del+0x23/0xf0 kobject_del+0x17/0x40 blk_mq_unregister_hctx+0x5d/0x80 blk_mq_sysfs_unregister_hctxs+0x94/0xd0 blk_mq_update_nr_hw_queues+0x124/0x760 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk] nullb_device_submit_queues_store+0x92/0x120 [null_blk] kobjct_del() was called unconditionally even if sysfs creation failed. Fix it by checkig the kobject creation statusbefore deleting it. Fixes: 477e19dedc9d ("blk-mq: adjust debugfs and sysfs register when updating nr_hw_queues") Signed-off-by: Li Nan <linan122@huawei.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20250826084854.1030545-1-linan666@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-26block: validate QoS before calling __rq_qos_done_bio()Nilay Shroff
If a bio has BIO_QOS_xxx set, it doesn't guarantee that q->rq_qos is also present at-least for stacked block devices. For instance, in case of NVMe when multipath is enabled, the bottom device may have QoS enabled but top device doesn't. So always validate QoS is enabled and q->rq_qos is present before calling __rq_qos_done_bio(). Fixes: 370ac285f23a ("block: avoid cpu_hotplug_lock depedency on freeze_lock") Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com> Closes: https://lore.kernel.org/all/3a07b752-06a4-4eee-b302-f4669feb859d@linux.ibm.com/ Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Link: https://lore.kernel.org/r/20250826163128.1952394-1-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-26blk-zoned: Fix a lockdep complaint about recursive lockingBart Van Assche
If preparing a write bio fails then blk_zone_wplug_bio_work() calls bio_endio() with zwplug->lock held. If a device mapper driver is stacked on top of the zoned block device then this results in nested locking of zwplug->lock. The resulting lockdep complaint is a false positive because this is nested locking and not recursive locking. Suppress this false positive by calling blk_zone_wplug_bio_io_error() without holding zwplug->lock. This is safe because no code in blk_zone_wplug_bio_io_error() depends on zwplug->lock being held. This patch suppresses the following lockdep complaint: WARNING: possible recursive locking detected -------------------------------------------- kworker/3:0H/46 is trying to acquire lock: ffffff882968b830 (&zwplug->lock){-...}-{2:2}, at: blk_zone_write_plug_bio_endio+0x64/0x1f0 but task is already holding lock: ffffff88315bc230 (&zwplug->lock){-...}-{2:2}, at: blk_zone_wplug_bio_work+0x8c/0x48c other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&zwplug->lock); lock(&zwplug->lock); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by kworker/3:0H/46: #0: ffffff8809486758 ((wq_completion)sdd_zwplugs){+.+.}-{0:0}, at: process_one_work+0x1bc/0x65c #1: ffffffc085de3d70 ((work_completion)(&zwplug->bio_work)){+.+.}-{0:0}, at: process_one_work+0x1e4/0x65c #2: ffffff88315bc230 (&zwplug->lock){-...}-{2:2}, at: blk_zone_wplug_bio_work+0x8c/0x48c stack backtrace: CPU: 3 UID: 0 PID: 46 Comm: kworker/3:0H Tainted: G W OE 6.12.38-android16-5-maybe-dirty-4k #1 8b362b6f76e3645a58cd27d86982bce10d150025 Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE Hardware name: Spacecraft board based on MALIBU (DT) Workqueue: sdd_zwplugs blk_zone_wplug_bio_work Call trace: dump_backtrace+0xfc/0x17c show_stack+0x18/0x28 dump_stack_lvl+0x40/0xa0 dump_stack+0x18/0x24 print_deadlock_bug+0x38c/0x398 __lock_acquire+0x13e8/0x2e1c lock_acquire+0x134/0x2b4 _raw_spin_lock_irqsave+0x5c/0x80 blk_zone_write_plug_bio_endio+0x64/0x1f0 bio_endio+0x9c/0x240 __dm_io_complete+0x214/0x260 clone_endio+0xe8/0x214 bio_endio+0x218/0x240 blk_zone_wplug_bio_work+0x204/0x48c process_one_work+0x26c/0x65c worker_thread+0x33c/0x498 kthread+0x110/0x134 ret_from_fork+0x10/0x20 Cc: stable@vger.kernel.org Cc: Damien Le Moal <dlemoal@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Fixes: dd291d77cc90 ("block: Introduce zone write plugging") Signed-off-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Damien Le Moal <dlemoal@kernel.org> Link: https://lore.kernel.org/r/20250825182720.1697203-1-bvanassche@acm.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25block: Move a misplaced comment in queue_wb_lat_store()Bart Van Assche
blk_mq_quiesce_queue() does not wait for pending I/O to finish. Freezing a queue waits for pending I/O to finish. Hence move the comment that refers to waiting for pending I/O above the call that freezes the request queue. This patch moves this comment back to the position where it was when this comment was introduced. See also commit c125311d96b1 ("blk-wbt: don't maintain inflight counts if disabled"). Cc: Christoph Hellwig <hch@lst.de> Cc: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Link: https://lore.kernel.org/r/20250825151424.1653910-1-bvanassche@acm.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25blk-integrity: use iterator for mapping sgKeith Busch
Modify blk_rq_map_integrity_sg to use the blk-mq mapping iterator. This produces more efficient code and converges the integrity mapping implementations to reduce future maintenance burdens. The function implementation moves from blk-integrity.c to blk-mq-dma.c in order to use the types and functions private to that file. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20250813153153.3260897-8-kbusch@meta.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25blk-mq-dma: add scatter-less integrity data DMA mappingKeith Busch
Similar to regular data, introduce more efficient integrity mapping helpers that does away with the scatterlist structure. This uses the block mapping iterator to add IOVA segments if IOMMU is enabled, or maps directly if not. This also supports P2P segements if integrity data ever wants to allocate that type of memory. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Kanchan Joshi <joshi.k@samsung.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Link: https://lore.kernel.org/r/20250813153153.3260897-7-kbusch@meta.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25blk-mq-dma: move common dma start code to a helperKeith Busch
In preparing for dma mapping integrity metadata, move the common dma setup to a helper. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Kanchan Joshi <joshi.k@samsung.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Link: https://lore.kernel.org/r/20250813153153.3260897-6-kbusch@meta.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25blk-mq: remove REQ_P2PDMA flagKeith Busch
It's not serving any particular purpose. pci_p2pdma_state() already has all the appropriate checks, so the config and flag checks are not guarding anything. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Kanchan Joshi <joshi.k@samsung.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Link: https://lore.kernel.org/r/20250813153153.3260897-5-kbusch@meta.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25blk-mq-dma: provide the bio_vec array being iteratedKeith Busch
This will make it easier to add different sources of the bvec array, like for upcoming integrity support, rather than assume to use the bio's bi_io_vec. It also makes iterating "special" payloads more in common with iterating normal payloads. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Kanchan Joshi <joshi.k@samsung.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Link: https://lore.kernel.org/r/20250813153153.3260897-3-kbusch@meta.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-25blk-mq-dma: create blk_map_iter typeKeith Busch
The req_iterator happens to have a similar fields to what the dma iterator needs, but we're not necessarily iterating a request's bi_io_vec. Create a new type that can be amended for additional future use. Signed-off-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Kanchan Joshi <joshi.k@samsung.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Link: https://lore.kernel.org/r/20250813153153.3260897-2-kbusch@meta.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-21block: avoid cpu_hotplug_lock depedency on freeze_lockNilay Shroff
A recent lockdep[1] splat observed while running blktest block/005 reveals a potential deadlock caused by the cpu_hotplug_lock dependency on ->freeze_lock. This dependency was introduced by commit 033b667a823e ("block: blk-rq-qos: guard rq-qos helpers by static key"). That change added a static key to avoid fetching q->rq_qos when neither blk-wbt nor blk-iolatency is configured. The static key dynamically patches kernel text to a NOP when disabled, eliminating overhead of fetching q->rq_qos in the I/O hot path. However, enabling a static key at runtime requires acquiring both cpu_hotplug_lock and jump_label_mutex. When this happens after the queue has already been frozen (i.e., while holding ->freeze_lock), it creates a locking dependency from cpu_hotplug_lock to ->freeze_lock, which leads to a potential deadlock reported by lockdep [1]. To resolve this, replace the static key mechanism with q->queue_flags: QUEUE_FLAG_QOS_ENABLED. This flag is evaluated in the fast path before accessing q->rq_qos. If the flag is set, we proceed to fetch q->rq_qos; otherwise, the access is skipped. Since q->queue_flags is commonly accessed in IO hotpath and resides in the first cacheline of struct request_queue, checking it imposes minimal overhead while eliminating the deadlock risk. This change avoids the lockdep splat without introducing performance regressions. [1] https://lore.kernel.org/linux-block/4fdm37so3o4xricdgfosgmohn63aa7wj3ua4e5vpihoamwg3ui@fq42f5q5t5ic/ Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com> Closes: https://lore.kernel.org/linux-block/4fdm37so3o4xricdgfosgmohn63aa7wj3ua4e5vpihoamwg3ui@fq42f5q5t5ic/ Fixes: 033b667a823e ("block: blk-rq-qos: guard rq-qos helpers by static key") Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20250814082612.500845-4-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-21block: decrement block_rq_qos static key in rq_qos_del()Nilay Shroff
rq_qos_add() increments the block_rq_qos static key when a QoS policy is attached. When a QoS policy is removed via rq_qos_del(), we must symmetrically decrement the static key. If this removal drops the last QoS policy from the queue (q->rq_qos becomes NULL), the static branch can be disabled and the jump label patched to a NOP, avoiding overhead on the hot path. This change ensures rq_qos_add()/rq_qos_del() keep the block_rq_qos static key balanced and prevents leaving the branch permanently enabled after the last policy is removed. Fixes: 033b667a823e ("block: blk-rq-qos: guard rq-qos helpers by static key") Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20250814082612.500845-3-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-21block: skip q->rq_qos check in rq_qos_done_bio()Nilay Shroff
If a bio has BIO_QOS_THROTTLED or BIO_QOS_MERGED set, it implicitly guarantees that q->rq_qos is present. Avoid re-checking q->rq_qos in this case and call __rq_qos_done_bio() directly as a minor optimization. Suggested-by : Yu Kuai <yukuai1@huaweicloud.com> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20250814082612.500845-2-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-08-21blk-mq: fix lockdep warning in __blk_mq_update_nr_hw_queuesMing Lei
Commit 5989bfe6ac6b ("block: restore two stage elevator switch while running nr_hw_queue update") reintroduced a lockdep warning by calling blk_mq_freeze_queue_nomemsave() before switching the I/O scheduler. The function blk_mq_elv_switch_none() calls elevator_change_done(). Running this while the queue is frozen causes a lockdep warning. Fix this by reordering the operations: first, switch the I/O scheduler to 'none', and then freeze the queue. This ensures that elevator_change_done() is not called on an already frozen queue. And this way is safe because elevator_set_none() does freeze queue before switching to none. Also we still have to rely on blk_mq_elv_switch_back() for switching back, and it has to cover unfrozen queue case. Cc: Nilay Shroff <nilay@linux.ibm.com> Cc: Yu Kuai <yukuai3@huawei.com> Fixes: 5989bfe6ac6b ("block: restore two stage elevator switch while running nr_hw_queue update") Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Nilay Shroff <nilay@linux.ibm.com> Link: https://lore.kernel.org/r/20250815131737.331692-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>