kernel/linux.git/block/blk.h, branch v6.18.33

block: add pgmap check to biovec_phys_mergeable

2026-05-14T13:30:17+00:00

commit 13920e4b7b784b40cf4519ff1f0f3e513476a499 upstream. biovec_phys_mergeable() is used by the request merge, DMA mapping, and integrity merge paths to decide if two physically contiguous bvec segments can be coalesced into one. It currently has no check for whether the segments belong to different dev_pagemaps. When zone device memory is registered in multiple chunks, each chunk gets its own dev_pagemap. A single bio can legitimately contain bvecs from different pgmaps -- iov_iter_extract_bvecs() breaks at pgmap boundaries but the outer loop in bio_iov_iter_get_pages() continues filling the same bio. If such bvecs are physically contiguous, biovec_phys_mergeable() will coalesce them, making it impossible to recover the correct pgmap for the merged segment via page_pgmap(). Add a zone_device_pages_have_same_pgmap() check to prevent merging bvec segments that span different pgmaps. Fixes: 49580e690755 ("block: add check when merging zone device pages") Cc: stable@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Naman Jain Link: https://patch.msgid.link/20260410153414.4159050-2-namjain@linux.microsoft.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: relax pgmap check in bio_add_page for compatible zone device pages

2026-05-07T04:11:42+00:00

commit 41c665aae2b5dbecddddcc8ace344caf630cc7a4 upstream. bio_add_page() and bio_integrity_add_page() reject pages from different dev_pagemaps entirely, returning 0 even when those pages have compatible DMA mapping requirements. This forces callers to start a new bio when buffers span pgmap boundaries, even though the pages could safely coexist as separate bvec entries. This matters for guests where memory is registered through devm_memremap_pages() with MEMORY_DEVICE_GENERIC in multiple calls, creating separate dev_pagemaps for each chunk. When a direct I/O buffer spans two such chunks, bio_add_page() rejects the second page, forcing an unnecessary bio split or I/O failure. Introduce zone_device_pages_compatible() in blk.h to check whether two pages can coexist in the same bio as separate bvec entries. The block DMA iterator (blk_dma_map_iter_start) caches the P2PDMA mapping state from the first segment and applies it to all others, so P2PDMA pages from different pgmaps must not be mixed, and neither must P2PDMA and non-P2PDMA pages. All other combinations (MEMORY_DEVICE_GENERIC pages from different pgmaps, or MEMORY_DEVICE_GENERIC with normal RAM) use the same dma_map_phys path and are safe. Replace the blanket zone_device_pages_have_same_pgmap() rejection with zone_device_pages_compatible(), while keeping zone_device_pages_have_same_pgmap() as a merge guard. Pages from different pgmaps can be added as separate bvec entries but must not be coalesced into the same segment, as that would make it impossible to recover the correct pgmap via page_pgmap(). Fixes: 49580e690755 ("block: add check when merging zone device pages") Cc: stable@vger.kernel.org Signed-off-by: Naman Jain Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260410153414.4159050-3-namjain@linux.microsoft.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: decouple secure erase size limit from discard size limit

2026-03-04T12:19:38+00:00

[ Upstream commit ee81212f74a57c5d2b56cf504f40d528dac6faaf ] Secure erase should use max_secure_erase_sectors instead of being limited by max_discard_sectors. Separate the handling of REQ_OP_SECURE_ERASE from REQ_OP_DISCARD to allow each operation to use its own size limit. Signed-off-by: Luke Wang Reviewed-by: Ulf Hansson Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

block: handle zone management operations completions

2026-01-08T09:16:52+00:00

commit efae226c2ef19528ffd81d29ba0eecf1b0896ca2 upstream. The functions blk_zone_wplug_handle_reset_or_finish() and blk_zone_wplug_handle_reset_all() both modify the zone write pointer offset of zone write plugs that are the target of a reset, reset all or finish zone management operation. However, these functions do this modification before the BIO is executed. So if the zone operation fails, the modified zone write pointer offsets become invalid. Avoid this by modifying the zone write pointer offset of a zone write plug that is the target of a zone management operation when the operation completes. To do so, modify blk_zone_bio_endio() to call the new function blk_zone_mgmt_bio_endio() which in turn calls the functions blk_zone_reset_all_bio_endio(), blk_zone_reset_bio_endio() or blk_zone_finish_bio_endio() depending on the operation of the completed BIO, to modify a zone write plug write pointer offset accordingly. These functions are called only if the BIO execution was successful. Fixes: dd291d77cc90 ("block: Introduce zone write plugging") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Christoph Hellwig Reviewed-by: Johannes Thumshirn Reviewed-by: Chaitanya Kulkarni Reviewed-by: Hannes Reinecke Reviewed-by: Martin K. Petersen Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: unify elevator tags and type xarrays into struct elv_change_ctx

2026-01-02T11:56:50+00:00

[ Upstream commit 232143b605387b372dee0ec7830f93b93df5f67d ] Currently, the nr_hw_queues update path manages two disjoint xarrays — one for elevator tags and another for elevator type — both used during elevator switching. Maintaining these two parallel structures for the same purpose adds unnecessary complexity and potential for mismatched state. This patch unifies both xarrays into a single structure, struct elv_change_ctx, which holds all per-queue elevator change context. A single xarray, named elv_tbl, now maps each queue (q->id) in a tagset to its corresponding elv_change_ctx entry, encapsulating the elevator tags, type and name references. This unification simplifies the code, improves maintainability, and clarifies ownership of per-queue elevator state. Reviewed-by: Ming Lei Reviewed-by: Yu Kuai Signed-off-by: Nilay Shroff Signed-off-by: Jens Axboe Stable-dep-of: 9869d3a6fed3 ("block: fix race between wbt_enable_default and IO submission") Signed-off-by: Sasha Levin

block: fix ordering of recursive split IO

2025-09-10T11:23:46+00:00

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 Closes: https://lore.kernel.org/all/7dro5o7u5t64d6bgiansesjavxcuvkq5p2pok7dtwkav7b7ape@3isfr44b6352/ Signed-off-by: Yu Kuai Reviewed-by: Bart Van Assche Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: skip unnecessary checks for split bio

2025-09-10T11:23:46+00:00

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 Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: cleanup bio_issue

2025-09-10T11:23:45+00:00

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 Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe

blk-mq: Defer freeing flush queue to SRCU callback

2025-09-08T14:05:32+00:00

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 Reviewed-by: Yu Kuai Signed-off-by: Ming Lei Reviewed-by: Martin K. Petersen Signed-off-by: Jens Axboe

block: fix kobject double initialization in add_disk

2025-08-11T14:00:49+00:00

Device-mapper can call add_disk() multiple times for the same gendisk due to its two-phase creation process (dm create + dm load). This leads to kobject double initialization errors when the underlying iSCSI devices become temporarily unavailable and then reappear. However, if the first add_disk() call fails and is retried, the queue_kobj gets initialized twice, causing: kobject: kobject (ffff88810c27bb90): tried to init an initialized object, something is seriously wrong. Call Trace: dump_stack_lvl+0x5b/0x80 kobject_init.cold+0x43/0x51 blk_register_queue+0x46/0x280 add_disk_fwnode+0xb5/0x280 dm_setup_md_queue+0x194/0x1c0 table_load+0x297/0x2d0 ctl_ioctl+0x2a2/0x480 dm_ctl_ioctl+0xe/0x20 __x64_sys_ioctl+0xc7/0x110 do_syscall_64+0x72/0x390 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fix this by separating kobject initialization from sysfs registration: - Initialize queue_kobj early during gendisk allocation - add_disk() only adds the already-initialized kobject to sysfs - del_gendisk() removes from sysfs but doesn't destroy the kobject - Final cleanup happens when the disk is released Fixes: 2bd85221a625 ("block: untangle request_queue refcounting from sysfs") Reported-by: Li Lingfeng Closes: https://lore.kernel.org/all/83591d0b-2467-433c-bce0-5581298eb161@huawei.com/ Signed-off-by: Zheng Qixing Reviewed-by: Ming Lei Reviewed-by: Yu Kuai Reviewed-by: Nilay Shroff Link: https://lore.kernel.org/r/20250808053609.3237836-1-zhengqixing@huaweicloud.com Signed-off-by: Jens Axboe