kernel/linux.git/drivers/md/raid5.c, branch v6.12.98

md/raid5: avoid R5_Overlap races while breaking stripe batches

2026-07-24T14:11:15+00:00

[ Upstream commit 55b77337bdd088c77461588e5ec094421b89911b ] KCSAN report a race in break_stripe_batch_list() vs. raid5_make_request() on sh->dev[i].flags (plain word write vs. atomic bit op).. and .. one possible scenario is: CPU1 CPU2 break_stripe_batch_list(sh1) -> handle sh2 -> lock(sh2) -> sh2->batch_head = NULL -> unlock(sh2) -> test_and_clear_bit(R5_Overlap, sh2->dev[i].flags) -> wake_up_bit(sh2->dev[i].flags) raid5_make_request() -> add_all_stripe_bios(sh2) -> lock(sh2) -> stripe_bio_overlaps(sh2) returns true batch_head is NULL, so new bio overlap exist bio on sh2 -> true -> set_bit(R5_Overlap, sh2->dev[i].flags) -> unlock(sh2) -> wait_on_bit(sh2->dev[i].flags) -> sh2->dev[i].flags = sh1->dev[i].flags & ~R5_Overlap No wait_up_bit(), CPU2 could be wait_on_bit() forever... Fix by : - Expand the protect zone. - Use batch_head's device flag's snaphot when no held head_sh->stripe_lock. - Move sh/head_sh->batch_head = NULL to the end of protected zone , and , any concurrent add_all_stripe_bios() grabs sh->stripe_lock now either: - see batch_head != null, and , is rejected by stripe_bio_overlaps() under the lock (no R5_Overlap wait ) , or , - sees batch_head == NULL, only after dev[i].flags has already been set and the prior R5_Overlap waiters worken. KCSAN report: ================================================ BUG: KCSAN: data-race in break_stripe_batch_list / raid5_make_request write (marked) to 0xffff8e89c8117548 of 8 bytes by task 4042 on cpu 0: raid5_make_request+0xea0/0x2930 md_handle_request+0x4a2/0xa40 md_submit_bio+0x109/0x1a0 __submit_bio+0x2ec/0x390 submit_bio_noacct_nocheck+0x457/0x710 submit_bio_noacct+0x2a7/0xc20 submit_bio+0x56/0x250 blkdev_direct_IO+0x54c/0xda0 blkdev_write_iter+0x38f/0x570 aio_write+0x22b/0x490 io_submit_one+0xa51/0xf70 __x64_sys_io_submit+0xf7/0x220 x64_sys_call+0x1907/0x1c60 do_syscall_64+0x130/0x570 entry_SYSCALL_64_after_hwframe+0x76/0x7e read to 0xffff8e89c8117548 of 8 bytes by task 4010 on cpu 5: break_stripe_batch_list+0x249/0x480 handle_stripe_clean_event+0x720/0x9b0 handle_stripe+0x32fb/0x4500 handle_active_stripes.isra.0+0x6e0/0xa50 raid5d+0x7e0/0xba0 md_thread+0x15a/0x2d0 kthread+0x1e3/0x220 ret_from_fork+0x37a/0x410 ret_from_fork_asm+0x1a/0x30 value changed: 0x0000000000000019 -> 0x0000000000000099 --> R5_Overlap Fixes: fb642b92c267 ("md/raid5: duplicate some more handle_stripe_clean_event code in break_stripe_batch_list") Signed-off-by: Chen Cheng Link: https://patch.msgid.link/20260619041013.1207148-1-chencheng@fnnas.com Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin

md/raid5: use stripe state snapshot in break_stripe_batch_list()

2026-07-24T14:11:14+00:00

[ Upstream commit 9b249f5ffbeda24c57e6c56ed896c5ca4fc70549 ] The patch just suppress KCSAN noise. No functional change. RAID-5 can group multi full-stripe-write aka stripe_head into a batch aka batch_list, with one head_sh leading them. Call break_stripe_batch_list() when the batch is finished, or, a stripe has to be dropped out of the batch. break_stripe_batch_list() reads stripe state several times while request paths can update thost state words concurrently with lockless bitops, which reported by KCSAN. Use a snapshot to guarantees that the value used for warning, copying, and handle checks is internally consistent at current read moment. KCSAN report: ============================================== BUG: KCSAN: data-race in __add_stripe_bio / break_stripe_batch_list write (marked) to 0xffff8e89d4f0b988 of 8 bytes by task 4323 on cpu 3: __add_stripe_bio+0x35e/0x400 raid5_make_request+0x6ac/0x2930 md_handle_request+0x4a2/0xa40 md_submit_bio+0x109/0x1a0 __submit_bio+0x2ec/0x390 submit_bio_noacct_nocheck+0x457/0x710 submit_bio_noacct+0x2a7/0xc20 submit_bio+0x56/0x250 blkdev_direct_IO+0x54c/0xda0 blkdev_write_iter+0x38f/0x570 aio_write+0x22b/0x490 io_submit_one+0xa51/0xf70 read to 0xffff8e89d4f0b988 of 8 bytes by task 4290 on cpu 4: break_stripe_batch_list+0x3ce/0x480 handle_stripe_clean_event+0x720/0x9b0 handle_stripe+0x32fb/0x4500 handle_active_stripes.isra.0+0x6e0/0xa50 raid5d+0x7e0/0xba0 Signed-off-by: Chen Cheng Link: https://patch.msgid.link/20260618134748.1168360-1-chencheng@fnnas.com Signed-off-by: Yu Kuai Stable-dep-of: 55b77337bdd0 ("md/raid5: avoid R5_Overlap races while breaking stripe batches") Signed-off-by: Sasha Levin

md/raid5: fix soft lockup in retry_aligned_read()

2026-05-07T04:09:39+00:00

commit 7f9f7c697474268d9ef9479df3ddfe7cdcfbbffc upstream. When retry_aligned_read() encounters an overlapped stripe, it releases the stripe via raid5_release_stripe() which puts it on the lockless released_stripes llist. In the next raid5d loop iteration, release_stripe_list() drains the stripe onto handle_list (since STRIPE_HANDLE is set by the original IO), but retry_aligned_read() runs before handle_active_stripes() and removes the stripe from handle_list via find_get_stripe() -> list_del_init(). This prevents handle_stripe() from ever processing the stripe to resolve the overlap, causing an infinite loop and soft lockup. Fix this by using __release_stripe() with temp_inactive_list instead of raid5_release_stripe() in the failure path, so the stripe does not go through the released_stripes llist. This allows raid5d to break out of its loop, and the overlap will be resolved when the stripe is eventually processed by handle_stripe(). Fixes: 773ca82fa1ee ("raid5: make release_stripe lockless") Cc: stable@vger.kernel.org Signed-off-by: FengWei Shih Signed-off-by: Chia-Ming Chang Link: https://lore.kernel.org/linux-raid/20260402061406.455755-1-chiamingc@synology.com/ Signed-off-by: Yu Kuai Signed-off-by: Greg Kroah-Hartman

md/raid5: fix raid5_run() to return error when log_init() fails

2026-03-04T12:19:28+00:00

[ Upstream commit 2d9f7150ac197ce79c9c917a004d4cf0b26ad7e0 ] Since commit f63f17350e53 ("md/raid5: use the atomic queue limit update APIs"), the abort path in raid5_run() returns 'ret' instead of -EIO. However, if log_init() fails, 'ret' is still 0 from the previous successful call, causing raid5_run() to return success despite the failure. Fix this by capturing the return value from log_init(). Link: https://lore.kernel.org/linux-raid/20260114171241.3043364-2-yukuai@fnnas.com Fixes: f63f17350e53 ("md/raid5: use the atomic queue limit update APIs") Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/202601130531.LGfcZsa4-lkp@intel.com/ Signed-off-by: Yu Kuai Reviewed-by: Li Nan Reviewed-by: Xiao Ni Reviewed-by: Christoph Hellwig Signed-off-by: Sasha Levin

md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

2026-01-08T09:14:37+00:00

[ Upstream commit 7ad6ef91d8745d04aff9cce7bdbc6320d8e05fe9 ] The variable mddev->private is first assigned to conf and then checked: conf = mddev->private; if (!conf) ... If conf is NULL, then mddev->private is also NULL. In this case, null-pointer dereferences can occur when calling raid5_quiesce(): raid5_quiesce(mddev, true); raid5_quiesce(mddev, false); since mddev->private is assigned to conf again in raid5_quiesce(), and conf is dereferenced in several places, for example: conf->quiesce = 0; wake_up(&conf->wait_for_quiescent); To fix this issue, the function should unlock mddev and return before invoking raid5_quiesce() when conf is NULL, following the existing pattern in raid5_change_consistency_policy(). Fixes: fa1944bbe622 ("md/raid5: Wait sync io to finish before changing group cnt") Signed-off-by: Tuo Li Reviewed-by: Xiao Ni Reviewed-by: Paul Menzel Link: https://lore.kernel.org/linux-raid/20251225130326.67780-1-islituo@gmail.com Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin

md/raid5: fix IO hang when array is broken with IO inflight

2025-12-18T12:55:13+00:00

[ Upstream commit a913d1f6a7f607c110aeef8b58c8988f47a4b24e ] Following test can cause IO hang: mdadm -CvR /dev/md0 -l10 -n4 /dev/sd[abcd] --assume-clean --chunk=64K --bitmap=none sleep 5 echo 1 > /sys/block/sda/device/delete echo 1 > /sys/block/sdb/device/delete echo 1 > /sys/block/sdc/device/delete echo 1 > /sys/block/sdd/device/delete dd if=/dev/md0 of=/dev/null bs=8k count=1 iflag=direct Root cause: 1) all disks removed, however all rdevs in the array is still in sync, IO will be issued normally. 2) IO failure from sda, and set badblocks failed, sda will be faulty and MD_SB_CHANGING_PENDING will be set. 3) error recovery try to recover this IO from other disks, IO will be issued to sdb, sdc, and sdd. 4) IO failure from sdb, and set badblocks failed again, now array is broken and will become read-only. 5) IO failure from sdc and sdd, however, stripe can't be handled anymore because MD_SB_CHANGING_PENDING is set: handle_stripe handle_stripe if (test_bit MD_SB_CHANGING_PENDING) set_bit STRIPE_HANDLE goto finish // skip handling failed stripe release_stripe if (test_bit STRIPE_HANDLE) list_add_tail conf->hand_list 6) later raid5d can't handle failed stripe as well: raid5d md_check_recovery md_update_sb if (!md_is_rdwr()) // can't clear pending bit return if (test_bit MD_SB_CHANGING_PENDING) break; // can't handle failed stripe Since MD_SB_CHANGING_PENDING can never be cleared for read-only array, fix this problem by skip this checking for read-only array. Link: https://lore.kernel.org/linux-raid/20251117085557.770572-3-yukuai@fnnas.com Fixes: d87f064f5874 ("md: never update metadata when array is read-only.") Signed-off-by: Yu Kuai Reviewed-by: Li Nan Signed-off-by: Sasha Levin

md: fix mssing blktrace bio split events

2025-10-23T14:20:42+00:00

[ Upstream commit 22f166218f7313e8fe2d19213b5f4b3265f8c39e ] If bio is split by internal handling like chunksize or badblocks, the corresponding 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: 4b1faf931650 ("block: Kill bio_pair_split()") Signed-off-by: Yu Kuai Reviewed-by: Damien Le Moal Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

md/md-bitmap: move bitmap_{start, end}write to md upper layer

2025-02-08T08:58:12+00:00

commit cd5fc653381811f1e0ba65f5d169918cab61476f upstream. There are two BUG reports that raid5 will hang at bitmap_startwrite([1],[2]), root cause is that bitmap start write and end write is unbalanced, it's not quite clear where, and while reviewing raid5 code, it's found that bitmap operations can be optimized. For example, for a 4 disks raid5, with chunksize=8k, if user issue a IO (0 + 48k) to the array: ┌────────────────────────────────────────────────────────────┐ │chunk 0 │ │ ┌────────────┬─────────────┬─────────────┬────────────┼ │ sh0 │A0: 0 + 4k │A1: 8k + 4k │A2: 16k + 4k │A3: P │ │ ┼────────────┼─────────────┼─────────────┼────────────┼ │ sh1 │B0: 4k + 4k │B1: 12k + 4k │B2: 20k + 4k │B3: P │ ┼──────┴────────────┴─────────────┴─────────────┴────────────┼ │chunk 1 │ │ ┌────────────┬─────────────┬─────────────┬────────────┤ │ sh2 │C0: 24k + 4k│C1: 32k + 4k │C2: P │C3: 40k + 4k│ │ ┼────────────┼─────────────┼─────────────┼────────────┼ │ sh3 │D0: 28k + 4k│D1: 36k + 4k │D2: P │D3: 44k + 4k│ └──────┴────────────┴─────────────┴─────────────┴────────────┘ Before this patch, 4 stripe head will be used, and each sh will attach bio for 3 disks, and each attached bio will trigger bitmap_startwrite() once, which means total 12 times. - 3 times (0 + 4k), for (A0, A1 and A2) - 3 times (4 + 4k), for (B0, B1 and B2) - 3 times (8 + 4k), for (C0, C1 and C3) - 3 times (12 + 4k), for (D0, D1 and D3) After this patch, md upper layer will calculate that IO range (0 + 48k) is corresponding to the bitmap (0 + 16k), and call bitmap_startwrite() just once. Noted that this patch will align bitmap ranges to the chunks, for example, if user issue a IO (0 + 4k) to array: - Before this patch, 1 time (0 + 4k), for A0; - After this patch, 1 time (0 + 8k) for chunk 0; Usually, one bitmap bit will represent more than one disk chunk, and this doesn't have any difference. And even if user really created a array that one chunk contain multiple bits, the overhead is that more data will be recovered after power failure. Also remove STRIPE_BITMAP_PENDING since it's not used anymore. [1] https://lore.kernel.org/all/CAJpMwyjmHQLvm6zg1cmQErttNNQPDAAXPKM3xgTjMhbfts986Q@mail.gmail.com/ [2] https://lore.kernel.org/all/ADF7D720-5764-4AF3-B68E-1845988737AA@flyingcircus.io/ Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20250109015145.158868-6-yukuai1@huaweicloud.com Signed-off-by: Song Liu Signed-off-by: Yu Kuai Signed-off-by: Greg Kroah-Hartman

md/raid5: implement pers->bitmap_sector()

2025-02-08T08:58:12+00:00

commit 9c89f604476cf15c31fbbdb043cff7fbf1dbe0cb upstream. Bitmap is used for the whole array for raid1/raid10, hence IO for the array can be used directly for bitmap. However, bitmap is used for underlying disks for raid5, hence IO for the array can't be used directly for bitmap. Implement pers->bitmap_sector() for raid5 to convert IO ranges from the array to the underlying disks. Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20250109015145.158868-5-yukuai1@huaweicloud.com Signed-off-by: Song Liu Signed-off-by: Yu Kuai Signed-off-by: Greg Kroah-Hartman

md/md-bitmap: remove the last parameter for bimtap_ops->endwrite()

2025-02-08T08:58:11+00:00

commit 4f0e7d0e03b7b80af84759a9e7cfb0f81ac4adae upstream. For the case that IO failed for one rdev, the bit will be mark as NEEDED in following cases: 1) If badblocks is set and rdev is not faulty; 2) If rdev is faulty; Case 1) is useless because synchronize data to badblocks make no sense. Case 2) can be replaced with mddev->degraded. Also remove R1BIO_Degraded, R10BIO_Degraded and STRIPE_DEGRADED since case 2) no longer use them. Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20250109015145.158868-3-yukuai1@huaweicloud.com Signed-off-by: Song Liu Signed-off-by: Yu Kuai Signed-off-by: Greg Kroah-Hartman