md: fix resync softlockup when bitmap size is less than array size
Is is reported that for dm-raid10, lvextend + lvchange --syncaction will trigger following softlockup: kernel:watchdog: BUG: soft lockup - CPU#3 stuck for 26s! [mdX_resync:6976] CPU: 7 PID: 3588 Comm: mdX_resync Kdump: loaded Not tainted 6.9.0-rc4-next-20240419 #1 RIP: 0010:_raw_spin_unlock_irq+0x13/0x30 Call Trace: <TASK> md_bitmap_start_sync+0x6b/0xf0 raid10_sync_request+0x25c/0x1b40 [raid10] md_do_sync+0x64b/0x1020 md_thread+0xa7/0x170 kthread+0xcf/0x100 ret_from_fork+0x30/0x50 ret_from_fork_asm+0x1a/0x30 And the detailed process is as follows: md_do_sync j = mddev->resync_min while (j < max_sectors) sectors = raid10_sync_request(mddev, j, &skipped) if (!md_bitmap_start_sync(..., &sync_blocks)) // md_bitmap_start_sync set sync_blocks to 0 return sync_blocks + sectors_skippe; // sectors = 0; j += sectors; // j never change Root cause is that commit301867b1c1
("md/raid10: check slab-out-of-bounds in md_bitmap_get_counter") return early from md_bitmap_get_counter(), without setting returned blocks. Fix this problem by always set returned blocks from md_bitmap_get_counter"(), as it used to be. Noted that this patch just fix the softlockup problem in kernel, the case that bitmap size doesn't match array size still need to be fixed. Fixes:301867b1c1
("md/raid10: check slab-out-of-bounds in md_bitmap_get_counter") Reported-and-tested-by: Nigel Croxon <ncroxon@redhat.com> Closes: https://lore.kernel.org/all/71ba5272-ab07-43ba-8232-d2da642acb4e@redhat.com/ Signed-off-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20240422065824.2516-1-yukuai1@huaweicloud.com Signed-off-by: Song Liu <song@kernel.org>
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@ -1424,7 +1424,7 @@ __acquires(bitmap->lock)
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sector_t chunk = offset >> bitmap->chunkshift;
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unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
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unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT;
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sector_t csize;
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sector_t csize = ((sector_t)1) << bitmap->chunkshift;
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int err;
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if (page >= bitmap->pages) {
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@ -1433,6 +1433,7 @@ __acquires(bitmap->lock)
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* End-of-device while looking for a whole page or
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* user set a huge number to sysfs bitmap_set_bits.
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*/
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*blocks = csize - (offset & (csize - 1));
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return NULL;
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}
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err = md_bitmap_checkpage(bitmap, page, create, 0);
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@ -1441,8 +1442,7 @@ __acquires(bitmap->lock)
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bitmap->bp[page].map == NULL)
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csize = ((sector_t)1) << (bitmap->chunkshift +
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PAGE_COUNTER_SHIFT);
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else
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csize = ((sector_t)1) << bitmap->chunkshift;
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*blocks = csize - (offset & (csize - 1));
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if (err < 0)
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