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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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Josh Hunt
965d6162dd
commit7d96f3120aupstream. When an array check is running it will raise the barrier at which point normal requests will become blocked and increment the nr_pending value to signal there is work pending inside of wait_barrier(). NOWAIT requests do not block and so will return immediately with an error, and additionally do not increment nr_pending in wait_barrier(). Upstream change commit43806c3d5b("raid10: cleanup memleak at raid10_make_request") added a call to raid_end_bio_io() to fix a memory leak when NOWAIT requests hit this condition. raid_end_bio_io() eventually calls allow_barrier() and it will unconditionally do an atomic_dec_and_test(&conf->nr_pending) even though the corresponding increment on nr_pending didn't happen in the NOWAIT case. This can be easily seen by starting a check operation while an application is doing nowait IO on the same array. This results in a deadlocked state due to nr_pending value underflowing and so the md resync thread gets stuck waiting for nr_pending to == 0. Output of r10conf state of the array when we hit this condition: crash> struct r10conf barrier = 1, nr_pending = { counter = -41 }, nr_waiting = 15, nr_queued = 0, Example of md_sync thread stuck waiting on raise_barrier() and other requests stuck in wait_barrier(): md1_resync [<0>] raise_barrier+0xce/0x1c0 [<0>] raid10_sync_request+0x1ca/0x1ed0 [<0>] md_do_sync+0x779/0x1110 [<0>] md_thread+0x90/0x160 [<0>] kthread+0xbe/0xf0 [<0>] ret_from_fork+0x34/0x50 [<0>] ret_from_fork_asm+0x1a/0x30 kworker/u1040:2+flush-253:4 [<0>] wait_barrier+0x1de/0x220 [<0>] regular_request_wait+0x30/0x180 [<0>] raid10_make_request+0x261/0x1000 [<0>] md_handle_request+0x13b/0x230 [<0>] __submit_bio+0x107/0x1f0 [<0>] submit_bio_noacct_nocheck+0x16f/0x390 [<0>] ext4_io_submit+0x24/0x40 [<0>] ext4_do_writepages+0x254/0xc80 [<0>] ext4_writepages+0x84/0x120 [<0>] do_writepages+0x7a/0x260 [<0>] __writeback_single_inode+0x3d/0x300 [<0>] writeback_sb_inodes+0x1dd/0x470 [<0>] __writeback_inodes_wb+0x4c/0xe0 [<0>] wb_writeback+0x18b/0x2d0 [<0>] wb_workfn+0x2a1/0x400 [<0>] process_one_work+0x149/0x330 [<0>] worker_thread+0x2d2/0x410 [<0>] kthread+0xbe/0xf0 [<0>] ret_from_fork+0x34/0x50 [<0>] ret_from_fork_asm+0x1a/0x30 Fixes:43806c3d5b("raid10: cleanup memleak at raid10_make_request") Cc: stable@vger.kernel.org Signed-off-by: Josh Hunt <johunt@akamai.com> Link: https://lore.kernel.org/linux-raid/20260303005619.1352958-1-johunt@akamai.com Signed-off-by: Yu Kuai <yukuai@fnnas.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.