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When adding devices that don't have a scsi_dh on a BIO based multipath, I was able to consistently hit the warning below and lock-up the system. The problem is that __map_bio reads the flag before it potentially being modified by choose_pgpath, and ends up using the older value. The WARN_ON below is not trivially linked to the issue. It goes like this: The activate_path delayed_work is not initialized for non-scsi_dh devices, but we always set MPATHF_QUEUE_IO, asking for initialization. That is fine, since MPATHF_QUEUE_IO would be cleared in choose_pgpath. Nevertheless, only for BIO-based mpath, we cache the flag before calling choose_pgpath, and use the older version when deciding if we should initialize the path. Therefore, we end up trying to initialize the paths, and calling the non-initialized activate_path work. [ 82.437100] ------------[ cut here ]------------ [ 82.437659] WARNING: CPU: 3 PID: 602 at kernel/workqueue.c:1624 __queue_delayed_work+0x71/0x90 [ 82.438436] Modules linked in: [ 82.438911] CPU: 3 PID: 602 Comm: systemd-udevd Not tainted 5.6.0-rc6+ #339 [ 82.439680] RIP: 0010:__queue_delayed_work+0x71/0x90 [ 82.440287] Code: c1 48 89 4a 50 81 ff 00 02 00 00 75 2a 4c 89 cf e9 94 d6 07 00 e9 7f e9 ff ff 0f 0b eb c7 0f 0b 48 81 7a 58 40 74 a8 94 74 a7 <0f> 0b 48 83 7a 48 00 74 a5 0f 0b eb a1 89 fe 4c 89 cf e9 c8 c4 07 [ 82.441719] RSP: 0018:ffffb738803977c0 EFLAGS: 00010007 [ 82.442121] RAX: ffffa086389f9740 RBX: 0000000000000002 RCX: 0000000000000000 [ 82.442718] RDX: ffffa086350dd930 RSI: ffffa0863d76f600 RDI: 0000000000000200 [ 82.443484] RBP: 0000000000000200 R08: 0000000000000000 R09: ffffa086350dd970 [ 82.444128] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa086350dd930 [ 82.444773] R13: ffffa0863d76f600 R14: 0000000000000000 R15: ffffa08636738008 [ 82.445427] FS: 00007f6abfe9dd40(0000) GS:ffffa0863dd80000(0000) knlGS:00000 [ 82.446040] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 82.446478] CR2: 0000557d288db4e8 CR3: 0000000078b36000 CR4: 00000000000006e0 [ 82.447104] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 82.447561] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 82.448012] Call Trace: [ 82.448164] queue_delayed_work_on+0x6d/0x80 [ 82.448472] __pg_init_all_paths+0x7b/0xf0 [ 82.448714] pg_init_all_paths+0x26/0x40 [ 82.448980] __multipath_map_bio.isra.0+0x84/0x210 [ 82.449267] __map_bio+0x3c/0x1f0 [ 82.449468] __split_and_process_non_flush+0x14a/0x1b0 [ 82.449775] __split_and_process_bio+0xde/0x340 [ 82.450045] ? dm_get_live_table+0x5/0xb0 [ 82.450278] dm_process_bio+0x98/0x290 [ 82.450518] dm_make_request+0x54/0x120 [ 82.450778] generic_make_request+0xd2/0x3e0 [ 82.451038] ? submit_bio+0x3c/0x150 [ 82.451278] submit_bio+0x3c/0x150 [ 82.451492] mpage_readpages+0x129/0x160 [ 82.451756] ? bdev_evict_inode+0x1d0/0x1d0 [ 82.452033] read_pages+0x72/0x170 [ 82.452260] __do_page_cache_readahead+0x1ba/0x1d0 [ 82.452624] force_page_cache_readahead+0x96/0x110 [ 82.452903] generic_file_read_iter+0x84f/0xae0 [ 82.453192] ? __seccomp_filter+0x7c/0x670 [ 82.453547] new_sync_read+0x10e/0x190 [ 82.453883] vfs_read+0x9d/0x150 [ 82.454172] ksys_read+0x65/0xe0 [ 82.454466] do_syscall_64+0x4e/0x210 [ 82.454828] entry_SYSCALL_64_after_hwframe+0x49/0xbe [...] [ 82.462501] ---[ end trace bb39975e9cf45daa ]--- Cc: stable@vger.kernel.org Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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.