ecb2ba8cb8
When CACHE_SET_IO_DISABLE is set on cache set flags, bcache allocator thread routine bch_allocator_thread() may stop the while-loops and exit. Then it is possible to observe the following kernel oops message, [ 631.068366] bcache: bch_btree_insert() error -5 [ 631.069115] bcache: cached_dev_detach_finish() Caching disabled for sdf [ 631.070220] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 631.070250] PGD 0 P4D 0 [ 631.070261] Oops: 0002 [#1] SMP PTI [snipped] [ 631.070578] Workqueue: events cache_set_flush [bcache] [ 631.070597] RIP: 0010:exit_creds+0x1b/0x50 [ 631.070610] RSP: 0018:ffffc9000705fe08 EFLAGS: 00010246 [ 631.070626] RAX: 0000000000000001 RBX: ffff880a622ad300 RCX: 000000000000000b [ 631.070645] RDX: 0000000000000601 RSI: 000000000000000c RDI: 0000000000000000 [ 631.070663] RBP: ffff880a622ad300 R08: ffffea00190c66e0 R09: 0000000000000200 [ 631.070682] R10: ffff880a48123000 R11: ffff880000000000 R12: 0000000000000000 [ 631.070700] R13: ffff880a4b160e40 R14: ffff880a4b160000 R15: 0ffff880667e2530 [ 631.070719] FS: 0000000000000000(0000) GS:ffff880667e00000(0000) knlGS:0000000000000000 [ 631.070740] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 631.070755] CR2: 0000000000000000 CR3: 000000000200a001 CR4: 00000000003606e0 [ 631.070774] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 631.070793] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 631.070811] Call Trace: [ 631.070828] __put_task_struct+0x55/0x160 [ 631.070845] kthread_stop+0xee/0x100 [ 631.070863] cache_set_flush+0x11d/0x1a0 [bcache] [ 631.070879] process_one_work+0x146/0x340 [ 631.070892] worker_thread+0x47/0x3e0 [ 631.070906] kthread+0xf5/0x130 [ 631.070917] ? max_active_store+0x60/0x60 [ 631.070930] ? kthread_bind+0x10/0x10 [ 631.070945] ret_from_fork+0x35/0x40 [snipped] [ 631.071017] RIP: exit_creds+0x1b/0x50 RSP: ffffc9000705fe08 [ 631.071033] CR2: 0000000000000000 [ 631.071045] ---[ end trace 011c63a24b22c927 ]--- [ 631.071085] bcache: bcache_device_free() bcache0 stopped The reason is when cache_set_flush() tries to call kthread_stop() to stop allocator thread, but it exits already due to cache device I/O errors. This patch adds wait_for_kthread_stop() at tail of bch_allocator_thread(), to prevent the thread routine exiting directly. Then the allocator thread can be blocked at wait_for_kthread_stop() and wait for cache_set_flush() to stop it by calling kthread_stop(). changelog: v3: add Reviewed-by from Hannnes. v2: not directly return from allocator_wait(), move 'return 0' to tail of bch_allocator_thread(). v1: initial version. Fixes: 771f393e8ffc ("bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags") Signed-off-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.