6547ebabda
This fixes a deadlock: 01305 WARNING: possible circular locking dependency detected 01305 6.3.0-ktest-gf4de9bee61af #5305 Tainted: G W 01305 ------------------------------------------------------ 01305 cat/14658 is trying to acquire lock: 01305 ffffffc00982f460 (fs_reclaim){+.+.}-{0:0}, at: __kmem_cache_alloc_node+0x48/0x278 01305 01305 but task is already holding lock: 01305 ffffff8011aaf040 (&lock->wait_lock){+.+.}-{2:2}, at: bch2_check_for_deadlock+0x4b8/0xa58 01305 01305 which lock already depends on the new lock. 01305 01305 01305 the existing dependency chain (in reverse order) is: 01305 01305 -> #2 (&lock->wait_lock){+.+.}-{2:2}: 01305 _raw_spin_lock+0x54/0x70 01305 __six_lock_wakeup+0x40/0x1b0 01305 six_unlock_ip+0xe8/0x248 01305 bch2_btree_key_cache_scan+0x720/0x940 01305 shrink_slab.constprop.0+0x284/0x770 01305 shrink_node+0x390/0x828 01305 balance_pgdat+0x390/0x6d0 01305 kswapd+0x2e4/0x718 01305 kthread+0x184/0x1a8 01305 ret_from_fork+0x10/0x20 01305 01305 -> #1 (&c->lock#2){+.+.}-{3:3}: 01305 __mutex_lock+0x104/0x14a0 01305 mutex_lock_nested+0x30/0x40 01305 bch2_btree_key_cache_scan+0x5c/0x940 01305 shrink_slab.constprop.0+0x284/0x770 01305 shrink_node+0x390/0x828 01305 balance_pgdat+0x390/0x6d0 01305 kswapd+0x2e4/0x718 01305 kthread+0x184/0x1a8 01305 ret_from_fork+0x10/0x20 01305 01305 -> #0 (fs_reclaim){+.+.}-{0:0}: 01305 __lock_acquire+0x19d0/0x2930 01305 lock_acquire+0x1dc/0x458 01305 fs_reclaim_acquire+0x9c/0xe0 01305 __kmem_cache_alloc_node+0x48/0x278 01305 __kmalloc_node_track_caller+0x5c/0x278 01305 krealloc+0x94/0x180 01305 bch2_printbuf_make_room.part.0+0xac/0x118 01305 bch2_prt_printf+0x150/0x1e8 01305 bch2_btree_bkey_cached_common_to_text+0x170/0x298 01305 bch2_btree_trans_to_text+0x244/0x348 01305 print_cycle+0x7c/0xb0 01305 break_cycle+0x254/0x528 01305 bch2_check_for_deadlock+0x59c/0xa58 01305 bch2_btree_deadlock_read+0x174/0x200 01305 full_proxy_read+0x94/0xf0 01305 vfs_read+0x15c/0x3a8 01305 ksys_read+0xb8/0x148 01305 __arm64_sys_read+0x48/0x60 01305 invoke_syscall.constprop.0+0x64/0x138 01305 do_el0_svc+0x84/0x138 01305 el0_svc+0x34/0x80 01305 el0t_64_sync_handler+0xb0/0xb8 01305 el0t_64_sync+0x14c/0x150 01305 01305 other info that might help us debug this: 01305 01305 Chain exists of: 01305 fs_reclaim --> &c->lock#2 --> &lock->wait_lock 01305 01305 Possible unsafe locking scenario: 01305 01305 CPU0 CPU1 01305 ---- ---- 01305 lock(&lock->wait_lock); 01305 lock(&c->lock#2); 01305 lock(&lock->wait_lock); 01305 lock(fs_reclaim); 01305 01305 *** DEADLOCK *** Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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.