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path: root/fs/bcachefs/btree_locking.c (follow)
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2025-03-24bcachefs: Fix race in print_chain()Kent Overstreet1-2/+2
00636 Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b0 00636 Mem abort info: 00636 ESR = 0x0000000096000005 00636 EC = 0x25: DABT (current EL), IL = 32 bits 00636 SET = 0, FnV = 0 00636 EA = 0, S1PTW = 0 00636 FSC = 0x05: level 1 translation fault 00636 Data abort info: 00636 ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 00636 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 00636 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 00636 user pgtable: 4k pages, 39-bit VAs, pgdp=0000000101b10000 00636 [00000000000000b0] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 00636 Internal error: Oops: 0000000096000005 [#1] SMP 00636 Modules linked in: 00636 CPU: 12 UID: 0 PID: 79369 Comm: cat Not tainted 6.14.0-rc6-ktest-g3783b8973ab7 #17757 00636 Hardware name: linux,dummy-virt (DT) 00636 pstate: 20001005 (nzCv daif -PAN -UAO -TCO -DIT +SSBS BTYPE=--) 00636 pc : print_chain+0xb8/0x170 00636 lr : print_chain+0xa0/0x170 00636 sp : ffffff80d9c1bbb0 00636 x29: ffffff80d9c1bbb0 x28: 0000000000000002 x27: ffffff80c1be8250 00636 x26: ffffff80dd9b0000 x25: 0000000000000020 x24: 000000000000002d 00636 x23: 000000000000003c x22: ffffffc080a54518 x21: ffffff80da6e00d0 00636 x20: ffffff80da6e0170 x19: ffffff80c1a1d240 x18: 00000000ffffffff 00636 x17: 3535303937202d3c x16: 203139202d3c2035 x15: 00000000ffffffff 00636 x14: 0000000000000000 x13: ffffff80d71b63f1 x12: 0000000000000006 00636 x11: ffffffc080beb1c0 x10: 0000000000000020 x9 : 00000000000134cc 00636 x8 : 0000000000000020 x7 : 0000000000000004 x6 : 0000000000000020 00636 x5 : ffffff80d71b63f7 x4 : ffffffc080a5451b x3 : 0000000000000000 00636 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000 00636 Call trace: 00636 print_chain+0xb8/0x170 (P) 00636 bch2_check_for_deadlock+0x444/0x5a0 00636 bch2_btree_deadlock_read+0xb4/0x1c8 00636 full_proxy_read+0x74/0xd8 00636 vfs_read+0x90/0x300 Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-03-24bcachefs: btree_trans_restart_foreign_task()Kent Overstreet1-1/+3
In debug mode, we save the call stack on transaction restart - but there's no locking, so we can't touch it if we're issuing the restart from another thread. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-02-26bcachefs: Fix deadlockAlan Huang1-2/+3
This fixes two deadlocks: 1.pcpu_alloc_mutex involved one as pointed by syzbot[1] 2.recursion deadlock. The root cause is that we hold the bc lock during alloc_percpu, fix it by following the pattern used by __btree_node_mem_alloc(). [1] https://lore.kernel.org/all/66f97d9a.050a0220.6bad9.001d.GAE@google.com/T/ Reported-by: syzbot+fe63f377148a6371a9db@syzkaller.appspotmail.com Tested-by: syzbot+fe63f377148a6371a9db@syzkaller.appspotmail.com Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-14bcachefs: Pop all the transactions from the abort oneAlan Huang1-0/+2
The transaction is going to abort, so there will be no cycle involving this transaction anymore. Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-14bcachefs: Only abort the transactions in the cycleAlan Huang1-7/+14
When the cycle doesn't involve the initiator of the cycle detection, we might choose a transaction that is not involved in the cycle to abort. It shouldn't be that since it won't break the cycle, this patch therefore chooses the transaction in the cycle to abort. Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-14bcachefs: Introduce lock_graph_pop_fromAlan Huang1-2/+7
This patch introduces a helper function called lock_graph_pop_from, it pops the graph from i. Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-14bcachefs: Convert open-coded lock_graph_pop_all to helperAlan Huang1-4/+2
Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-14bcachefs: Do not allow no fail lock request to failAlan Huang1-1/+1
If the transaction chose itself as a victim before and restarted, it might request a no fail lock request this time. But it might be added to others' lock graph and be chose as the victim again, it's no longer safe without additional check. We can also convert the cycle detector to be fully RCU-based to solve that unsoundness, but the latency added to trans_put and additional memory required may not worth it. Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-14Revert "bcachefs: Fix bch2_btree_node_upgrade()"Alan Huang1-18/+4
This reverts commit 62448afee714354a26db8a0f3c644f58628f0792. six_lock_tryupgrade fails only if there is an intent lock held, it won't fail no matter how many read locks are held. Signed-off-by: Alan Huang <mmpgouride@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-09bcachefs: bch2_trans_unlock_write()Kent Overstreet1-0/+11
New helper for dropping all write locks; which is distinct from the helper the transaction commit path uses, which is faster and only touches updates. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2025-01-09bcachefs: btree_path_very_locks(): verify lock seqKent Overstreet1-0/+3
If the btree_path's lock seq is wrong, the next bch2_trans_relock() operation is guaranteed to fail and we take an unnecessary transaction restart. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-12-21bcachefs: bch2_trans_relock() is trylock for lockdepKent Overstreet1-1/+1
fix some spurious lockdep splats Reported-by: syzbot+e088be3c2d5c05aaac35@syzkaller.appspotmail.com Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-07-14bcachefs: Kill bch2_assert_btree_nodes_not_locked()Kent Overstreet1-10/+0
We no longer track individual btree node locks with lockdep, so this will never be enabled. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-07-14lockdep: lockdep_set_notrack_class()Kent Overstreet1-1/+1
Add a new helper to disable lockdep tracking entirely for a given class. This is needed for bcachefs, which takes too many btree node locks for lockdep to track. Instead, we have a single lockdep_map for "btree_trans has any btree nodes locked", which makes more since given that we have centralized lock management and a cycle detector. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Will Deacon <will@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-07-11bcachefs: Set PF_MEMALLOC_NOFS when trans->lockedKent Overstreet1-5/+3
proper lock ordering is: fs_reclaim -> btree node locks Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-07-10bcachefs: fix scheduling while atomic in break_cycle()Kent Overstreet1-1/+1
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-06-05bcachefs: Fix GFP_KERNEL allocation in break_cycle()Kent Overstreet1-0/+1
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-05-08bcachefs: bch2_trans_verify_not_unlocked()Kent Overstreet1-2/+9
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-05-08bcachefs: trans->lockedKent Overstreet1-19/+33
Add a field for tracking whether a transaction object holds btree locks, and assertions to verify state. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-05-08bcachefs: bch2_btree_path_upgrade() checks nodes_locked, not uptodateKent Overstreet1-7/+6
In the key cache fill path, we use path_upgrade() on a path that isn't uptodate yet but should be locked. This change makes bch2_btree_path_upgrade() slightly looser so we can use it in key cache upgrade, instead of the __ version. Also, make the related assert - that path->uptodate implies nodes_locked - slightly clearer. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-05-08bcachefs: bch2_trans_relock_fail() - factor out slowpathKent Overstreet1-46/+52
Factor out slowpath into a separate helper Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-05-08bcachefs: bch2_btree_path_to_text()Kent Overstreet1-0/+5
Long form version of bch2_btree_path_to_text() - useful in error messages and tracepoints. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-05-08bcachefs: prt_printf() now respects \r\n\tKent Overstreet1-4/+2
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-04-10bcachefs: Kill read lock dropping in bch2_btree_node_lock_write_nofail()Kent Overstreet1-27/+1
dropping read locks in bch2_btree_node_lock_write_nofail() dates from before we had the cycle detector; we can now tell the cycle detector directly when taking a lock may not fail because we can't handle transaction restarts. This is needed for adding should_be_locked asserts. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-03-13bcachefs: Drop redundant btree_path_downgrade()sKent Overstreet1-1/+2
If a path doesn't have any active references, we shouldn't downgrade it; it'll either be reused, possibly with intent refs again, or dropped at bch2_trans_begin() time. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-22bcachefs: Add gfp flags param to bch2_prt_task_backtrace()Kent Overstreet1-2/+2
Fixes: e6a2566f7a00 ("bcachefs: Better journal tracepoints") Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> Reported-by: smatch
2024-01-21bcachefs: Improve trace_trans_restart_relockKent Overstreet1-7/+33
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-05bcachefs: Improve would_deadlock trace eventKent Overstreet1-7/+12
We now include backtraces for every thread involved in the cycle. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: optimize __bch2_trans_get(), kill DEBUG_TRANSACTIONSKent Overstreet1-1/+2
- Some tweaks to greatly reduce locking overhead for the list of btree transactions, so that it can always be enabled: leave btree_trans objects on the list when they're on the percpu single item freelist, and only check for duplicates in the same process when CONFIG_BCACHEFS_DEBUG is enabled - don't zero out the full btree_trans() unless we allocated it from the mempool Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: rcu protect trans->pathsKent Overstreet1-7/+24
Upcoming patches are going to be changing trans->paths to a reallocatable buffer. We need to guard against use after free when it's used by other threads; this introduces RCU protection to those paths and changes them to check for trans->paths == NULL Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: kill btree_path.idxKent Overstreet1-1/+1
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: trans_for_each_path() no longer uses path->idxKent Overstreet1-14/+24
path->idx is now a code smell: we should be using path_idx_t, since it's stable across btree path reallocation. This is also a bit faster, using the same loop counter vs. fetching path->idx from each path we iterate over. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: kill btree_path->(alloc_seq|downgrade_seq)Kent Overstreet1-1/+0
These were for extra info in tracepoints for debugging a specialized issue - we do not want to bloat btree_path for this, at least in release builds. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: Improve trace_trans_restart_would_deadlockKent Overstreet1-3/+22
In the CI, we're seeing tests failing due to excessive would_deadlock transaction restarts - the tracepoint now includes the lock cycle that occured. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-01-01bcachefs: Improve btree_path_dowgrade tracepointKent Overstreet1-2/+2
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-11-04bcachefs: Ensure srcu lock is not held too longKent Overstreet1-0/+6
The SRCU read lock that btree_trans takes exists to make it safe for bch2_trans_relock() to deref pointers to btree nodes/key cache items we don't have locked, but as a side effect it blocks reclaim from freeing those items. Thus, it's important to not hold it for too long: we need to differentiate between bch2_trans_unlock() calls that will be only for a short duration, and ones that will be for an unbounded duration. This introduces bch2_trans_unlock_long(), to be used mainly by the data move paths. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-11-01bcachefs: Don't downgrade locks on transaction restartKent Overstreet1-9/+29
We should only be downgrading locks on success - otherwise, our transaction restarts won't be getting the correct locks and we'll livelock. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: Assorted fixes for clangKent Overstreet1-3/+3
clang had a few more warnings about enum conversion, and also didn't like the opts.c initializer. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: Assorted sparse fixesKent Overstreet1-7/+0
- endianness fixes - mark some things static - fix a few __percpu annotations - fix silent enum conversions Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: Don't call lock_graph_descend() with wait lock heldKent Overstreet1-6/+15
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>
2023-10-22bcachefs: bch2_trans_unlock_noassert()Kent Overstreet1-0/+8
This fixes a spurious assert in the btree node read path. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: drop_locks_do()Kent Overstreet1-4/+1
Add a new helper for the common pattern of: - trans_unlock() - do something - trans_relock() Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: trans_for_each_path_safe()Kent Overstreet1-3/+4
bch2_btree_trans_to_text() is used on btree_trans objects that are owned by different threads - when printing out deadlock cycles - so we need a safe version of trans_for_each_path(), else we race with seeing a btree_path that was just allocated and not fully initialized: Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22six locks: Kill six_lock_pcpu_(alloc|free)Kent Overstreet1-2/+3
six_lock_pcpu_alloc() is an unsafe interface: it's not safe to allocate or free the percpu reader count on an existing lock that's in use, the only safe time to allocate percpu readers is when the lock is first being initialized. This patch adds a flags parameter to six_lock_init(), and instead of six_lock_pcpu_free() we now expose six_lock_exit(), which does the same thing but is less likely to be misused. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22six locks: six_lock_readers_add()Kent Overstreet1-10/+0
This moves a helper out of the bcachefs code that shouldn't have been there, since it touches six lock internals. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: Centralize btree node lock initializationKent Overstreet1-1/+17
This fixes some confusion in the lockdep code due to initializing btree node/key cache locks with the same lockdep key, but different names. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: Fix erasure coding lockingKent Overstreet1-0/+13
This adds a new helper, bch2_trans_mutex_lock(), for locking a mutex - dropping and retaking btree locks as needed. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: New backtrace utility codeKent Overstreet1-1/+1
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: trans->notrace_relock_failKent Overstreet1-1/+1
When we unlock in order to submit IO, the next relock event is likely to fail if submit_bio() blocked - we shouldn't those events in our _fail stats, since those are expected events and shouldn't cause test failures. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2023-10-22bcachefs: Use six_lock_ip()Kent Overstreet1-1/+2
This uses the new _ip() interface to six locks and hooks it up to btree_path->ip_allocated, when available. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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