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>
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>
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>
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>
This reverts commit 62448afee7.
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>
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>
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>
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>
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>
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>
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>
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>
- 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>
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>
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>
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>
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>
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>
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>
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>
- endianness fixes
- mark some things static
- fix a few __percpu annotations
- fix silent enum conversions
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Add a new helper for the common pattern of:
- trans_unlock()
- do something
- trans_relock()
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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>
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>
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>
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>
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>
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>
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>
- Marking a non-static function as inline doesn't actually work and is
now causing problems - drop that
- Introduce BCACHEFS_LOG_PREFIX for when we want to prefix log messages
with bcachefs (filesystem name)
- Userspace doesn't have real percpu variables (maybe we can get this
fixed someday), put an #ifdef around bch2_disk_reservation_add()
fastpath
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
