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Similar to previous fixes, we can't incur page faults while holding
btree locks.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Add two new helpers for allocating memory with btree locks held: The
idea is to first try the allocation with GFP_NOWAIT|__GFP_NOWARN, then
if that fails - unlock, retry with GFP_KERNEL, and then call
trans_relock().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Add a new helper for the common pattern of:
- trans_unlock()
- do something
- trans_relock()
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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As with previous conversions, replace -ENOENT uses with more informative
private error codes.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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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>
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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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As suggested by Linus, this drops the six_lock_state union in favor of
raw bitmasks.
On the one hand, bitfields give more type-level structure to the code.
However, a significant amount of the code was working with
six_lock_state as a u64/atomic64_t, and the conversions from the
bitfields to the u64 were deemed a bit too out-there.
More significantly, because bitfield order is poorly defined (#ifdef
__LITTLE_ENDIAN_BITFIELD can be used, but is gross), incrementing the
sequence number would overflow into the rest of the bitfield if the
compiler didn't put the sequence number at the high end of the word.
The new code is a bit saner when we're on an architecture without real
atomic64_t support - all accesses to lock->state now go through
atomic64_*() operations.
On architectures with real atomic64_t support, we additionally use
atomic bit ops for setting/clearing individual bits.
Text size: 7467 bytes -> 4649 bytes - compilers still suck at
bitfields.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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It's for doing updates - this is where it belongs, and next pathes will
be changing these helpers to use items from btree_update.h.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Introduce new helpers for a common pattern:
bch2_trans_iter_init();
bch2_btree_iter_peek_slot();
- bch2_bkey_get_iter_type() returns -ENOENT if it doesn't find a key of
the correct type
- bch2_bkey_get_val_typed() copies the val out of the btree to a
(typically stack allocated) variable; it handles the case where the
value in the btree is smaller than the current version of the type,
zeroing out the remainder.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Minor refactoring for the Rust interface.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Needed for interfacing with Rust - bindgen can't handle inline
functions, alas.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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These are two different things - this improves our debug assert
messages.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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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>
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It's important that in BTREE_ITER_FILTER_SNAPSHOTS mode we always use
peek_upto() and provide an end for the interval we're searching for -
otherwise, when we hit the end of the inode the next inode be in a
different subvolume and not have any keys in the current snapshot, and
we'd iterate over arbitrarily many keys before returning one.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This replaces various BUG_ON() assertions with panics that tell us where
the restart was done and the restart type.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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In debug mode, we now track where btree iterators and paths are
initialized/allocated - helpful in tracking down btree path overflows.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This introduces some new conveniences, to help cut down on boilerplate:
- bch2_trans_kmalloc_nomemzero() - performance optimiation
- bch2_bkey_make_mut()
- bch2_bkey_get_mut()
- bch2_bkey_get_mut_typed()
- bch2_bkey_alloc()
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This patch introduces
- bpos_eq()
- bpos_lt()
- bpos_le()
- bpos_gt()
- bpos_ge()
and equivalent replacements for bkey_cmp().
Looking at the generated assembly these could probably be improved
further, but we already see a significant code size improvement with
this patch.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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When flags & btree_id are constants, we can constant fold the entire
calculation of the actual iterator flags - and the whole thing becomes
small enough to inline.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Previously, when we exited from the loop body with a break statement
_ret wouldn't have been assigned to yet, and we could spuriously return
a transaction restart error.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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trans->restarted is a positive error code, not the usual negative
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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- 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>
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Now we store the transaction's fn idx in a local variable, instead of
redoing the lookup every time we call bch2_trans_init().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Useful debugging function.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Small performance optimization.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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We've outgrown our own deadlock avoidance strategy.
The btree iterator API provides an interface where the user doesn't need
to concern themselves with lock ordering - different btree iterators can
be traversed in any order. Without special care, this will lead to
deadlocks.
Our previous strategy was to define a lock ordering internally, and
whenever we attempt to take a lock and trylock() fails, we'd check if
the current btree transaction is holding any locks that cause a lock
ordering violation. If so, we'd issue a transaction restart, and then
bch2_trans_begin() would re-traverse all previously used iterators, but
in the correct order.
That approach had some issues, though.
- Sometimes we'd issue transaction restarts unnecessarily, when no
deadlock would have actually occured. Lock ordering restarts have
become our primary cause of transaction restarts, on some workloads
totally 20% of actual transaction commits.
- To avoid deadlock or livelock, we'd often have to take intent locks
when we only wanted a read lock: with the lock ordering approach, it
is actually illegal to hold _any_ read lock while blocking on an intent
lock, and this has been causing us unnecessary lock contention.
- It was getting fragile - the various lock ordering rules are not
trivial, and we'd been seeing occasional livelock issues related to
this machinery.
So, since bcachefs is already a relational database masquerading as a
filesystem, we're stealing the next traditional database technique and
switching to a cycle detector for avoiding deadlocks.
When we block taking a btree lock, after adding ourself to the waitlist
but before sleeping, we do a DFS of btree transactions waiting on other
btree transactions, starting with the current transaction and walking
our held locks, and transactions blocking on our held locks.
If we find a cycle, we emit a transaction restart. Occasionally (e.g.
the btree split path) we can not allow the lock() operation to fail, so
if necessary we'll tell another transaction that it has to fail.
Result: trans_restart_would_deadlock events are reduced by a factor of
10 to 100, and we'll be able to delete a whole bunch of grotty, fragile
code.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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With the new deadlock cycle detector, it's critical that all held locks
be marked in a btree_path, because that's what the cycle detector
traverses - any locks that aren't correctly marked will cause deadlocks.
This changes the btree_path to allocate some btree_paths for the new
nodes, since until the final update is done we otherwise don't have a
path referencing them.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Also, do some reorganizing/renaming, convert atomic counters in bch_fs
to persistent counters, and add a few missing counters.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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- Don't decrease BTREE_ITER_MAX when building with CONFIG_LOCKDEP
anymore. The lockdep table sizes are configurable now, we don't need
this anymore.
- btree_trans_too_many_iters() is less conservative now. Previously it
was causing a transaction restart if we had used more than
BTREE_ITER_MAX / 2 paths, change this to BTREE_ITER_MAX - 8.
This helps with excessive transaction restarts/livelocks in the bucket
allocator path.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This patch
- tracks maximum bch2_trans_kmalloc() memory used in btree_transaction_stats
- makes it available in debugfs
- switches bch2_trans_init() to using that for the amount of memory to
preallocate, instead of the parameter passed in
This drastically reduces transaction restarts, and means we no longer
need to track this in the source code.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Start to centralize some of the locking code in a new file; more locking
code will be moving here in the future.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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Instead of counting transaction restarts, count when the transaction is
restarted: if bch2_trans_begin() was called when the transaction wasn't
restarted we need to ensure restart_count is still incremented.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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We need a way to check if the machinery for handling btree_paths with in
a transaction is behaving reasonably, as it often has not been - we've
had bugs with transaction path overflows caused by duplicate paths and
plenty of other things.
This patch tracks, per transaction fn, the most btree paths ever
allocated by that transaction and makes it available in debugfs.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Our types are exported to the tracepoint code, so it's not necessary to
break things out individually when passing them to tracepoints - we can
also call other functions from TP_fast_assign().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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Clearing path->preserve means the path will be dropping in
bch2_trans_begin() - but on transaction restart, we're likely to need
that path again.
This fixes a livelock in the allocation path.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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This adds a new macro, like for_each_btree_key2(), but for iterating in
reverse order.
Also, change for_each_btree_key2() to properly check the return value of
bch2_btree_iter_advance().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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Now that we have error codes, with subtypes, we can switch to our own
error code for transaction restarts - and even better, a distinct error
code for each transaction restart reason: clearer code and better
debugging.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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All transaction restarts need a tracepoint - this is essential for
debugging
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This will help us improve nested transactions - we need to add
assertions that whenever an inner transaction handles a restart, it
still returns -EINTR to the outer transaction.
This also adds nested_lockrestart_do() and nested_commit_do() which use
the new counters to correctly return -EINTR when the transaction was
restarted.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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We need the caller name and a place to store our results, btree_trans provides this.
Signed-off-by: Daniel Hill <daniel@gluo.nz>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This introduces two new macros for iterating through the btree, with
transaction restart handling
- for_each_btree_key2()
- for_each_btree_key_commit()
Every iteration is now in an implicit transaction, and - as with
lockrestart_do() and commit_do() - returning -EINTR will cause the
transaction to be restarted, at the same key.
This patch converts a bunch of code that was open coding this to these
new macros, saving a substantial amount of code.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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When inserting a key type that's not valid for a given btree, we should
print out which btree we were inserting into.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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Previously, on every btree_iter_peek() operation we were searching the
journal keys, doing a full binary search - which was slow.
This patch fixes that by saving our position in the journal keys, so
that we only do a full binary search when moving our position backwards
or a large jump forwards.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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This adds bch2_btree_iter_peek_all_levels(), which returns keys from
every level of the btree - interior nodes included - in monotonically
increasing order, soon to be used by the backpointers check & repair
code.
- BTREE_ITER_ALL_LEVELS can now be passed to for_each_btree_key() to
iterate thusly, much like BTREE_ITER_SLOTS
- The existing algorithm in bch2_btree_iter_advance() doesn't work with
peek_all_levels(): we have to defer the actual advancing until the
next time we call peek, where we have the btree path traversed and
uptodate. So, we add an advanced bit to btree_iter; when
BTREE_ITER_ALL_LEVELS is set bch2_btree_iter_advanced() just marks
the iterator as advanced.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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This fixes a bug where __bch2_btree_node_update_key() wasn't clearing
should_be_locked, leading to bch2_btree_path_traverse() always failing -
all callers of btree_path_make_mut() want should_be_locked cleared, so
do it there.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
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This turns bch2_dump_trans_updates() into a to_text() method - this way
it can be used by debug tracing.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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