lwn.git/fs/bcachefs/btree_write_buffer.h, branch docs-next

Remove bcachefs core code

2025-09-29T20:43:52+00:00

bcachefs was marked 'externally maintained' in 6.17 but the code remained to make the transition smoother. It's now a DKMS module, making the in-kernel code stale, so remove it to avoid any version confusion. Link: https://lore.kernel.org/linux-bcachefs/yokpt2d2g2lluyomtqrdvmkl3amv3kgnipmenobkpgx537kay7@xgcgjviv3n7x/T/ Signed-off-by: Linus Torvalds

bcachefs: Check for bad write buffer key when moving from journal

2025-06-24T19:48:00+00:00

Signed-off-by: Kent Overstreet

bcachefs: Move various init code to _init_early()

2025-05-22T00:14:02+00:00

_init_early() is for initialization that cannot fail, and often must happen for teardown partway through initialization to work. Signed-off-by: Kent Overstreet

bcachefs: bch2_btree_write_buffer_flush_going_ro()

2024-11-08T04:31:11+00:00

The write buffer needs to be specifically flushed when going RO: keys in the journal that haven't yet been moved to the write buffer don't have a journal pin yet. This fixes numerous syzbot bugs, all with symptoms of still doing writes after we've got RO. Signed-off-by: Kent Overstreet

bcachefs: Eytzinger accumulation for accounting keys

2024-07-14T23:00:14+00:00

The btree write buffer takes as input keys from the journal, sorts them, deduplicates them, and flushes them back to the btree in sorted order. The disk space accounting rewrite is moving accounting to normal btree keys, with update (in this case deltas) accumulated in the write buffer and then flushed to the btree; but this is going to increase the number of keys handled by the write buffer by perhaps as much as a factor of 3x-5x. The overhead from copying around and sorting this many keys would cause a significant performance regression, but: there is huge locality in updates to accounting keys that we can take advantage of. Instead of appending accounting keys to the list of keys to be sorted, this patch adds an eytzinger search tree of recently seen accounting keys. We look up the accounting key in the eytzinger search tree and apply the delta directly, adding it if it doesn't exist, and periodically prune the eytzinger tree of unused entries. Signed-off-by: Kent Overstreet

bcachefs: bch2_btree_write_buffer_maybe_flush()

2024-06-29T22:34:52+00:00

Add a new helper for checking references to write buffer btrees, where we need a flush before we definitively know we have an inconsistency. Signed-off-by: Kent Overstreet

bcachefs: __bch2_journal_key_to_wb -> bch2_journal_key_to_wb_slowpath

2024-01-06T04:24:19+00:00

Signed-off-by: Kent Overstreet

bcachefs: btree write buffer now slurps keys from journal

2024-01-01T16:47:41+00:00

Previosuly, the transaction commit path would have to add keys to the btree write buffer as a separate operation, requiring additional global synchronization. This patch introduces a new journal entry type, which indicates that the keys need to be copied into the btree write buffer prior to being written out. We switch the journal entry type back to JSET_ENTRY_btree_keys prior to write, so this is not an on disk format change. Flushing the btree write buffer may require pulling keys out of journal entries yet to be written, and quiescing outstanding journal reservations; we previously added journal->buf_lock for synchronization with the journal write path. We also can't put strict bounds on the number of keys in the journal destined for the write buffer, which means we might overflow the size of the preallocated buffer and have to reallocate - this introduces a potentially fatal memory allocation failure. This is something we'll have to watch for, if it becomes an issue in practice we can do additional mitigation. The transaction commit path no longer has to explicitly check if the write buffer is full and wait on flushing; this is another performance optimization. Instead, when the btree write buffer is close to full we change the journal watermark, so that only reservations for journal reclaim are allowed. Signed-off-by: Kent Overstreet

bcachefs: bch2_btree_write_buffer_flush() -> bch2_btree_write_buffer_tryflush()

2024-01-01T16:47:39+00:00

More accurate naming. Signed-off-by: Kent Overstreet

bcachefs: bch2_btree_write_buffer_flush_locked()

2024-01-01T16:47:39+00:00

Minor refactoring - improved naming, and move the responsibility for flush_lock to the caller instead of having it be shared. Signed-off-by: Kent Overstreet