kernel/git/stable/linux.git/fs/btrfs/ctree.c, branch master

btrfs: switch local indicator variables to bools

2026-06-09T16:22:46+00:00

For all local indicator variables do simple switch to bool, done on all files. Signed-off-by: David Sterba

btrfs: pass a valid btrfs_tree_parent_check when possible

2026-06-08T13:53:27+00:00

Commit 6e181cfe2409 ("btrfs: revalidate cached tree blocks on the uptodate path") introduced the @check parameter for btrfs_buffer_uptodate() to allow re-validation of a cached extent buffer. But there are still call sites that don't utilize this parameter, which exposes them to possible corrupted tree blocks, e.g. an empty child leaf of a parent node, which should be rejected by btrfs_verify_level_key() but if @check is NULL such check will be skipped and cause problems. Thankfully for a lot of cases there is already an existing @check structure around and we can pass it directly to btrfs_buffer_uptodate(). Reviewed-by: Boris Burkov Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: rename local variable for offset in folio

2026-04-07T16:56:07+00:00

Use proper abbreviation of the 'offset in folio' in the variable name, same as we have in accessors.c. Reviewed-by: Boris Burkov Signed-off-by: David Sterba

btrfs: unify types for binary search variables

2026-04-07T16:56:07+00:00

The variables calculating where to jump next are using mixed in types which requires some conversions on the instruction level. Using 'u32' removes one call to 'movslq', making the main loop shorter. This complements type conversion done in a724f313f84beb ("btrfs: do unsigned integer division in the extent buffer binary search loop") Signed-off-by: David Sterba

btrfs: remove duplicate calculation of eb offset in btrfs_bin_search()

2026-04-07T16:56:07+00:00

In the main search loop the variable 'oil' (offset in folio) is set twice, one duplicated when the key fits completely to the contiguous range. We can remove it and while it's just a simple calculation, the binary search loop is executed many times so micro optimizations add up. The code size is reduced by 64 bytes on release config, the loop is reorganized a bit and a few instructions shorter. Reviewed-by: Boris Burkov Signed-off-by: David Sterba

btrfs: remove atomic parameter from btrfs_buffer_uptodate()

2026-04-07T16:56:02+00:00

That parameter was introduced by commit b9fab919b748 ("Btrfs: avoid sleeping in verify_parent_transid while atomic"). At that time we needed to lock the extent buffer range inside the io tree to avoid content changes, thus it could sleep. But that behavior is no longer there, as later commit 9e2aff90fc2a ("btrfs: stop using lock_extent in btrfs_buffer_uptodate") dropped the io tree lock. We can remove the @atomic parameter safely now. Reviewed-by: Filipe Manana Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: revalidate cached tree blocks on the uptodate path

2026-04-07T16:56:02+00:00

read_extent_buffer_pages_nowait() returns immediately when an extent buffer is already marked uptodate. On that cache-hit path, the caller supplied btrfs_tree_parent_check is not re-run. This can let read_tree_root_path() accept a cached tree block whose actual header level/owner does not match the expected value derived from the parent. E.g. a corrupted root item that points to a tree block which doesn't even belong to that root, and has mismatching level/owner. But that tree block is already read and cached, later the corrupted tree root got read from disk and hit the cached tree block. Fix this by re-validating cached extent buffers against the supplied btrfs_tree_parent_check on the uptodate path, and make read_tree_root_path() pass its check to btrfs_buffer_uptodate(). This makes cache hits and fresh reads follow the same tree-parent verification rules, and turns the corruption into a read failure instead of constructing an inconsistent root object. Signed-off-by: ZhengYuan Huang Reviewed-by: Qu Wenruo [ Resolve the conflict with extent_buffer_uptodate() helper, handle transid mismatch case ] Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: add tracepoint for search slot restart tracking

2026-04-07T16:56:00+00:00

Add a btrfs_search_slot_restart tracepoint that fires at each restart site in btrfs_search_slot(), recording the root, tree level, and reason for the restart. This enables tracking search slot restarts which contribute to COW amplification under memory pressure. The four restart reasons are: - write_lock: insufficient write lock level, need to restart with higher lock - setup_nodes: node setup returned -EAGAIN - slot_zero: insertion at slot 0 requires higher write lock level - read_block: read_block_for_search returned -EAGAIN (block not cached or lock contention) COW counts are already tracked by the existing trace_btrfs_cow_block() tracepoint. The per-restart-site tracepoint avoids counter overhead in the critical path when tracepoints are disabled, and provides richer per-event information that bpftrace scripts can aggregate into counts, histograms, and per-root breakdowns. Reviewed-by: Filipe Manana Reviewed-by: Boris Burkov Signed-off-by: Leo Martins Signed-off-by: David Sterba

btrfs: inhibit extent buffer writeback to prevent COW amplification

2026-04-07T16:56:00+00:00

Inhibit writeback on COW'd extent buffers for the lifetime of the transaction handle, preventing background writeback from setting BTRFS_HEADER_FLAG_WRITTEN and causing unnecessary re-COW. COW amplification occurs when background writeback flushes an extent buffer that a transaction handle is still actively modifying. When lock_extent_buffer_for_io() transitions a buffer from dirty to writeback, it sets BTRFS_HEADER_FLAG_WRITTEN, marking the block as having been persisted to disk at its current bytenr. Once WRITTEN is set, should_cow_block() must either COW the block again or overwrite it in place, both of which are unnecessary overhead when the buffer is still being modified by the same handle that allocated it. By inhibiting background writeback on actively-used buffers, WRITTEN is never set while a transaction handle holds a reference to the buffer, avoiding this overhead entirely. Add an atomic_t writeback_inhibitors counter to struct extent_buffer, which fits in an existing 6-byte hole without increasing struct size. When a buffer is COW'd in btrfs_force_cow_block(), call btrfs_inhibit_eb_writeback() to store the eb in the transaction handle's writeback_inhibited_ebs xarray (keyed by eb->start), take a reference, and increment writeback_inhibitors. The function handles dedup (same eb inhibited twice by the same handle) and replacement (different eb at the same logical address). Allocation failure is graceful: the buffer simply falls back to the pre-existing behavior where it may be written back and re-COW'd. Also inhibit writeback in should_cow_block() when COW is skipped, so that every transaction handle that reuses an already-COW'd buffer also inhibits its writeback. Without this, if handle A COWs a block and inhibits it, and handle B later reuses the same block without inhibiting, handle A's uninhibit on end_transaction leaves the buffer unprotected while handle B is still using it. This ensures all handles that access a COW'd buffer contribute to the inhibitor count, and the buffer remains protected until the last handle releases it. In lock_extent_buffer_for_io(), when writeback_inhibitors is non-zero and the writeback mode is WB_SYNC_NONE, skip the buffer. WB_SYNC_NONE is used by the VM flusher threads for background and periodic writeback, which are the only paths that cause COW amplification by opportunistically writing out dirty extent buffers mid-transaction. Skipping these is safe because the buffers remain dirty in the page cache and will be written out at transaction commit time. WB_SYNC_ALL must always proceed regardless of writeback_inhibitors. This is required for correctness in the fsync path: btrfs_sync_log() writes log tree blocks via filemap_fdatawrite_range() (WB_SYNC_ALL) while the transaction handle that inhibited those same blocks is still active. Without the WB_SYNC_ALL bypass, those inhibited log tree blocks would be silently skipped, resulting in an incomplete log on disk and corruption on replay. btrfs_write_and_wait_transaction() also uses WB_SYNC_ALL via filemap_fdatawrite_range(); for that path, inhibitors are already cleared beforehand, but the bypass ensures correctness regardless. Uninhibit in __btrfs_end_transaction() before atomic_dec(num_writers) to prevent a race where the committer proceeds while buffers are still inhibited. Also uninhibit in btrfs_commit_transaction() before writing and in cleanup_transaction() for the error path. Reviewed-by: Filipe Manana Reviewed-by: Sun YangKai Reviewed-by: Boris Burkov Signed-off-by: Leo Martins Signed-off-by: David Sterba

btrfs: pass literal booleans to functions that take boolean arguments

2026-04-07T16:55:56+00:00

We have several functions with parameters defined as booleans but then we have callers passing integers, 0 or 1, instead of false and true. While this isn't a bug since 0 and 1 are converted to false and true, it is odd and less readable. Change the callers to pass true and false literals instead. Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba