5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Josef Bacik josef@toxicpanda.com
[ Upstream commit 4048daedb910f83f080c6bb03c78af794aebdff5 ]
Now that we're no longer using recursion, rip out all of the supporting code. Follow up patches will clean up the callers of these functions.
The extent_buffer::lock_owner is still retained as it allows safety checks in btrfs_init_new_buffer for the case that the free space cache is corrupted and we try to allocate a block that we are currently using and have locked in the path.
Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Josef Bacik josef@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Stable-dep-of: 97e86631bccd ("btrfs: don't set lock_owner when locking extent buffer for reading") Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/locking.c | 68 +++------------------------------------------- 1 file changed, 4 insertions(+), 64 deletions(-)
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index 5260660b655a..1e36a66fcefa 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -25,43 +25,18 @@ * - reader/reader sharing * - try-lock semantics for readers and writers * - * Additionally we need one level nesting recursion, see below. The rwsem - * implementation does opportunistic spinning which reduces number of times the - * locking task needs to sleep. - * - * - * Lock recursion - * -------------- - * - * A write operation on a tree might indirectly start a look up on the same - * tree. This can happen when btrfs_cow_block locks the tree and needs to - * lookup free extents. - * - * btrfs_cow_block - * .. - * alloc_tree_block_no_bg_flush - * btrfs_alloc_tree_block - * btrfs_reserve_extent - * .. - * load_free_space_cache - * .. - * btrfs_lookup_file_extent - * btrfs_search_slot - * + * The rwsem implementation does opportunistic spinning which reduces number of + * times the locking task needs to sleep. */
/* * __btrfs_tree_read_lock - lock extent buffer for read * @eb: the eb to be locked * @nest: the nesting level to be used for lockdep - * @recurse: if this lock is able to be recursed + * @recurse: unused * * This takes the read lock on the extent buffer, using the specified nesting * level for lockdep purposes. - * - * If you specify recurse = true, then we will allow this to be taken if we - * currently own the lock already. This should only be used in specific - * usecases, and the subsequent unlock will not change the state of the lock. */ void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest, bool recurse) @@ -71,31 +46,7 @@ void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting ne if (trace_btrfs_tree_read_lock_enabled()) start_ns = ktime_get_ns();
- if (unlikely(recurse)) { - /* First see if we can grab the lock outright */ - if (down_read_trylock(&eb->lock)) - goto out; - - /* - * Ok still doesn't necessarily mean we are already holding the - * lock, check the owner. - */ - if (eb->lock_owner != current->pid) { - down_read_nested(&eb->lock, nest); - goto out; - } - - /* - * Ok we have actually recursed, but we should only be recursing - * once, so blow up if we're already recursed, otherwise set - * ->lock_recursed and carry on. - */ - BUG_ON(eb->lock_recursed); - eb->lock_recursed = true; - goto out; - } down_read_nested(&eb->lock, nest); -out: eb->lock_owner = current->pid; trace_btrfs_tree_read_lock(eb, start_ns); } @@ -136,22 +87,11 @@ int btrfs_try_tree_write_lock(struct extent_buffer *eb) }
/* - * Release read lock. If the read lock was recursed then the lock stays in the - * original state that it was before it was recursively locked. + * Release read lock. */ void btrfs_tree_read_unlock(struct extent_buffer *eb) { trace_btrfs_tree_read_unlock(eb); - /* - * if we're nested, we have the write lock. No new locking - * is needed as long as we are the lock owner. - * The write unlock will do a barrier for us, and the lock_recursed - * field only matters to the lock owner. - */ - if (eb->lock_recursed && current->pid == eb->lock_owner) { - eb->lock_recursed = false; - return; - } eb->lock_owner = 0; up_read(&eb->lock); }