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Commit 89e60548 authored by Nick Piggin's avatar Nick Piggin
Browse files

fs: dcache reduce prune_one_dentry locking 



prune_one_dentry can avoid quite a bit of locking in the common case where
ancestors have an elevated refcount. Alternatively, we could have gone the
other way and made fewer trylocks in the case where d_count goes to zero, but
is probably less common.

Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
parent a734eb45

fs/dcache.c

+15 −12
Original line number Diff line number Diff line
@@ -582,26 +582,29 @@ static void prune_one_dentry(struct dentry *dentry, struct dentry *parent) 
	 * Prune ancestors.

	 */

	while (dentry) {

		spin_lock(&dcache_inode_lock);

again:

relock:

		spin_lock(&dentry->d_lock);

		if (dentry->d_count > 1) {

			dentry->d_count--;

			spin_unlock(&dentry->d_lock);

			return;

		}

		if (!spin_trylock(&dcache_inode_lock)) {

relock2:

			spin_unlock(&dentry->d_lock);

			cpu_relax();

			goto relock;

		}



		if (IS_ROOT(dentry))

			parent = NULL;

		else

			parent = dentry->d_parent;

		if (parent && !spin_trylock(&parent->d_lock)) {

			spin_unlock(&dentry->d_lock);

			goto again;

		}

		dentry->d_count--;

		if (dentry->d_count) {

			if (parent)

				spin_unlock(&parent->d_lock);

			spin_unlock(&dentry->d_lock);

			spin_unlock(&dcache_inode_lock);

			return;

			goto relock2;

		}



		dentry->d_count--;

		dentry_lru_del(dentry);

		__d_drop(dentry);

		dentry = d_kill(dentry, parent);