fs: dcache reduce dput locking
It is possible to run dput without taking data structure locks up-front. In
many cases where we don't kill the dentry anyway, these locks are not required.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/fs/dcache.c b/fs/dcache.c
index bf6294a..98a0569 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -323,35 +323,16 @@
if (dentry->d_count == 1)
might_sleep();
spin_lock(&dentry->d_lock);
- if (IS_ROOT(dentry))
- parent = NULL;
- else
- parent = dentry->d_parent;
- if (dentry->d_count == 1) {
- if (!spin_trylock(&dcache_inode_lock)) {
-drop2:
- spin_unlock(&dentry->d_lock);
- goto repeat;
- }
- if (parent && !spin_trylock(&parent->d_lock)) {
- spin_unlock(&dcache_inode_lock);
- goto drop2;
- }
- }
- dentry->d_count--;
- if (dentry->d_count) {
+ BUG_ON(!dentry->d_count);
+ if (dentry->d_count > 1) {
+ dentry->d_count--;
spin_unlock(&dentry->d_lock);
- if (parent)
- spin_unlock(&parent->d_lock);
return;
}
- /*
- * AV: ->d_delete() is _NOT_ allowed to block now.
- */
if (dentry->d_op && dentry->d_op->d_delete) {
if (dentry->d_op->d_delete(dentry))
- goto unhash_it;
+ goto kill_it;
}
/* Unreachable? Get rid of it */
@@ -362,17 +343,30 @@
dentry->d_flags |= DCACHE_REFERENCED;
dentry_lru_add(dentry);
- spin_unlock(&dentry->d_lock);
- if (parent)
- spin_unlock(&parent->d_lock);
- spin_unlock(&dcache_inode_lock);
+ dentry->d_count--;
+ spin_unlock(&dentry->d_lock);
return;
-unhash_it:
- __d_drop(dentry);
kill_it:
+ if (!spin_trylock(&dcache_inode_lock)) {
+relock:
+ spin_unlock(&dentry->d_lock);
+ cpu_relax();
+ goto repeat;
+ }
+ if (IS_ROOT(dentry))
+ parent = NULL;
+ else
+ parent = dentry->d_parent;
+ if (parent && !spin_trylock(&parent->d_lock)) {
+ spin_unlock(&dcache_inode_lock);
+ goto relock;
+ }
+ dentry->d_count--;
/* if dentry was on the d_lru list delete it from there */
dentry_lru_del(dentry);
+ /* if it was on the hash (d_delete case), then remove it */
+ __d_drop(dentry);
dentry = d_kill(dentry, parent);
if (dentry)
goto repeat;