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authorAl Viro <viro@zeniv.linux.org.uk>2018-02-23 21:25:42 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2018-03-29 15:07:44 -0400
commitf657a666fd1b1b9fe59963943c74c245ae66f4cc (patch)
treecf01b5b08611520699f8425b24029f7076a6357a
parent62d9956cefe6ecc4b43a7fae37af78ba7adaceaa (diff)
get rid of trylock loop around dentry_kill()
In case when trylock in there fails, deal with it directly in dentry_kill(). Note that in cases when we drop and retake ->d_lock, we need to recheck whether to retain the dentry. Another thing is that dropping/retaking ->d_lock might have ended up with negative dentry turning into positive; that, of course, can happen only once... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/dcache.c34
1 files changed, 27 insertions, 7 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index f5609902c6dd..f2d945688025 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -651,23 +651,43 @@ static struct dentry *dentry_kill(struct dentry *dentry)
struct dentry *parent = NULL;
if (inode && unlikely(!spin_trylock(&inode->i_lock)))
- goto failed;
+ goto slow_positive;
if (!IS_ROOT(dentry)) {
parent = dentry->d_parent;
if (unlikely(!spin_trylock(&parent->d_lock))) {
- if (inode)
- spin_unlock(&inode->i_lock);
- goto failed;
+ parent = __lock_parent(dentry);
+ if (likely(inode || !dentry->d_inode))
+ goto got_locks;
+ /* negative that became positive */
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ inode = dentry->d_inode;
+ goto slow_positive;
}
}
-
__dentry_kill(dentry);
return parent;
-failed:
+slow_positive:
+ spin_unlock(&dentry->d_lock);
+ spin_lock(&inode->i_lock);
+ spin_lock(&dentry->d_lock);
+ parent = lock_parent(dentry);
+got_locks:
+ if (unlikely(dentry->d_lockref.count != 1)) {
+ dentry->d_lockref.count--;
+ } else if (likely(!retain_dentry(dentry))) {
+ __dentry_kill(dentry);
+ return parent;
+ }
+ /* we are keeping it, after all */
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
spin_unlock(&dentry->d_lock);
- return dentry; /* try again with same dentry */
+ return NULL;
}
/*