From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit 5c47e6d0ad608987b91affbcf7d1fc12dfbe8fb4 upstream.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
fs/dcache.c | 75 +++++++++++++++++++++----------------------------------------
1 file changed, 25 insertions(+), 50 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 42ac7548ae67..533a44b8e021 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -809,47 +809,9 @@ restart:
}
EXPORT_SYMBOL(d_prune_aliases);
-/*
- * Try to throw away a dentry - free the inode, dput the parent.
- * Requires dentry->d_lock is held, and dentry->d_count == 0.
- * Releases dentry->d_lock.
- *
- * This may fail if locks cannot be acquired no problem, just try again.
- */
-static struct dentry * try_prune_one_dentry(struct dentry *dentry)
- __releases(dentry->d_lock)
-{
- struct dentry *parent;
-
- parent = dentry_kill(dentry, 0);
- /*
- * If dentry_kill returns NULL, we have nothing more to do.
- * if it returns the same dentry, trylocks failed. In either
- * case, just loop again.
- *
- * Otherwise, we need to prune ancestors too. This is necessary
- * to prevent quadratic behavior of shrink_dcache_parent(), but
- * is also expected to be beneficial in reducing dentry cache
- * fragmentation.
- */
- if (!parent)
- return NULL;
- if (parent == dentry)
- return dentry;
-
- /* Prune ancestors. */
- dentry = parent;
- while (dentry) {
- if (lockref_put_or_lock(&dentry->d_lockref))
- return NULL;
- dentry = dentry_kill(dentry, 1);
- }
- return NULL;
-}
-
static void shrink_dentry_list(struct list_head *list)
{
- struct dentry *dentry;
+ struct dentry *dentry, *parent;
rcu_read_lock();
for (;;) {
@@ -885,22 +847,35 @@ static void shrink_dentry_list(struct list_head *list)
}
rcu_read_unlock();
+ parent = dentry_kill(dentry, 0);
/*
- * If 'try_to_prune()' returns a dentry, it will
- * be the same one we passed in, and d_lock will
- * have been held the whole time, so it will not
- * have been added to any other lists. We failed
- * to get the inode lock.
- *
- * We just add it back to the shrink list.
+ * If dentry_kill returns NULL, we have nothing more to do.
*/
- dentry = try_prune_one_dentry(dentry);
-
- rcu_read_lock();
- if (dentry) {
+ if (!parent) {
+ rcu_read_lock();
+ continue;
+ }
+ if (unlikely(parent == dentry)) {
+ /*
+ * trylocks have failed and d_lock has been held the
+ * whole time, so it could not have been added to any
+ * other lists. Just add it back to the shrink list.
+ */
+ rcu_read_lock();
d_shrink_add(dentry, list);
spin_unlock(&dentry->d_lock);
+ continue;
}
+ /*
+ * We need to prune ancestors too. This is necessary to prevent
+ * quadratic behavior of shrink_dcache_parent(), but is also
+ * expected to be beneficial in reducing dentry cache
+ * fragmentation.
+ */
+ dentry = parent;
+ while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
+ dentry = dentry_kill(dentry, 1);
+ rcu_read_lock();
}
rcu_read_unlock();
}
--
2.1.2
--
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