A delete lock prevents a dentry from being unlinked and renamed,
for as long as the dentry remains in cache.
Introduce the helpers delete_trylock() and delete_unlock(), which
use test_and_set and test_and_clear semantics to ser/clear a delete
lock on a dentry.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
include/linux/dcache.h | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 94cd40c..90584b9 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -356,11 +356,33 @@ static inline int cant_delete(const struct dentry *dentry)
return (dentry->d_flags & DCACHE_DELETE_LOCK);
}
-static inline void dont_delete(struct dentry *dentry)
+static inline int delete_trylock(struct dentry *dentry)
{
+ int locked;
+
spin_lock(&dentry->d_lock);
+ locked = likely(!cant_delete(dentry));
dentry->d_flags |= DCACHE_DELETE_LOCK;
spin_unlock(&dentry->d_lock);
+
+ return locked;
+}
+
+static inline void dont_delete(struct dentry *dentry)
+{
+ delete_trylock(dentry);
+}
+
+static inline int delete_unlock(struct dentry *dentry)
+{
+ int unlocked;
+
+ spin_lock(&dentry->d_lock);
+ unlocked = likely(cant_delete(dentry));
+ dentry->d_flags &= ~DCACHE_DELETE_LOCK;
+ spin_unlock(&dentry->d_lock);
+
+ return unlocked;
}
extern void __d_lookup_done(struct dentry *);
--
2.7.4
--
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