This patch attempts to enable RCU-walk for fscrypt.
It looks harmless at glance and could have better
performance than do ref-walk only.
Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
---
fs/crypto/crypto.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index b38c574..9bd21c0 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -319,20 +319,24 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
{
struct dentry *dir;
int dir_has_key, cached_with_key;
-
- if (flags & LOOKUP_RCU)
- return -ECHILD;
-
- dir = dget_parent(dentry);
- if (!IS_ENCRYPTED(d_inode(dir))) {
- dput(dir);
+ struct inode *dir_inode;
+
+ rcu_read_lock();
+repeat:
+ dir = READ_ONCE(dentry->d_parent);
+ dir_inode = d_inode_rcu(dir);
+ if (!IS_ENCRYPTED(dir_inode)) {
+ rcu_read_unlock();
return 0;
}
+ dir_has_key = (dir_inode->i_crypt_info != NULL);
+ if (unlikely(READ_ONCE(dir->d_lockref.count) < 0 ||
+ READ_ONCE(dir->d_parent) != dir))
+ goto repeat;
+ rcu_read_unlock();
cached_with_key = READ_ONCE(dentry->d_flags) &
DCACHE_ENCRYPTED_WITH_KEY;
- dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
- dput(dir);
/*
* If the dentry was cached without the key, and it is a
--
1.9.1
|