When a file is only in a lower layer, after lookup a negative
dentry will be generated in the upper layer or even worse many
negetive dentries will be generated in upper/lower layers. These
negative dentries will be useless after construction of overlayfs'
own dentry and may keep in the memory long time even after unmount
of overlayfs instance. This patch tries to kill unnecessary negative
dentry during lookup.
Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
---
fs/overlayfs/namei.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 723d17744758..cf0ec4d7bcec 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -200,7 +200,7 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
int err;
bool last_element = !post[0];
- this = lookup_positive_unlocked(name, base, namelen);
+ this = lookup_one_len_unlocked(name, base, namelen);
if (IS_ERR(this)) {
err = PTR_ERR(this);
this = NULL;
@@ -209,6 +209,15 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
goto out_err;
}
+ /* Borrow the check from lookup_positive_unlocked */
+ if (d_flags_negative(smp_load_acquire(&this->d_flags))) {
+ d_drop(this);
+ dput(this);
+ this = NULL;
+ err = -ENOENT;
+ goto out;
+ }
+
if (ovl_dentry_weird(this)) {
/* Don't support traversing automounts and other weirdness */
err = -EREMOTE;
--
2.20.1
