ovl: lookup indexed ancestor of lower dir
ovl_lookup_real() in lower layer walks back lower parents to find the
topmost indexed parent. If an indexed ancestor is found before reaching
lower layer root, ovl_lookup_real() is called recursively with upper
layer to walk back from indexed upper to the topmost connected/hashed
upper parent (or up to root).
ovl_lookup_real() in upper layer then walks forward to connect the topmost
upper overlay dir dentry and ovl_lookup_real() in lower layer continues to
walk forward to connect the decoded lower overlay dir dentry.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 092e6e8..b65ea49 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -294,6 +294,10 @@ static struct dentry *ovl_lookup_real_one(struct dentry *connected,
goto out;
}
+static struct dentry *ovl_lookup_real(struct super_block *sb,
+ struct dentry *real,
+ struct ovl_layer *layer);
+
/*
* Lookup an indexed or hashed overlay dentry by real inode.
*/
@@ -301,9 +305,16 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
struct dentry *real,
struct ovl_layer *layer)
{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt };
+ struct dentry *index = NULL;
struct dentry *this = NULL;
struct inode *inode;
+ /*
+ * Decoding upper dir from index is expensive, so first try to lookup
+ * overlay dentry in inode/dcache.
+ */
inode = ovl_lookup_inode(sb, real, !layer->idx);
if (IS_ERR(inode))
return ERR_CAST(inode);
@@ -312,7 +323,35 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
iput(inode);
}
- /* TODO: use index when looking up by origin inode */
+ /*
+ * For decoded lower dir file handle, lookup index by origin to check
+ * if lower dir was copied up and and/or removed.
+ */
+ if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) {
+ index = ovl_lookup_index(ofs, NULL, real, false);
+ if (IS_ERR(index))
+ return index;
+ }
+
+ /* Get connected upper overlay dir from index */
+ if (index) {
+ struct dentry *upper = ovl_index_upper(ofs, index);
+
+ dput(index);
+ if (IS_ERR_OR_NULL(upper))
+ return upper;
+
+ /*
+ * ovl_lookup_real() in lower layer may call recursively once to
+ * ovl_lookup_real() in upper layer. The first level call walks
+ * back lower parents to the topmost indexed parent. The second
+ * recursive call walks back from indexed upper to the topmost
+ * connected/hashed upper parent (or up to root).
+ */
+ this = ovl_lookup_real(sb, upper, &upper_layer);
+ dput(upper);
+ }
+
if (!this)
return NULL;