To allow reconnecting of pure upper overlay dentry based on its
real parent, we restrict the implementation to encoding of overlay
dentries with pure upper ancestry up to overlay root.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/export.c | 70 ++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 61 insertions(+), 9 deletions(-)
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 33914f23530e..263415dd929b 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -17,15 +17,40 @@
#include "overlayfs.h"
#include "ovl_entry.h"
+/* Check if dentry is pure upper ancestry up to root */
+static bool ovl_is_pure_upper_or_root(struct dentry *dentry, int connectable)
+{
+ struct dentry *parent = NULL;
+
+ /* For non-connectable non-dir we don't need to check ancestry */
+ if (!d_is_dir(dentry) && !connectable)
+ return !ovl_dentry_lower(dentry);
+
+ dget(dentry);
+ while (!IS_ROOT(dentry) && !ovl_dentry_lower(dentry)) {
+ parent = dget_parent(dentry);
+ dput(dentry);
+ dentry = parent;
+ }
+ dput(dentry);
+
+ return dentry == dentry->d_sb->s_root;
+}
+
/* TODO: add export_operations method dentry_to_fh() ??? */
static int ovl_dentry_to_fh(struct dentry *dentry, struct fid *fid,
int *max_len, int connectable)
{
- struct dentry *lower = ovl_dentry_lower(dentry);
int type;
- /* TODO: handle encoding of non pure upper */
- if (lower)
+ /*
+ * Overlay root dir inode is hashed and encoded as pure upper, because
+ * root dir dentry is born upper and not indexed. It is not a problem
+ * that root dir is not indexed, because root dentry is pinned to cache.
+ *
+ * TODO: handle encoding of non pure upper.
+ */
+ if (!ovl_is_pure_upper_or_root(dentry, connectable))
return FILEID_INVALID;
/*
@@ -40,20 +65,47 @@ static int ovl_dentry_to_fh(struct dentry *dentry, struct fid *fid,
return type;
}
+/* Find an alias of inode. If @dir is non NULL, find a child alias */
+static struct dentry *ovl_find_alias(struct inode *inode, struct inode *dir)
+{
+ struct dentry *parent, *child;
+ struct dentry *alias = NULL;
+
+ /* Parent inode is never provided when encoding a directory */
+ if (!dir || WARN_ON(!S_ISDIR(dir->i_mode) || S_ISDIR(inode->i_mode)))
+ return d_find_alias(inode);
+
+ /*
+ * Run all of the dentries associated with this parent. Since this is
+ * a directory, there damn well better only be one item on this list.
+ */
+ spin_lock(&dir->i_lock);
+ hlist_for_each_entry(parent, &dir->i_dentry, d_u.d_alias) {
+ /* Find an alias of inode who is a child of parent */
+ spin_lock(&parent->d_lock);
+ list_for_each_entry(child, &parent->d_subdirs, d_child) {
+ if (child->d_inode == inode) {
+ alias = dget(child);
+ break;
+ }
+ }
+ spin_unlock(&parent->d_lock);
+ }
+ spin_unlock(&dir->i_lock);
+
+ return alias;
+}
+
static int ovl_encode_inode_fh(struct inode *inode, u32 *fh, int *max_len,
struct inode *parent)
{
- struct dentry *dentry = d_find_alias(inode);
+ struct dentry *dentry = ovl_find_alias(inode, parent);
int type;
if (!dentry)
return FILEID_INVALID;
- /* TODO: handle encoding of non-dir connectable file handle */
- if (parent)
- return FILEID_INVALID;
-
- type = ovl_dentry_to_fh(dentry, (struct fid *)fh, max_len, 0);
+ type = ovl_dentry_to_fh(dentry, (struct fid *)fh, max_len, !!parent);
dput(dentry);
return type;
--
2.7.4
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