[PATCH v2 03/20] ovl: relax same fs constrain for ovl_check_origin()

Amir Goldstein
2017-06-07T07:51:15Z

For the case of all layers not on the same fs, try to decode the copy up
origin file handle on any of the lower layers.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/namei.c | 43 +++++++++++++++++++++++++------------------
1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 1ec1499fc672..4ca6061f7bfa 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -272,28 +272,24 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry,
struct path **stackp, unsigned int *ctrp)
{
- struct super_block *same_sb = ovl_same_sb(dentry->d_sb);
struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
struct vfsmount *mnt;
- struct dentry *origin;
+ struct dentry *origin = NULL;
+ int i;

- if (!same_sb || !roe->numlower)
- return 0;

- /*
- * Since all layers are on the same fs, we use the first layer for
- * decoding the file handle. We may get a disconnected dentry,
- * which is fine, because we only need to hold the origin inode in
- * cache and use its inode number. We may even get a connected dentry,
- * that is not under the first layer's root. That is also fine for
- * using it's inode number - it's the same as if we held a reference
- * to a dentry in first layer that was moved under us.
- */
- mnt = roe->lowerstack[0].mnt;
-
- origin = ovl_get_origin(upperdentry, mnt);
- if (IS_ERR_OR_NULL(origin))
- return PTR_ERR(origin);
+ for (i = 0; i < roe->numlower; i++) {
+ mnt = roe->lowerstack[i].mnt;
+ origin = ovl_get_origin(upperdentry, mnt);
+ if (IS_ERR(origin))
+ return PTR_ERR(origin);
+
+ if (origin)
+ break;
+ }
+
+ if (!origin)
+ return 0;

BUG_ON(*stackp || *ctrp);
*stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
@@ -301,6 +297,7 @@ static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry,
dput(origin);
return -ENOMEM;
}
+
**stackp = (struct path) { .dentry = origin, .mnt = mnt };
*ctrp = 1;

@@ -375,6 +372,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
}
if (upperdentry && !d.is_dir) {
BUG_ON(!d.stop || d.redirect);
+ /*
+ * Lookup copy up origin by decoding origin file handle.
+ * We may get a disconnected dentry, which is fine,
+ * because we only need to hold the origin inode in
+ * cache and use its inode number. We may even get a
+ * connected dentry, that is not under any of the lower
+ * layers root. That is also fine for using it's inode
+ * number - it's the same as if we held a reference
+ * to a dentry in lower layer that was moved under us.
+ */
err = ovl_check_origin(dentry, upperdentry,
&stack, &ctr);
if (err)
--
2.7.4