ovl: multi-layer lookup

Look up dentry in all relevant layers.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 94 insertions, 49 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index c245043aa1b9..f72b82fdc1e6 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -333,82 +333,127 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                           unsigned int flags)
 {
         struct ovl_entry *oe;
-        struct dentry *upperdir;
-        struct path lowerdir;
-        struct dentry *upperdentry = NULL;
-        struct dentry *lowerdentry = NULL;
+        struct ovl_entry *poe = dentry->d_parent->d_fsdata;
+        struct path *stack = NULL;
+        struct dentry *upperdir, *upperdentry = NULL;
+        unsigned int ctr = 0;
         struct inode *inode = NULL;
+        bool upperopaque = false;
+        struct dentry *this, *prev = NULL;
+        unsigned int i;
         int err;
 
-        err = -ENOMEM;
-        oe = ovl_alloc_entry(1);
-        if (!oe)
-                goto out;
-
-        upperdir = ovl_dentry_upper(dentry->d_parent);
-        ovl_path_lower(dentry->d_parent, &lowerdir);
-
+        upperdir = ovl_upperdentry_dereference(poe);
         if (upperdir) {
-                upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
-                err = PTR_ERR(upperdentry);
-                if (IS_ERR(upperdentry))
-                        goto out_put_dir;
-
-                if (lowerdir.dentry && upperdentry) {
-                        if (ovl_is_whiteout(upperdentry)) {
-                                dput(upperdentry);
-                                upperdentry = NULL;
-                                oe->opaque = true;
-                        } else if (ovl_is_opaquedir(upperdentry)) {
-                                oe->opaque = true;
+                this = ovl_lookup_real(upperdir, &dentry->d_name);
+                err = PTR_ERR(this);
+                if (IS_ERR(this))
+                        goto out;
+
+                /*
+                 * If this is not the lowermost layer, check whiteout and opaque
+                 * directory.
+                 */
+                if (poe->numlower && this) {
+                        if (ovl_is_whiteout(this)) {
+                                dput(this);
+                                this = NULL;
+                                upperopaque = true;
+                        } else if (ovl_is_opaquedir(this)) {
+                                upperopaque = true;
                         }
                 }
+                upperdentry = prev = this;
         }
-        if (lowerdir.dentry && !oe->opaque) {
-                lowerdentry = ovl_lookup_real(lowerdir.dentry, &dentry->d_name);
-                err = PTR_ERR(lowerdentry);
-                if (IS_ERR(lowerdentry))
-                        goto out_dput_upper;
+
+        if (!upperopaque && poe->numlower) {
+                err = -ENOMEM;
+                stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
+                if (!stack)
+                        goto out_put_upper;
         }
 
-        if (lowerdentry && upperdentry &&
-            (!S_ISDIR(upperdentry->d_inode->i_mode) ||
-             !S_ISDIR(lowerdentry->d_inode->i_mode))) {
-                dput(lowerdentry);
-                lowerdentry = NULL;
-                oe->opaque = true;
+        for (i = 0; !upperopaque && i < poe->numlower; i++) {
+                bool opaque = false;
+                struct path lowerpath = poe->lowerstack[i];
+
+                opaque = false;
+                this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
+                err = PTR_ERR(this);
+                if (IS_ERR(this))
+                        goto out_put;
+                if (!this)
+                        continue;
+
+                /*
+                 * If this is not the lowermost layer, check whiteout and opaque
+                 * directory.
+                 */
+                if (i < poe->numlower - 1) {
+                        if (ovl_is_whiteout(this)) {
+                                dput(this);
+                                break;
+                        } else if (ovl_is_opaquedir(this)) {
+                                opaque = true;
+                        }
+                }
+                /*
+                 * If this is a non-directory then stop here.
+                 *
+                 * FIXME: check for opaqueness maybe better done in remove code.
+                 */
+                if (!S_ISDIR(this->d_inode->i_mode)) {
+                        opaque = true;
+                } else if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
+                                    !S_ISDIR(this->d_inode->i_mode))) {
+                        if (prev == upperdentry)
+                                upperopaque = true;
+                        dput(this);
+                        break;
+                }
+                stack[ctr].dentry = this;
+                stack[ctr].mnt = lowerpath.mnt;
+                ctr++;
+                prev = this;
+                if (opaque)
+                        break;
         }
 
-        if (lowerdentry || upperdentry) {
+        oe = ovl_alloc_entry(ctr);
+        err = -ENOMEM;
+        if (!oe)
+                goto out_put;
+
+        if (upperdentry || ctr) {
                 struct dentry *realdentry;
 
-                realdentry = upperdentry ? upperdentry : lowerdentry;
+                realdentry = upperdentry ? upperdentry : stack[0].dentry;
+
                 err = -ENOMEM;
                 inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
                                       oe);
                 if (!inode)
-                        goto out_dput;
+                        goto out_free_oe;
                 ovl_copyattr(realdentry->d_inode, inode);
         }
 
+        oe->opaque = upperopaque;
         oe->__upperdentry = upperdentry;
-        if (lowerdentry) {
-                oe->lowerstack[0].dentry = lowerdentry;
-                oe->lowerstack[0].mnt = lowerdir.mnt;
-        } else {
-                oe->numlower = 0;
-        }
+        memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
+        kfree(stack);
         dentry->d_fsdata = oe;
         d_add(dentry, inode);
 
         return NULL;
 
-out_dput:
-        dput(lowerdentry);
-out_dput_upper:
-        dput(upperdentry);
-out_put_dir:
+out_free_oe:
         kfree(oe);
+out_put:
+        for (i = 0; i < ctr; i++)
+                dput(stack[i].dentry);
+        kfree(stack);
+out_put_upper:
+        dput(upperdentry);
 out:
         return ERR_PTR(err);
 }