fs/9p: Always ask new inode in lookup for cache mode disabled

This make sure we don't end up reusing the unlinked inode object.
The ideal way is to use inode i_generation. But i_generation is
not available in userspace always.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

1 files changed, 21 insertions, 7 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 9e3ea6ce6951..e3c03db3c788 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -825,6 +825,7 @@ static int v9fs_vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
                                       struct nameidata *nameidata)
 {
+        struct dentry *res;
         struct super_block *sb;
         struct v9fs_session_info *v9ses;
         struct p9_fid *dfid, *fid;
@@ -856,22 +857,35 @@ struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 
                 return ERR_PTR(result);
         }
-
-        inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
+        /*
+         * Make sure we don't use a wrong inode due to parallel
+         * unlink. For cached mode create calls request for new
+         * inode. But with cache disabled, lookup should do this.
+         */
+        if (v9ses->cache)
+                inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
+        else
+                inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
         if (IS_ERR(inode)) {
                 result = PTR_ERR(inode);
                 inode = NULL;
                 goto error;
         }
-
         result = v9fs_fid_add(dentry, fid);
         if (result < 0)
                 goto error_iput;
-
 inst_out:
-        d_add(dentry, inode);
-        return NULL;
-
+        /*
+         * If we had a rename on the server and a parallel lookup
+         * for the new name, then make sure we instantiate with
+         * the new name. ie look up for a/b, while on server somebody
+         * moved b under k and client parallely did a lookup for
+         * k/b.
+         */
+        res = d_materialise_unique(dentry, inode);
+        if (!IS_ERR(res))
+                return res;
+        result = PTR_ERR(res);
 error_iput:
         iput(inode);
 error: