NFS: Fix a race in sillyrename

lookup() and sillyrename() can race one another because the sillyrename()
completion cannot take the parent directory's inode->i_mutex since the
latter may be held by whoever is calling dput().

We therefore have little option but to add extra locking to ensure that
nfs_lookup() and nfs_atomic_open() do not race with the sillyrename
completion.
If somebody has looked up the sillyrenamed file in the meantime, we just
transfer the sillydelete information to the new dentry.

Please refer to the bug-report at
	http://bugzilla.linux-nfs.org/show_bug.cgi?id=150

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 8ec7fbd8240c..35334539d947 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -562,6 +562,7 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
         nfs_fattr_init(&fattr);
         desc->entry = &my_entry;
 
+        nfs_block_sillyrename(dentry);
         while(!desc->entry->eof) {
                 res = readdir_search_pagecache(desc);
 
@@ -592,6 +593,7 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                         break;
                 }
         }
+        nfs_unblock_sillyrename(dentry);
         unlock_kernel();
         if (res > 0)
                 res = 0;
@@ -866,6 +868,7 @@ struct dentry_operations nfs_dentry_operations = {
 static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
 {
         struct dentry *res;
+        struct dentry *parent;
         struct inode *inode = NULL;
         int error;
         struct nfs_fh fhandle;
@@ -894,26 +897,31 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
                 goto out_unlock;
         }
 
+        parent = dentry->d_parent;
+        /* Protect against concurrent sillydeletes */
+        nfs_block_sillyrename(parent);
         error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
         if (error == -ENOENT)
                 goto no_entry;
         if (error < 0) {
                 res = ERR_PTR(error);
-                goto out_unlock;
+                goto out_unblock_sillyrename;
         }
         inode = nfs_fhget(dentry->d_sb, &fhandle, &fattr);
         res = (struct dentry *)inode;
         if (IS_ERR(res))
-                goto out_unlock;
+                goto out_unblock_sillyrename;
 
 no_entry:
         res = d_materialise_unique(dentry, inode);
         if (res != NULL) {
                 if (IS_ERR(res))
-                        goto out_unlock;
+                        goto out_unblock_sillyrename;
                 dentry = res;
         }
         nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
+out_unblock_sillyrename:
+        nfs_unblock_sillyrename(parent);
 out_unlock:
         unlock_kernel();
 out: