nfs: don't open in ->d_revalidate

NFSv4 can't do reliable opens in d_revalidate, since it cannot know whether a
mount needs to be followed or not.  It does check d_mountpoint() on the dentry,
which can result in a weird error if the VFS found that the mount does not in
fact need to be followed, e.g.:

  # mount --bind /mnt/nfs /mnt/nfs-clone
  # echo something > /mnt/nfs/tmp/bar
  # echo x > /tmp/file
  # mount --bind /tmp/file /mnt/nfs-clone/tmp/bar
  # cat  /mnt/nfs/tmp/bar
  cat: /mnt/nfs/tmp/bar: Not a directory

Which should, by any sane filesystem, result in "something" being printed.

So instead do the open in f_op->open() and in the unlikely case that the cached
dentry turned out to be invalid, drop the dentry and return EOPENSTALE to let
the VFS retry.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 51 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 0989a2099688..f430057ff3b3 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1354,10 +1354,10 @@ out:
 }
 
 #ifdef CONFIG_NFS_V4
-static int nfs_open_revalidate(struct dentry *, struct nameidata *);
+static int nfs4_lookup_revalidate(struct dentry *, struct nameidata *);
 
 const struct dentry_operations nfs4_dentry_operations = {
-	.d_revalidate	= nfs_open_revalidate,
+	.d_revalidate	= nfs4_lookup_revalidate,
 	.d_delete	= nfs_dentry_delete,
 	.d_iput		= nfs_dentry_iput,
 	.d_automount	= nfs_d_automount,
@@ -1519,13 +1519,11 @@ no_open:
 	return nfs_lookup(dir, dentry, nd);
 }
 
-static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)
+static int nfs4_lookup_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
 	struct dentry *parent = NULL;
 	struct inode *inode;
 	struct inode *dir;
-	struct nfs_open_context *ctx;
-	struct iattr attr;
 	int openflags, ret = 0;
 
 	if (nd->flags & LOOKUP_RCU)
@@ -1554,57 +1552,13 @@ static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)
 	/* We cannot do exclusive creation on a positive dentry */
 	if ((openflags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
 		goto no_open_dput;
-	/* We can't create new files here */
-	openflags &= ~(O_CREAT|O_EXCL);
-
-	ctx = create_nfs_open_context(dentry, openflags);
-	ret = PTR_ERR(ctx);
-	if (IS_ERR(ctx))
-		goto out;
 
-	attr.ia_valid = ATTR_OPEN;
-	if (openflags & O_TRUNC) {
-		attr.ia_valid |= ATTR_SIZE;
-		attr.ia_size = 0;
-		nfs_wb_all(inode);
-	}
-
-	/*
-	 * Note: we're not holding inode->i_mutex and so may be racing with
-	 * operations that change the directory. We therefore save the
-	 * change attribute *before* we do the RPC call.
-	 */
-	inode = NFS_PROTO(dir)->open_context(dir, ctx, openflags, &attr);
-	if (IS_ERR(inode)) {
-		ret = PTR_ERR(inode);
-		switch (ret) {
-		case -EPERM:
-		case -EACCES:
-		case -EDQUOT:
-		case -ENOSPC:
-		case -EROFS:
-			goto out_put_ctx;
-		default:
-			goto out_drop;
-		}
-	}
-	iput(inode);
-	if (inode != dentry->d_inode)
-		goto out_drop;
+	/* Let f_op->open() actually open (and revalidate) the file */
+	ret = 1;
 
-	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
-	ret = nfs_intent_set_file(nd, ctx);
-	if (ret >= 0)
-		ret = 1;
 out:
 	dput(parent);
 	return ret;
-out_drop:
-	d_drop(dentry);
-	ret = 0;
-out_put_ctx:
-	put_nfs_open_context(ctx);
-	goto out;
 
 no_open_dput:
 	dput(parent);