NFSv4: Fix problem with OPEN_DOWNGRADE

 RFC 3530 states that for OPEN_DOWNGRADE "The share_access and share_deny
 bits specified must be exactly equal to the union of the share_access and
 share_deny bits specified for some subset of the OPENs in effect for
 current openowner on the current file.

 Setattr is currently violating the NFSv4 rules for OPEN_DOWNGRADE in that
 it may cause a downgrade from OPEN4_SHARE_ACCESS_BOTH to
 OPEN4_SHARE_ACCESS_WRITE despite the fact that there exists no open file
 with O_WRONLY access mode.

 Fix the problem by replacing nfs4_find_state() with a modified version of
 nfs_find_open_context().

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

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index fc0f12ba89c..24d2fbf549b 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1009,13 +1009,18 @@ void nfs_file_set_open_context(struct file *filp, struct nfs_open_context *ctx)
 	spin_unlock(&inode->i_lock);
 }
 
-struct nfs_open_context *nfs_find_open_context(struct inode *inode, int mode)
+/*
+ * Given an inode, search for an open context with the desired characteristics
+ */
+struct nfs_open_context *nfs_find_open_context(struct inode *inode, struct rpc_cred *cred, int mode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct nfs_open_context *pos, *ctx = NULL;
 
 	spin_lock(&inode->i_lock);
 	list_for_each_entry(pos, &nfsi->open_files, list) {
+		if (cred != NULL && pos->cred != cred)
+			continue;
 		if ((pos->mode & mode) == mode) {
 			ctx = get_nfs_open_context(pos);
 			break;