NFS: remove BUG possibility in nfs4_open_and_get_state

commit 4fa2c54 NFS: nfs4_do_open should add negative results to the dcache. used "d_drop(); d_add();" to ensure that a dentry was hashed as a negative cached entry. This is not safe if the dentry has an non-NULL ->d_inode. It will trigger a BUG_ON in d_instantiate(). In that case, d_delete() is needed. Also, only d_add if the dentry is currently unhashed, it seems pointless removed and re-adding it unchanged. Reported-by: Christoph Hellwig <[email protected]> Fixes: 4fa2c54 Cc: Jeff Layton <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: NeilBrown <[email protected]> Acked-by: Jeff Layton <[email protected]> Signed-off-by: Trond Myklebust <[email protected]>
torvalds · Sep 12, 2014 · f39c010 · f39c010
1 parent 224ecbf
commit f39c010
Showing 1 changed file with 7 additions and 3 deletions.
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
@@ -2226,9 +2226,13 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
 	ret = _nfs4_proc_open(opendata);
 	if (ret != 0) {
 		if (ret == -ENOENT) {
-			d_drop(opendata->dentry);
-			d_add(opendata->dentry, NULL);
-			nfs_set_verifier(opendata->dentry,
+			dentry = opendata->dentry;
+			if (dentry->d_inode)
+				d_delete(dentry);
+			else if (d_unhashed(dentry))
+				d_add(dentry, NULL);
+
+			nfs_set_verifier(dentry,
 					 nfs_save_change_attribute(opendata->dir->d_inode));
 		}
 		goto out;