Prevent xattr remove from creating xattr directory

Attempting to remove an xattr from a file which does not contain
any directory based xattrs would result in the xattr directory
being created.  This behavior is non-optimal because it results
in write operations to the pool in addition to the expected error
being returned.

To prevent this the CREATE_XATTR_DIR flag is only passed in
zpl_xattr_set_dir() when setting a non-NULL xattr value.  In
addition, zpl_xattr_set() is updated similarly such that it will
return immediately if passed an xattr name which doesn't exist
and a NULL value.

Signed-off-by: Massimo Maggi <me@massimo-maggi.eu>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #170

diff --git a/module/zfs/zpl_xattr.c b/module/zfs/zpl_xattr.c
index d79d35bce75b85ca76adcc5f931ad3d284de9d8f..0918e7404636f9021a87f85f6bf4d867b9cf2830 100644 (file)
--- a/module/zfs/zpl_xattr.c
+++ b/module/zfs/zpl_xattr.c
@@ -355,12 +355,20 @@ zpl_xattr_set_dir(struct inode *ip, const char *name, const void *value,
        struct inode *xip = NULL;
        vattr_t *vap = NULL;
        ssize_t wrote;
-       int error;
+       int lookup_flags, error;
        const int xattr_mode = S_IFREG | 0644;
 
-       /* Lookup the xattr directory and create it if required. */
-       error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR | CREATE_XATTR_DIR,
-           cr, NULL, NULL);
+       /*
+        * Lookup the xattr directory.  When we're adding an entry pass
+        * CREATE_XATTR_DIR to ensure the xattr directory is created.
+        * When removing an entry this flag is not passed to avoid
+        * unnecessarily creating a new xattr directory.
+        */
+       lookup_flags = LOOKUP_XATTR;
+       if (value != NULL)
+               lookup_flags |= CREATE_XATTR_DIR;
+
+       error = -zfs_lookup(ip, NULL, &dxip, lookup_flags, cr, NULL, NULL);
        if (error)
                goto out;
 
@@ -493,7 +501,12 @@ zpl_xattr_set(struct inode *ip, const char *name, const void *value,
                if (error != -ENODATA)
                        goto out;
 
-               if ((error == -ENODATA) && (flags & XATTR_REPLACE))
+               if (flags & XATTR_REPLACE)
+                       goto out;
+
+               /* The xattr to be removed already doesn't exist */
+               error = 0;
+               if (value == NULL)
                        goto out;
        } else {
                error = -EEXIST;