From: Jeff Layton <jlayton@redhat.com>
Subject: [RHEL5.2 PATCH] have cifs client recognize when a file is no longer read-only (BZ 231657)
Date: Tue, 13 Mar 2007 10:38:42 -0400
Bugzilla: 231657
Message-Id: <200703131438.l2DEcg4V004961@dantu.rdu.redhat.com>
Changelog: [cifs] recognize when a file is no longer read-only


This problem and patch were discovered and written by Alan Tyson of HP. The
problem is this:

When the CIFS client mounts a share that does not have Unix extensions, it
will turn off the "w" bits in the file mode if it sees that ATTR_READONLY is
set. It has no corresponding logic, however, to reenable write permissions if
the ATTR_READONLY flag is later removed. This results in a situation where a
file gets "stuck" as read-only. The patch below corrects this with the
following logic:

If unix extensions were not negotiated for the mount, and the server does not
report ATTR_READONLY being set for the file then check the mode bits on the
inode. If no write bits are set, then assume that ATTR_READONLY was previously
set for this file but is not now, and set any write bits allowed by the
mnt_file_mode.

I've tested the patch and it seems to do the right thing. It's now in the
upstream CIFS git tree, and should be in -mm soon. This patch fixes
BZ 231657.

--- linux-2.6.18.noarch/fs/cifs/inode.c.~1~
+++ linux-2.6.18.noarch/fs/cifs/inode.c
@@ -477,6 +477,12 @@ int cifs_get_inode_info(struct inode **p
 			   mode e.g. 555 */
 			if (cifsInfo->cifsAttrs & ATTR_READONLY)
 				inode->i_mode &= ~(S_IWUGO);
+			else if ((inode->i_mode & S_IWUGO) == 0)
+				/* the ATTR_READONLY flag may have been	*/
+				/* changed on server -- set any w bits	*/
+				/* allowed by mnt_file_mode		*/
+				inode->i_mode |= (S_IWUGO &
+						  cifs_sb->mnt_file_mode);
 		/* BB add code here -
 		   validate if device or weird share or device type? */
 		}
--- linux-2.6.18.noarch/fs/cifs/readdir.c.~1~
+++ linux-2.6.18.noarch/fs/cifs/readdir.c
@@ -197,6 +197,10 @@ static void fill_in_inode(struct inode *
 		tmp_inode->i_mode |= S_IFREG;
 		if (attr & ATTR_READONLY)
 			tmp_inode->i_mode &= ~(S_IWUGO);
+		else if ((tmp_inode->i_mode & S_IWUGO) == 0)
+			/* the ATTR_READONLY flag may have been changed on   */
+		   	/* server -- set any w bits allowed by mnt_file_mode */
+			tmp_inode->i_mode |= (S_IWUGO & cifs_sb->mnt_file_mode);
 	} /* could add code here - to validate if device or weird share type? */
 
 	/* can not fill in nlink here as in qpathinfo version and Unx search */