GFS2: Add S_NOSEC support

This adds S_NOSEC support to GFS2. We set/reset the flag either when
a user calls setattr or when we have just regained the glock
from another node. The flag is only set if there are no xattrs
on the inode and there is no suid bit set.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>

fs/gfs2/file.c

@@ -174,7 +174,9 @@ void gfs2_set_inode_flags(struct inode *inode)
 	struct gfs2_inode *ip = GFS2_I(inode);
 	unsigned int flags = inode->i_flags;
 
-	flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
+	flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_NOSEC);
+	if ((ip->i_eattr == 0) && !is_sxid(inode->i_mode))
+		inode->i_flags |= S_NOSEC;
 	if (ip->i_diskflags & GFS2_DIF_IMMUTABLE)
 		flags |= S_IMMUTABLE;
 	if (ip->i_diskflags & GFS2_DIF_APPENDONLY)

fs/gfs2/glops.c

@@ -318,6 +318,8 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 	ip->i_generation = be64_to_cpu(str->di_generation);
 
 	ip->i_diskflags = be32_to_cpu(str->di_flags);
+	ip->i_eattr = be64_to_cpu(str->di_eattr);
+	/* i_diskflags and i_eattr must be set before gfs2_set_inode_flags() */
 	gfs2_set_inode_flags(&ip->i_inode);
 	height = be16_to_cpu(str->di_height);
 	if (unlikely(height > GFS2_MAX_META_HEIGHT))
@@ -330,7 +332,6 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 	ip->i_depth = (u8)depth;
 	ip->i_entries = be32_to_cpu(str->di_entries);
 
-	ip->i_eattr = be64_to_cpu(str->di_eattr);
 	if (S_ISREG(ip->i_inode.i_mode))
 		gfs2_set_aops(&ip->i_inode);
 

fs/gfs2/ops_fstype.c

@@ -1094,6 +1094,7 @@ static int fill_super(struct super_block *sb, struct gfs2_args *args, int silent
 	if (sdp->sd_args.ar_nobarrier)
 		set_bit(SDF_NOBARRIERS, &sdp->sd_flags);
 
+	sb->s_flags |= MS_NOSEC;
 	sb->s_magic = GFS2_MAGIC;
 	sb->s_op = &gfs2_super_ops;
 	sb->s_d_op = &gfs2_dops;