[PATCH] hfsplus: don't modify journaled volume

Access to a journaled HFS+ volume is not officially supported under Linux, so
mount such a volume read-only, but users can override this behaviour using the
"force" mount option.

The minimum requirement to relax this check is to at least check that the
journal is empty and so nothing needs to be replayed to make sure the volume
is consistent.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/hfsplus/hfsplus_fs.h

@@ -151,6 +151,7 @@ struct hfsplus_sb_info {
 
 #define HFSPLUS_SB_WRITEBACKUP	0x0001
 #define HFSPLUS_SB_NODECOMPOSE	0x0002
+#define HFSPLUS_SB_FORCE	0x0004
 
 
 struct hfsplus_inode_info {

fs/hfsplus/hfsplus_raw.h

@@ -127,6 +127,8 @@ struct hfsplus_vh {
 #define HFSPLUS_VOL_SPARE_BLK		(1 << 9)
 #define HFSPLUS_VOL_NOCACHE		(1 << 10)
 #define HFSPLUS_VOL_INCNSTNT		(1 << 11)
+#define HFSPLUS_VOL_NODEID_REUSED	(1 << 12)
+#define HFSPLUS_VOL_JOURNALED		(1 << 13)
 #define HFSPLUS_VOL_SOFTLOCK		(1 << 15)
 
 /* HFS+ BTree node descriptor */

fs/hfsplus/options.c

@@ -22,7 +22,7 @@ enum {
 	opt_umask, opt_uid, opt_gid,
 	opt_part, opt_session, opt_nls,
 	opt_nodecompose, opt_decompose,
-	opt_err
+	opt_force, opt_err
 };
 
 static match_table_t tokens = {
@@ -36,6 +36,7 @@ static match_table_t tokens = {
 	{ opt_nls, "nls=%s" },
 	{ opt_decompose, "decompose" },
 	{ opt_nodecompose, "nodecompose" },
+	{ opt_force, "force" },
 	{ opt_err, NULL }
 };
 
@@ -145,6 +146,9 @@ int hfsplus_parse_options(char *input, struct hfsplus_sb_info *sbi)
 		case opt_nodecompose:
 			sbi->flags |= HFSPLUS_SB_NODECOMPOSE;
 			break;
+		case opt_force:
+			sbi->flags |= HFSPLUS_SB_FORCE;
+			break;
 		default:
 			return 0;
 		}

fs/hfsplus/super.c

@@ -251,16 +251,28 @@ static int hfsplus_remount(struct super_block *sb, int *flags, char *data)
 		return 0;
 	if (!(*flags & MS_RDONLY)) {
 		struct hfsplus_vh *vhdr = HFSPLUS_SB(sb).s_vhdr;
+		struct hfsplus_sb_info sbi;
+
+		memset(&sbi, 0, sizeof(struct hfsplus_sb_info));
+		sbi.nls = HFSPLUS_SB(sb).nls;
+		if (!hfsplus_parse_options(data, &sbi))
+			return -EINVAL;
 
 		if (!(vhdr->attributes & cpu_to_be32(HFSPLUS_VOL_UNMNT))) {
 			printk("HFS+-fs warning: Filesystem was not cleanly unmounted, "
 			       "running fsck.hfsplus is recommended.  leaving read-only.\n");
 			sb->s_flags |= MS_RDONLY;
 			*flags |= MS_RDONLY;
+		} else if (sbi.flags & HFSPLUS_SB_FORCE) {
+			/* nothing */
 		} else if (vhdr->attributes & cpu_to_be32(HFSPLUS_VOL_SOFTLOCK)) {
 			printk("HFS+-fs: Filesystem is marked locked, leaving read-only.\n");
 			sb->s_flags |= MS_RDONLY;
 			*flags |= MS_RDONLY;
+		} else if (vhdr->attributes & cpu_to_be32(HFSPLUS_VOL_JOURNALED)) {
+			printk("HFS+-fs: Filesystem is marked journaled, leaving read-only.\n");
+			sb->s_flags |= MS_RDONLY;
+			*flags |= MS_RDONLY;
 		}
 	}
 	return 0;
@@ -352,11 +364,19 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
 			printk("HFS+-fs warning: Filesystem was not cleanly unmounted, "
 			       "running fsck.hfsplus is recommended.  mounting read-only.\n");
 		sb->s_flags |= MS_RDONLY;
+	} else if (sbi->flags & HFSPLUS_SB_FORCE) {
+		/* nothing */
 	} else if (vhdr->attributes & cpu_to_be32(HFSPLUS_VOL_SOFTLOCK)) {
 		if (!silent)
 			printk("HFS+-fs: Filesystem is marked locked, mounting read-only.\n");
 		sb->s_flags |= MS_RDONLY;
+	} else if (vhdr->attributes & cpu_to_be32(HFSPLUS_VOL_JOURNALED)) {
+		if (!silent)
+			printk("HFS+-fs: write access to a jounaled filesystem is not supported, "
+			       "use the force option at your own risk, mounting read-only.\n");
+		sb->s_flags |= MS_RDONLY;
 	}
+	sbi->flags &= ~HFSPLUS_SB_FORCE;
 
 	/* Load metadata objects (B*Trees) */
 	HFSPLUS_SB(sb).ext_tree = hfs_btree_open(sb, HFSPLUS_EXT_CNID);