hfsplus: introduce alloc_mutex

Use a new per-sb alloc_mutex instead of abusing i_mutex of the alloc_file
to protect block allocations.  This gets rid of lockdep nesting warnings
and prepares for extending the scope of alloc_mutex.

Signed-off-by: Christoph Hellwig <hch@tuxera.com>

fs/hfsplus/bitmap.c

@@ -29,7 +29,7 @@ int hfsplus_block_allocate(struct super_block *sb, u32 size, u32 offset, u32 *ma
 		return size;
 
 	dprint(DBG_BITMAP, "block_allocate: %u,%u,%u\n", size, offset, len);
-	mutex_lock(&HFSPLUS_SB(sb).alloc_file->i_mutex);
+	mutex_lock(&HFSPLUS_SB(sb).alloc_mutex);
 	mapping = HFSPLUS_SB(sb).alloc_file->i_mapping;
 	page = read_mapping_page(mapping, offset / PAGE_CACHE_BITS, NULL);
 	if (IS_ERR(page)) {
@@ -154,7 +154,7 @@ int hfsplus_block_allocate(struct super_block *sb, u32 size, u32 offset, u32 *ma
 	sb->s_dirt = 1;
 	dprint(DBG_BITMAP, "-> %u,%u\n", start, *max);
 out:
-	mutex_unlock(&HFSPLUS_SB(sb).alloc_file->i_mutex);
+	mutex_unlock(&HFSPLUS_SB(sb).alloc_mutex);
 	return start;
 }
 
@@ -175,7 +175,7 @@ int hfsplus_block_free(struct super_block *sb, u32 offset, u32 count)
 	if ((offset + count) > HFSPLUS_SB(sb).total_blocks)
 		return -2;
 
-	mutex_lock(&HFSPLUS_SB(sb).alloc_file->i_mutex);
+	mutex_lock(&HFSPLUS_SB(sb).alloc_mutex);
 	mapping = HFSPLUS_SB(sb).alloc_file->i_mapping;
 	pnr = offset / PAGE_CACHE_BITS;
 	page = read_mapping_page(mapping, pnr, NULL);
@@ -226,7 +226,7 @@ int hfsplus_block_free(struct super_block *sb, u32 offset, u32 count)
 	kunmap(page);
 	HFSPLUS_SB(sb).free_blocks += len;
 	sb->s_dirt = 1;
-	mutex_unlock(&HFSPLUS_SB(sb).alloc_file->i_mutex);
+	mutex_unlock(&HFSPLUS_SB(sb).alloc_mutex);
 
 	return 0;
 }

fs/hfsplus/hfsplus_fs.h

@@ -116,6 +116,9 @@ struct hfsplus_sb_info {
 	struct inode *hidden_dir;
 	struct nls_table *nls;
 
+	/* synchronize block allocations */
+	struct mutex alloc_mutex;
+
 	/* Runtime variables */
 	u32 blockoffset;
 	u32 sect_count;

fs/hfsplus/super.c

@@ -321,6 +321,7 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
 
 	sb->s_fs_info = sbi;
 	INIT_HLIST_HEAD(&sbi->rsrc_inodes);
+	mutex_init(&sbi->alloc_mutex);
 	hfsplus_fill_defaults(sbi);
 	if (!hfsplus_parse_options(data, sbi)) {
 		printk(KERN_ERR "hfs: unable to parse mount options\n");