ext4: cleanup GFP flags inside resize path

We must use GFP_NOFS instead GFP_KERNEL inside ext4_mb_add_groupinfo
and ext4_calculate_overhead() because they are called from inside a
journal transaction. Call trace:

ioctl
 ->ext4_group_add
   ->journal_start
   ->ext4_setup_new_descs
     ->ext4_mb_add_groupinfo -> GFP_KERNEL
   ->ext4_flex_group_add
     ->ext4_update_super
       ->ext4_calculate_overhead  -> GFP_KERNEL
   ->journal_stop
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -2385,7 +2385,7 @@ int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
 	if (group % EXT4_DESC_PER_BLOCK(sb) == 0) {
 		metalen = sizeof(*meta_group_info) <<
 			EXT4_DESC_PER_BLOCK_BITS(sb);
-		meta_group_info = kmalloc(metalen, GFP_KERNEL);
+		meta_group_info = kmalloc(metalen, GFP_NOFS);
 		if (meta_group_info == NULL) {
 			ext4_msg(sb, KERN_ERR, "can't allocate mem "
 				 "for a buddy group");
@@ -2399,7 +2399,7 @@ int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
 		sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)];
 	i = group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 
-	meta_group_info[i] = kmem_cache_zalloc(cachep, GFP_KERNEL);
+	meta_group_info[i] = kmem_cache_zalloc(cachep, GFP_NOFS);
 	if (meta_group_info[i] == NULL) {
 		ext4_msg(sb, KERN_ERR, "can't allocate buddy mem");
 		goto exit_group_info;
@@ -2428,7 +2428,7 @@ int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
 	{
 		struct buffer_head *bh;
 		meta_group_info[i]->bb_bitmap =
-			kmalloc(sb->s_blocksize, GFP_KERNEL);
+			kmalloc(sb->s_blocksize, GFP_NOFS);
 		BUG_ON(meta_group_info[i]->bb_bitmap == NULL);
 		bh = ext4_read_block_bitmap(sb, group);
 		BUG_ON(bh == NULL);

fs/ext4/super.c

@@ -3300,7 +3300,7 @@ int ext4_calculate_overhead(struct super_block *sb)
 	struct ext4_super_block *es = sbi->s_es;
 	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
 	ext4_fsblk_t overhead = 0;
-	char *buf = (char *) get_zeroed_page(GFP_KERNEL);
+	char *buf = (char *) get_zeroed_page(GFP_NOFS);
 
 	if (!buf)
 		return -ENOMEM;