ext4: return ENOMEM rather than EIO when find_###_page() fails

Return ENOMEM rather than EIO when find_get_page() fails in
ext4_mb_get_buddy_page_lock() and find_or_create_page() fails in
ext4_mb_load_buddy().
Signed-off-by: NYounger Liu <younger.liucn@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -989,7 +989,7 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
 	poff = block % blocks_per_page;
 	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
 	if (!page)
-		return -EIO;
+		return -ENOMEM;
 	BUG_ON(page->mapping != inode->i_mapping);
 	e4b->bd_bitmap_page = page;
 	e4b->bd_bitmap = page_address(page) + (poff * sb->s_blocksize);
@@ -1003,7 +1003,7 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
 	pnum = block / blocks_per_page;
 	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
 	if (!page)
-		return -EIO;
+		return -ENOMEM;
 	BUG_ON(page->mapping != inode->i_mapping);
 	e4b->bd_buddy_page = page;
 	return 0;
@@ -1168,7 +1168,11 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
 			unlock_page(page);
 		}
 	}
-	if (page == NULL || !PageUptodate(page)) {
+	if (page == NULL) {
+		ret = -ENOMEM;
+		goto err;
+	}
+	if (!PageUptodate(page)) {
 		ret = -EIO;
 		goto err;
 	}
@@ -1197,7 +1201,11 @@ ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
 			unlock_page(page);
 		}
 	}
-	if (page == NULL || !PageUptodate(page)) {
+	if (page == NULL) {
+		ret = -ENOMEM;
+		goto err;
+	}
+	if (!PageUptodate(page)) {
 		ret = -EIO;
 		goto err;
 	}