+#define FALL_BACK_TO_NONDELALLOC 1
+static int ext4_nonda_switch(struct super_block *sb)
+{
+ s64 free_blocks, dirty_blocks;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+ /*
+ * switch to non delalloc mode if we are running low
+ * on free block. The free block accounting via percpu
+ * counters can get slightly wrong with FBC_BATCH getting
+ * accumulated on each CPU without updating global counters
+ * Delalloc need an accurate free block accounting. So switch
+ * to non delalloc when we are near to error range.
+ */
+ free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
+ dirty_blocks = percpu_counter_read_positive(&sbi->s_dirtyblocks_counter);
+ if (2 * free_blocks < 3 * dirty_blocks ||
+ free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) {
+ /*
+ * free block count is less that 150% of dirty blocks
+ * or free blocks is less that watermark
+ */
+ return 1;
+ }
+ return 0;
+}
+