diff -r -u linux-stage.orig/fs/ext4/mballoc.c linux-stage/fs/ext4/mballoc.c
--- linux-stage.orig/fs/ext4/mballoc.c	2012-12-31 15:18:15.000000000 -0500
+++ linux-stage/fs/ext4/mballoc.c	2012-12-31 15:23:38.000000000 -0500
@@ -3643,6 +3643,7 @@
 	INIT_LIST_HEAD(&pa->pa_group_list);
 	pa->pa_deleted = 0;
 	pa->pa_type = MB_INODE_PA;
+	pa->pa_error = 0;

 	mb_debug(1, "new inode pa %p: %llu/%u for %u\n", pa,
 			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
@@ -3704,6 +3705,7 @@
 	INIT_LIST_HEAD(&pa->pa_group_list);
 	pa->pa_deleted = 0;
 	pa->pa_type = MB_GROUP_PA;
+	pa->pa_error = 0;

 	mb_debug(1, "new group pa %p: %llu/%u for %u\n", pa,
 			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
@@ -3764,7 +3766,9 @@
 	int err = 0;
 	int free = 0;

+	assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));
 	BUG_ON(pa->pa_deleted == 0);
+	BUG_ON(pa->pa_inode == NULL);
 	ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
 	grp_blk_start = pa->pa_pstart - bit;
 	BUG_ON(group != e4b->bd_group && pa->pa_len != 0);
@@ -3786,19 +3790,27 @@
 		mb_free_blocks(pa->pa_inode, e4b, bit, next - bit);
 		bit = next + 1;
 	}
-	if (free != pa->pa_free) {
-		ext4_msg(e4b->bd_sb, KERN_CRIT,
-			 "pa %p: logic %lu, phys. %lu, len %lu",
-			 pa, (unsigned long) pa->pa_lstart,
-			 (unsigned long) pa->pa_pstart,
-			 (unsigned long) pa->pa_len);
-		ext4_grp_locked_error(sb, group, 0, 0, "free %u, pa_free %u",
+
+	/* "free < pa->pa_free" means we maybe double alloc the same blocks,
+	 * otherwise maybe leave some free blocks unavailable, no need to BUG.*/
+	if ((free > pa->pa_free && !pa->pa_error) || (free < pa->pa_free)) {
+		ext4_error(sb, "pa free mismatch: [pa %p] "
+				"[phy %lu] [logic %lu] [len %u] [free %u] "
+				"[error %u] [inode %lu] [freed %u]", pa,
+				(unsigned long)pa->pa_pstart,
+				(unsigned long)pa->pa_lstart,
+				(unsigned)pa->pa_len, (unsigned)pa->pa_free,
+				(unsigned)pa->pa_error, pa->pa_inode->i_ino,
+				free);
+		ext4_grp_locked_error(sb, group, 0, 0,
+					"free %u, pa_free %u",
 					free, pa->pa_free);
 		/*
 		 * pa is already deleted so we use the value obtained
 		 * from the bitmap and continue.
 		 */
 	}
+	BUG_ON(pa->pa_free != free);
 	atomic_add(free, &sbi->s_mb_discarded);

 	return err;
@@ -4542,6 +4555,25 @@
 		ac->ac_b_ex.fe_len = 0;
 		ar->len = 0;
 		ext4_mb_show_ac(ac);
+		if (ac->ac_pa) {
+			struct ext4_prealloc_space *pa = ac->ac_pa;
+
+			/* We can not make sure whether the bitmap has
+			* been updated or not when fail case. So can
+			* not revert pa_free back, just mark pa_error*/
+			pa->pa_error++;
+			ext4_error(sb,
+				"Updating bitmap error: [err %d] "
+				"[pa %p] [phy %lu] [logic %lu] "
+				"[len %u] [free %u] [error %u] "
+				"[inode %lu]", *errp, pa,
+				(unsigned long)pa->pa_pstart,
+				(unsigned long)pa->pa_lstart,
+				(unsigned)pa->pa_len,
+				(unsigned)pa->pa_free,
+				(unsigned)pa->pa_error,
+				pa->pa_inode ? pa->pa_inode->i_ino : 0);
+		}
 	}
 	ext4_mb_release_context(ac);
 out:
diff -r -u linux-stage.orig/fs/ext4/mballoc.h linux-stage/fs/ext4/mballoc.h
--- linux-stage.orig/fs/ext4/mballoc.h	2012-12-31 15:18:15.000000000 -0500
+++ linux-stage/fs/ext4/mballoc.h	2012-12-31 15:19:22.000000000 -0500
@@ -19,6 +19,7 @@
 #include <linux/seq_file.h>
 #include <linux/blkdev.h>
 #include <linux/mutex.h>
+#include <linux/genhd.h>
 #include "ext4_jbd2.h"
 #include "ext4.h"

@@ -129,6 +130,7 @@
 	ext4_grpblk_t		pa_free;	/* how many blocks are free */
 	unsigned short		pa_type;	/* pa type. inode or group */
 	spinlock_t		*pa_obj_lock;
+	unsigned short		pa_error;
 	struct inode		*pa_inode;	/* hack, for history only */
 };