Index: linux-stage/fs/ext4/mballoc.c
===================================================================
--- linux-stage.orig/fs/ext4/mballoc.c	2011-03-14 16:34:39.790758415 +0800
+++ linux-stage/fs/ext4/mballoc.c	2011-03-14 16:38:36.211681104 +0800
@@ -3593,6 +3593,7 @@
 	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);
@@ -3654,6 +3655,7 @@
 	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);
@@ -3716,7 +3718,9 @@
 	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);
@@ -3752,19 +3756,27 @@
 		mb_free_blocks(pa->pa_inode, e4b, bit, next - bit);
 		bit = next + 1;
 	}
-	if (free != pa->pa_free) {
-		printk(KERN_CRIT "pa %p: logic %lu, phys. %lu, len %lu\n",
-			pa, (unsigned long) pa->pa_lstart,
-			(unsigned long) pa->pa_pstart,
-			(unsigned long) pa->pa_len);
+
+	/* "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,
-					__func__, "free %u, pa_free %u",
-					free, pa->pa_free);
+				__func__, "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;
@@ -4511,6 +4541,25 @@
 			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);
+			}
 		} else {
 			block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
 			ar->len = ac->ac_b_ex.fe_len;
Index: linux-stage/fs/ext4/mballoc.h
===================================================================
--- linux-stage.orig/fs/ext4/mballoc.h	2011-03-14 16:32:50.859552482 +0800
+++ linux-stage/fs/ext4/mballoc.h	2011-03-14 16:39:20.928429776 +0800
@@ -20,6 +20,7 @@
 #include <linux/version.h>
 #include <linux/blkdev.h>
 #include <linux/mutex.h>
+#include <linux/genhd.h>
 #include "ext4_jbd2.h"
 #include "ext4.h"
 
@@ -130,6 +131,7 @@
 	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 */
 };