Index: linux-stage/fs/ext3/mballoc.c
===================================================================
--- linux-stage.orig/fs/ext3/mballoc.c	2010-01-26 23:36:25.000000000 +0800
+++ linux-stage/fs/ext3/mballoc.c	2010-01-26 23:42:57.000000000 +0800
@@ -35,6 +35,7 @@
 #include <linux/pagemap.h>
 #include <linux/seq_file.h>
 #include <linux/version.h>
+#include <linux/genhd.h>
 
 #include "group.h"
 
@@ -360,6 +361,7 @@
 	unsigned short		pa_free;	/* how many blocks are free */
 	unsigned short		pa_linear;	/* consumed in one direction
 						 * strictly, for group prealloc */
+	unsigned short		pa_error;
 	spinlock_t		*pa_obj_lock;
 	struct inode		*pa_inode;	/* hack, for history only */
 };
@@ -3558,6 +3560,7 @@
 	spin_lock_init(&pa->pa_lock);
 	pa->pa_deleted = 0;
 	pa->pa_linear = 0;
+	pa->pa_error = 0;
 
 	mb_debug("new inode pa %p: %lu/%lu for %lu\n", pa,
 			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
@@ -3615,6 +3618,7 @@
 	spin_lock_init(&pa->pa_lock);
 	pa->pa_deleted = 0;
 	pa->pa_linear = 1;
+	pa->pa_error = 0;
 
 	mb_debug("new group pa %p: %lu/%lu for %lu\n", pa,
 			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
@@ -3671,7 +3675,10 @@
 	sector_t start;
 	int err = 0, free = 0;
 
+	BUG_ON(!ext3_is_group_locked(sb, e3b->bd_group));
 	BUG_ON(pa->pa_deleted == 0);
+	BUG_ON(pa->pa_linear != 0);
+	BUG_ON(pa->pa_inode == NULL);
 	ext3_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
 	BUG_ON(group != e3b->bd_group && pa->pa_len != 0);
 	end = bit + pa->pa_len;
@@ -3704,14 +3711,19 @@
 		mb_free_blocks(pa->pa_inode, e3b, bit, next - bit);
 		bit = next + 1;
 	}
-	if (free != pa->pa_free) {
-		printk("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);
-		printk("free %u, pa_free %u\n", free, pa->pa_free);
-	}
-	BUG_ON(free != pa->pa_free);
+
+	/* "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))
+		ext3_error(sb, __FUNCTION__, "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);
+	BUG_ON(pa->pa_free != free);
 	atomic_add(free, &sbi->s_mb_discarded);
 
 	return err;
@@ -4189,6 +4201,19 @@
 		*errp = -EDQUOT;
 		return 0;
 	}
+
+	if (dev_check_rdonly(sb->s_bdev)) {
+		struct block_device *bdev = sb->s_bdev;
+
+		printk(KERN_WARNING "Alloc from readonly device %s (%#x): "
+		       "[inode %lu] [logic %lu] [goal %lu] [ll %lu] [pl %lu] "
+		       "[lr %lu] [pr %lu] [len %lu] [flags %lu]\n",
+		       bdev->bd_disk ? bdev->bd_disk->disk_name : "",
+		       bdev->bd_dev, ar->inode->i_ino, ar->logical, ar->goal,
+		       ar->lleft, ar->pleft, ar->lright, ar->pright, ar->len,
+		       ar->flags);
+	}
+
 	inquota = ar->len;
 
 	ext3_mb_poll_new_transaction(sb, handle);
@@ -4217,10 +4242,34 @@
 	}
 
 	if (likely(ac.ac_status == AC_STATUS_FOUND)) {
-		ext3_mb_mark_diskspace_used(&ac, handle);
-		*errp = 0;
-		block = ext3_grp_offs_to_block(sb, &ac.ac_b_ex);
-		ar->len = ac.ac_b_ex.fe_len;
+		*errp = ext3_mb_mark_diskspace_used(&ac, handle);
+		if (!*errp) {
+			block = ext3_grp_offs_to_block(sb, &ac.ac_b_ex);
+			ar->len = ac.ac_b_ex.fe_len;
+		} else {
+                        ac.ac_b_ex.fe_len = 0;
+                        ar->len = 0;
+                        ext3_mb_show_ac(&ac);
+                        if (ac.ac_pa) {
+                                struct ext3_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++;
+                                ext3_error(sb, __FUNCTION__,
+					      "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 {
 		freed  = ext3_mb_discard_preallocations(sb, ac.ac_o_ex.fe_len);
 		if (freed)
@@ -4388,6 +4437,15 @@
 		goto error_return;
 	}
 
+	if (dev_check_rdonly(sb->s_bdev)) {
+		struct block_device *bdev = sb->s_bdev;
+
+		printk(KERN_WARNING "Release to readonly device %s (%#x): "
+		       "[inode %lu] [block %lu] [count %lu] [is_meta %d]\n",
+		       bdev->bd_disk ? bdev->bd_disk->disk_name : "",
+		       bdev->bd_dev, inode->i_ino, block, count, metadata);
+	}
+
 	ext3_debug("freeing block %lu\n", block);
 
 	ac.ac_op = EXT3_MB_HISTORY_FREE;