Re: 3.11.4: kernel BUG at fs/buffer.c:1268

["George Spelvin" <linux@horizon.com>]

Due to wanting to stick with 3.11.x baseline, as opposed to whatever you
based your diff on, I had to amend the last hunk slightly.  Included
just FYI.

Compiled, rebooting now.  It may take some days to get a
bug report.

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4bbbf13b..e6f0d6b 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4734,6 +4734,7 @@ do_more:
 	if (err)
 		goto error_return;
 
+	might_sleep();
 	if ((flags & EXT4_FREE_BLOCKS_METADATA) && ext4_handle_valid(handle)) {
 		struct ext4_free_data *new_entry;
 		/*
@@ -4741,6 +4742,7 @@ do_more:
 		 * be used until this transaction is committed
 		 */
 	retry:
+		might_sleep();
 		new_entry = kmem_cache_alloc(ext4_free_data_cachep, GFP_NOFS);
 		if (!new_entry) {
 			/*
@@ -4756,6 +4758,7 @@ do_more:
 		new_entry->efd_count = count_clusters;
 		new_entry->efd_tid = handle->h_transaction->t_tid;
 
+		might_sleep();
 		ext4_lock_group(sb, block_group);
 		mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
 		ext4_mb_free_metadata(handle, &e4b, new_entry);
@@ -4773,7 +4776,7 @@ do_more:
 					 err);
 		}
 
-
+		might_sleep();
 		ext4_lock_group(sb, block_group);
 		mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
 		mb_free_blocks(inode, &e4b, bit, count_clusters);
@@ -4785,6 +4788,7 @@ do_more:
 	ext4_group_desc_csum_set(sb, block_group, gdp);
 	ext4_unlock_group(sb, block_group);
 	percpu_counter_add(&sbi->s_freeclusters_counter, count_clusters);
+	might_sleep();
 
 	if (sbi->s_log_groups_per_flex) {
 		ext4_group_t flex_group = ext4_flex_group(sbi, block_group);