jbd2: use GFP_NOFS in jbd2_cleanup_journal_tail()

jbd2_cleanup_journal_tail() can be invoked by jbd2__journal_start()
So allocations should be done with GFP_NOFS

[Full stack trace snipped from 3.10-rh7]
[<ffffffff815c4bd4>] dump_stack+0x19/0x1b
[<ffffffff8105dba1>] warn_slowpath_common+0x61/0x80
[<ffffffff8105dcca>] warn_slowpath_null+0x1a/0x20
[<ffffffff815c2142>] slab_pre_alloc_hook.isra.31.part.32+0x15/0x17
[<ffffffff8119c045>] kmem_cache_alloc+0x55/0x210
[<ffffffff811477f5>] ? mempool_alloc_slab+0x15/0x20
[<ffffffff811477f5>] mempool_alloc_slab+0x15/0x20
[<ffffffff81147939>] mempool_alloc+0x69/0x170
[<ffffffff815cb69e>] ? _raw_spin_unlock_irq+0xe/0x20
[<ffffffff8109160d>] ? finish_task_switch+0x5d/0x150
[<ffffffff811f1a8e>] bio_alloc_bioset+0x1be/0x2e0
[<ffffffff8127ee49>] blkdev_issue_flush+0x99/0x120
[<ffffffffa019a733>] jbd2_cleanup_journal_tail+0x93/0xa0 [jbd2] -->GFP_KERNEL
[<ffffffffa019aca1>] jbd2_log_do_checkpoint+0x221/0x4a0 [jbd2]
[<ffffffffa019afc7>] __jbd2_log_wait_for_space+0xa7/0x1e0 [jbd2]
[<ffffffffa01952d8>] start_this_handle+0x2d8/0x550 [jbd2]
[<ffffffff811b02a9>] ? __memcg_kmem_put_cache+0x29/0x30
[<ffffffff8119c120>] ? kmem_cache_alloc+0x130/0x210
[<ffffffffa019573a>] jbd2__journal_start+0xba/0x190 [jbd2]
[<ffffffff811532ce>] ? lru_cache_add+0xe/0x10
[<ffffffffa01c9549>] ? ext4_da_write_begin+0xf9/0x330 [ext4]
[<ffffffffa01f2c77>] __ext4_journal_start_sb+0x77/0x160 [ext4]
[<ffffffffa01c9549>] ext4_da_write_begin+0xf9/0x330 [ext4]
[<ffffffff811446ec>] generic_file_buffered_write_iter+0x10c/0x270
[<ffffffff81146918>] __generic_file_write_iter+0x178/0x390
[<ffffffff81146c6b>] __generic_file_aio_write+0x8b/0xb0
[<ffffffff81146ced>] generic_file_aio_write+0x5d/0xc0
[<ffffffffa01bf289>] ext4_file_write+0xa9/0x450 [ext4]
[<ffffffff811c31d9>] ? pipe_read+0x379/0x4f0
[<ffffffff811b93f0>] do_sync_write+0x90/0xe0
[<ffffffff811b9b6d>] vfs_write+0xbd/0x1e0
[<ffffffff811ba5b8>] SyS_write+0x58/0xb0
[<ffffffff815d4799>] system_call_fastpath+0x16/0x1b

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

fs/jbd2/checkpoint.c

@@ -405,7 +405,7 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
 	 * jbd2_cleanup_journal_tail() doesn't get called all that often.
 	 */
 	if (journal->j_flags & JBD2_BARRIER)
-		blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
+		blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS, NULL);
 
 	__jbd2_update_log_tail(journal, first_tid, blocknr);
 	return 0;