From d3ad8434aa83ef7c88bc91edcfe012cdcbab9f3e Mon Sep 17 00:00:00 2001 From: Tao Ma Date: Mon, 27 Jun 2011 12:36:29 -0400 Subject: [PATCH] jbd2: use WRITE_SYNC in journal checkpoint In journal checkpoint, we write the buffer and wait for its finish. But in cfq, the async queue has a very low priority, and in our test, if there are too many sync queues and every queue is filled up with requests, the write request will be delayed for quite a long time and all the tasks which are waiting for journal space will end with errors like: INFO: task attr_set:3816 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. attr_set D ffff880028393480 0 3816 1 0x00000000 ffff8802073fbae8 0000000000000086 ffff8802140847c8 ffff8800283934e8 ffff8802073fb9d8 ffffffff8103e456 ffff8802140847b8 ffff8801ed728080 ffff8801db4bc080 ffff8801ed728450 ffff880028393480 0000000000000002 Call Trace: [] ? __dequeue_entity+0x33/0x38 [] ? need_resched+0x23/0x2d [] ? thread_return+0xa2/0xbc [] ? jbd2_journal_dirty_metadata+0x116/0x126 [jbd2] [] ? jbd2_journal_dirty_metadata+0x116/0x126 [jbd2] [] __mutex_lock_common+0x14e/0x1a9 [] ? brelse+0x13/0x15 [ext4] [] __mutex_lock_slowpath+0x19/0x1b [] mutex_lock+0x1b/0x32 [] __jbd2_journal_insert_checkpoint+0xe3/0x20c [jbd2] [] start_this_handle+0x438/0x527 [jbd2] [] ? autoremove_wake_function+0x0/0x3e [] jbd2_journal_start+0xa1/0xcc [jbd2] [] ext4_journal_start_sb+0x57/0x81 [ext4] [] ext4_xattr_set+0x6c/0xe3 [ext4] [] ext4_xattr_user_set+0x42/0x4b [ext4] [] generic_setxattr+0x6b/0x76 [] __vfs_setxattr_noperm+0x47/0xc0 [] vfs_setxattr+0x7f/0x9a [] setxattr+0xb5/0xe8 [] ? do_filp_open+0x571/0xa6e [] sys_fsetxattr+0x6b/0x91 [] system_call_fastpath+0x16/0x1b So this patch tries to use WRITE_SYNC in __flush_batch so that the request will be moved into sync queue and handled by cfq timely. We also use the new plug, sot that all the WRITE_SYNC requests can be given as a whole when we unplug it. Signed-off-by: Tao Ma Signed-off-by: "Theodore Ts'o" Cc: Jan Kara Reported-by: Robin Dong --- fs/jbd2/checkpoint.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c index 2c62c5aae82f..16a698bd906d 100644 --- a/fs/jbd2/checkpoint.c +++ b/fs/jbd2/checkpoint.c @@ -257,9 +257,12 @@ static void __flush_batch(journal_t *journal, int *batch_count) { int i; + struct blk_plug plug; + blk_start_plug(&plug); for (i = 0; i < *batch_count; i++) - write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE); + write_dirty_buffer(journal->j_chkpt_bhs[i], WRITE_SYNC); + blk_finish_plug(&plug); for (i = 0; i < *batch_count; i++) { struct buffer_head *bh = journal->j_chkpt_bhs[i];