Commit 211ad4b7 authored by zhangyi (F)'s avatar zhangyi (F) Committed by Mike Snitzer
Browse files

dm log writes: make sure super sector log updates are written in order 



Currently, although we submit super bios in order (and super.nr_entries
is incremented by each logged entry), submit_bio() is async so each
super sector may not be written to log device in order and then the
final nr_entries may be smaller than it should be.

This problem can be reproduced by the xfstests generic/455 with ext4:

  QA output created by 455
 -Silence is golden
 +mark 'end' does not exist

Fix this by serializing submission of super sectors to make sure each
is written to the log disk in order.

Fixes: 0e9cebe7 ("dm: add log writes target")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarzhangyi (F) <yi.zhang@huawei.com>
Suggested-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 10c9c8e7

drivers/md/dm-log-writes.c

+21 −2
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ 


#define WRITE_LOG_VERSION 1ULL

#define WRITE_LOG_MAGIC 0x6a736677736872ULL

#define WRITE_LOG_SUPER_SECTOR 0



/*

 * The disk format for this is braindead simple.
@@ -115,6 +116,7 @@ struct log_writes_c { 
	struct list_head logging_blocks;

	wait_queue_head_t wait;

	struct task_struct *log_kthread;

	struct completion super_done;

};



struct pending_block {
@@ -180,6 +182,14 @@ static void log_end_io(struct bio *bio) 
	bio_put(bio);

}



static void log_end_super(struct bio *bio)

{

	struct log_writes_c *lc = bio->bi_private;



	complete(&lc->super_done);

	log_end_io(bio);

}



/*

 * Meant to be called if there is an error, it will free all the pages

 * associated with the block.
@@ -215,7 +225,8 @@ static int write_metadata(struct log_writes_c *lc, void *entry, 
	bio->bi_iter.bi_size = 0;

	bio->bi_iter.bi_sector = sector;

	bio_set_dev(bio, lc->logdev->bdev);

	bio->bi_end_io = log_end_io;

	bio->bi_end_io = (sector == WRITE_LOG_SUPER_SECTOR) ?

			  log_end_super : log_end_io;

	bio->bi_private = lc;

	bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
@@ -418,11 +429,18 @@ static int log_super(struct log_writes_c *lc) 
	super.nr_entries = cpu_to_le64(lc->logged_entries);

	super.sectorsize = cpu_to_le32(lc->sectorsize);



	if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) {

	if (write_metadata(lc, &super, sizeof(super), NULL, 0,

			   WRITE_LOG_SUPER_SECTOR)) {

		DMERR("Couldn't write super");

		return -1;

	}



	/*

	 * Super sector should be writen in-order, otherwise the

	 * nr_entries could be rewritten incorrectly by an old bio.

	 */

	wait_for_completion_io(&lc->super_done);



	return 0;

}
@@ -531,6 +549,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	INIT_LIST_HEAD(&lc->unflushed_blocks);

	INIT_LIST_HEAD(&lc->logging_blocks);

	init_waitqueue_head(&lc->wait);

	init_completion(&lc->super_done);

	atomic_set(&lc->io_blocks, 0);

	atomic_set(&lc->pending_blocks, 0);

CRA Git | Maintained and supported by SUSTech CRA and CCSE