The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 211ad4b733037f66f9be0a79eade3da7ab11cbb8 Mon Sep 17 00:00:00 2001

From: "zhangyi (F)" yi.zhang@huawei.com Date: Wed, 5 Jun 2019 21:27:08 +0800 Subject: [PATCH] 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: 0e9cebe724597 ("dm: add log writes target") Cc: stable@vger.kernel.org Signed-off-by: zhangyi (F) yi.zhang@huawei.com Suggested-by: Josef Bacik josef@toxicpanda.com Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Mike Snitzer snitzer@redhat.com

diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c index 9ea2b0291f20..e549392e0ea5 100644 --- a/drivers/md/dm-log-writes.c +++ b/drivers/md/dm-log-writes.c @@ -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);