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FAILED: patch "[PATCH] dm log writes: make sure super sector log updates are written" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jul 1, 2019

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Stable branch Device mapper
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The patch below does not apply to the 4.9-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 <[email protected]>.

thanks,

greg k-h

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

From 211ad4b733037f66f9be0a79eade3da7ab11cbb8 Mon Sep 17 00:00:00 2001
From: "zhangyi (F)" <[email protected]>
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 [email protected]
Signed-off-by zhangyi (F) <[email protected]>
Suggested-by Josef Bacik <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Signed-off-by Mike Snitzer <[email protected]>
drivers/md/dm-log-writes.c +21 -2
index 9ea2b0291f20..e549392e0ea5 100644
@@ -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);