Commit 8c0f0e8c authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm thin: requeue bios to DM core if no_free_space and in read-only mode 



Now that we switch the pool to read-only mode when the data device runs
out of space it causes active writers to get IO errors once we resume
after resizing the data device.

If no_free_space is set, save bios to the 'retry_on_resume_list' and
requeue them on resume (once the data or metadata device may have been
resized).

With this patch the resize_io test passes again (on slower storage):
 dmtest run --suite thin-provisioning -n /resize_io/

Later patches fix some subtle races associated with the pool mode
transitions done as part of the pool's -ENOSPC handling.  These races
are exposed on fast storage (e.g. PCIe SSD).

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Acked-by: default avatarJoe Thornber <ejt@redhat.com>
parent 399caddf

drivers/md/dm-thin.c

+20 −6
Original line number Diff line number Diff line
@@ -164,7 +164,7 @@ struct pool { 


	struct pool_features pf;

	bool low_water_triggered:1;	/* A dm event has been sent */

	bool no_free_space:1;		/* A -ENOSPC warning has been issued */

	bool no_free_space:1;		/* bios will be requeued if set */



	struct dm_bio_prison *prison;

	struct dm_kcopyd_client *copier;
@@ -982,6 +982,20 @@ static void retry_on_resume(struct bio *bio) 
	spin_unlock_irqrestore(&pool->lock, flags);

}



static void handle_unserviceable_bio(struct pool *pool, struct bio *bio)

{

	/*

	 * When pool is read-only, no cell locking is needed because

	 * nothing is changing.

	 */

	WARN_ON_ONCE(get_pool_mode(pool) != PM_READ_ONLY);



	if (pool->no_free_space)

		retry_on_resume(bio);

	else

		bio_io_error(bio);

}



static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *cell)

{

	struct bio *bio;
@@ -991,7 +1005,7 @@ static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *c 
	cell_release(pool, cell, &bios);



	while ((bio = bio_list_pop(&bios)))

		retry_on_resume(bio);

		handle_unserviceable_bio(pool, bio);

}



static void process_discard(struct thin_c *tc, struct bio *bio)
@@ -1245,7 +1259,7 @@ static void process_bio_read_only(struct thin_c *tc, struct bio *bio) 
	switch (r) {

	case 0:

		if (lookup_result.shared && (rw == WRITE) && bio->bi_size)

			bio_io_error(bio);

			handle_unserviceable_bio(tc->pool, bio);

		else {

			inc_all_io_entry(tc->pool, bio);

			remap_and_issue(tc, bio, lookup_result.block);
@@ -1254,7 +1268,7 @@ static void process_bio_read_only(struct thin_c *tc, struct bio *bio) 


	case -ENODATA:

		if (rw != READ) {

			bio_io_error(bio);

			handle_unserviceable_bio(tc->pool, bio);

			break;

		}
@@ -1565,9 +1579,9 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) 
		if (get_pool_mode(tc->pool) == PM_READ_ONLY) {

			/*

			 * This block isn't provisioned, and we have no way

			 * of doing so.  Just error it.

			 * of doing so.

			 */

			bio_io_error(bio);

			handle_unserviceable_bio(tc->pool, bio);

			return DM_MAPIO_SUBMITTED;

		}

		/* fall through */

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