Commit bcc696fa authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm thin: stay in out-of-data-space mode once no_space_timeout expires 



This fixes an issue where running out of data space would cause the
thin-pool's metadata to become read-only.  There was no reason to make
metadata read-only -- calling set_pool_mode() with PM_READ_ONLY was a
misguided way to error all queued and future write IOs.  We can
accomplish the same by degrading from PM_OUT_OF_DATA_SPACE to
PM_OUT_OF_DATA_SPACE with error_if_no_space enabled.

Otherwise, the use of PM_READ_ONLY could cause a race where commit() was
started before the PM_READ_ONLY transition but dm_pool_commit_metadata()
would go on to fail because the block manager had transitioned to
read-only.  The return of -EPERM from dm_pool_commit_metadata(), due to
attempting to commit while in read-only mode, caused the thin-pool to
set 'needs_check' because a metadata_operation_failed().  This needless
cascade of failures makes life for users more difficult than needed.

Reported-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent b06075a9

drivers/md/dm-thin.c

+17 −4
Original line number Diff line number Diff line
@@ -2282,18 +2282,23 @@ static void do_waker(struct work_struct *ws) 
	queue_delayed_work(pool->wq, &pool->waker, COMMIT_PERIOD);

}



static void notify_of_pool_mode_change_to_oods(struct pool *pool);



/*

 * We're holding onto IO to allow userland time to react.  After the

 * timeout either the pool will have been resized (and thus back in

 * PM_WRITE mode), or we degrade to PM_READ_ONLY and start erroring IO.

 * PM_WRITE mode), or we degrade to PM_OUT_OF_DATA_SPACE w/ error_if_no_space.

 */

static void do_no_space_timeout(struct work_struct *ws)

{

	struct pool *pool = container_of(to_delayed_work(ws), struct pool,

					 no_space_timeout);



	if (get_pool_mode(pool) == PM_OUT_OF_DATA_SPACE && !pool->pf.error_if_no_space)

		set_pool_mode(pool, PM_READ_ONLY);

	if (get_pool_mode(pool) == PM_OUT_OF_DATA_SPACE && !pool->pf.error_if_no_space) {

		pool->pf.error_if_no_space = true;

		notify_of_pool_mode_change_to_oods(pool);

		error_retry_list(pool);

	}

}



/*----------------------------------------------------------------*/
@@ -2371,6 +2376,14 @@ static void notify_of_pool_mode_change(struct pool *pool, const char *new_mode) 
	       dm_device_name(pool->pool_md), new_mode);

}



static void notify_of_pool_mode_change_to_oods(struct pool *pool)

{

	if (!pool->pf.error_if_no_space)

		notify_of_pool_mode_change(pool, "out-of-data-space (queue IO)");

	else

		notify_of_pool_mode_change(pool, "out-of-data-space (error IO)");

}



static bool passdown_enabled(struct pool_c *pt)

{

	return pt->adjusted_pf.discard_passdown;
@@ -2455,7 +2468,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode) 
		 * frequently seeing this mode.

		 */

		if (old_mode != new_mode)

			notify_of_pool_mode_change(pool, "out-of-data-space");

			notify_of_pool_mode_change_to_oods(pool);

		pool->process_bio = process_bio_read_only;

		pool->process_discard = process_discard_bio;

		pool->process_cell = process_cell_read_only;

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