dm thin: remove __bio_inc_remaining() and switch to using bio_inc_remaining() (13e4f8a6) · Commits · 戴 / test

DM thinp's use of bio_inc_remaining() is critical to ensure the original parent discard bio isn't completed before sub-discards have. DM thinp needs this due to the extra quiescing that occurs, via multiple DM thinp mappings, while processing large discards. As such DM thinp must build the async discard bio chain after some delay -- so bio_inc_remaining() is used to enable DM thinp to take a reference on the original parent discard bio for each mapping. This allows the immediate use of bio_endio() on that discard bio; but with the understanding that the actual completion won't occur until each of the sub-discards' per-mapping references are dropped. Signed-off-by:

Mike Snitzer <snitzer@redhat.com> Acked-by:

Joe Thornber <ejt@redhat.com>

drivers/md/dm-thin.c

+1 −12

Original line number	Diff line number	Diff line
		@@ -1494,17 +1494,6 @@ static void process_discard_cell_no_passdown(struct thin_c *tc,
		pool->process_prepared_discard(m);
		}

		/*
		* __bio_inc_remaining() is used to defer parent bios's end_io until
		* we _know_ all chained sub range discard bios have completed.
		*/
		static inline void __bio_inc_remaining(struct bio *bio)
		{
		bio->bi_flags \|= (1 << BIO_CHAIN);
		smp_mb__before_atomic();
		atomic_inc(&bio->__bi_remaining);
		}

		static void break_up_discard_bio(struct thin_c *tc, dm_block_t begin, dm_block_t end,
		struct bio *bio)
		{
		@@ -1560,7 +1549,7 @@ static void break_up_discard_bio(struct thin_c *tc, dm_block_t begin, dm_block_t
		* the implicit decrement that occurs via bio_endio() in
		* process_prepared_discard_{passdown,no_passdown}.
		*/
		__bio_inc_remaining(bio);
		bio_inc_remaining(bio);
		if (!dm_deferred_set_add_work(pool->all_io_ds, &m->list))
		pool->process_prepared_discard(m);

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