Commit 0ef5a50c authored May 05, 2016 by Mike Snitzer Committed by Jens Axboe May 05, 2016

block: make bio_inc_remaining() interface accessible again



Commit 326e1dbb ("block: remove management of bi_remaining when
restoring original bi_end_io") made bio_inc_remaining() private to bio.c
because the only use-case that made sense was confined to the
bio_chain() interface.

Since that time DM thinp went on to use bio_chain() in its relatively
complex implementation of async discard support.  That implementation,
even when converted over to use the new async __blkdev_issue_discard()
interface, depends on deferred completion of the original discard bio --
which is most appropriately implemented using bio_inc_remaining().

DM thinp foolishly duplicated bio_inc_remaining(), local to dm-thin.c as
__bio_inc_remaining(), so re-exporting bio_inc_remaining() allows us to
put an end to that foolishness.

All said, bio_inc_remaining() should really only be used in conjunction
with bio_chain().  It isn't intended for generic bio reference counting.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent bbd848e0

block/bio.c

+0 −11

Original line number	Diff line number	Diff line
		@@ -311,17 +311,6 @@ static void bio_chain_endio(struct bio *bio)
		bio_endio(__bio_chain_endio(bio));
		}

		/*
		* Increment chain count for the bio. Make sure the CHAIN flag update
		* is visible before the raised count.
		*/
		static inline void bio_inc_remaining(struct bio *bio)
		{
		bio_set_flag(bio, BIO_CHAIN);
		smp_mb__before_atomic();
		atomic_inc(&bio->__bi_remaining);
		}

		/**
		* bio_chain - chain bio completions
		* @bio: the target bio

include/linux/bio.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -702,6 +702,17 @@ static inline struct bio bio_list_get(struct bio_list bl)
		return bio;
		}

		/*
		* Increment chain count for the bio. Make sure the CHAIN flag update
		* is visible before the raised count.
		*/
		static inline void bio_inc_remaining(struct bio *bio)
		{
		bio_set_flag(bio, BIO_CHAIN);
		smp_mb__before_atomic();
		atomic_inc(&bio->__bi_remaining);
		}

		/*
		* bio_set is used to allow other portions of the IO system to
		* allocate their own private memory pools for bio and iovec structures.