Commit 671cc8a5 authored by Kent Overstreet's avatar Kent Overstreet Committed by Kent Overstreet
Browse files

bcachefs: Eliminate memory barrier from fast path of journal_preres_put() 



Signed-off-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 08e33761

fs/bcachefs/journal.c

+1 −1
Original line number Diff line number Diff line
@@ -520,7 +520,7 @@ static bool journal_preres_available(struct journal *j, 
				     unsigned new_u64s,

				     unsigned flags)

{

	bool ret = bch2_journal_preres_get_fast(j, res, new_u64s, flags);

	bool ret = bch2_journal_preres_get_fast(j, res, new_u64s, flags, true);



	if (!ret && mutex_trylock(&j->reclaim_lock)) {

		bch2_journal_reclaim(j);

fs/bcachefs/journal.h

+22 −17
Original line number Diff line number Diff line
@@ -411,7 +411,12 @@ static inline void bch2_journal_preres_put(struct journal *j, 


	s.v = atomic64_sub_return(s.v, &j->prereserved.counter);

	res->u64s = 0;



	if (unlikely(s.waiting)) {

		clear_bit(ilog2((((union journal_preres_state) { .waiting = 1 }).v)),

			  (unsigned long *) &j->prereserved.v);

		closure_wake_up(&j->preres_wait);

	}



	if (s.reserved <= s.remaining &&

	    !test_bit(JOURNAL_MAY_GET_UNRESERVED, &j->flags)) {
@@ -427,32 +432,32 @@ int __bch2_journal_preres_get(struct journal *, 
static inline int bch2_journal_preres_get_fast(struct journal *j,

					       struct journal_preres *res,

					       unsigned new_u64s,

					       unsigned flags)

					       unsigned flags,

					       bool set_waiting)

{

	int d = new_u64s - res->u64s;

	union journal_preres_state old, new;

	u64 v = atomic64_read(&j->prereserved.counter);

	int ret;



	do {

		old.v = new.v = v;

		ret = 0;



		if ((flags & JOURNAL_RES_GET_RESERVED) ||

		    new.reserved + d < new.remaining) {

			new.reserved += d;



		/*

		 * If we're being called from the journal reclaim path, we have

		 * to unconditionally give out the pre-reservation, there's

		 * nothing else sensible we can do - otherwise we'd recurse back

		 * into the reclaim path and deadlock:

		 */



		if (!(flags & JOURNAL_RES_GET_RESERVED) &&

		    new.reserved > new.remaining)

			ret = 1;

		} else if (set_waiting && !new.waiting)

			new.waiting = true;

		else

			return 0;

	} while ((v = atomic64_cmpxchg(&j->prereserved.counter,

				       old.v, new.v)) != old.v);



	if (ret)

		res->u64s += d;

	return 1;

	return ret;

}



static inline int bch2_journal_preres_get(struct journal *j,
@@ -463,7 +468,7 @@ static inline int bch2_journal_preres_get(struct journal *j, 
	if (new_u64s <= res->u64s)

		return 0;



	if (bch2_journal_preres_get_fast(j, res, new_u64s, flags))

	if (bch2_journal_preres_get_fast(j, res, new_u64s, flags, false))

		return 0;



	if (flags & JOURNAL_RES_GET_NONBLOCK)

fs/bcachefs/journal_types.h

+3 −2
Original line number Diff line number Diff line
@@ -105,8 +105,9 @@ union journal_preres_state { 
	};



	struct {

		u32		reserved;

		u32		remaining;

		u64		waiting:1,

				reserved:31,

				remaining:32;

	};

};