Commit 0e825862 authored Oct 01, 2014 by Mikulas Patocka Committed by Mike Snitzer Oct 05, 2014

dm bufio: when done scanning return from __scan immediately



When __scan frees the required number of buffer entries that the
shrinker requested (nr_to_scan becomes zero) it must return.  Before
this fix the __scan code exited only the inner loop and continued in the
outer loop -- which could result in reduced performance due to extra
buffers being freed (e.g. unnecessarily evicted thinp metadata needing
to be synchronously re-read into bufio's cache).

Also, move dm_bufio_cond_resched to __scan's inner loop, so that
iterating the bufio client's lru lists doesn't result in scheduling
latency.

Reported-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.2+

parent eb76faf5

drivers/md/dm-bufio.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1473,10 +1473,10 @@ static long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
		freed += __cleanup_old_buffer(b, gfp_mask, 0);
		if (!--nr_to_scan)
		break;
		}
		return freed;
		dm_bufio_cond_resched();
		}
		}
		return freed;
		}

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