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Commit 390020ad authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
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dm bufio: check new buffer allocation watermark every 30 seconds 



dm-bufio checks a watermark when it allocates a new buffer in
__bufio_new().  However, it doesn't check the watermark when the user
changes /sys/module/dm_bufio/parameters/max_cache_size_bytes.

This may result in a problem - if the watermark is high enough so that
all possible buffers are allocated and if the user lowers the value of
"max_cache_size_bytes", the watermark will never be checked against the
new value because no new buffer would be allocated.

To fix this, change __evict_old_buffers() so that it checks the
watermark.  __evict_old_buffers() is called every 30 seconds, so if the
user reduces "max_cache_size_bytes", dm-bufio will react to this change
within 30 seconds and decrease memory consumption.

Depends-on: 1b0fb5a5 ("dm bufio: avoid a possible ABBA deadlock")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 1b0fb5a5

drivers/md/dm-bufio.c

+10 −0
Original line number Diff line number Diff line
@@ -1796,9 +1796,17 @@ static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz) 
	struct dm_buffer *b, *tmp;

	unsigned retain_target = get_retain_buffers(c);

	unsigned count;

	LIST_HEAD(write_list);



	dm_bufio_lock(c);



	__check_watermark(c, &write_list);

	if (unlikely(!list_empty(&write_list))) {

		dm_bufio_unlock(c);

		__flush_write_list(&write_list);

		dm_bufio_lock(c);

	}



	count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];

	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {

		if (count <= retain_target)
@@ -1823,6 +1831,8 @@ static void cleanup_old_buffers(void) 


	mutex_lock(&dm_bufio_clients_lock);



	__cache_size_refresh();



	list_for_each_entry(c, &dm_bufio_all_clients, client_list)

		__evict_old_buffers(c, max_age_hz);