4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
commit 390020ad2af9ca04844c4f3b1f299ad8746d84c8 upstream.
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: 1b0fb5a5b2 ("dm bufio: avoid a possible ABBA deadlock")
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-bufio.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -1755,9 +1755,17 @@ static void __evict_old_buffers(struct d
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)
@@ -1782,6 +1790,8 @@ 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);