This is a note to let you know that I've just added the patch titled dm bufio: check new buffer allocation watermark every 30 seconds to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: dm-bufio-check-new-buffer-allocation-watermark-every-30-seconds.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 390020ad2af9ca04844c4f3b1f299ad8746d84c8 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka <mpatocka@xxxxxxxxxx> Date: Sun, 30 Apr 2017 17:34:53 -0400 Subject: dm bufio: check new buffer allocation watermark every 30 seconds 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 @@ -1782,9 +1782,17 @@ 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) @@ -1809,6 +1817,8 @@ 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); Patches currently in stable-queue which might be from mpatocka@xxxxxxxxxx are queue-4.9/dm-bufio-avoid-a-possible-abba-deadlock.patch queue-4.9/dm-cache-metadata-fail-operations-if-fail_io-mode-has-been-established.patch queue-4.9/dm-raid-select-the-kconfig-option-config_md_raid0.patch queue-4.9/dm-bufio-make-the-parameter-retain_bytes-unsigned-long.patch queue-4.9/dm-bufio-check-new-buffer-allocation-watermark-every-30-seconds.patch