zram: add set_max_streams knob

This patch allows to change max_comp_streams on initialised zcomp.

Introduce zcomp set_max_streams() knob, zcomp_strm_multi_set_max_streams()
and zcomp_strm_single_set_max_streams() callbacks to change streams limit
for zcomp_strm_multi and zcomp_strm_single, accordingly.  set_max_streams
for single steam zcomp does nothing.

If user has lowered the limit, then zcomp_strm_multi_set_max_streams()
attempts to immediately free extra streams (as much as it can, depending
on idle streams availability).

Note, this patch does not allow to change stream 'policy' from single to
multi stream (or vice versa) on already initialised compression backend.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index bdc7eb8c6df7..3a5f24c341dc 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -133,9 +133,8 @@ static ssize_t max_comp_streams_store(struct device *dev,
 		return -EINVAL;
 	down_write(&zram->init_lock);
 	if (init_done(zram)) {
-		up_write(&zram->init_lock);
-		pr_info("Can't set max_comp_streams for initialized device\n");
-		return -EBUSY;
+		if (zcomp_set_max_streams(zram->comp, num))
+			pr_info("Cannot change max compression streams\n");
 	}
 	zram->max_comp_streams = num;
 	up_write(&zram->init_lock);