[PATCHv3 10/11] zram: filter out recomp targets based on priority

[Sergey Senozhatsky <senozhatsky@chromium.org>]

Do no select for post processing slots that are already
compressed with same or higher priority compression
algorithm.

This should save some memory, as previously we would still
put those entries into corresponding post-processing buckets
and filter them out later in recompress_slot().

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/block/zram/zram_drv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 3e91fd1dcfc7..500d6c8b17fc 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1813,7 +1813,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 #define RECOMPRESS_IDLE		(1 << 0)
 #define RECOMPRESS_HUGE		(1 << 1)
 
-static int scan_slots_for_recompress(struct zram *zram, u32 mode,
+static int scan_slots_for_recompress(struct zram *zram, u32 mode, u32 prio_max,
 				     struct zram_pp_ctl *ctl)
 {
 	unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
@@ -1845,6 +1845,10 @@ static int scan_slots_for_recompress(struct zram *zram, u32 mode,
 		    zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
 			goto next;
 
+		/* Already compressed with same of higher priority */
+		if (zram_get_priority(zram, index) + 1 >= prio_max)
+			goto next;
+
 		pps->index = index;
 		place_pp_slot(zram, ctl, pps);
 		pps = NULL;
@@ -2134,7 +2138,7 @@ static ssize_t recompress_store(struct device *dev,
 		goto release_init_lock;
 	}
 
-	scan_slots_for_recompress(zram, mode, ctl);
+	scan_slots_for_recompress(zram, mode, prio_max, ctl);
 
 	ret = len;
 	while ((pps = select_pp_slot(ctl))) {
-- 
2.48.1.262.g85cc9f2d1e-goog