From e7be8d1dd983156bbdd22c0319b71119a8fbb697 Mon Sep 17 00:00:00 2001 From: Alexey Romanov Date: Thu, 12 May 2022 20:23:07 -0700 Subject: [PATCH] zram: remove double compression logic The 2nd trial allocation under per-cpu presumption has been used to prevent regression of allocation failure. However, it makes trouble for maintenance without significant benefit. The slowpath branch is executed extremely rarely: getting there is problematic. Therefore, we delete this branch. Since b09ab054b69b ("zram: support BDI_CAP_STABLE_WRITES"), zram has used QUEUE_FLAG_STABLE_WRITES to prevent buffer change between 1st and 2nd memory allocations. Since we remove second trial memory allocation logic, we could remove the STABLE_WRITES flag because there is no change buffer to be modified under us. Link: https://lkml.kernel.org/r/20220505094443.11728-1-avromanov@sberdevices.ru Signed-off-by: Alexey Romanov Signed-off-by: Dmitry Rokosov Acked-by: Minchan Kim Reviewed-by: Sergey Senozhatsky Cc: Nitin Gupta Signed-off-by: Andrew Morton --- drivers/block/zram/zram_drv.c | 42 ++++++++++-------------------------------- drivers/block/zram/zram_drv.h | 1 - 2 files changed, 10 insertions(+), 33 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 8562a7c..7e84965 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1144,15 +1144,14 @@ static ssize_t bd_stat_show(struct device *dev, static ssize_t debug_stat_show(struct device *dev, struct device_attribute *attr, char *buf) { - int version = 1; + int version = 2; struct zram *zram = dev_to_zram(dev); ssize_t ret; down_read(&zram->init_lock); ret = scnprintf(buf, PAGE_SIZE, - "version: %d\n%8llu %8llu\n", + "version: %d\n%8llu\n", version, - (u64)atomic64_read(&zram->stats.writestall), (u64)atomic64_read(&zram->stats.miss_free)); up_read(&zram->init_lock); @@ -1368,7 +1367,6 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, } kunmap_atomic(mem); -compress_again: zstrm = zcomp_stream_get(zram->comp); src = kmap_atomic(page); ret = zcomp_compress(zstrm, src, &comp_len); @@ -1377,39 +1375,20 @@ compress_again: if (unlikely(ret)) { zcomp_stream_put(zram->comp); pr_err("Compression failed! err=%d\n", ret); - zs_free(zram->mem_pool, handle); return ret; } if (comp_len >= huge_class_size) comp_len = PAGE_SIZE; - /* - * handle allocation has 2 paths: - * a) fast path is executed with preemption disabled (for - * per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear, - * since we can't sleep; - * b) slow path enables preemption and attempts to allocate - * the page with __GFP_DIRECT_RECLAIM bit set. we have to - * put per-cpu compression stream and, thus, to re-do - * the compression once handle is allocated. - * - * if we have a 'non-null' handle here then we are coming - * from the slow path and handle has already been allocated. - */ - if (!handle) - handle = zs_malloc(zram->mem_pool, comp_len, - __GFP_KSWAPD_RECLAIM | - __GFP_NOWARN | - __GFP_HIGHMEM | - __GFP_MOVABLE); - if (!handle) { + + handle = zs_malloc(zram->mem_pool, comp_len, + __GFP_KSWAPD_RECLAIM | + __GFP_NOWARN | + __GFP_HIGHMEM | + __GFP_MOVABLE); + + if (unlikely(!handle)) { zcomp_stream_put(zram->comp); - atomic64_inc(&zram->stats.writestall); - handle = zs_malloc(zram->mem_pool, comp_len, - GFP_NOIO | __GFP_HIGHMEM | - __GFP_MOVABLE); - if (handle) - goto compress_again; return -ENOMEM; } @@ -1967,7 +1946,6 @@ static int zram_add(void) if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE) blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX); - blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, zram->disk->queue); ret = device_add_disk(NULL, zram->disk, zram_disk_groups); if (ret) goto out_cleanup_disk; diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index 80c3b43..158c91e 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -81,7 +81,6 @@ struct zram_stats { atomic64_t huge_pages_since; /* no. of huge pages since zram set up */ atomic64_t pages_stored; /* no. of pages currently stored */ atomic_long_t max_used_pages; /* no. of maximum pages stored */ - atomic64_t writestall; /* no. of write slow paths */ atomic64_t miss_free; /* no. of missed free */ #ifdef CONFIG_ZRAM_WRITEBACK atomic64_t bd_count; /* no. of pages in backing device */ -- 2.7.4