Commit e7be8d1d authored by Alexey Romanov's avatar Alexey Romanov Committed by Andrew Morton
Browse files

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 b09ab054 ("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: default avatarAlexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: default avatarDmitry Rokosov <ddrokosov@sberdevices.ru>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Reviewed-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f67bed13

drivers/block/zram/zram_drv.c

+10 −32
Original line number Diff line number Diff line
@@ -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 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, 
	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) {



	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;

drivers/block/zram/zram_drv.h

+0 −1
Original line number Diff line number Diff line
@@ -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 */