From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DE41C32772 for ; Wed, 17 Aug 2022 20:57:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242092AbiHQU5l (ORCPT ); Wed, 17 Aug 2022 16:57:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242088AbiHQU5T (ORCPT ); Wed, 17 Aug 2022 16:57:19 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50261AB425; Wed, 17 Aug 2022 13:57:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 8A348B81F6E; Wed, 17 Aug 2022 20:57:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29199C433D7; Wed, 17 Aug 2022 20:57:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1660769825; bh=KpB8e88xng+lmGGW5mDJoJBBuFDsfnIpEyQOs6vWrM4=; h=Date:To:From:Subject:From; b=Eo1DeDkAIW5tk5p0mQP5dVmyV5uxUaPaOUidNpVgeo68ZYAHGORxoj15uJUJCKZ3v 8nXJZh1ErnfVntf7qjVgO2p+a32YsBzk3kekcPGQbdy+Clph4JGf7admXzTCnBd8ke vfGASYZzRZ748N9biiIji5neH1sJEghQhv9VXk6w= Date: Wed, 17 Aug 2022 13:57:04 -0700 To: mm-commits@vger.kernel.org, stable@vger.kernel.org, senozhatsky@chromium.org, ngupta@vflare.org, minchan@kernel.org, lczerner@redhat.com, ddrokosov@sberdevices.ru, avromanov@sberdevices.ru, jslaby@suse.cz, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] revert-zram-remove-double-compression-logic.patch removed from -mm tree Message-Id: <20220817205705.29199C433D7@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: Revert "zram: remove double compression logic" has been removed from the -mm tree. Its filename was revert-zram-remove-double-compression-logic.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Jiri Slaby Subject: Revert "zram: remove double compression logic" Date: Wed, 10 Aug 2022 09:06:09 +0200 This reverts commit e7be8d1dd983156b ("zram: remove double compression logic") as it causes zram failures. It does not revert cleanly, PTR_ERR handling was introduced in the meantime. This is handled by appropriate IS_ERR. When under memory pressure, zs_malloc() can fail. Before the above commit, the allocation was retried with direct reclaim enabled (GFP_NOIO). After the commit, it is not -- only __GFP_KSWAPD_RECLAIM is tried. So when the failure occurs under memory pressure, the overlaying filesystem such as ext2 (mounted by ext4 module in this case) can emit failures, making the (file)system unusable: EXT4-fs warning (device zram0): ext4_end_bio:343: I/O error 10 writing to inode 16386 starting block 159744) Buffer I/O error on device zram0, logical block 159744 With direct reclaim, memory is really reclaimed and allocation succeeds, eventually. In the worst case, the oom killer is invoked, which is proper outcome if user sets up zram too large (in comparison to available RAM). This very diff doesn't apply to 5.19 (stable) cleanly (see PTR_ERR note above). Use revert of e7be8d1dd983 directly. Link: https://bugzilla.suse.com/show_bug.cgi?id=1202203 Link: https://lkml.kernel.org/r/20220810070609.14402-1-jslaby@suse.cz Fixes: e7be8d1dd983 ("zram: remove double compression logic") Signed-off-by: Jiri Slaby Reviewed-by: Sergey Senozhatsky Cc: Minchan Kim Cc: Nitin Gupta Cc: Alexey Romanov Cc: Dmitry Rokosov Cc: Lukas Czerner Cc: [5.19] Signed-off-by: Andrew Morton --- drivers/block/zram/zram_drv.c | 42 ++++++++++++++++++++++++-------- drivers/block/zram/zram_drv.h | 1 2 files changed, 33 insertions(+), 10 deletions(-) --- a/drivers/block/zram/zram_drv.c~revert-zram-remove-double-compression-logic +++ a/drivers/block/zram/zram_drv.c @@ -1146,14 +1146,15 @@ static ssize_t bd_stat_show(struct devic static ssize_t debug_stat_show(struct device *dev, struct device_attribute *attr, char *buf) { - int version = 2; + int version = 1; struct zram *zram = dev_to_zram(dev); ssize_t ret; down_read(&zram->init_lock); ret = scnprintf(buf, PAGE_SIZE, - "version: %d\n%8llu\n", + "version: %d\n%8llu %8llu\n", version, + (u64)atomic64_read(&zram->stats.writestall), (u64)atomic64_read(&zram->stats.miss_free)); up_read(&zram->init_lock); @@ -1351,7 +1352,7 @@ static int __zram_bvec_write(struct zram { int ret = 0; unsigned long alloced_pages; - unsigned long handle = 0; + unsigned long handle = -ENOMEM; unsigned int comp_len = 0; void *src, *dst, *mem; struct zcomp_strm *zstrm; @@ -1369,6 +1370,7 @@ static int __zram_bvec_write(struct zram } kunmap_atomic(mem); +compress_again: zstrm = zcomp_stream_get(zram->comp); src = kmap_atomic(page); ret = zcomp_compress(zstrm, src, &comp_len); @@ -1377,20 +1379,39 @@ static int __zram_bvec_write(struct zram 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 = zs_malloc(zram->mem_pool, comp_len, - __GFP_KSWAPD_RECLAIM | - __GFP_NOWARN | - __GFP_HIGHMEM | - __GFP_MOVABLE); - + /* + * 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 (IS_ERR((void *)handle)) + handle = zs_malloc(zram->mem_pool, comp_len, + __GFP_KSWAPD_RECLAIM | + __GFP_NOWARN | + __GFP_HIGHMEM | + __GFP_MOVABLE); if (IS_ERR((void *)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 (!IS_ERR((void *)handle)) + goto compress_again; return PTR_ERR((void *)handle); } @@ -1948,6 +1969,7 @@ 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; --- a/drivers/block/zram/zram_drv.h~revert-zram-remove-double-compression-logic +++ a/drivers/block/zram/zram_drv.h @@ -81,6 +81,7 @@ 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 */ _ Patches currently in -mm which might be from jslaby@suse.cz are