From nobody Thu Dec 18 05:59:48 2025 Received: from mail-pl1-f173.google.com (mail-pl1-f173.google.com [209.85.214.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58960253F1B for ; Fri, 21 Feb 2025 22:30:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740177022; cv=none; b=nIgw6q0LQ1QDTF+FFl0D0zp7ixuOBmeWTjU2Ht//1DH1Qxeema8For/qALXAHT/OVt9y9N7Zi5e8YSW5hcvg47+v1VnYO14IDH9IO0GwSB1WQRafwfPvW89hq/OkiDzPyNFuFC4GSxLd1D2j+HzRl1TGrSDqTNX90rdEO4ttYUI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740177022; c=relaxed/simple; bh=5x/1sdhhRwLz01MCzfUBMqojwL2jNzuceIxbwNVccM0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=D7bLVfCYSz9P34hz2QBcLiUxiPTNQmnSbX0Z9a2es6wk2ZtD5SYKj42KGam0qnIsk72DAiKj83I0hRCbdMhnAUfKe9qWHu3HZw4XfYVJ2pyu6oAhOVZ0+19oQTQGTr7h5pqQT2zYScgODep55pn5OoEB4T995S291JGl7naUJzc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=iDcqeRJW; arc=none smtp.client-ip=209.85.214.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="iDcqeRJW" Received: by mail-pl1-f173.google.com with SMTP id d9443c01a7336-221057b6ac4so51451735ad.2 for ; Fri, 21 Feb 2025 14:30:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1740177019; x=1740781819; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=bQZ6+kL2+QjAG1mCzi3fyv64KzDue4pptM4PWageRhE=; b=iDcqeRJW7MOYVcQV5hzSVugbawPFedKmyBiG1Oa7Qs+M9p9ETxFh0L9FDQWcbipe06 z9mC2ZH5yssRVgB8K01oQ0xL0VzDXHq3mPkvlX9THnNzEnyFxhu44tfJor8zQXRjQDzj IZwJ5mhGsuCuHWen0SO0VOI6LmCy8wXxfVCa4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740177019; x=1740781819; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=bQZ6+kL2+QjAG1mCzi3fyv64KzDue4pptM4PWageRhE=; b=dpP35wrGZlRwlTtMPJWkL6z4VWwuOw+n+skTVFREUhDjswPpVpPZSztvlG0ZajmJa1 TN32jiKusZeZ2pS5DPBN0GtutnXOgZt5MG0Q0OIjVwST8nB15HWAD3gzrslfme1lfwws W+DmqEQmA4dt4Tu7mQpGB+3yd33S90yLhvj0UPOXxtrC6hR9HzXJyh4tvqnxqNS1iSJ3 iBznaI/USylHy/aFjoap0BlMN51ReU7mGHLOoxsyJh8eBCZLcThY2KX2Y0tB/qRpXFao 7If+7X0MOPEC9wiQLNAMgmUU5MEjYZaItNKSlEKDb0vaOHilkVJoJgNXqLDFSON6TYsZ XMWQ== X-Forwarded-Encrypted: i=1; AJvYcCUyVtXVTpkEf8p3nf4J17cjbJNA55jO40tDzatUE6pLiPKgfX+mVbsXlw1ZIIk+KZM3P+7Bg3kuqoedYHU=@vger.kernel.org X-Gm-Message-State: AOJu0YwiL03pUZ2ZGBIJj5M3kAdlEY8RAHWv8+HtYnqa04UEShl68zan ciUK7L8xq7xvzJxeYVqprwJeb6KZZYUlqOLUkE2L6hKDHIXFS4tcttqGdqx0Kg== X-Gm-Gg: ASbGncsnZA2SAHJkheZ+S7kQVKoLoXCDKmX9OJV31T7aJsvVkzC9/6NQHFzCO++oRRI z5iK90eWQsDGt+vnzaAMSa0ka1coIvghiEV7SP/9Iwcd8Qse0Awz+UzI9baCjqkqfOyd6zvuWv/ LgJZPE9lTmgSP7ymTqjXWecILZb8GYBKzvCWH6KYaz7qePbPsKPB8RNwufmhzD51/bpkgKEyvJj Ou2eo9mtYGHy7gX2keqZqt4AoKOQBLeqGNDKyHEGVmmFKi0V5aonWGsHyorQ5ipvQdxHeIFBPks hXWWAhrFawcNLolpiR2dF+RdFIY= X-Google-Smtp-Source: AGHT+IHFhs7hFYEDScLROxnrA8v6yUZmmj9MauSx4nCbk/5QH6SmEjHqOBlgJx/hpKYsI1k0DH+1eg== X-Received: by 2002:a17:902:da8f:b0:220:fe50:5b44 with SMTP id d9443c01a7336-221a1103431mr80781945ad.31.1740177019665; Fri, 21 Feb 2025 14:30:19 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:f987:e1e:3dbb:2191]) by smtp.gmail.com with UTF8SMTPSA id d9443c01a7336-220d558fe3asm141026215ad.234.2025.02.21.14.30.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Feb 2025 14:30:19 -0800 (PST) From: Sergey Senozhatsky To: Andrew Morton Cc: Yosry Ahmed , Hillf Danton , Kairui Song , Sebastian Andrzej Siewior , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: [PATCH v8 02/17] zram: permit preemption with active compression stream Date: Sat, 22 Feb 2025 07:25:33 +0900 Message-ID: <20250221222958.2225035-3-senozhatsky@chromium.org> X-Mailer: git-send-email 2.48.1.601.g30ceb7b040-goog In-Reply-To: <20250221222958.2225035-1-senozhatsky@chromium.org> References: <20250221222958.2225035-1-senozhatsky@chromium.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, per-CPU stream access is done from a non-preemptible (atomic) section, which imposes the same atomicity requirements on compression backends as entry spin-lock, and makes it impossible to use algorithms that can schedule/wait/sleep during compression and decompression. Switch to preemptible per-CPU model, similar to the one used in zswap. Instead of a per-CPU local lock, each stream carries a mutex which is locked throughout entire time zram uses it for compression or decompression, so that cpu-dead event waits for zram to stop using a particular per-CPU stream and release it. Suggested-by: Yosry Ahmed Reviewed-by: Yosry Ahmed Signed-off-by: Sergey Senozhatsky --- drivers/block/zram/zcomp.c | 41 +++++++++++++++++++++++++---------- drivers/block/zram/zcomp.h | 6 ++--- drivers/block/zram/zram_drv.c | 20 ++++++++--------- 3 files changed, 42 insertions(+), 25 deletions(-) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index bb514403e305..53e4c37441be 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -6,7 +6,7 @@ #include #include #include -#include +#include #include #include =20 @@ -109,13 +109,29 @@ ssize_t zcomp_available_show(const char *comp, char *= buf) =20 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp) { - local_lock(&comp->stream->lock); - return this_cpu_ptr(comp->stream); + for (;;) { + struct zcomp_strm *zstrm =3D raw_cpu_ptr(comp->stream); + + /* + * Inspired by zswap + * + * stream is returned with ->mutex locked which prevents + * cpu_dead() from releasing this stream under us, however + * there is still a race window between raw_cpu_ptr() and + * mutex_lock(), during which we could have been migrated + * from a CPU that has already destroyed its stream. If + * so then unlock and re-try on the current CPU. + */ + mutex_lock(&zstrm->lock); + if (likely(zstrm->buffer)) + return zstrm; + mutex_unlock(&zstrm->lock); + } } =20 -void zcomp_stream_put(struct zcomp *comp) +void zcomp_stream_put(struct zcomp_strm *zstrm) { - local_unlock(&comp->stream->lock); + mutex_unlock(&zstrm->lock); } =20 int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm, @@ -151,12 +167,9 @@ int zcomp_decompress(struct zcomp *comp, struct zcomp_= strm *zstrm, int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node) { struct zcomp *comp =3D hlist_entry(node, struct zcomp, node); - struct zcomp_strm *zstrm; + struct zcomp_strm *zstrm =3D per_cpu_ptr(comp->stream, cpu); int ret; =20 - zstrm =3D per_cpu_ptr(comp->stream, cpu); - local_lock_init(&zstrm->lock); - ret =3D zcomp_strm_init(comp, zstrm); if (ret) pr_err("Can't allocate a compression stream\n"); @@ -166,16 +179,17 @@ int zcomp_cpu_up_prepare(unsigned int cpu, struct hli= st_node *node) int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node) { struct zcomp *comp =3D hlist_entry(node, struct zcomp, node); - struct zcomp_strm *zstrm; + struct zcomp_strm *zstrm =3D per_cpu_ptr(comp->stream, cpu); =20 - zstrm =3D per_cpu_ptr(comp->stream, cpu); + mutex_lock(&zstrm->lock); zcomp_strm_free(comp, zstrm); + mutex_unlock(&zstrm->lock); return 0; } =20 static int zcomp_init(struct zcomp *comp, struct zcomp_params *params) { - int ret; + int ret, cpu; =20 comp->stream =3D alloc_percpu(struct zcomp_strm); if (!comp->stream) @@ -186,6 +200,9 @@ static int zcomp_init(struct zcomp *comp, struct zcomp_= params *params) if (ret) goto cleanup; =20 + for_each_possible_cpu(cpu) + mutex_init(&per_cpu_ptr(comp->stream, cpu)->lock); + ret =3D cpuhp_state_add_instance(CPUHP_ZCOMP_PREPARE, &comp->node); if (ret < 0) goto cleanup; diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h index ad5762813842..23b8236b9090 100644 --- a/drivers/block/zram/zcomp.h +++ b/drivers/block/zram/zcomp.h @@ -3,7 +3,7 @@ #ifndef _ZCOMP_H_ #define _ZCOMP_H_ =20 -#include +#include =20 #define ZCOMP_PARAM_NO_LEVEL INT_MIN =20 @@ -31,7 +31,7 @@ struct zcomp_ctx { }; =20 struct zcomp_strm { - local_lock_t lock; + struct mutex lock; /* compression buffer */ void *buffer; struct zcomp_ctx ctx; @@ -77,7 +77,7 @@ struct zcomp *zcomp_create(const char *alg, struct zcomp_= params *params); void zcomp_destroy(struct zcomp *comp); =20 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp); -void zcomp_stream_put(struct zcomp *comp); +void zcomp_stream_put(struct zcomp_strm *zstrm); =20 int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm, const void *src, unsigned int *dst_len); diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 37c5651305c2..1b5bb206239f 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1613,7 +1613,7 @@ static int read_compressed_page(struct zram *zram, st= ruct page *page, u32 index) ret =3D zcomp_decompress(zram->comps[prio], zstrm, src, size, dst); kunmap_local(dst); zs_unmap_object(zram->mem_pool, handle); - zcomp_stream_put(zram->comps[prio]); + zcomp_stream_put(zstrm); =20 return ret; } @@ -1774,14 +1774,14 @@ static int zram_write_page(struct zram *zram, struc= t page *page, u32 index) kunmap_local(mem); =20 if (unlikely(ret)) { - zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]); + zcomp_stream_put(zstrm); pr_err("Compression failed! err=3D%d\n", ret); zs_free(zram->mem_pool, handle); return ret; } =20 if (comp_len >=3D huge_class_size) { - zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]); + zcomp_stream_put(zstrm); return write_incompressible_page(zram, page, index); } =20 @@ -1805,7 +1805,7 @@ static int zram_write_page(struct zram *zram, struct = page *page, u32 index) __GFP_HIGHMEM | __GFP_MOVABLE); if (IS_ERR_VALUE(handle)) { - zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]); + zcomp_stream_put(zstrm); atomic64_inc(&zram->stats.writestall); handle =3D zs_malloc(zram->mem_pool, comp_len, GFP_NOIO | __GFP_HIGHMEM | @@ -1817,7 +1817,7 @@ static int zram_write_page(struct zram *zram, struct = page *page, u32 index) } =20 if (!zram_can_store_page(zram)) { - zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]); + zcomp_stream_put(zstrm); zs_free(zram->mem_pool, handle); return -ENOMEM; } @@ -1825,7 +1825,7 @@ static int zram_write_page(struct zram *zram, struct = page *page, u32 index) dst =3D zs_map_object(zram->mem_pool, handle, ZS_MM_WO); =20 memcpy(dst, zstrm->buffer, comp_len); - zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]); + zcomp_stream_put(zstrm); zs_unmap_object(zram->mem_pool, handle); =20 zram_slot_lock(zram, index); @@ -1984,7 +1984,7 @@ static int recompress_slot(struct zram *zram, u32 ind= ex, struct page *page, kunmap_local(src); =20 if (ret) { - zcomp_stream_put(zram->comps[prio]); + zcomp_stream_put(zstrm); return ret; } =20 @@ -1994,7 +1994,7 @@ static int recompress_slot(struct zram *zram, u32 ind= ex, struct page *page, /* Continue until we make progress */ if (class_index_new >=3D class_index_old || (threshold && comp_len_new >=3D threshold)) { - zcomp_stream_put(zram->comps[prio]); + zcomp_stream_put(zstrm); continue; } =20 @@ -2052,13 +2052,13 @@ static int recompress_slot(struct zram *zram, u32 i= ndex, struct page *page, __GFP_HIGHMEM | __GFP_MOVABLE); if (IS_ERR_VALUE(handle_new)) { - zcomp_stream_put(zram->comps[prio]); + zcomp_stream_put(zstrm); return PTR_ERR((void *)handle_new); } =20 dst =3D zs_map_object(zram->mem_pool, handle_new, ZS_MM_WO); memcpy(dst, zstrm->buffer, comp_len_new); - zcomp_stream_put(zram->comps[prio]); + zcomp_stream_put(zstrm); =20 zs_unmap_object(zram->mem_pool, handle_new); =20 --=20 2.48.1.601.g30ceb7b040-goog