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Tue, 11 Feb 2025 22:33:17 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:69f5:6852:451e:8142]) by smtp.gmail.com with UTF8SMTPSA id d2e1a72fcca58-73218c206a6sm2581185b3a.49.2025.02.11.22.33.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Feb 2025 22:33:17 -0800 (PST) From: Sergey Senozhatsky To: Andrew Morton Cc: Yosry Ahmed , Kairui Song , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: [PATCH v5 15/18] zram: permit reclaim in zstd custom allocator Date: Wed, 12 Feb 2025 15:27:13 +0900 Message-ID: <20250212063153.179231-16-senozhatsky@chromium.org> X-Mailer: git-send-email 2.48.1.502.g6dc24dfdaf-goog In-Reply-To: <20250212063153.179231-1-senozhatsky@chromium.org> References: <20250212063153.179231-1-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" When configured with pre-trained compression/decompression dictionary support, zstd requires custom memory allocator, which it calls internally from compression()/decompression() routines. That means allocation from atomic context (either under entry spin-lock, or per-CPU local-lock or both). Now, with non-atomic zram read()/write(), those limitations are relaxed and we can allow direct and indirect reclaim. Signed-off-by: Sergey Senozhatsky --- drivers/block/zram/backend_zstd.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/drivers/block/zram/backend_zstd.c b/drivers/block/zram/backend= _zstd.c index 1184c0036f44..53431251ea62 100644 --- a/drivers/block/zram/backend_zstd.c +++ b/drivers/block/zram/backend_zstd.c @@ -24,19 +24,14 @@ struct zstd_params { /* * For C/D dictionaries we need to provide zstd with zstd_custom_mem, * which zstd uses internally to allocate/free memory when needed. - * - * This means that allocator.customAlloc() can be called from zcomp_compre= ss() - * under local-lock (per-CPU compression stream), in which case we must use - * GFP_ATOMIC. - * - * Another complication here is that we can be configured as a swap device. */ static void *zstd_custom_alloc(void *opaque, size_t size) { - if (!preemptible()) + /* Technically this should not happen */ + if (WARN_ON_ONCE(!preemptible())) return kvzalloc(size, GFP_ATOMIC); =20 - return kvzalloc(size, __GFP_KSWAPD_RECLAIM | __GFP_NOWARN); + return kvzalloc(size, GFP_NOIO | __GFP_NOWARN); } =20 static void zstd_custom_free(void *opaque, void *address) --=20 2.48.1.502.g6dc24dfdaf-goog