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[2003:cf:d700:f38d:3df6:a1ca:7d40:fe1f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a88c7facf9sm12913901f8f.22.2025.07.01.04.45.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Jul 2025 04:45:26 -0700 (PDT) From: Hanna Czenczek To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Hanna Czenczek , Stefan Hajnoczi , Kevin Wolf , Markus Armbruster , Brian Song Subject: [PATCH v3 14/21] fuse: Reduce max read size Date: Tue, 1 Jul 2025 13:44:30 +0200 Message-ID: <20250701114437.207419-15-hreitz@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250701114437.207419-1-hreitz@redhat.com> References: <20250701114437.207419-1-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org We are going to introduce parallel processing via coroutines, a maximum read size of 64 MB may be problematic, allowing users of the export to force us to allocate quite large amounts of memory with just a few requests. At least tone it down to 1 MB, which is still probably far more than enough. (Larger requests are split automatically by the FUSE kernel driver anyway.) (Yes, we inadvertently already had parallel request processing due to nested polling before. Better to fix this late than never.) Reviewed-by: Stefan Hajnoczi Signed-off-by: Hanna Czenczek --- block/export/fuse.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/export/fuse.c b/block/export/fuse.c index 85ebc6bda8..8ea590ba67 100644 --- a/block/export/fuse.c +++ b/block/export/fuse.c @@ -45,7 +45,7 @@ #endif /* Prevent overly long bounce buffer allocations */ -#define FUSE_MAX_READ_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 64 * 1024 * 1024)) +#define FUSE_MAX_READ_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 1 * 1024 * 1024)) /* Small enough to fit in the request buffer */ #define FUSE_MAX_WRITE_BYTES (4 * 1024) -- 2.49.0