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Sat, 03 Jun 2023 13:16:22 -0700 (PDT) From: Russell Harmon To: bagasdotme@gmail.com Date: Sat, 3 Jun 2023 13:15:23 -0700 Message-Id: <20230603201525.9409-3-eatnumber1@gmail.com> In-Reply-To: <20230603201525.9409-1-eatnumber1@gmail.com> References: <20230603201525.9409-1-eatnumber1@gmail.com> MIME-Version: 1.0 X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Subject: [dm-devel] [PATCH 2/4] Documents the meaning of "buffer" in dm-integrity. X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Russell Harmon , dm-devel@redhat.com, mpatocka@redhat.com, snitzer@redhat.com, linux-doc@vger.kernel.org Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: gmail.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Signed-off-by: Russell Harmon --- .../admin-guide/device-mapper/dm-integrity.rst | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/Documentation/admin-guide/device-mapper/dm-integrity.rst b/Documentation/admin-guide/device-mapper/dm-integrity.rst index b2a698e955a3..31f514675809 100644 --- a/Documentation/admin-guide/device-mapper/dm-integrity.rst +++ b/Documentation/admin-guide/device-mapper/dm-integrity.rst @@ -38,6 +38,15 @@ the device. But it will only format the device if the superblock contains zeroes. If the superblock is neither valid nor zeroed, the dm-integrity target can't be loaded. +Accesses to the on-disk metadata area containing checksums (aka tags) are +buffered using dm-bufio. When an access to any given metadata area +occurs, each unique metadata area gets its own buffer(s). The buffer size +is capped at the size of the metadata area, but may be smaller, thereby +requiring multiple buffers to represent the full metadata area. A smaller +buffer size will produce a smaller resulting read/write operation to the +metadata area for small reads/writes. The metadata is still read even in +a full write to the data covered by a single buffer. + To use the target for the first time: 1. overwrite the superblock with zeroes @@ -106,10 +115,6 @@ buffer_sectors:number The number of sectors in one buffer. The value is rounded down to a power of two. - The tag area is accessed using buffers, the buffer size is - configurable. The large buffer size means that the I/O size will - be larger, but there could be less I/Os issued. - journal_watermark:number The journal watermark in percents. When the size of the journal exceeds this watermark, the thread that flushes the journal will -- 2.34.1 -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel