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Mon, 12 Jul 2021 00:47:07 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwxo6cbOdK8GtnZr48+t/zqcsbPjRIV5a6GvEbJpJLGvigOrNRa9iX2X6KvnE6ltqoogRYtpQ== X-Received: by 2002:a1c:ed0a:: with SMTP id l10mr54003814wmh.151.1626076026937; Mon, 12 Jul 2021 00:47:06 -0700 (PDT) Received: from dresden.str.redhat.com ([2a02:908:1e46:160:b272:8083:d5:bc7d]) by smtp.gmail.com with ESMTPSA id m7sm17534849wms.0.2021.07.12.00.47.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Jul 2021 00:47:06 -0700 (PDT) Subject: Re: [PATCH v2 3/6] block: Clarify that @bytes is no limit on *pnum To: Eric Blake References: <20210623150143.188184-1-mreitz@redhat.com> <20210623150143.188184-4-mreitz@redhat.com> <3c4ae0ed-a7d7-b6c3-1785-f6e4a9efec7e@redhat.com> <20210628191044.or4e2h7jza6r4a4m@redhat.com> From: Max Reitz Message-ID: Date: Mon, 12 Jul 2021 09:47:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210628191044.or4e2h7jza6r4a4m@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=216.205.24.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.631, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 28.06.21 21:10, Eric Blake wrote: >>>> +++ b/include/block/block_int.h >>>> @@ -347,6 +347,11 @@ struct BlockDriver { >>>>        * clamped to bdrv_getlength() and aligned to request_alignment, >>>>        * as well as non-NULL pnum, map, and file; in turn, the driver >>>>        * must return an error or set pnum to an aligned non-zero value. >>>> +     * >>>> +     * Note that @bytes is just a hint on how big of a region the >>>> +     * caller wants to inspect.  It is not a limit on *pnum. >>>> +     * Implementations are free to return larger values of *pnum if >>>> +     * doing so does not incur a performance penalty. >>> Worth mention that the cache will benefit of it? >> Oh, right, absolutely.  Like so: >> >> "block/io.c's bdrv_co_block_status() will clamp *pnum before returning it to >> its caller, but it itself can still make use of the unclamped *pnum value. >> Specifically, the block-status cache for protocol nodes will benefit from >> storing as large a region as possible." > How about this tweak to the wording to make it flow a little better: > > block/io.c's bdrv_co_block_status() will utilize an unclamped *pnum > value for the block-status cache on protocol nodes, prior to clamping > *pnum for return to its caller. Sure, thanks! Max