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De Francesco" , Luis Chamberlain , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC] vmap_folio() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="AsCF/Dmt"; spf=pass (imf26.hostedemail.com: domain of urezki@gmail.com designates 209.85.167.49 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661198064; a=rsa-sha256; cv=none; b=cF4V7nbOeYdNTz99lAM3CA83ckQaxRxkD2GV3NG+ifUoa5/QRH1MBS5jdfC+7MLgGEXYxC VvCloI6UWlYr63mQx4ff3fKmpoMjFgxRl4tOCWGAfKYdFdKAP5N/8HOTSTsLAd0s5iBxtV 8N7rHACdgEYzMSZBcrzzaLrOX61jVI8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661198064; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=mJYkjoFM1MNYDjxafvXKEPUbvJhzVrTSHnNsQsuncUA=; b=ce9upCthpPzroo8pCJrxWV81eUiorepurBO6173afDUJ36ggsXb1BXaqP69ZWkqjqCFKiZ nbHwVnk0vDiuRCORgtMFzQ9cPZNWjZylVHq6NWFejDBVfIFTKS3I5Jt8amBD+f18g3Alpw fZDF+0y5MPt1HWQ7g+u2AvKvGoed08U= Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="AsCF/Dmt"; spf=pass (imf26.hostedemail.com: domain of urezki@gmail.com designates 209.85.167.49 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 0BCFA1401C2 X-Stat-Signature: 7w6z9h5f7g9jrs4faqy6hx7yshhp5hgn X-HE-Tag: 1661198063-853928 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Aug 19, 2022 at 04:45:05PM +0100, Matthew Wilcox wrote: > On Fri, Aug 19, 2022 at 12:53:32PM +0200, Uladzislau Rezki wrote: > > Looks pretty straightforward. One thing though, if we can combine it > > together with vmap(), since it is a copy paste in some sense, say to > > have something __vmap() to reuse it in the vmap_folio() and vmap(). > > > > But that is just a thought. > > Thanks for looking it over! > You are welcome. > > Combining it with vmap() or vm_map_ram() is tricky. Today, we assume > that each struct page pointer refers to exactly PAGE_SIZE bytes, so if > somebody calls alloc_pages(GFP_COMPOUND, 4) and then passes the head > page to vmap(), only that one page gets mapped. I don't know whether > any current callers depend on that behaviour. > > Now that I look at the future customers of this, I think I erred in basing > this on vmap(), it looks like vm_map_ram() is preferred. So I'll redo > based on vm_map_ram(). > Indeed, the vmap code has no knowledge about comound pages. You can add me to CC, so i can have a look on it to help out with it if there will be a need. -- Uladzislau Rezki