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Wed, 25 Mar 2020 15:32:48 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=L8UzQwxATOZdjWZ+3tNM04b2mH/5tj4IRSDfIFAnCq4=; b=nwr8fvcCAKrcOHuwe8r/p16lMc bZh3DEdAU9aGBWN3F5ynv1Ne93Ij03ZhftdP2p/j/SwKFdDbTLj5/ZaltpVeKwhDVOtZpmt6dBgOM Y5kNAkTDyJM9LmxIOgZivD4BtHVK41PC4z2UtEwA8qUzMYjVHQwzjfESuvsJdyTL91AdLqA/lHmDm b4ONx8n6tUgKbzMesC9PHNx/tJe345Szba01BQVbNkeQ4aBKyS9/rqkTgJMFlzt5JsbGeTzjBPG19 tW79XBGQHh8i08Okr8byBxVFG1QH7u5q9rAcay5PaTaRDoWupoIchhUNkRzhk4f/AQVLTP2rNvR7K 5pnTChzQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jH816-0004oZ-U3; Wed, 25 Mar 2020 15:32:28 +0000 Date: Wed, 25 Mar 2020 08:32:28 -0700 From: Matthew Wilcox To: Miklos Szeredi Message-ID: <20200325153228.GB22483@bombadil.infradead.org> References: <20200323202259.13363-1-willy@infradead.org> <20200323202259.13363-25-willy@infradead.org> <20200325120254.GA22483@bombadil.infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1jH81N-006lbF-99 Subject: Re: [f2fs-dev] [PATCH v10 24/25] fuse: Convert from readpages to readahead X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-xfs , William Kucharski , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, ocfs2-devel@oss.oracle.com, Dave Chinner , linux-fsdevel@vger.kernel.org, Andrew Morton , linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Wed, Mar 25, 2020 at 03:43:02PM +0100, Miklos Szeredi wrote: > > > > - while ((page = readahead_page(rac))) { > > - if (fuse_readpages_fill(&data, page) != 0) > > + nr_pages = min(readahead_count(rac), fc->max_pages); > > Missing fc->max_read clamp. Yeah, I realised that. I ended up doing ... + unsigned int i, max_pages, nr_pages = 0; ... + max_pages = min(fc->max_pages, fc->max_read / PAGE_SIZE); > > + ia = fuse_io_alloc(NULL, nr_pages); > > + if (!ia) > > return; > > + ap = &ia->ap; > > + __readahead_batch(rac, ap->pages, nr_pages); > > nr_pages = __readahead_batch(...)? That's the other bug ... this was designed for btrfs which has a fixed-size buffer. But you want to dynamically allocate fuse_io_args(), so we need to figure out the number of pages beforehand, which is a little awkward. I've settled on this for the moment: for (;;) { struct fuse_io_args *ia; struct fuse_args_pages *ap; nr_pages = readahead_count(rac) - nr_pages; if (nr_pages > max_pages) nr_pages = max_pages; if (nr_pages == 0) break; ia = fuse_io_alloc(NULL, nr_pages); if (!ia) return; ap = &ia->ap; __readahead_batch(rac, ap->pages, nr_pages); for (i = 0; i < nr_pages; i++) { fuse_wait_on_page_writeback(inode, readahead_index(rac) + i); ap->descs[i].length = PAGE_SIZE; } ap->num_pages = nr_pages; fuse_send_readpages(ia, rac->file); } but I'm not entirely happy with that either. Pondering better options. > This will give consecutive pages, right? readpages() was already being called with consecutive pages. Several filesystems had code to cope with the pages being non-consecutive, but that wasn't how the core code worked; if there was a discontiguity it would send off the pages that were consecutive and start a new batch. __readahead_batch() can't return fewer than nr_pages, so you don't need to check for that. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel