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Tue, 18 Feb 2020 23:08:49 +0000 To: Matthew Wilcox , References: <20200217184613.19668-1-willy@infradead.org> <20200217184613.19668-8-willy@infradead.org> From: John Hubbard X-Nvconfidentiality: public Message-ID: Date: Tue, 18 Feb 2020 15:08:49 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200217184613.19668-8-willy@infradead.org> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1582067316; bh=M7N9Wj3+9XwAeFwQi6TOYJxPABg1BqYz4tVXoRpCkIA=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=IeItEZERl8RgD9gMu8hyrKs9zDAELxc/pcSyWfpoGI0TB2mLKgncHMG394p6px4ju zmtAMOymP1/ZtJoe4HlOHDlOUZc/uVCaP5RY2LCqtWb4PFiTTWf0yQduIPEsPrRM6I 7+ZxiupuOA683TN7ev8l4qf1ne9j9TMe9yxP+4Gnp/KCmRvKAlcJ1KhnSHEd/mtvXA kETqqZe9Hl6tljU3UyeJaS2R5RC2d7bjB/6ICvno2hVU7UkwwH0PxFr9ixgVpcc7ww OuFMigzNUu1o/1PB1x64JUqXhqwxHJk3vxspEehlY/0wVnC7QAKbRSRGKmSy0mZ60N Ry89dWBs1XZZg== X-Headers-End: 1j4Bz5-007QXe-F0 Subject: Re: [f2fs-dev] [PATCH v6 05/19] mm: Remove 'page_offset' from readahead loop 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@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, ocfs2-devel@oss.oracle.com, 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 2/17/20 10:45 AM, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" > > Eliminate the page_offset variable which was confusing with the > 'offset' parameter and record the start of each consecutive run of > pages in the readahead_control. ...presumably for the benefit of a subsequent patch, since it's not consumed in this patch. Thanks for breaking these up, btw, it really helps. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/readahead.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index 3eca59c43a45..74791b96013f 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -162,6 +162,7 @@ void __do_page_cache_readahead(struct address_space *mapping, > struct readahead_control rac = { > .mapping = mapping, > .file = filp, > + ._start = offset, > ._nr_pages = 0, > }; > > @@ -175,12 +176,11 @@ void __do_page_cache_readahead(struct address_space *mapping, > */ > for (page_idx = 0; page_idx < nr_to_read; page_idx++) { > struct page *page; > - pgoff_t page_offset = offset + page_idx; OK, this is still something I want to mention (I wrote the same thing when reviewing the wrong version of this patch, a moment ago). You know...this ends up incrementing offset each time through the loop, so yes, the behavior is the same as when using "offset + page_idx". However, now it's a little harder to see that. IMHO the page_offset variable is not actually a bad thing, here. I'd rather keep it, all other things being equal (and I don't see any other benefits here: line count is about the same, for example). What do you think? (I don't feel strongly about this fine point.) thanks, -- John Hubbard NVIDIA > > - if (page_offset > end_index) > + if (offset > end_index) > break; > > - page = xa_load(&mapping->i_pages, page_offset); > + page = xa_load(&mapping->i_pages, offset); > if (page && !xa_is_value(page)) { > /* > * Page already present? Kick off the current batch > @@ -196,16 +196,18 @@ void __do_page_cache_readahead(struct address_space *mapping, > page = __page_cache_alloc(gfp_mask); > if (!page) > break; > - page->index = page_offset; > + page->index = offset; > list_add(&page->lru, &page_pool); > if (page_idx == nr_to_read - lookahead_size) > SetPageReadahead(page); > rac._nr_pages++; > + offset++; > continue; > read: > if (readahead_count(&rac)) > read_pages(&rac, &page_pool, gfp_mask); > rac._nr_pages = 0; > + rac._start = ++offset; > } > > /* > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel