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Tue, 18 Feb 2020 22:33:19 +0000 To: Matthew Wilcox , References: <20200217184613.19668-1-willy@infradead.org> <20200217184613.19668-5-willy@infradead.org> X-Nvconfidentiality: public From: John Hubbard Message-ID: <6ecedc28-a999-8673-e4b1-349b0c23fdfd@nvidia.com> Date: Tue, 18 Feb 2020 14:33:19 -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: <20200217184613.19668-5-willy@infradead.org> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) 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=1582065129; bh=yWG75TuvaIkixcYjAReAuF+49IUj/8WtcUdupEFzEyw=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=klykhDzbfDnFoiAzHG0F/sl3+zuD/yu0U05wkkG5YL25K0mXMn/SZDKS/OPYoMjVi mBSMyFlXKKo4UAQQuQv/lsdIWAvE7WxiS+oOmcGMSJDykk7YuHI6JFzdcykchFj71k zIa5A9cfCBqyTcR6zGjigkGmcGSCKI7dxvmn+IuKHqErApkB59r3L/Gj+RxcTKKVSI +btrOqRw+4ZZVhqAz1RhfcawzguTRlv7l99v2wGxH6VlakfW2nQLeICs16ez9TeiWQ ZpdA450G/HarSR+IiezZDL9QVYoCyXag0rX4h00yKEt9Soza8Wdn/b85Sc2AMZZmq3 fR1BnLTnbzkPg== X-Headers-End: 1j4BQj-007kto-Sx Subject: Re: [f2fs-dev] [PATCH v6 04/19] mm: Rearrange 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)" > > Move the declaration of 'page' to inside the loop and move the 'kick > off a fresh batch' code to the end of the function for easier use in > subsequent patches. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/readahead.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index 15329309231f..3eca59c43a45 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -154,7 +154,6 @@ void __do_page_cache_readahead(struct address_space *mapping, > unsigned long lookahead_size) > { > struct inode *inode = mapping->host; > - struct page *page; > unsigned long end_index; /* The last page we want to read */ > LIST_HEAD(page_pool); > int page_idx; > @@ -175,6 +174,7 @@ void __do_page_cache_readahead(struct address_space *mapping, > * Preallocate as many pages as we will need. > */ > for (page_idx = 0; page_idx < nr_to_read; page_idx++) { > + struct page *page; > pgoff_t page_offset = offset + page_idx; > > if (page_offset > end_index) > @@ -183,14 +183,14 @@ void __do_page_cache_readahead(struct address_space *mapping, > page = xa_load(&mapping->i_pages, page_offset); > if (page && !xa_is_value(page)) { > /* > - * Page already present? Kick off the current batch of > - * contiguous pages before continuing with the next > - * batch. > + * Page already present? Kick off the current batch > + * of contiguous pages before continuing with the > + * next batch. This page may be the one we would > + * have intended to mark as Readahead, but we don't > + * have a stable reference to this page, and it's > + * not worth getting one just for that. > */ > - if (readahead_count(&rac)) > - read_pages(&rac, &page_pool, gfp_mask); > - rac._nr_pages = 0; > - continue; A fine point: you'll get better readability and a less complex function by factoring that into a static subroutine, instead of jumping around with goto's. (This clearly wants to be a subroutine, and in fact you've effectively created one inside this function, at the "read:" label. Either way, though... > + goto read; > } > > page = __page_cache_alloc(gfp_mask); > @@ -201,6 +201,11 @@ void __do_page_cache_readahead(struct address_space *mapping, > if (page_idx == nr_to_read - lookahead_size) > SetPageReadahead(page); > rac._nr_pages++; > + continue; > +read: > + if (readahead_count(&rac)) > + read_pages(&rac, &page_pool, gfp_mask); > + rac._nr_pages = 0; > } > > /* > ...no errors spotted, I'm confident that this patch is correct, Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel