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Fri, 21 Feb 2020 04:30:38 +0000 To: Matthew Wilcox , References: <20200219210103.32400-1-willy@infradead.org> <20200219210103.32400-11-willy@infradead.org> X-Nvconfidentiality: public From: John Hubbard Message-ID: <45d67cb1-9ca3-e2b8-d71f-1f0c2e085155@nvidia.com> Date: Thu, 20 Feb 2020 20:30:37 -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: <20200219210103.32400-11-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=1582259366; bh=+Wm3044wXz/CoDYYTB4qibyZMJiORNPZJOuYKY+0G8w=; 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=UitvsuI1yoXnzml76+cSz7F+oTZFS/iyT7dOV5LH/5L9YZnf2JDmcICsW5QQsDOWw JEmxfGjJhpm6Mw0DpkQ4I97JHP2YxMVlsg4TdE5MBveHV+wfxOmkMx2E9X1fQGLWfG f8znlDQrWpx92I4FW23hWS3bxNs0j+rkOmq+Rdu1ptzaIP6nxGv9ByYUjCJJs79YE7 seWhQosGZtfe20jPzoLRnPNfNQlt0kzqk9SCpCzrG7HeKnuVPkQFIfGbTqOGCn3/Pw /XB5cMIwzFk+62xO1plJYkkUcmyRC6IeEYi54p0+giupM67/DiXtRdSSVw1QBxLyH7 Qd6o1BBujjHhg== X-Headers-End: 1j4zxc-00ClYC-6F Subject: Re: [f2fs-dev] [PATCH v7 10/24] mm: Add readahead address space operation 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 2/19/20 1:00 PM, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" > > This replaces ->readpages with a saner interface: > - Return void instead of an ignored error code. > - Page cache is already populated with locked pages when ->readahead > is called. > - New arguments can be passed to the implementation without changing > all the filesystems that use a common helper function like > mpage_readahead(). > > Signed-off-by: Matthew Wilcox (Oracle) > --- > Documentation/filesystems/locking.rst | 6 +++++- > Documentation/filesystems/vfs.rst | 15 +++++++++++++++ > include/linux/fs.h | 2 ++ > include/linux/pagemap.h | 18 ++++++++++++++++++ > mm/readahead.c | 12 ++++++++++-- > 5 files changed, 50 insertions(+), 3 deletions(-) This all looks correct to me, so: Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > > diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst > index 5057e4d9dcd1..0af2e0e11461 100644 > --- a/Documentation/filesystems/locking.rst > +++ b/Documentation/filesystems/locking.rst > @@ -239,6 +239,7 @@ prototypes:: > int (*readpage)(struct file *, struct page *); > int (*writepages)(struct address_space *, struct writeback_control *); > int (*set_page_dirty)(struct page *page); > + void (*readahead)(struct readahead_control *); > int (*readpages)(struct file *filp, struct address_space *mapping, > struct list_head *pages, unsigned nr_pages); > int (*write_begin)(struct file *, struct address_space *mapping, > @@ -271,7 +272,8 @@ writepage: yes, unlocks (see below) > readpage: yes, unlocks > writepages: > set_page_dirty no > -readpages: > +readahead: yes, unlocks > +readpages: no > write_begin: locks the page exclusive > write_end: yes, unlocks exclusive > bmap: > @@ -295,6 +297,8 @@ the request handler (/dev/loop). > ->readpage() unlocks the page, either synchronously or via I/O > completion. > > +->readahead() unlocks the pages that I/O is attempted on like ->readpage(). > + > ->readpages() populates the pagecache with the passed pages and starts > I/O against them. They come unlocked upon I/O completion. > > diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst > index 7d4d09dd5e6d..ed17771c212b 100644 > --- a/Documentation/filesystems/vfs.rst > +++ b/Documentation/filesystems/vfs.rst > @@ -706,6 +706,7 @@ cache in your filesystem. The following members are defined: > int (*readpage)(struct file *, struct page *); > int (*writepages)(struct address_space *, struct writeback_control *); > int (*set_page_dirty)(struct page *page); > + void (*readahead)(struct readahead_control *); > int (*readpages)(struct file *filp, struct address_space *mapping, > struct list_head *pages, unsigned nr_pages); > int (*write_begin)(struct file *, struct address_space *mapping, > @@ -781,12 +782,26 @@ cache in your filesystem. The following members are defined: > If defined, it should set the PageDirty flag, and the > PAGECACHE_TAG_DIRTY tag in the radix tree. > > +``readahead`` > + Called by the VM to read pages associated with the address_space > + object. The pages are consecutive in the page cache and are > + locked. The implementation should decrement the page refcount > + after starting I/O on each page. Usually the page will be > + unlocked by the I/O completion handler. If the filesystem decides > + to stop attempting I/O before reaching the end of the readahead > + window, it can simply return. The caller will decrement the page > + refcount and unlock the remaining pages for you. Set PageUptodate > + if the I/O completes successfully. Setting PageError on any page > + will be ignored; simply unlock the page if an I/O error occurs. > + > ``readpages`` > called by the VM to read pages associated with the address_space > object. This is essentially just a vector version of readpage. > Instead of just one page, several pages are requested. > readpages is only used for read-ahead, so read errors are > ignored. If anything goes wrong, feel free to give up. > + This interface is deprecated and will be removed by the end of > + 2020; implement readahead instead. > > ``write_begin`` > Called by the generic buffered write code to ask the filesystem > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 3cd4fe6b845e..d4e2d2964346 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -292,6 +292,7 @@ enum positive_aop_returns { > struct page; > struct address_space; > struct writeback_control; > +struct readahead_control; > > /* > * Write life time hint values. > @@ -375,6 +376,7 @@ struct address_space_operations { > */ > int (*readpages)(struct file *filp, struct address_space *mapping, > struct list_head *pages, unsigned nr_pages); > + void (*readahead)(struct readahead_control *); > > int (*write_begin)(struct file *, struct address_space *mapping, > loff_t pos, unsigned len, unsigned flags, > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index 4989d330fada..b3008605fd1b 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -669,6 +669,24 @@ static inline struct page *readahead_page(struct readahead_control *rac) > return page; > } > > +/* The byte offset into the file of this readahead block */ > +static inline loff_t readahead_pos(struct readahead_control *rac) > +{ > + return (loff_t)rac->_index * PAGE_SIZE; > +} > + > +/* The number of bytes in this readahead block */ > +static inline loff_t readahead_length(struct readahead_control *rac) > +{ > + return (loff_t)rac->_nr_pages * PAGE_SIZE; > +} > + > +/* The index of the first page in this readahead block */ > +static inline unsigned int readahead_index(struct readahead_control *rac) > +{ > + return rac->_index; > +} > + > /* The number of pages in this readahead block */ > static inline unsigned int readahead_count(struct readahead_control *rac) > { > diff --git a/mm/readahead.c b/mm/readahead.c > index aaa209559ba2..07cdfbf00f4b 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -124,7 +124,14 @@ static void read_pages(struct readahead_control *rac, struct list_head *pages) > > blk_start_plug(&plug); > > - if (aops->readpages) { > + if (aops->readahead) { > + aops->readahead(rac); > + /* Clean up the remaining pages */ > + while ((page = readahead_page(rac))) { > + unlock_page(page); > + put_page(page); > + } > + } else if (aops->readpages) { > aops->readpages(rac->file, rac->mapping, pages, > readahead_count(rac)); > /* Clean up the remaining pages */ > @@ -234,7 +241,8 @@ void force_page_cache_readahead(struct address_space *mapping, > struct file_ra_state *ra = &filp->f_ra; > unsigned long max_pages; > > - if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages)) > + if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages && > + !mapping->a_ops->readahead)) > return; > > /* > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel