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Thu, 20 Feb 2020 15:00:34 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 20 Feb 2020 07:00:00 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 20 Feb 2020 07:00:33 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 20 Feb 2020 07:00:33 -0800 Received: from [10.2.165.18] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 20 Feb 2020 15:00:32 +0000 From: Zi Yan To: Matthew Wilcox CC: , , , , , , , , , Subject: Re: [PATCH v7 10/24] mm: Add readahead address space operation Date: Thu, 20 Feb 2020 10:00:30 -0500 X-Mailer: MailMate (1.13.1r5678) Message-ID: <5D7CE6BD-FABD-4901-AEF0-E0F10FC00EB1@nvidia.com> In-Reply-To: <20200219210103.32400-11-willy@infradead.org> References: <20200219210103.32400-1-willy@infradead.org> <20200219210103.32400-11-willy@infradead.org> MIME-Version: 1.0 X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: multipart/signed; boundary="=_MailMate_D3452F35-D86E-413E-A05C-9E5444344EF4_="; micalg=pgp-sha1; protocol="application/pgp-signature" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1582210800; bh=1ntWOoaWtNpHqLxJK1XQ1SdhWsITIFuo6dr1tEBt2WE=; h=X-PGP-Universal:From:To:CC:Subject:Date:X-Mailer:Message-ID: In-Reply-To:References:MIME-Version:X-Originating-IP: X-ClientProxiedBy:Content-Type; b=YtTAS8bnX87BGK5w3lMdP9+458E9VtjDQ0fiiXkrkqS0mYcPltP6gqMHw4D0ZSzBM E1YhnSrzQvcKkF3Zto6UlqoOsOgpKE/NbXYGkimuFhR34xFm94uVexe3iOFwhSk6h2 12/zcf497+YJzmP9TNrW43CQItw//lHNZ7BpxCqTnuYhxrdsvNbZfdHqeChfGPhfwR yyZBZ/QVbd2bSgyWP3NHl0VKcXZyFYJudagruOezn6PPp2ctR1x5hwjmiuRzW+Gg9w AJCl22QILCyz5lXp0TqvGllCCAiAw9ghV96heGAaDRve6pJTfWWtAC+iiu25BQOY4f N5DMQB97caaDA== 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: --=_MailMate_D3452F35-D86E-413E-A05C-9E5444344EF4_= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On 19 Feb 2020, at 16:00, 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(-) > > diff --git a/Documentation/filesystems/locking.rst b/Documentation/file= systems/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 ->readpa= ge(). > + > ->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/filesyst= ems/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 ar= e 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 r= eadahead_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 *r= ac) > +{ > + return rac->_index; > +} rac->_index is pgoff_t, so readahead_index() should return the same type,= right? BTW, pgoff_t is unsigned long. > + > /* The number of pages in this readahead block */ > static inline unsigned int readahead_count(struct readahead_control *r= ac) > { > 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 *r= ac, struct list_head *pages) > > blk_start_plug(&plug); > > - if (aops->readpages) { > + if (aops->readahead) { > + aops->readahead(rac); > + /* Clean up the remaining pages */ > + while ((page =3D 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_spac= e *mapping, > struct file_ra_state *ra =3D &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; > > /* > -- = > 2.25.0 -- Best Regards, Yan Zi --=_MailMate_D3452F35-D86E-413E-A05C-9E5444344EF4_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQJDBAEBAgAtFiEEh7yFAW3gwjwQ4C9anbJR82th+ooFAl5Onw4PHHppeUBudmlk aWEuY29tAAoJEJ2yUfNrYfqKP0AQAJ8rKk4f4gJQCLy1BEarhc0jqEJxv+LP4T93 thazkNgMM87L6fUgs2i0V2lUTkOQ9kN56mQH0wNc47I0tWm/5vVCPnDyS8MUFBeY 0sQiI3uTOVZcrz3GaZfrVJTUQHhIQ84wSAfUaRbaDKVlsGg4j1rZJocZrtKiXFoQ afay88LB8I0MMBXGS6eM4Ep+ABD1Dp+awB7sOnuZOrvuWfNaULR4f8sGyyim/QjY ZsJzs5rF5JIRkrCspYEnNbg7vx1orAAJBCxyVFgmAOIp2rNsnoDbHXhXE1LLCNgF sIl6bfNbL/1hpJRWa6RegKxN9AiWCoDlKcqTOlHh5edI6ukk7oRSB7WJkcKgVSIA ITkR/USPckkT4ZXP+5fYsfKMGgmPX00W9muaq6+/qWRFxjP1GY39zOlAgMoMMz82 AiBkYTLsp3L6SZ4f7GVLM8efNHFXk7cjjRDbN4GaGRzZhoz7yx3vGJaP/q9fssld PXpx/80pWMoSQQQ1o3ouW1XdZdV6rh8slBFoXeYpFQXLs3Q/j7njrK4drJniuHz5 qySleNBceQp4y9l4FVC7G7t23VSRTHzcrff5wA+H+tVOjddzKC/L7rrZROsVk9uF RBTotQ4VHR/fLoic/7IXBjQMD0nkS4UpaG71v9Rk4RwsusZU0f34h4zmuFQ4nfrU hNoR35aP =9x1/ -----END PGP SIGNATURE----- --=_MailMate_D3452F35-D86E-413E-A05C-9E5444344EF4_=--