From: Matthew Wilcox <willy@infradead.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org, John Hubbard <jhubbard@nvidia.com>, Christoph Hellwig <hch@lst.de>, William Kucharski <william.kucharski@oracle.com> Subject: [PATCH v10 11/25] mm: Add readahead address space operation Date: Mon, 23 Mar 2020 13:22:45 -0700 Message-ID: <20200323202259.13363-12-willy@infradead.org> (raw) In-Reply-To: <20200323202259.13363-1-willy@infradead.org> From: "Matthew Wilcox (Oracle)" <willy@infradead.org> 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) <willy@infradead.org> Reviewed-by: John Hubbard <jhubbard@nvidia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: William Kucharski <william.kucharski@oracle.com> --- Documentation/filesystems/locking.rst | 6 +++++- Documentation/filesystems/vfs.rst | 15 +++++++++++++++ include/linux/fs.h | 2 ++ mm/readahead.c | 12 ++++++++++-- 4 files changed, 32 insertions(+), 3 deletions(-) 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 2c097c0793f3..3b505aabebde 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/mm/readahead.c b/mm/readahead.c index e52b3a7b9da5..d01531ef9f3c 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -125,7 +125,14 @@ 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 */ @@ -233,7 +240,8 @@ 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; /* -- 2.25.1
next prev parent reply index Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-23 20:22 [PATCH v10 00/25] Change readahead API Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 02/25] mm: Return void from various readahead functions Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 03/25] mm: Ignore return value of ->readpages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 05/25] mm: Add new readahead_control API Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox 2020-03-23 20:22 ` Matthew Wilcox [this message] 2020-03-23 20:22 ` [PATCH v10 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox 2020-03-23 20:49 ` Eric Biggers 2020-03-24 8:40 ` Christoph Hellwig 2020-03-23 20:22 ` [PATCH v10 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox 2020-03-26 16:53 ` David Sterba 2020-03-23 20:22 ` [PATCH v10 18/25] erofs: Convert uncompressed files " Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 19/25] erofs: Convert compressed " Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 20/25] ext4: Convert " Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox 2020-03-23 20:22 ` [PATCH v10 24/25] fuse: Convert from readpages to readahead Matthew Wilcox 2020-03-25 9:42 ` Miklos Szeredi 2020-03-25 12:02 ` Matthew Wilcox 2020-03-25 14:43 ` Miklos Szeredi 2020-03-25 15:32 ` Matthew Wilcox 2020-03-25 15:54 ` Miklos Szeredi 2020-03-23 20:22 ` [PATCH v10 25/25] iomap: " Matthew Wilcox
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