Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753300AbaBYOTJ (ORCPT ); Tue, 25 Feb 2014 09:19:09 -0500 Received: from mga02.intel.com ([134.134.136.20]:34065 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752598AbaBYOTG (ORCPT ); Tue, 25 Feb 2014 09:19:06 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,540,1389772800"; d="scan'208";a="461939330" From: Matthew Wilcox To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, willy@linux.intel.com Cc: Matthew Wilcox Subject: [PATCH v6 10/22] Remove get_xip_mem Date: Tue, 25 Feb 2014 09:18:26 -0500 Message-Id: <1393337918-28265-11-git-send-email-matthew.r.wilcox@intel.com> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1393337918-28265-1-git-send-email-matthew.r.wilcox@intel.com> References: <1393337918-28265-1-git-send-email-matthew.r.wilcox@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org All callers of get_xip_mem() are now gone. Remove checks for it, initialisers of it, documentation of it and the only implementation of it. Add documentation for writing a filesystem that supports DAX. Signed-off-by: Matthew Wilcox Reviewed-by: Randy Dunlap --- Documentation/filesystems/Locking | 3 -- Documentation/filesystems/dax.txt | 82 +++++++++++++++++++++++++++++++++++++++ Documentation/filesystems/xip.txt | 71 --------------------------------- fs/exofs/inode.c | 1 - fs/ext2/inode.c | 1 - fs/ext2/xip.c | 37 ------------------ fs/ext2/xip.h | 3 -- fs/open.c | 5 +-- include/linux/fs.h | 2 - mm/fadvise.c | 6 ++- mm/madvise.c | 2 +- 11 files changed, 88 insertions(+), 125 deletions(-) create mode 100644 Documentation/filesystems/dax.txt delete mode 100644 Documentation/filesystems/xip.txt diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index 5b0c083..2780d47 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -194,8 +194,6 @@ prototypes: void (*freepage)(struct page *); int (*direct_IO)(int, struct kiocb *, const struct iovec *iov, loff_t offset, unsigned long nr_segs); - int (*get_xip_mem)(struct address_space *, pgoff_t, int, void **, - unsigned long *); int (*migratepage)(struct address_space *, struct page *, struct page *); int (*launder_page)(struct page *); int (*is_partially_uptodate)(struct page *, read_descriptor_t *, unsigned long); @@ -220,7 +218,6 @@ invalidatepage: yes releasepage: yes freepage: yes direct_IO: -get_xip_mem: maybe migratepage: yes (both) launder_page: yes is_partially_uptodate: yes diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt new file mode 100644 index 0000000..06f84e5 --- /dev/null +++ b/Documentation/filesystems/dax.txt @@ -0,0 +1,82 @@ +Execute-in-place for file mappings +---------------------------------- + +Motivation +---------- + +File mappings are usually performed by mapping page cache pages to +userspace. In addition, read & write file operations also transfer data +between the page cache and storage. + +For memory backed storage devices that use the block device interface, +the page cache pages are just copies of the original storage. The +execute-in-place code removes the extra copy by performing reads and +writes directly on the memory backed storage device. For file mappings, +the storage device itself is mapped directly into userspace. + + +Implementation Tips for Block Driver Writers +-------------------------------------------- + +To support DAX in your block driver, implement the 'direct_access' +block device operation. It is used to translate the sector number +(expressed in units of 512-byte sectors) to a page frame number (pfn) +that identifies the physical page for the memory. It also returns a +kernel virtual address that can be used to access the memory. + +The direct_access method takes a 'size' parameter that indicates the +number of bytes being requested. The function should return the number +of bytes that it can provide, although it must not exceed the number of +bytes requested. It may also return a negative errno if an error occurs. + +In order to support this method, the storage must be byte-accessible by +the CPU at all times. If your device uses paging techniques to expose +a large amount of memory through a smaller window, then you cannot +implement direct_access. Equally, if your device can occasionally +stall the CPU for an extended period, you should also not attempt to +implement direct_access. + +These block devices may be used for inspiration: +- axonram: Axon DDR2 device driver +- brd: RAM backed block device driver +- dcssblk: s390 dcss block device driver + + +Implementation Tips for Filesystem Writers +------------------------------------------ + +Filesystem support consists of +- adding support to mark inodes as being DAX by setting the S_DAX flag in + i_flags +- implementing the direct_IO address space operation, and calling + dax_do_io() instead of blockdev_direct_IO() if S_DAX is set +- implementing an mmap file operation for DAX files which sets the + VM_MIXEDMAP flag on the VMA, and setting the vm_ops to include handlers + for fault and page_mkwrite (which should probably call dax_fault() and + dax_mkwrite(), passing the appropriate get_block() callback) +- calling dax_truncate_page() instead of block_truncate_page() for DAX files +- ensuring that there is sufficient locking between reads, writes, + truncates and page faults + +The get_block() callback passed to the DAX functions may return +uninitialised extents. If it does, it must ensure that simultaneous +calls to get_block() (for example by a page-fault racing with a read() +or a write()) work correctly. + +These filesystems may be used for inspiration: +- ext2: the second extended filesystem, see Documentation/filesystems/ext2.txt + + +Shortcomings +------------ + +Even if the kernel or its modules are stored on a filesystem that supports +DAX on a block device that supports DAX, they will still be copied into RAM. + +Calling get_user_pages() on a range of user memory that has been mmaped +from a DAX file will fail as there are no 'struct page' to describe +those pages. This problem is being worked on. That means that O_DIRECT +reads/writes to those memory ranges from a non-DAX file will fail (note +that O_DIRECT reads/writes _of a DAX file_ do work, it is the memory +that is being accessed that is key here). Other things that will not +work include RDMA, sendfile() and splice(). diff --git a/Documentation/filesystems/xip.txt b/Documentation/filesystems/xip.txt deleted file mode 100644 index b62eabf..0000000 --- a/Documentation/filesystems/xip.txt +++ /dev/null @@ -1,71 +0,0 @@ -Execute-in-place for file mappings ----------------------------------- - -Motivation ----------- -File mappings are performed by mapping page cache pages to userspace. In -addition, read&write type file operations also transfer data from/to the page -cache. - -For memory backed storage devices that use the block device interface, the page -cache pages are in fact copies of the original storage. Various approaches -exist to work around the need for an extra copy. The ramdisk driver for example -does read the data into the page cache, keeps a reference, and discards the -original data behind later on. - -Execute-in-place solves this issue the other way around: instead of keeping -data in the page cache, the need to have a page cache copy is eliminated -completely. With execute-in-place, read&write type operations are performed -directly from/to the memory backed storage device. For file mappings, the -storage device itself is mapped directly into userspace. - -This implementation was initially written for shared memory segments between -different virtual machines on s390 hardware to allow multiple machines to -share the same binaries and libraries. - -Implementation --------------- -Execute-in-place is implemented in three steps: block device operation, -address space operation, and file operations. - -A block device operation named direct_access is used to translate the -block device sector number to a page frame number (pfn) that identifies -the physical page for the memory. It also returns a kernel virtual -address that can be used to access the memory. - -The direct_access method takes a 'size' parameter that indicates the -number of bytes being requested. The function should return the number -of bytes that it can provide, although it must not exceed the number of -bytes requested. It may also return a negative errno if an error occurs. - -The block device operation is optional, these block devices support it as of -today: -- dcssblk: s390 dcss block device driver - -An address space operation named get_xip_mem is used to retrieve references -to a page frame number and a kernel address. To obtain these values a reference -to an address_space is provided. This function assigns values to the kmem and -pfn parameters. The third argument indicates whether the function should allocate -blocks if needed. - -This address space operation is mutually exclusive with readpage&writepage that -do page cache read/write operations. -The following filesystems support it as of today: -- ext2: the second extended filesystem, see Documentation/filesystems/ext2.txt - -A set of file operations that do utilize get_xip_page can be found in -mm/filemap_xip.c . The following file operation implementations are provided: -- aio_read/aio_write -- readv/writev -- sendfile - -The generic file operations do_sync_read/do_sync_write can be used to implement -classic synchronous IO calls. - -Shortcomings ------------- -This implementation is limited to storage devices that are cpu addressable at -all times (no highmem or such). It works well on rom/ram, but enhancements are -needed to make it work with flash in read+write mode. -Putting the Linux kernel and/or its modules on a xip filesystem does not mean -they are not copied. diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c index ee4317fa..f9a5bf6 100644 --- a/fs/exofs/inode.c +++ b/fs/exofs/inode.c @@ -985,7 +985,6 @@ const struct address_space_operations exofs_aops = { .direct_IO = exofs_direct_IO, /* With these NULL has special meaning or default is not exported */ - .get_xip_mem = NULL, .migratepage = NULL, .launder_page = NULL, .is_partially_uptodate = NULL, diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c index 252481f..b156fe8 100644 --- a/fs/ext2/inode.c +++ b/fs/ext2/inode.c @@ -891,7 +891,6 @@ const struct address_space_operations ext2_aops = { const struct address_space_operations ext2_aops_xip = { .bmap = ext2_bmap, - .get_xip_mem = ext2_get_xip_mem, .direct_IO = ext2_direct_IO, }; diff --git a/fs/ext2/xip.c b/fs/ext2/xip.c index fa40091..ca745ff 100644 --- a/fs/ext2/xip.c +++ b/fs/ext2/xip.c @@ -22,27 +22,6 @@ static inline long __inode_direct_access(struct inode *inode, sector_t block, return ops->direct_access(bdev, sector, kaddr, pfn, size); } -static inline int -__ext2_get_block(struct inode *inode, pgoff_t pgoff, int create, - sector_t *result) -{ - struct buffer_head tmp; - int rc; - - memset(&tmp, 0, sizeof(struct buffer_head)); - tmp.b_size = 1 << inode->i_blkbits; - rc = ext2_get_block(inode, pgoff, &tmp, create); - *result = tmp.b_blocknr; - - /* did we get a sparse block (hole in the file)? */ - if (!tmp.b_blocknr && !rc) { - BUG_ON(create); - rc = -ENODATA; - } - - return rc; -} - int ext2_clear_xip_target(struct inode *inode, sector_t block) { @@ -69,19 +48,3 @@ void ext2_xip_verify_sb(struct super_block *sb) "not supported by bdev"); } } - -int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create, - void **kmem, unsigned long *pfn) -{ - long rc; - sector_t block; - - /* first, retrieve the sector number */ - rc = __ext2_get_block(mapping->host, pgoff, create, &block); - if (rc) - return rc; - - /* retrieve address of the target data */ - rc = __inode_direct_access(mapping->host, block, kmem, pfn, PAGE_SIZE); - return (rc < 0) ? rc : 0; -} diff --git a/fs/ext2/xip.h b/fs/ext2/xip.h index 29be737..0fa8b7f 100644 --- a/fs/ext2/xip.h +++ b/fs/ext2/xip.h @@ -14,11 +14,8 @@ static inline int ext2_use_xip (struct super_block *sb) struct ext2_sb_info *sbi = EXT2_SB(sb); return (sbi->s_mount_opt & EXT2_MOUNT_XIP); } -int ext2_get_xip_mem(struct address_space *, pgoff_t, int, - void **, unsigned long *); #else #define ext2_xip_verify_sb(sb) do { } while (0) #define ext2_use_xip(sb) 0 #define ext2_clear_xip_target(inode, chain) 0 -#define ext2_get_xip_mem NULL #endif diff --git a/fs/open.c b/fs/open.c index 4b3e1ed..4b16abe 100644 --- a/fs/open.c +++ b/fs/open.c @@ -665,11 +665,8 @@ int open_check_o_direct(struct file *f) { /* NB: we're sure to have correct a_ops only after f_op->open */ if (f->f_flags & O_DIRECT) { - if (!f->f_mapping->a_ops || - ((!f->f_mapping->a_ops->direct_IO) && - (!f->f_mapping->a_ops->get_xip_mem))) { + if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO) return -EINVAL; - } } return 0; } diff --git a/include/linux/fs.h b/include/linux/fs.h index 02eeeb7..c7945fd 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -372,8 +372,6 @@ struct address_space_operations { void (*freepage)(struct page *); ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov, loff_t offset, unsigned long nr_segs); - int (*get_xip_mem)(struct address_space *, pgoff_t, int, - void **, unsigned long *); /* * migrate the contents of a page to the specified target. If * migrate_mode is MIGRATE_ASYNC, it must not block. diff --git a/mm/fadvise.c b/mm/fadvise.c index 3bcfd81..1f1925f 100644 --- a/mm/fadvise.c +++ b/mm/fadvise.c @@ -28,6 +28,7 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice) { struct fd f = fdget(fd); + struct inode *inode; struct address_space *mapping; struct backing_dev_info *bdi; loff_t endbyte; /* inclusive */ @@ -39,7 +40,8 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice) if (!f.file) return -EBADF; - if (S_ISFIFO(file_inode(f.file)->i_mode)) { + inode = file_inode(f.file); + if (S_ISFIFO(inode->i_mode)) { ret = -ESPIPE; goto out; } @@ -50,7 +52,7 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice) goto out; } - if (mapping->a_ops->get_xip_mem) { + if (IS_DAX(inode)) { switch (advice) { case POSIX_FADV_NORMAL: case POSIX_FADV_RANDOM: diff --git a/mm/madvise.c b/mm/madvise.c index 539eeb9..b6a2f52 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -236,7 +236,7 @@ static long madvise_willneed(struct vm_area_struct *vma, if (!file) return -EBADF; - if (file->f_mapping->a_ops->get_xip_mem) { + if (IS_DAX(file_inode(file))) { /* no bad return value, but ignore advice */ return 0; } -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/