From 25726bc15731d42112b579cf73f30edbc43d3973 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 16 Feb 2015 15:59:35 -0800 Subject: [PATCH] dax: add dax_zero_page_range This new function allows us to support hole-punch for DAX files by zeroing a partial page, as opposed to the dax_truncate_page() function which can only truncate to the end of the page. Reimplement dax_truncate_page() to call dax_zero_page_range(). [ross.zwisler@linux.intel.com: ported to 3.13-rc2] [akpm@linux-foundation.org: fix typos in comments] Signed-off-by: Matthew Wilcox Signed-off-by: Ross Zwisler Cc: Andreas Dilger Cc: Boaz Harrosh Cc: Christoph Hellwig Cc: Dave Chinner Cc: Jan Kara Cc: Jens Axboe Cc: Kirill A. Shutemov Cc: Mathieu Desnoyers Cc: Randy Dunlap Cc: Theodore Ts'o Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/filesystems/dax.txt | 1 + fs/dax.c | 38 ++++++++++++++++++++++++++----- include/linux/fs.h | 1 + 3 files changed, 34 insertions(+), 6 deletions(-) diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt index 635adaa1e425..ebcd97f03654 100644 --- a/Documentation/filesystems/dax.txt +++ b/Documentation/filesystems/dax.txt @@ -62,6 +62,7 @@ Filesystem support consists of 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 +- calling dax_zero_page_range() instead of zero_user() for DAX files - ensuring that there is sufficient locking between reads, writes, truncates and page faults diff --git a/fs/dax.c b/fs/dax.c index ebf9b2231b0f..ed1619ec6537 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -464,31 +464,35 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, EXPORT_SYMBOL_GPL(dax_fault); /** - * dax_truncate_page - handle a partial page being truncated in a DAX file + * dax_zero_page_range - zero a range within a page of a DAX file * @inode: The file being truncated * @from: The file offset that is being truncated to + * @length: The number of bytes to zero * @get_block: The filesystem method used to translate file offsets to blocks * - * Similar to block_truncate_page(), this function can be called by a - * filesystem when it is truncating an DAX file to handle the partial page. + * This function can be called by a filesystem when it is zeroing part of a + * page in a DAX file. This is intended for hole-punch operations. If + * you are truncating a file, the helper function dax_truncate_page() may be + * more convenient. * * We work in terms of PAGE_CACHE_SIZE here for commonality with * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem * took care of disposing of the unnecessary blocks. Even if the filesystem * block size is smaller than PAGE_SIZE, we have to zero the rest of the page - * since the file might be mmaped. + * since the file might be mmapped. */ -int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) +int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, + get_block_t get_block) { struct buffer_head bh; pgoff_t index = from >> PAGE_CACHE_SHIFT; unsigned offset = from & (PAGE_CACHE_SIZE-1); - unsigned length = PAGE_CACHE_ALIGN(from) - from; int err; /* Block boundary? Nothing to do */ if (!length) return 0; + BUG_ON((offset + length) > PAGE_CACHE_SIZE); memset(&bh, 0, sizeof(bh)); bh.b_size = PAGE_CACHE_SIZE; @@ -505,4 +509,26 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) return 0; } +EXPORT_SYMBOL_GPL(dax_zero_page_range); + +/** + * dax_truncate_page - handle a partial page being truncated in a DAX file + * @inode: The file being truncated + * @from: The file offset that is being truncated to + * @get_block: The filesystem method used to translate file offsets to blocks + * + * Similar to block_truncate_page(), this function can be called by a + * filesystem when it is truncating a DAX file to handle the partial page. + * + * We work in terms of PAGE_CACHE_SIZE here for commonality with + * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem + * took care of disposing of the unnecessary blocks. Even if the filesystem + * block size is smaller than PAGE_SIZE, we have to zero the rest of the page + * since the file might be mmapped. + */ +int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) +{ + unsigned length = PAGE_CACHE_ALIGN(from) - from; + return dax_zero_page_range(inode, from, length, get_block); +} EXPORT_SYMBOL_GPL(dax_truncate_page); diff --git a/include/linux/fs.h b/include/linux/fs.h index d46f8fe6a0ea..ed5a0900b94d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2589,6 +2589,7 @@ extern int nonseekable_open(struct inode * inode, struct file * filp); ssize_t dax_do_io(int rw, struct kiocb *, struct inode *, struct iov_iter *, loff_t, get_block_t, dio_iodone_t, int flags); int dax_clear_blocks(struct inode *, sector_t block, long size); +int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t); int dax_truncate_page(struct inode *, loff_t from, get_block_t); int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t); #define dax_mkwrite(vma, vmf, gb) dax_fault(vma, vmf, gb) -- 2.20.1