Commit 25726bc1 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

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: default avatarMatthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9c3ce9ec

Documentation/filesystems/dax.txt

+1 −0
Original line number Diff line number Diff line
@@ -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

fs/dax.c

+32 −6
Original line number Diff line number Diff line
@@ -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);

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

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