Current File : //var/lib/dkms/blksnap/6.3.0.73/source/diff_buffer.h
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __BLK_SNAP_DIFF_BUFFER_H
#define __BLK_SNAP_DIFF_BUFFER_H
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/blkdev.h>
struct diff_area;
/**
* struct diff_buffer - Difference buffer.
* @link:
* The list header allows to create a pool of the diff_buffer structures.
* @size:
* Count of bytes in the buffer.
* @page_count:
* The number of pages reserved for the buffer.
* @pages:
* An array of pointers to pages.
*
* Describes the memory buffer for a chunk in the memory.
*/
struct diff_buffer {
struct list_head link;
size_t size;
#ifdef BLK_SNAP_DEBUG_DIFF_BUFFER
int number;
#endif
size_t page_count;
struct page *pages[];
};
/**
* struct diff_buffer_iter - Iterator for &struct diff_buffer.
* @page:
* A pointer to the current page.
* @offset:
* The offset in bytes in the current page.
* @bytes:
* The number of bytes that can be read or written from the current page.
*
* It is convenient to use when copying data from or to &struct bio_vec.
*/
struct diff_buffer_iter {
struct page *page;
size_t offset;
size_t bytes;
};
#define SECTOR_IN_PAGE (1 << (PAGE_SHIFT - SECTOR_SHIFT))
static inline bool diff_buffer_iter_get(struct diff_buffer *diff_buffer,
size_t buff_offset,
struct diff_buffer_iter *iter)
{
if (diff_buffer->size <= buff_offset)
return false;
iter->page = diff_buffer->pages[buff_offset >> PAGE_SHIFT];
iter->offset = (size_t)(buff_offset & (PAGE_SIZE - 1));
/*
* The size cannot exceed the size of the page, taking into account
* the offset in this page.
* But at the same time it is unacceptable to go beyond the allocated
* buffer.
*/
iter->bytes = min_t(size_t, (PAGE_SIZE - iter->offset),
(diff_buffer->size - buff_offset));
return true;
};
struct diff_buffer *diff_buffer_take(struct diff_area *diff_area,
const bool is_nowait);
void diff_buffer_release(struct diff_area *diff_area,
struct diff_buffer *diff_buffer);
void diff_buffer_cleanup(struct diff_area *diff_area);
#endif /* __BLK_SNAP_DIFF_BUFFER_H */
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