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Commit 3e1e8bb7 authored by Omar Sandoval's avatar Omar Sandoval Committed by Chris Mason
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Btrfs: add extent buffer bitmap operations 



These are going to be used for the free space tree bitmap items.

Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 6a13feb9

fs/btrfs/extent_io.c

+149 −0
Original line number Diff line number Diff line
@@ -5527,6 +5527,155 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src, 
	}

}



/*

 * The extent buffer bitmap operations are done with byte granularity because

 * bitmap items are not guaranteed to be aligned to a word and therefore a

 * single word in a bitmap may straddle two pages in the extent buffer.

 */

#define BIT_BYTE(nr) ((nr) / BITS_PER_BYTE)

#define BYTE_MASK ((1 << BITS_PER_BYTE) - 1)

#define BITMAP_FIRST_BYTE_MASK(start) \

	((BYTE_MASK << ((start) & (BITS_PER_BYTE - 1))) & BYTE_MASK)

#define BITMAP_LAST_BYTE_MASK(nbits) \

	(BYTE_MASK >> (-(nbits) & (BITS_PER_BYTE - 1)))



/*

 * eb_bitmap_offset() - calculate the page and offset of the byte containing the

 * given bit number

 * @eb: the extent buffer

 * @start: offset of the bitmap item in the extent buffer

 * @nr: bit number

 * @page_index: return index of the page in the extent buffer that contains the

 * given bit number

 * @page_offset: return offset into the page given by page_index

 *

 * This helper hides the ugliness of finding the byte in an extent buffer which

 * contains a given bit.

 */

static inline void eb_bitmap_offset(struct extent_buffer *eb,

				    unsigned long start, unsigned long nr,

				    unsigned long *page_index,

				    size_t *page_offset)

{

	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);

	size_t byte_offset = BIT_BYTE(nr);

	size_t offset;



	/*

	 * The byte we want is the offset of the extent buffer + the offset of

	 * the bitmap item in the extent buffer + the offset of the byte in the

	 * bitmap item.

	 */

	offset = start_offset + start + byte_offset;



	*page_index = offset >> PAGE_CACHE_SHIFT;

	*page_offset = offset & (PAGE_CACHE_SIZE - 1);

}



/**

 * extent_buffer_test_bit - determine whether a bit in a bitmap item is set

 * @eb: the extent buffer

 * @start: offset of the bitmap item in the extent buffer

 * @nr: bit number to test

 */

int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,

			   unsigned long nr)

{

	char *kaddr;

	struct page *page;

	unsigned long i;

	size_t offset;



	eb_bitmap_offset(eb, start, nr, &i, &offset);

	page = eb->pages[i];

	WARN_ON(!PageUptodate(page));

	kaddr = page_address(page);

	return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));

}



/**

 * extent_buffer_bitmap_set - set an area of a bitmap

 * @eb: the extent buffer

 * @start: offset of the bitmap item in the extent buffer

 * @pos: bit number of the first bit

 * @len: number of bits to set

 */

void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,

			      unsigned long pos, unsigned long len)

{

	char *kaddr;

	struct page *page;

	unsigned long i;

	size_t offset;

	const unsigned int size = pos + len;

	int bits_to_set = BITS_PER_BYTE - (pos % BITS_PER_BYTE);

	unsigned int mask_to_set = BITMAP_FIRST_BYTE_MASK(pos);



	eb_bitmap_offset(eb, start, pos, &i, &offset);

	page = eb->pages[i];

	WARN_ON(!PageUptodate(page));

	kaddr = page_address(page);



	while (len >= bits_to_set) {

		kaddr[offset] |= mask_to_set;

		len -= bits_to_set;

		bits_to_set = BITS_PER_BYTE;

		mask_to_set = ~0U;

		if (++offset >= PAGE_CACHE_SIZE && len > 0) {

			offset = 0;

			page = eb->pages[++i];

			WARN_ON(!PageUptodate(page));

			kaddr = page_address(page);

		}

	}

	if (len) {

		mask_to_set &= BITMAP_LAST_BYTE_MASK(size);

		kaddr[offset] |= mask_to_set;

	}

}





/**

 * extent_buffer_bitmap_clear - clear an area of a bitmap

 * @eb: the extent buffer

 * @start: offset of the bitmap item in the extent buffer

 * @pos: bit number of the first bit

 * @len: number of bits to clear

 */

void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,

				unsigned long pos, unsigned long len)

{

	char *kaddr;

	struct page *page;

	unsigned long i;

	size_t offset;

	const unsigned int size = pos + len;

	int bits_to_clear = BITS_PER_BYTE - (pos % BITS_PER_BYTE);

	unsigned int mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos);



	eb_bitmap_offset(eb, start, pos, &i, &offset);

	page = eb->pages[i];

	WARN_ON(!PageUptodate(page));

	kaddr = page_address(page);



	while (len >= bits_to_clear) {

		kaddr[offset] &= ~mask_to_clear;

		len -= bits_to_clear;

		bits_to_clear = BITS_PER_BYTE;

		mask_to_clear = ~0U;

		if (++offset >= PAGE_CACHE_SIZE && len > 0) {

			offset = 0;

			page = eb->pages[++i];

			WARN_ON(!PageUptodate(page));

			kaddr = page_address(page);

		}

	}

	if (len) {

		mask_to_clear &= BITMAP_LAST_BYTE_MASK(size);

		kaddr[offset] &= ~mask_to_clear;

	}

}



static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)

{

	unsigned long distance = (src > dst) ? src - dst : dst - src;

fs/btrfs/extent_io.h

+6 −0
Original line number Diff line number Diff line
@@ -309,6 +309,12 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, 
			   unsigned long src_offset, unsigned long len);

void memset_extent_buffer(struct extent_buffer *eb, char c,

			  unsigned long start, unsigned long len);

int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,

			   unsigned long pos);

void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,

			      unsigned long pos, unsigned long len);

void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,

				unsigned long pos, unsigned long len);

void clear_extent_buffer_dirty(struct extent_buffer *eb);

int set_extent_buffer_dirty(struct extent_buffer *eb);

int set_extent_buffer_uptodate(struct extent_buffer *eb);