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Btrfs: add extent buffer bitmap operations

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

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Omar Sandoval 2015-09-29 20:50:30 -07:00 committed by Chris Mason
parent 6a13feb9c8
commit 3e1e8bb770
2 changed files with 155 additions and 0 deletions
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149
fs/btrfs/extent_io.c
View File

@ -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;

6
fs/btrfs/extent_io.h
View File

@ -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);