Btrfs: add extent buffer bitmap operations
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>
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@ -5527,6 +5527,155 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
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}
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}
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/*
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* The extent buffer bitmap operations are done with byte granularity because
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* bitmap items are not guaranteed to be aligned to a word and therefore a
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* single word in a bitmap may straddle two pages in the extent buffer.
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*/
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#define BIT_BYTE(nr) ((nr) / BITS_PER_BYTE)
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#define BYTE_MASK ((1 << BITS_PER_BYTE) - 1)
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#define BITMAP_FIRST_BYTE_MASK(start) \
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((BYTE_MASK << ((start) & (BITS_PER_BYTE - 1))) & BYTE_MASK)
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#define BITMAP_LAST_BYTE_MASK(nbits) \
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(BYTE_MASK >> (-(nbits) & (BITS_PER_BYTE - 1)))
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/*
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* eb_bitmap_offset() - calculate the page and offset of the byte containing the
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* given bit number
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* @eb: the extent buffer
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* @start: offset of the bitmap item in the extent buffer
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* @nr: bit number
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* @page_index: return index of the page in the extent buffer that contains the
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* given bit number
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* @page_offset: return offset into the page given by page_index
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*
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* This helper hides the ugliness of finding the byte in an extent buffer which
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* contains a given bit.
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*/
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static inline void eb_bitmap_offset(struct extent_buffer *eb,
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unsigned long start, unsigned long nr,
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unsigned long *page_index,
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size_t *page_offset)
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{
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size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
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size_t byte_offset = BIT_BYTE(nr);
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size_t offset;
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/*
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* The byte we want is the offset of the extent buffer + the offset of
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* the bitmap item in the extent buffer + the offset of the byte in the
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* bitmap item.
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*/
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offset = start_offset + start + byte_offset;
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*page_index = offset >> PAGE_CACHE_SHIFT;
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*page_offset = offset & (PAGE_CACHE_SIZE - 1);
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}
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/**
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* extent_buffer_test_bit - determine whether a bit in a bitmap item is set
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* @eb: the extent buffer
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* @start: offset of the bitmap item in the extent buffer
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* @nr: bit number to test
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*/
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int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,
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unsigned long nr)
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{
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char *kaddr;
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struct page *page;
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unsigned long i;
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size_t offset;
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eb_bitmap_offset(eb, start, nr, &i, &offset);
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page = eb->pages[i];
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WARN_ON(!PageUptodate(page));
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kaddr = page_address(page);
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return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));
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}
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/**
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* extent_buffer_bitmap_set - set an area of a bitmap
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* @eb: the extent buffer
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* @start: offset of the bitmap item in the extent buffer
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* @pos: bit number of the first bit
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* @len: number of bits to set
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*/
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void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
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unsigned long pos, unsigned long len)
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{
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char *kaddr;
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struct page *page;
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unsigned long i;
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size_t offset;
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const unsigned int size = pos + len;
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int bits_to_set = BITS_PER_BYTE - (pos % BITS_PER_BYTE);
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unsigned int mask_to_set = BITMAP_FIRST_BYTE_MASK(pos);
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eb_bitmap_offset(eb, start, pos, &i, &offset);
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page = eb->pages[i];
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WARN_ON(!PageUptodate(page));
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kaddr = page_address(page);
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while (len >= bits_to_set) {
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kaddr[offset] |= mask_to_set;
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len -= bits_to_set;
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bits_to_set = BITS_PER_BYTE;
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mask_to_set = ~0U;
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if (++offset >= PAGE_CACHE_SIZE && len > 0) {
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offset = 0;
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page = eb->pages[++i];
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WARN_ON(!PageUptodate(page));
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kaddr = page_address(page);
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}
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}
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if (len) {
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mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
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kaddr[offset] |= mask_to_set;
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}
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}
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/**
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* extent_buffer_bitmap_clear - clear an area of a bitmap
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* @eb: the extent buffer
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* @start: offset of the bitmap item in the extent buffer
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* @pos: bit number of the first bit
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* @len: number of bits to clear
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*/
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void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
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unsigned long pos, unsigned long len)
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{
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char *kaddr;
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struct page *page;
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unsigned long i;
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size_t offset;
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const unsigned int size = pos + len;
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int bits_to_clear = BITS_PER_BYTE - (pos % BITS_PER_BYTE);
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unsigned int mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos);
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eb_bitmap_offset(eb, start, pos, &i, &offset);
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page = eb->pages[i];
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WARN_ON(!PageUptodate(page));
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kaddr = page_address(page);
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while (len >= bits_to_clear) {
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kaddr[offset] &= ~mask_to_clear;
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len -= bits_to_clear;
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bits_to_clear = BITS_PER_BYTE;
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mask_to_clear = ~0U;
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if (++offset >= PAGE_CACHE_SIZE && len > 0) {
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offset = 0;
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page = eb->pages[++i];
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WARN_ON(!PageUptodate(page));
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kaddr = page_address(page);
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}
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}
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if (len) {
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mask_to_clear &= BITMAP_LAST_BYTE_MASK(size);
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kaddr[offset] &= ~mask_to_clear;
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}
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}
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static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)
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{
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unsigned long distance = (src > dst) ? src - dst : dst - src;
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@ -309,6 +309,12 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
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unsigned long src_offset, unsigned long len);
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void memset_extent_buffer(struct extent_buffer *eb, char c,
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unsigned long start, unsigned long len);
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int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,
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unsigned long pos);
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void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
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unsigned long pos, unsigned long len);
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void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
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unsigned long pos, unsigned long len);
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void clear_extent_buffer_dirty(struct extent_buffer *eb);
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int set_extent_buffer_dirty(struct extent_buffer *eb);
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int set_extent_buffer_uptodate(struct extent_buffer *eb);
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