From cb22964f1dad228fc2a1e5aba50c16b4b5680cd5 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Sat, 15 Jul 2023 19:08:29 +0800 Subject: btrfs: refactor extent buffer bitmaps operations [BACKGROUND] Currently we handle extent bitmaps manually in extent_buffer_bitmap_set() and extent_buffer_bitmap_clear(). Although with various helpers like eb_bitmap_offset() it's still a little messy to read. The code seems to be a copy of bitmap_set(), but with all the cross-page handling embedded into the code. [ENHANCEMENT] This patch would enhance the readability by introducing two helpers: - memset_extent_buffer() To handle the byte aligned range, thus all the cross-page handling is done there. - extent_buffer_get_byte() This for the first and the last byte operations, which only need to grab one byte, thus no need for any cross-page handling. So we can split both extent_buffer_bitmap_set() and extent_buffer_bitmap_clear() into 3 parts: - Handle the first byte If the range fits inside the first byte, we can exit early. - Handle the byte aligned part This is the part which can have cross-page operations, and it would be handled by memset_extent_buffer(). - Handle the last byte This refactoring does not only make the code a little easier to read, but also makes later folio/page switch much easier, as the switch only needs to be done inside memset_extent_buffer() and extent_buffer_get_byte(). Reviewed-by: Sweet Tea Dorminy Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/extent_io.c | 137 ++++++++++++++++++++++++--------------------------- 1 file changed, 65 insertions(+), 72 deletions(-) (limited to 'fs/btrfs/extent_io.c') diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 90a58a38a9f3..3e9f39bda9f2 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4183,34 +4183,32 @@ void write_extent_buffer(const struct extent_buffer *eb, const void *srcv, } } -void memzero_extent_buffer(const struct extent_buffer *eb, unsigned long start, - unsigned long len) +static void memset_extent_buffer(const struct extent_buffer *eb, int c, + unsigned long start, unsigned long len) { - size_t cur; - size_t offset; - struct page *page; - char *kaddr; - unsigned long i = get_eb_page_index(start); + unsigned long cur = start; - if (check_eb_range(eb, start, len)) - return; - - offset = get_eb_offset_in_page(eb, start); + while (cur < start + len) { + unsigned long index = get_eb_page_index(cur); + unsigned int offset = get_eb_offset_in_page(eb, cur); + unsigned int cur_len = min(start + len - cur, PAGE_SIZE - offset); + struct page *page = eb->pages[index]; - while (len > 0) { - page = eb->pages[i]; assert_eb_page_uptodate(eb, page); + memset(page_address(page) + offset, c, cur_len); - cur = min(len, PAGE_SIZE - offset); - kaddr = page_address(page); - memset(kaddr + offset, 0, cur); - - len -= cur; - offset = 0; - i++; + cur += cur_len; } } +void memzero_extent_buffer(const struct extent_buffer *eb, unsigned long start, + unsigned long len) +{ + if (check_eb_range(eb, start, len)) + return; + return memset_extent_buffer(eb, 0, start, len); +} + void copy_extent_buffer_full(const struct extent_buffer *dst, const struct extent_buffer *src) { @@ -4325,6 +4323,15 @@ int extent_buffer_test_bit(const struct extent_buffer *eb, unsigned long start, return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1))); } +static u8 *extent_buffer_get_byte(const struct extent_buffer *eb, unsigned long bytenr) +{ + unsigned long index = get_eb_page_index(bytenr); + + if (check_eb_range(eb, bytenr, 1)) + return NULL; + return page_address(eb->pages[index]) + get_eb_offset_in_page(eb, bytenr); +} + /* * Set an area of a bitmap to 1. * @@ -4336,35 +4343,28 @@ int extent_buffer_test_bit(const struct extent_buffer *eb, unsigned long start, void extent_buffer_bitmap_set(const struct extent_buffer *eb, unsigned long start, unsigned long pos, unsigned long len) { + unsigned int first_byte = start + BIT_BYTE(pos); + unsigned int last_byte = start + BIT_BYTE(pos + len - 1); + const bool same_byte = (first_byte == last_byte); + u8 mask = BITMAP_FIRST_BYTE_MASK(pos); u8 *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); - u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(pos); - eb_bitmap_offset(eb, start, pos, &i, &offset); - page = eb->pages[i]; - assert_eb_page_uptodate(eb, page); - kaddr = page_address(page); + if (same_byte) + mask &= BITMAP_LAST_BYTE_MASK(pos + len); - while (len >= bits_to_set) { - kaddr[offset] |= mask_to_set; - len -= bits_to_set; - bits_to_set = BITS_PER_BYTE; - mask_to_set = ~0; - if (++offset >= PAGE_SIZE && len > 0) { - offset = 0; - page = eb->pages[++i]; - assert_eb_page_uptodate(eb, page); - kaddr = page_address(page); - } - } - if (len) { - mask_to_set &= BITMAP_LAST_BYTE_MASK(size); - kaddr[offset] |= mask_to_set; - } + /* Handle the first byte. */ + kaddr = extent_buffer_get_byte(eb, first_byte); + *kaddr |= mask; + if (same_byte) + return; + + /* Handle the byte aligned part. */ + ASSERT(first_byte + 1 <= last_byte); + memset_extent_buffer(eb, 0xff, first_byte + 1, last_byte - first_byte - 1); + + /* Handle the last byte. */ + kaddr = extent_buffer_get_byte(eb, last_byte); + *kaddr |= BITMAP_LAST_BYTE_MASK(pos + len); } @@ -4380,35 +4380,28 @@ void extent_buffer_bitmap_clear(const struct extent_buffer *eb, unsigned long start, unsigned long pos, unsigned long len) { + unsigned int first_byte = start + BIT_BYTE(pos); + unsigned int last_byte = start + BIT_BYTE(pos + len - 1); + const bool same_byte = (first_byte == last_byte); + u8 mask = BITMAP_FIRST_BYTE_MASK(pos); u8 *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); - u8 mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos); - eb_bitmap_offset(eb, start, pos, &i, &offset); - page = eb->pages[i]; - assert_eb_page_uptodate(eb, page); - kaddr = page_address(page); + if (same_byte) + mask &= BITMAP_LAST_BYTE_MASK(pos + len); - while (len >= bits_to_clear) { - kaddr[offset] &= ~mask_to_clear; - len -= bits_to_clear; - bits_to_clear = BITS_PER_BYTE; - mask_to_clear = ~0; - if (++offset >= PAGE_SIZE && len > 0) { - offset = 0; - page = eb->pages[++i]; - assert_eb_page_uptodate(eb, page); - kaddr = page_address(page); - } - } - if (len) { - mask_to_clear &= BITMAP_LAST_BYTE_MASK(size); - kaddr[offset] &= ~mask_to_clear; - } + /* Handle the first byte. */ + kaddr = extent_buffer_get_byte(eb, first_byte); + *kaddr &= ~mask; + if (same_byte) + return; + + /* Handle the byte aligned part. */ + ASSERT(first_byte + 1 <= last_byte); + memset_extent_buffer(eb, 0, first_byte + 1, last_byte - first_byte - 1); + + /* Handle the last byte. */ + kaddr = extent_buffer_get_byte(eb, last_byte); + *kaddr &= ~BITMAP_LAST_BYTE_MASK(pos + len); } static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len) -- cgit v1.2.3