@@ -4229,32 +4229,30 @@ void write_extent_buffer(const struct extent_buffer *eb, const void *srcv,
}
}
+static void memset_extent_buffer(const struct extent_buffer *eb, int c,
+ unsigned long start, unsigned long len)
+{
+ unsigned long cur = start;
+
+ while (cur < start + len) {
+ int index = get_eb_page_index(cur);
+ int offset = get_eb_offset_in_page(eb, cur);
+ int cur_len = min(start + len - cur, PAGE_SIZE - offset);
+ struct page *page = eb->pages[index];
+
+ assert_eb_page_uptodate(eb, page);
+ memset(page_address(page) + offset, c, cur_len);
+
+ cur += cur_len;
+ }
+}
+
void memzero_extent_buffer(const struct extent_buffer *eb, 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);
-
if (check_eb_range(eb, start, len))
return;
-
- offset = get_eb_offset_in_page(eb, start);
-
- while (len > 0) {
- page = eb->pages[i];
- assert_eb_page_uptodate(eb, page);
-
- cur = min(len, PAGE_SIZE - offset);
- kaddr = page_address(page);
- memset(kaddr + offset, 0, cur);
-
- len -= cur;
- offset = 0;
- i++;
- }
+ return memset_extent_buffer(eb, 0, start, len);
}
void copy_extent_buffer_full(const struct extent_buffer *dst,
@@ -4371,6 +4369,15 @@ 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.
*
@@ -4382,35 +4389,29 @@ 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);
+ 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);
}
@@ -4426,35 +4427,29 @@ void extent_buffer_bitmap_clear(const struct extent_buffer *eb,
unsigned long start, unsigned long pos,
unsigned long len)
{
+ int first_byte = start + BIT_BYTE(pos);
+ int last_byte = start + BIT_BYTE(pos + len - 1);
+ 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)
[BACKGROUND] Currently we handle extent bitmaps manually in extent_buffer_bitmap_set() and extent_buffer_bitmap_clear(). Although with various helper 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 operation, which only needs 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 refactor does not only make the code a little easier to read, but also make later folio/page switch much easier, as the switch only needs to be done inside memset_extent_buffer() and extent_buffer_get_byte(). Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/extent_io.c | 141 +++++++++++++++++++++---------------------- 1 file changed, 68 insertions(+), 73 deletions(-)