On 1/16/21 2:15 AM, Qu Wenruo wrote:
This patch introduce the following functions to handle btrfs subpage
uptodate status:
- btrfs_subpage_set_uptodate()
- btrfs_subpage_clear_uptodate()
- btrfs_subpage_test_uptodate()
Those helpers can only be called when the range is ensured to be
inside the page.
- btrfs_page_set_uptodate()
- btrfs_page_clear_uptodate()
- btrfs_page_test_uptodate()
Those helpers can handle both regular sector size and subpage without
problem.
Although caller should still ensure that the range is inside the page.
Signed-off-by: Qu Wenruo <w...@suse.com>
---
fs/btrfs/subpage.h | 115 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 115 insertions(+)
diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
index d8b34879368d..3373ef4ffec1 100644
--- a/fs/btrfs/subpage.h
+++ b/fs/btrfs/subpage.h
@@ -23,6 +23,7 @@
struct btrfs_subpage {
/* Common members for both data and metadata pages */
spinlock_t lock;
+ u16 uptodate_bitmap;
union {
/* Structures only used by metadata */
bool under_alloc;
@@ -78,4 +79,118 @@ static inline void btrfs_page_end_meta_alloc(struct
btrfs_fs_info *fs_info,
int btrfs_attach_subpage(struct btrfs_fs_info *fs_info, struct page *page);
void btrfs_detach_subpage(struct btrfs_fs_info *fs_info, struct page *page);
+/*
+ * Convert the [start, start + len) range into a u16 bitmap
+ *
+ * E.g. if start == page_offset() + 16K, len = 16K, we get 0x00f0.
+ */
+static inline u16 btrfs_subpage_calc_bitmap(struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len)
+{
+ int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits;
+ int nbits = len >> fs_info->sectorsize_bits;
+
+ /* Basic checks */
+ ASSERT(PagePrivate(page) && page->private);
+ ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
+ IS_ALIGNED(len, fs_info->sectorsize));
+
+ /*
+ * The range check only works for mapped page, we can
+ * still have unampped page like dummy extent buffer pages.
+ */
+ if (page->mapping)
+ ASSERT(page_offset(page) <= start &&
+ start + len <= page_offset(page) + PAGE_SIZE);
Once you gate the helpers on UNMAPPED you'll always have page->mapping set and
you can drop the if statement. Thanks,
Josef