On 2021/1/20 下午10:55, Josef Bacik wrote:
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,
I'd say, if we make ASSERT() to really do nothing if CONFIG_BTRFS_ASSERT is not selected, we won't really need to bother then. As in that case, the function will do nothing. For now, it's a mixed bag as we can still have subpage UNMAPPED eb go into such subpage helpers, and doing the UNMAPPED checks in so many helpers itself can be a big load. Thus I prefer to keep the if here. Thanks, Qu
Josef
