btrfs: introduce read_extent_buffer_subpage()
Introduce a helper, read_extent_buffer_subpage(), to do the subpage extent buffer read. The difference between regular and subpage routines are: - No page locking Here we completely rely on extent locking. Page locking can reduce the concurrency greatly, as if we lock one page to read one extent buffer, all the other extent buffers in the same page will have to wait. - Extent uptodate condition Despite the existing PageUptodate() and EXTENT_BUFFER_UPTODATE check, We also need to check btrfs_subpage::uptodate_bitmap. - No page iteration Just one page, no need to loop, this greatly simplified the subpage routine. This patch only implements the bio submit part, no endio support yet. Reviewed-by:Josef Bacik <josef@toxicpanda.com> Signed-off-by:
Qu Wenruo <wqu@suse.com> Reviewed-by:
David Sterba <dsterba@suse.com> Signed-off-by:
David Sterba <dsterba@suse.com>
parent
d1e86e3f
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