In MD's resync I/O path, there are lots of direct access to bio's bvec table. This patchset kills almost all, and the conversion is quite straightforward. One root cause of direct access to bvec table is that resync I/O uses the bio's bvec to manage pages. In V1, as suggested by Shaohua, a new approach is used to manage these pages for resync I/O, turns out code becomes more clean and readable. Once direct access to bvec table in MD is cleaned up, we may make multipage bvec moving on. V3: - improve pages allocation & bio clone for write behind(10/14) - retrieve pages from preallocated page array, and avoid to user bio helpers(14/14) - change on helpers about managing resync io pages(03/14) V2: - remove the patch for introducing/applying bio_remove_last_page() V1: - allocate page array to manage resync pages Thanks, Ming Ming Lei (14): md: raid1/raid10: don't handle failure of bio_add_page() md: move two macros into md.h md: prepare for managing resync I/O pages in clean way md: raid1: simplify r1buf_pool_free() md: raid1: don't use bio's vec table to manage resync pages md: raid1: retrieve page from pre-allocated resync page array md: raid1: use bio helper in process_checks() block: introduce bio_copy_data_partial md: raid1: move 'offset' out of loop md: raid1: improve write behind md: raid10: refactor code of read reshape's .bi_end_io md: raid10: don't use bio's vec table to manage resync pages md: raid10: retrieve page from preallocated resync page array md: raid10: avoid direct access to bvec table in handle_reshape_read_error block/bio.c | 60 +++++++++--- drivers/md/md.h | 55 +++++++++++ drivers/md/raid1.c | 267 ++++++++++++++++++++++++++++------------------------ drivers/md/raid1.h | 10 +- drivers/md/raid10.c | 224 +++++++++++++++++++++++-------------------- include/linux/bio.h | 2 + 6 files changed, 376 insertions(+), 242 deletions(-) -- 2.9.3