user/sven/linux.git/include/linux/bvec.h, branch v5.1.14

block: make sure that bvec length can't be overflow

2019-04-19T17:32:14Z

bvec->bv_offset may be bigger than PAGE_SIZE sometimes, such as, when one bio is splitted in the middle of one bvec via bio_split(), and bi_iter.bi_bvec_done is used to build offset of the 1st bvec of remained bio. And the remained bio's bvec may be re-submitted to fs layer via ITER_IBVEC, such as loop and nvme-loop. So we have to make sure that every bvec's offset is less than PAGE_SIZE from bio_for_each_segment_all() because some drivers(loop, nvme-loop) passes the splitted bvec to fs layer via ITER_BVEC. This patch fixes this issue reported by Zhang Yi When running nvme/011. Cc: Christoph Hellwig Cc: Yi Zhang Reported-by: Yi Zhang Reviewed-by: Christoph Hellwig Fixes: 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec") Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: don't use for-inside-for in bio_for_each_segment_all

2019-04-08T14:19:41Z

Commit 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec") changes bio_for_each_segment_all() to use for-inside-for. This way breaks all bio_for_each_segment_all() call with error out branch via 'break', since now 'break' can only break from the inner loop. Fixes this issue by implementing bio_for_each_segment_all() via single 'for' loop, and now the logic is very similar with normal bvec iterator. Cc: Qu Wenruo Cc: linux-btrfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: Omar Sandoval Reviewed-by: Johannes Thumshirn Reported-and-Tested-by: Qu Wenruo Fixes: 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec") Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: optimize bvec iteration in bvec_iter_advance

2019-02-28T20:49:22Z

There is no need to only iterate in chunks of PAGE_SIZE or less in bvec_iter_advance, given that the callers pass in the chunk length that they are operating on - either that already is less than PAGE_SIZE because they do classic page-based iteration, or it is larger because the caller operates on multi-page bvecs. This should help shaving off a few cycles of the I/O hot path. Reviewed-by: Johannes Thumshirn Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: introduce mp_bvec_for_each_page() for iterating over page

2019-02-28T12:56:03Z

mp_bvec_for_each_segment() is a bit big for the iteration, so introduce a light-weight helper for iterating over pages, then 32bytes stack space can be saved. Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: introduce bvec_nth_page()

2019-02-27T13:18:52Z

Single-page bvec can often be seen in small BS workloads, so introduce bvec_nth_page() for avoiding to call nth_page() unnecessarily, which looks not cheap. Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: allow bio_for_each_segment_all() to iterate over multi-page bvec

2019-02-15T15:40:11Z

This patch introduces one extra iterator variable to bio_for_each_segment_all(), then we can allow bio_for_each_segment_all() to iterate over multi-page bvec. Given it is just one mechannical & simple change on all bio_for_each_segment_all() users, this patch does tree-wide change in one single patch, so that we can avoid to use a temporary helper for this conversion. Reviewed-by: Omar Sandoval Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: introduce mp_bvec_last_segment()

2019-02-15T15:40:11Z

BTRFS and guard_bio_eod() need to get the last singlepage segment from one multipage bvec, so introduce this helper to make them happy. Reviewed-by: Omar Sandoval Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: introduce multi-page bvec helpers

2019-02-15T15:40:10Z

This patch introduces helpers of 'mp_bvec_iter_*' for multi-page bvec support. The introduced helpers treate one bvec as real multi-page segment, which may include more than one pages. The existed helpers of bvec_iter_* are interfaces for supporting current bvec iterator which is thought as single-page by drivers, fs, dm and etc. These introduced helpers will build single-page bvec in flight, so this way won't break current bio/bvec users, which needn't any change. Follows some multi-page bvec background: - bvecs stored in bio->bi_io_vec is always multi-page style - bvec(struct bio_vec) represents one physically contiguous I/O buffer, now the buffer may include more than one page after multi-page bvec is supported, and all these pages represented by one bvec is physically contiguous. Before multi-page bvec support, at most one page is included in one bvec, we call it single-page bvec. - .bv_page of the bvec points to the 1st page in the multi-page bvec - .bv_offset of the bvec is the offset of the buffer in the bvec The effect on the current drivers/filesystem/dm/bcache/...: - almost everyone supposes that one bvec only includes one single page, so we keep the sp interface not changed, for example, bio_for_each_segment() still returns single-page bvec - bio_for_each_segment_all() will return single-page bvec too - during iterating, iterator variable(struct bvec_iter) is always updated in multi-page bvec style, and bvec_iter_advance() is kept not changed - returned(copied) single-page bvec is built in flight by bvec helpers from the stored multi-page bvec Reviewed-by: Christoph Hellwig Reviewed-by: Omar Sandoval Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: remove bvec_iter_rewind()

2019-02-15T15:40:10Z

Commit 7759eb23fd980 ("block: remove bio_rewind_iter()") removes bio_rewind_iter(), then no one uses bvec_iter_rewind() any more, so remove it. Reviewed-by: Omar Sandoval Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe

block: remove bio_rewind_iter()

2018-09-06T21:12:24Z

It is pointed that bio_rewind_iter() is one very bad API[1]: 1) bio size may not be restored after rewinding 2) it causes some bogus change, such as 5151842b9d8732 (block: reset bi_iter.bi_done after splitting bio) 3) rewinding really makes things complicated wrt. bio splitting 4) unnecessary updating of .bi_done in fast path [1] https://marc.info/?t=153549924200005&r=1&w=2 So this patch takes Kent's suggestion to restore one bio into its original state via saving bio iterator(struct bvec_iter) in bio_integrity_prep(), given now bio_rewind_iter() is only used by bio integrity code. Cc: Dmitry Monakhov Cc: Hannes Reinecke Suggested-by: Kent Overstreet Acked-by: Kent Overstreet Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe