| Message ID | 20180719093918.28876-2-mwilck@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/19/2018 11:39 AM, Martin Wilck wrote: > If the last page of the bio is not "full", the length of the last > vector slot needs to be corrected. This slot has the index > (bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper > array, which is shifted by the value of bio->bi_vcnt at function > invocation, the correct index is (nr_pages - 1). > > V2: improved readability following suggestions from Ming Lei. > > Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()") > Signed-off-by: Martin Wilck <mwilck@suse.com> > --- > block/bio.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
On Thu, Jul 19, 2018 at 5:39 PM, Martin Wilck <mwilck@suse.com> wrote: > If the last page of the bio is not "full", the length of the last > vector slot needs to be corrected. This slot has the index > (bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper > array, which is shifted by the value of bio->bi_vcnt at function > invocation, the correct index is (nr_pages - 1). > > V2: improved readability following suggestions from Ming Lei. > > Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()") > Signed-off-by: Martin Wilck <mwilck@suse.com> > --- > block/bio.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 67eff5e..0964328 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -912,16 +912,16 @@ EXPORT_SYMBOL(bio_add_page); > */ > int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > { > - unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt; > + unsigned short idx, nr_pages = bio->bi_max_vecs - bio->bi_vcnt; > struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt; > struct page **pages = (struct page **)bv; > - size_t offset, diff; > + size_t offset; > ssize_t size; > > size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); > if (unlikely(size <= 0)) > return size ? size : -EFAULT; > - nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; > + idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; > > /* > * Deep magic below: We need to walk the pinned pages backwards > @@ -934,17 +934,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > bio->bi_iter.bi_size += size; > bio->bi_vcnt += nr_pages; > > - diff = (nr_pages * PAGE_SIZE - offset) - size; > - while (nr_pages--) { > - bv[nr_pages].bv_page = pages[nr_pages]; > - bv[nr_pages].bv_len = PAGE_SIZE; > - bv[nr_pages].bv_offset = 0; > + while (idx--) { > + bv[idx].bv_page = pages[idx]; > + bv[idx].bv_len = PAGE_SIZE; > + bv[idx].bv_offset = 0; > } > > bv[0].bv_offset += offset; > bv[0].bv_len -= offset; > - if (diff) > - bv[bio->bi_vcnt - 1].bv_len -= diff; > + bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size; > > iov_iter_advance(iter, size); > return 0; > -- > 2.17.1 > Reviewed-by: Ming Lei <ming.lei@redhat.com> BTW, we can make it for mainline too, then rebase Christoph's new patch against this one. Thanks, Ming Lei
On Thu 19-07-18 11:39:17, Martin Wilck wrote: > If the last page of the bio is not "full", the length of the last > vector slot needs to be corrected. This slot has the index > (bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper > array, which is shifted by the value of bio->bi_vcnt at function > invocation, the correct index is (nr_pages - 1). > > V2: improved readability following suggestions from Ming Lei. > > Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()") > Signed-off-by: Martin Wilck <mwilck@suse.com> Looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> BTW, explicit CC: stable@vger.kernel.org would be good. But Jens can add it I guess. Honza > --- > block/bio.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 67eff5e..0964328 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -912,16 +912,16 @@ EXPORT_SYMBOL(bio_add_page); > */ > int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > { > - unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt; > + unsigned short idx, nr_pages = bio->bi_max_vecs - bio->bi_vcnt; > struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt; > struct page **pages = (struct page **)bv; > - size_t offset, diff; > + size_t offset; > ssize_t size; > > size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); > if (unlikely(size <= 0)) > return size ? size : -EFAULT; > - nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; > + idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; > > /* > * Deep magic below: We need to walk the pinned pages backwards > @@ -934,17 +934,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > bio->bi_iter.bi_size += size; > bio->bi_vcnt += nr_pages; > > - diff = (nr_pages * PAGE_SIZE - offset) - size; > - while (nr_pages--) { > - bv[nr_pages].bv_page = pages[nr_pages]; > - bv[nr_pages].bv_len = PAGE_SIZE; > - bv[nr_pages].bv_offset = 0; > + while (idx--) { > + bv[idx].bv_page = pages[idx]; > + bv[idx].bv_len = PAGE_SIZE; > + bv[idx].bv_offset = 0; > } > > bv[0].bv_offset += offset; > bv[0].bv_len -= offset; > - if (diff) > - bv[bio->bi_vcnt - 1].bv_len -= diff; > + bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size; > > iov_iter_advance(iter, size); > return 0; > -- > 2.17.1 >
On Thu, Jul 19, 2018 at 11:39:17AM +0200, Martin Wilck wrote: > If the last page of the bio is not "full", the length of the last > vector slot needs to be corrected. This slot has the index > (bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper > array, which is shifted by the value of bio->bi_vcnt at function > invocation, the correct index is (nr_pages - 1). > > V2: improved readability following suggestions from Ming Lei. > > Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()") > Signed-off-by: Martin Wilck <mwilck@suse.com> > --- > block/bio.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 67eff5e..0964328 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -912,16 +912,16 @@ EXPORT_SYMBOL(bio_add_page); > */ > int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > { > - unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt; > + unsigned short idx, nr_pages = bio->bi_max_vecs - bio->bi_vcnt; Nipick: I prefer to keep the variable(s) that are initialized first on any given line. Otherwise this looks fine: Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/block/bio.c b/block/bio.c index 67eff5e..0964328 100644 --- a/block/bio.c +++ b/block/bio.c @@ -912,16 +912,16 @@ EXPORT_SYMBOL(bio_add_page); */ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) { - unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt; + unsigned short idx, nr_pages = bio->bi_max_vecs - bio->bi_vcnt; struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt; struct page **pages = (struct page **)bv; - size_t offset, diff; + size_t offset; ssize_t size; size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); if (unlikely(size <= 0)) return size ? size : -EFAULT; - nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; + idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; /* * Deep magic below: We need to walk the pinned pages backwards @@ -934,17 +934,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) bio->bi_iter.bi_size += size; bio->bi_vcnt += nr_pages; - diff = (nr_pages * PAGE_SIZE - offset) - size; - while (nr_pages--) { - bv[nr_pages].bv_page = pages[nr_pages]; - bv[nr_pages].bv_len = PAGE_SIZE; - bv[nr_pages].bv_offset = 0; + while (idx--) { + bv[idx].bv_page = pages[idx]; + bv[idx].bv_len = PAGE_SIZE; + bv[idx].bv_offset = 0; } bv[0].bv_offset += offset; bv[0].bv_len -= offset; - if (diff) - bv[bio->bi_vcnt - 1].bv_len -= diff; + bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size; iov_iter_advance(iter, size); return 0;
If the last page of the bio is not "full", the length of the last vector slot needs to be corrected. This slot has the index (bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper array, which is shifted by the value of bio->bi_vcnt at function invocation, the correct index is (nr_pages - 1). V2: improved readability following suggestions from Ming Lei. Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()") Signed-off-by: Martin Wilck <mwilck@suse.com> --- block/bio.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-)