Re: [Cluster-devel] [PATCH V10 05/19] block: introduce bvec_last_segment()
On Thu, Nov 15, 2018 at 03:23:56PM -0800, Omar Sandoval wrote:
> On Thu, Nov 15, 2018 at 04:52:52PM +0800, Ming Lei wrote:
> > BTRFS and guard_bio_eod() need to get the last singlepage segment
> > from one multipage bvec, so introduce this helper to make them happy.
> >
> > Cc: Dave Chinner
> > Cc: Kent Overstreet
> > Cc: Mike Snitzer
> > Cc: dm-de...@redhat.com
> > Cc: Alexander Viro
> > Cc: linux-fsde...@vger.kernel.org
> > Cc: Shaohua Li
> > Cc: linux-r...@vger.kernel.org
> > Cc: linux-er...@lists.ozlabs.org
> > Cc: David Sterba
> > Cc: linux-bt...@vger.kernel.org
> > Cc: Darrick J. Wong
> > Cc: linux-...@vger.kernel.org
> > Cc: Gao Xiang
> > Cc: Christoph Hellwig
> > Cc: Theodore Ts'o
> > Cc: linux-e...@vger.kernel.org
> > Cc: Coly Li
> > Cc: linux-bca...@vger.kernel.org
> > Cc: Boaz Harrosh
> > Cc: Bob Peterson
> > Cc: cluster-devel@redhat.com
>
> Reviewed-by: Omar Sandoval
>
> Minor comments below.
>
> > Signed-off-by: Ming Lei
> > ---
> > include/linux/bvec.h | 25 +
> > 1 file changed, 25 insertions(+)
> >
> > diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> > index 3d61352cd8cf..01616a0b6220 100644
> > --- a/include/linux/bvec.h
> > +++ b/include/linux/bvec.h
> > @@ -216,4 +216,29 @@ static inline bool mp_bvec_iter_advance(const struct
> > bio_vec *bv,
> > .bi_bvec_done = 0,\
> > }
> >
> > +/*
> > + * Get the last singlepage segment from the multipage bvec and store it
> > + * in @seg
> > + */
> > +static inline void bvec_last_segment(const struct bio_vec *bvec,
> > + struct bio_vec *seg)
>
> Indentation is all messed up here.
Will fix it.
>
> > +{
> > + unsigned total = bvec->bv_offset + bvec->bv_len;
> > + unsigned last_page = total / PAGE_SIZE;
> > +
> > + if (last_page * PAGE_SIZE == total)
> > + last_page--;
>
> I think this could just be
>
> unsigned int last_page = (total - 1) / PAGE_SIZE;
This way is really elegant.
Thanks,
Ming
Re: [Cluster-devel] [PATCH V10 05/19] block: introduce bvec_last_segment()
> + unsigned last_page = total / PAGE_SIZE; > + > + if (last_page * PAGE_SIZE == total) Not sure it matters much with modern compilers, but generally we shit by PAGE_SHIFT instead of multiplying with or dividing by PAGE_SIZE.
Re: [Cluster-devel] [PATCH V10 05/19] block: introduce bvec_last_segment()
On Thu, Nov 15, 2018 at 04:52:52PM +0800, Ming Lei wrote:
> BTRFS and guard_bio_eod() need to get the last singlepage segment
> from one multipage bvec, so introduce this helper to make them happy.
>
> Cc: Dave Chinner
> Cc: Kent Overstreet
> Cc: Mike Snitzer
> Cc: dm-de...@redhat.com
> Cc: Alexander Viro
> Cc: linux-fsde...@vger.kernel.org
> Cc: Shaohua Li
> Cc: linux-r...@vger.kernel.org
> Cc: linux-er...@lists.ozlabs.org
> Cc: David Sterba
> Cc: linux-bt...@vger.kernel.org
> Cc: Darrick J. Wong
> Cc: linux-...@vger.kernel.org
> Cc: Gao Xiang
> Cc: Christoph Hellwig
> Cc: Theodore Ts'o
> Cc: linux-e...@vger.kernel.org
> Cc: Coly Li
> Cc: linux-bca...@vger.kernel.org
> Cc: Boaz Harrosh
> Cc: Bob Peterson
> Cc: cluster-devel@redhat.com
Reviewed-by: Omar Sandoval
Minor comments below.
> Signed-off-by: Ming Lei
> ---
> include/linux/bvec.h | 25 +
> 1 file changed, 25 insertions(+)
>
> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> index 3d61352cd8cf..01616a0b6220 100644
> --- a/include/linux/bvec.h
> +++ b/include/linux/bvec.h
> @@ -216,4 +216,29 @@ static inline bool mp_bvec_iter_advance(const struct
> bio_vec *bv,
> .bi_bvec_done = 0,\
> }
>
> +/*
> + * Get the last singlepage segment from the multipage bvec and store it
> + * in @seg
> + */
> +static inline void bvec_last_segment(const struct bio_vec *bvec,
> + struct bio_vec *seg)
Indentation is all messed up here.
> +{
> + unsigned total = bvec->bv_offset + bvec->bv_len;
> + unsigned last_page = total / PAGE_SIZE;
> +
> + if (last_page * PAGE_SIZE == total)
> + last_page--;
I think this could just be
unsigned int last_page = (total - 1) / PAGE_SIZE;
> + seg->bv_page = nth_page(bvec->bv_page, last_page);
> +
> + /* the whole segment is inside the last page */
> + if (bvec->bv_offset >= last_page * PAGE_SIZE) {
> + seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
> + seg->bv_len = bvec->bv_len;
> + } else {
> + seg->bv_offset = 0;
> + seg->bv_len = total - last_page * PAGE_SIZE;
> + }
> +}
> +
> #endif /* __LINUX_BVEC_ITER_H */
> --
> 2.9.5
>
[Cluster-devel] [PATCH V10 05/19] block: introduce bvec_last_segment()
BTRFS and guard_bio_eod() need to get the last singlepage segment
from one multipage bvec, so introduce this helper to make them happy.
Cc: Dave Chinner
Cc: Kent Overstreet
Cc: Mike Snitzer
Cc: dm-de...@redhat.com
Cc: Alexander Viro
Cc: linux-fsde...@vger.kernel.org
Cc: Shaohua Li
Cc: linux-r...@vger.kernel.org
Cc: linux-er...@lists.ozlabs.org
Cc: David Sterba
Cc: linux-bt...@vger.kernel.org
Cc: Darrick J. Wong
Cc: linux-...@vger.kernel.org
Cc: Gao Xiang
Cc: Christoph Hellwig
Cc: Theodore Ts'o
Cc: linux-e...@vger.kernel.org
Cc: Coly Li
Cc: linux-bca...@vger.kernel.org
Cc: Boaz Harrosh
Cc: Bob Peterson
Cc: cluster-devel@redhat.com
Signed-off-by: Ming Lei
---
include/linux/bvec.h | 25 +
1 file changed, 25 insertions(+)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 3d61352cd8cf..01616a0b6220 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -216,4 +216,29 @@ static inline bool mp_bvec_iter_advance(const struct
bio_vec *bv,
.bi_bvec_done = 0,\
}
+/*
+ * Get the last singlepage segment from the multipage bvec and store it
+ * in @seg
+ */
+static inline void bvec_last_segment(const struct bio_vec *bvec,
+ struct bio_vec *seg)
+{
+ unsigned total = bvec->bv_offset + bvec->bv_len;
+ unsigned last_page = total / PAGE_SIZE;
+
+ if (last_page * PAGE_SIZE == total)
+ last_page--;
+
+ seg->bv_page = nth_page(bvec->bv_page, last_page);
+
+ /* the whole segment is inside the last page */
+ if (bvec->bv_offset >= last_page * PAGE_SIZE) {
+ seg->bv_offset = bvec->bv_offset % PAGE_SIZE;
+ seg->bv_len = bvec->bv_len;
+ } else {
+ seg->bv_offset = 0;
+ seg->bv_len = total - last_page * PAGE_SIZE;
+ }
+}
+
#endif /* __LINUX_BVEC_ITER_H */
--
2.9.5
