| Message ID | 20230317175019.10857-2-hreitz@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: Split padded I/O vectors exceeding IOV_MAX | expand |
On Fri, Mar 17, 2023 at 06:50:16PM +0100, Hanna Czenczek wrote: > We want to inline qemu_iovec_init_extended() in block/io.c for padding > requests, and having access to qiov_slice() is useful for this. > > (We will need to count the number of I/O vector elements of a slice > there, and then later process this slice. Without qiov_slice(), we > would need to call qemu_iovec_subvec_niov(), and all further > IOV-processing functions may need to skip prefixing elements to > accomodate for a qiov_offset. Because qemu_iovec_subvec_niov() > internally calls qiov_slice(), we can just have the block/io.c code call > qiov_slice() itself, thus get the number of elements, and also create an > iovec array with the superfluous prefixing elements stripped, so the > following processing functions no longer need to skip them.) Might be worth mentioning in the commit message that you also renamed it to qemu_iovec_slice() as part of exporting. > > Signed-off-by: Hanna Czenczek <hreitz@redhat.com> > --- > include/qemu/iov.h | 3 +++ > util/iov.c | 14 +++++++------- > 2 files changed, 10 insertions(+), 7 deletions(-) Reviewed-by: Eric Blake <eblake@redhat.com>
On 17.03.23 20:50, Hanna Czenczek wrote: > We want to inline qemu_iovec_init_extended() in block/io.c for padding > requests, and having access to qiov_slice() is useful for this. > > (We will need to count the number of I/O vector elements of a slice > there, and then later process this slice. Without qiov_slice(), we > would need to call qemu_iovec_subvec_niov(), and all further > IOV-processing functions may need to skip prefixing elements to > accomodate for a qiov_offset. Because qemu_iovec_subvec_niov() > internally calls qiov_slice(), we can just have the block/io.c code call > qiov_slice() itself, thus get the number of elements, and also create an > iovec array with the superfluous prefixing elements stripped, so the > following processing functions no longer need to skip them.) > > Signed-off-by: Hanna Czenczek<hreitz@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
diff --git a/include/qemu/iov.h b/include/qemu/iov.h index 9330746680..46fadfb27a 100644 --- a/include/qemu/iov.h +++ b/include/qemu/iov.h @@ -229,6 +229,9 @@ int qemu_iovec_init_extended( void *tail_buf, size_t tail_len); void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source, size_t offset, size_t len); +struct iovec *qemu_iovec_slice(QEMUIOVector *qiov, + size_t offset, size_t len, + size_t *head, size_t *tail, int *niov); int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len); void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len); void qemu_iovec_concat(QEMUIOVector *dst, diff --git a/util/iov.c b/util/iov.c index b4be580022..65a70449da 100644 --- a/util/iov.c +++ b/util/iov.c @@ -378,15 +378,15 @@ static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset, } /* - * qiov_slice + * qemu_iovec_slice * * Find subarray of iovec's, containing requested range. @head would * be offset in first iov (returned by the function), @tail would be * count of extra bytes in last iovec (returned iov + @niov - 1). */ -static struct iovec *qiov_slice(QEMUIOVector *qiov, - size_t offset, size_t len, - size_t *head, size_t *tail, int *niov) +struct iovec *qemu_iovec_slice(QEMUIOVector *qiov, + size_t offset, size_t len, + size_t *head, size_t *tail, int *niov) { struct iovec *iov, *end_iov; @@ -411,7 +411,7 @@ int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len) size_t head, tail; int niov; - qiov_slice(qiov, offset, len, &head, &tail, &niov); + qemu_iovec_slice(qiov, offset, len, &head, &tail, &niov); return niov; } @@ -439,8 +439,8 @@ int qemu_iovec_init_extended( } if (mid_len) { - mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len, - &mid_head, &mid_tail, &mid_niov); + mid_iov = qemu_iovec_slice(mid_qiov, mid_offset, mid_len, + &mid_head, &mid_tail, &mid_niov); } total_niov = !!head_len + mid_niov + !!tail_len;
We want to inline qemu_iovec_init_extended() in block/io.c for padding requests, and having access to qiov_slice() is useful for this. (We will need to count the number of I/O vector elements of a slice there, and then later process this slice. Without qiov_slice(), we would need to call qemu_iovec_subvec_niov(), and all further IOV-processing functions may need to skip prefixing elements to accomodate for a qiov_offset. Because qemu_iovec_subvec_niov() internally calls qiov_slice(), we can just have the block/io.c code call qiov_slice() itself, thus get the number of elements, and also create an iovec array with the superfluous prefixing elements stripped, so the following processing functions no longer need to skip them.) Signed-off-by: Hanna Czenczek <hreitz@redhat.com> --- include/qemu/iov.h | 3 +++ util/iov.c | 14 +++++++------- 2 files changed, 10 insertions(+), 7 deletions(-)