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Re: [Qemu-block] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_ex
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [Qemu-block] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_extended |
Date: |
Wed, 5 Jun 2019 11:54:55 +0000 |
04.06.2019 19:15, Vladimir Sementsov-Ogievskiy wrote:
> Introduce new initialization API, to create requests with padding. Will
> be used in the following patch. New API uses qemu_iovec_init_buf if
> resulting io vector has only one element, to avoid extra allocations.
> So, we need to update qemu_iovec_destroy to support destroying such
> QIOVs.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> include/qemu/iov.h | 7 +++
> util/iov.c | 112 +++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 114 insertions(+), 5 deletions(-)
>
> diff --git a/include/qemu/iov.h b/include/qemu/iov.h
> index 48b45987b7..f3787a0cf7 100644
> --- a/include/qemu/iov.h
> +++ b/include/qemu/iov.h
> @@ -199,6 +199,13 @@ static inline void *qemu_iovec_buf(QEMUIOVector *qiov)
>
> void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
> void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int
> niov);
> +void qemu_iovec_init_extended(
> + QEMUIOVector *qiov,
> + void *head_buf, size_t head_len,
> + QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
> + void *tail_buf, size_t tail_len);
> +void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
> + size_t offset, size_t len);
> void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
> void qemu_iovec_concat(QEMUIOVector *dst,
> QEMUIOVector *src, size_t soffset, size_t sbytes);
> diff --git a/util/iov.c b/util/iov.c
> index 74e6ca8ed7..39b6e31494 100644
> --- a/util/iov.c
> +++ b/util/iov.c
> @@ -353,6 +353,103 @@ void qemu_iovec_concat(QEMUIOVector *dst,
> qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
> }
>
> +/*
> + * qiov_find_iov
> + *
> + * Return pointer to iovec structure, where byte at @offset in original
> vector
> + * @iov exactly is.
> + * Set @remaining_offset to be offset inside that iovec to the same byte.
> + */
> +static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset,
> + size_t *remaining_offset)
> +{
> + while (offset > 0 && offset >= iov->iov_len) {
> + offset -= iov->iov_len;
> + iov++;
> + }
> + *remaining_offset = offset;
> +
> + return iov;
> +}
> +
> +/*
> + * qiov_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 *iov, *end_iov;
> +
> + assert(offset + len <= qiov->size);
> +
> + iov = iov_skip_offset(qiov->iov, offset, head);
> + end_iov = iov_skip_offset(iov, *head + len, tail);
> +
> + if (*tail > 0) {
> + assert(*tail < end_iov->iov_len);
> + *tail = end_iov->iov_len - *tail;
> + end_iov++;
> + }
> +
> + *niov = end_iov - iov;
> +
> + return iov;
> +}
> +
> +/*
> + * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
> + * and @tail_buf buffer into new qiov.
> + */
> +void qemu_iovec_init_extended(
> + QEMUIOVector *qiov,
> + void *head_buf, size_t head_len,
> + QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
> + void *tail_buf, size_t tail_len)
> +{
> + size_t mid_head, mid_tail;
> + int total_niov, mid_niov;
Oops, clang is right, mid_niov may be uninitialized. So, here should be
"mid_niov = 0".
> + struct iovec *p, *mid_iov;
> +
> + if (mid_len) {
> + mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len,
> + &mid_head, &mid_tail, &mid_niov);
> + }
> +
> + total_niov = !!head_len + mid_niov + !!tail_len;
> + if (total_niov == 1) {
> + qemu_iovec_init_buf(qiov, NULL, 0);
> + p = &qiov->local_iov;
> + } else {
> + qiov->niov = qiov->nalloc = total_niov;
> + qiov->size = head_len + mid_len + tail_len;
> + p = qiov->iov = g_new(struct iovec, qiov->niov);
> + }
> +
> + if (head_len) {
> + p->iov_base = head_buf;
> + p->iov_len = head_len;
> + p++;
> + }
> +
> + if (mid_len) {
> + memcpy(p, mid_iov, mid_niov * sizeof(*p));
> + p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;
> + p[0].iov_len -= mid_head;
> + p[mid_niov - 1].iov_len -= mid_tail;
> + p += mid_niov;
> + }
> +
> + if (tail_len) {
> + p->iov_base = tail_buf;
> + p->iov_len = tail_len;
> + }
> +}
> +
> /*
> * Check if the contents of the iovecs are all zero
> */
> @@ -374,14 +471,19 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov)
> return true;
> }
>
> +void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
> + size_t offset, size_t len)
> +{
> + qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
> +}
> +
> void qemu_iovec_destroy(QEMUIOVector *qiov)
> {
> - assert(qiov->nalloc != -1);
> + if (qiov->nalloc != -1) {
> + g_free(qiov->iov);
> + }
>
> - qemu_iovec_reset(qiov);
> - g_free(qiov->iov);
> - qiov->nalloc = 0;
> - qiov->iov = NULL;
> + memset(qiov, 0, sizeof(*qiov));
> }
>
> void qemu_iovec_reset(QEMUIOVector *qiov)
>
--
Best regards,
Vladimir
- [Qemu-block] [PATCH v2 00/12] block: qiov_offset parameter for io, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 12/12] block/qcow2: implement .bdrv_co_pwritev(_compressed)_part, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 10/12] block/qcow2: refactor qcow2_co_preadv to use buffer-based io, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 08/12] block/io: bdrv_aligned_pwritev: use and support qiov_offset, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 07/12] block/io: bdrv_aligned_preadv: use and support qiov_offset, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 06/12] block/io: bdrv_co_do_copy_on_readv: lazy allocation, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_extended, Vladimir Sementsov-Ogievskiy, 2019/06/04
- Re: [Qemu-block] [PATCH v2 01/12] util/iov: introduce qemu_iovec_init_extended,
Vladimir Sementsov-Ogievskiy <=
- [Qemu-block] [PATCH v2 02/12] util/iov: improve qemu_iovec_is_zero, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 05/12] block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 11/12] block/qcow2: implement .bdrv_co_preadv_part, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 04/12] block: define .*_part io handlers in BlockDriver, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 03/12] block/io: refactor padding, Vladimir Sementsov-Ogievskiy, 2019/06/04
- [Qemu-block] [PATCH v2 09/12] block/io: introduce bdrv_co_p{read, write}v_part, Vladimir Sementsov-Ogievskiy, 2019/06/04
- Re: [Qemu-block] [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io, no-reply, 2019/06/05
- Re: [Qemu-block] [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io, Stefan Hajnoczi, 2019/06/28