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util/iov: Remove qemu_iovec_init_extended()

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bdrv_pad_request() was the main user of qemu_iovec_init_extended().
HEAD^ has removed that use, so we can remove qemu_iovec_init_extended()
now.

The only remaining user is qemu_iovec_init_slice(), which can easily
inline the small part it really needs.

Note that qemu_iovec_init_extended() offered a memcpy() optimization to
initialize the new I/O vector.  qemu_iovec_concat_iov(), which is used
to replace its functionality, does not, but calls qemu_iovec_add() for
every single element.  If we decide this optimization was important, we
will need to re-implement it in qemu_iovec_concat_iov(), which might
also benefit its pre-existing users.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20230411173418.19549-4-hreitz@redhat.com>
This commit is contained in:
Hanna Czenczek 2023-04-11 19:34:17 +02:00
parent 18743311b8
commit cc63f6f6fa
2 changed files with 11 additions and 73 deletions
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5
include/qemu/iov.h
View file

@ -222,11 +222,6 @@ 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);
int 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);
struct iovec *qemu_iovec_slice(QEMUIOVector *qiov,

79
util/iov.c
View file

@ -416,70 +416,6 @@ int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len)
return niov;
}
/*
* Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
* and @tail_buf buffer into new qiov.
*/
int 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 = 0;
struct iovec *p, *mid_iov = NULL;
assert(mid_qiov->niov <= IOV_MAX);
if (SIZE_MAX - head_len < mid_len ||
SIZE_MAX - head_len - mid_len < tail_len)
{
return -EINVAL;
}
if (mid_len) {
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;
if (total_niov > IOV_MAX) {
return -EINVAL;
}
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++;
}
assert(!mid_niov == !mid_len);
if (mid_niov) {
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;
}
return 0;
}
/*
* Check if the contents of subrange of qiov data is all zeroes.
*/
@ -511,14 +447,21 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes)
void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
size_t offset, size_t len)
{
int ret;
struct iovec *slice_iov;
int slice_niov;
size_t slice_head, slice_tail;
assert(source->size >= len);
assert(source->size - len >= offset);
/* We shrink the request, so we can't overflow neither size_t nor MAX_IOV */
ret = qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
assert(ret == 0);
slice_iov = qemu_iovec_slice(source, offset, len,
&slice_head, &slice_tail, &slice_niov);
if (slice_niov == 1) {
qemu_iovec_init_buf(qiov, slice_iov[0].iov_base + slice_head, len);
} else {
qemu_iovec_init(qiov, slice_niov);
qemu_iovec_concat_iov(qiov, slice_iov, slice_niov, slice_head, len);
}
}
void qemu_iovec_destroy(QEMUIOVector *qiov)