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util/iov: Make qiov_slice() public 

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.  As a
public function, it is renamed to qemu_iovec_slice().

(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.)

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: <20230411173418.19549-2-hreitz@redhat.com>
master
Hanna Czenczek 2023-04-11 19:34:15 +02:00
parent 848a6caa88
commit 3d06cea825
2 changed files with 10 additions and 7 deletions
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3
include/qemu/iov.h
View File

@ -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,

14
util/iov.c
View File

@ -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;