qemu/util/iov.c
Hanna Czenczek cc63f6f6fa util/iov: Remove qemu_iovec_init_extended()
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>
2023-06-05 13:11:24 +02:00

713 lines
19 KiB
C

/*
* Helpers for getting linearized buffers from iov / filling buffers into iovs
*
* Copyright IBM, Corp. 2007, 2008
* Copyright (C) 2010 Red Hat, Inc.
*
* Author(s):
* Anthony Liguori <aliguori@us.ibm.com>
* Amit Shah <amit.shah@redhat.com>
* Michael Tokarev <mjt@tls.msk.ru>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
* Contributions after 2012-01-13 are licensed under the terms of the
* GNU GPL, version 2 or (at your option) any later version.
*/
#include "qemu/osdep.h"
#include "qemu/iov.h"
#include "qemu/sockets.h"
#include "qemu/cutils.h"
size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
size_t offset, const void *buf, size_t bytes)
{
size_t done;
unsigned int i;
for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
if (offset < iov[i].iov_len) {
size_t len = MIN(iov[i].iov_len - offset, bytes - done);
memcpy(iov[i].iov_base + offset, buf + done, len);
done += len;
offset = 0;
} else {
offset -= iov[i].iov_len;
}
}
assert(offset == 0);
return done;
}
size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, void *buf, size_t bytes)
{
size_t done;
unsigned int i;
for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
if (offset < iov[i].iov_len) {
size_t len = MIN(iov[i].iov_len - offset, bytes - done);
memcpy(buf + done, iov[i].iov_base + offset, len);
done += len;
offset = 0;
} else {
offset -= iov[i].iov_len;
}
}
assert(offset == 0);
return done;
}
size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, int fillc, size_t bytes)
{
size_t done;
unsigned int i;
for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
if (offset < iov[i].iov_len) {
size_t len = MIN(iov[i].iov_len - offset, bytes - done);
memset(iov[i].iov_base + offset, fillc, len);
done += len;
offset = 0;
} else {
offset -= iov[i].iov_len;
}
}
assert(offset == 0);
return done;
}
size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
{
size_t len;
unsigned int i;
len = 0;
for (i = 0; i < iov_cnt; i++) {
len += iov[i].iov_len;
}
return len;
}
/* helper function for iov_send_recv() */
static ssize_t
do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
{
#ifdef CONFIG_POSIX
ssize_t ret;
struct msghdr msg;
memset(&msg, 0, sizeof(msg));
msg.msg_iov = iov;
msg.msg_iovlen = iov_cnt;
do {
ret = do_send
? sendmsg(sockfd, &msg, 0)
: recvmsg(sockfd, &msg, 0);
} while (ret < 0 && errno == EINTR);
return ret;
#else
/* else send piece-by-piece */
/*XXX Note: windows has WSASend() and WSARecv() */
unsigned i = 0;
ssize_t ret = 0;
ssize_t off = 0;
while (i < iov_cnt) {
ssize_t r = do_send
? send(sockfd, iov[i].iov_base + off, iov[i].iov_len - off, 0)
: recv(sockfd, iov[i].iov_base + off, iov[i].iov_len - off, 0);
if (r > 0) {
ret += r;
off += r;
if (off < iov[i].iov_len) {
continue;
}
} else if (!r) {
break;
} else if (errno == EINTR) {
continue;
} else {
/* else it is some "other" error,
* only return if there was no data processed. */
if (ret == 0) {
ret = -1;
}
break;
}
off = 0;
i++;
}
return ret;
#endif
}
ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt,
size_t offset, size_t bytes,
bool do_send)
{
ssize_t total = 0;
ssize_t ret;
size_t orig_len, tail;
unsigned niov;
struct iovec *local_iov, *iov;
if (bytes <= 0) {
return 0;
}
local_iov = g_new0(struct iovec, iov_cnt);
iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes);
offset = 0;
iov = local_iov;
while (bytes > 0) {
/* Find the start position, skipping `offset' bytes:
* first, skip all full-sized vector elements, */
for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
offset -= iov[niov].iov_len;
}
/* niov == iov_cnt would only be valid if bytes == 0, which
* we already ruled out in the loop condition. */
assert(niov < iov_cnt);
iov += niov;
iov_cnt -= niov;
if (offset) {
/* second, skip `offset' bytes from the (now) first element,
* undo it on exit */
iov[0].iov_base += offset;
iov[0].iov_len -= offset;
}
/* Find the end position skipping `bytes' bytes: */
/* first, skip all full-sized elements */
tail = bytes;
for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
tail -= iov[niov].iov_len;
}
if (tail) {
/* second, fixup the last element, and remember the original
* length */
assert(niov < iov_cnt);
assert(iov[niov].iov_len > tail);
orig_len = iov[niov].iov_len;
iov[niov++].iov_len = tail;
ret = do_send_recv(sockfd, iov, niov, do_send);
/* Undo the changes above before checking for errors */
iov[niov-1].iov_len = orig_len;
} else {
ret = do_send_recv(sockfd, iov, niov, do_send);
}
if (offset) {
iov[0].iov_base -= offset;
iov[0].iov_len += offset;
}
if (ret < 0) {
assert(errno != EINTR);
g_free(local_iov);
if (errno == EAGAIN && total > 0) {
return total;
}
return -1;
}
if (ret == 0 && !do_send) {
/* recv returns 0 when the peer has performed an orderly
* shutdown. */
break;
}
/* Prepare for the next iteration */
offset += ret;
total += ret;
bytes -= ret;
}
g_free(local_iov);
return total;
}
void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
FILE *fp, const char *prefix, size_t limit)
{
int v;
size_t size = 0;
char *buf;
for (v = 0; v < iov_cnt; v++) {
size += iov[v].iov_len;
}
size = size > limit ? limit : size;
buf = g_malloc(size);
iov_to_buf(iov, iov_cnt, 0, buf, size);
qemu_hexdump(fp, prefix, buf, size);
g_free(buf);
}
unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
const struct iovec *iov, unsigned int iov_cnt,
size_t offset, size_t bytes)
{
size_t len;
unsigned int i, j;
for (i = 0, j = 0;
i < iov_cnt && j < dst_iov_cnt && (offset || bytes); i++) {
if (offset >= iov[i].iov_len) {
offset -= iov[i].iov_len;
continue;
}
len = MIN(bytes, iov[i].iov_len - offset);
dst_iov[j].iov_base = iov[i].iov_base + offset;
dst_iov[j].iov_len = len;
j++;
bytes -= len;
offset = 0;
}
assert(offset == 0);
return j;
}
/* io vectors */
void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
{
qiov->iov = g_new(struct iovec, alloc_hint);
qiov->niov = 0;
qiov->nalloc = alloc_hint;
qiov->size = 0;
}
void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
{
int i;
qiov->iov = iov;
qiov->niov = niov;
qiov->nalloc = -1;
qiov->size = 0;
for (i = 0; i < niov; i++)
qiov->size += iov[i].iov_len;
}
void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
{
assert(qiov->nalloc != -1);
if (qiov->niov == qiov->nalloc) {
qiov->nalloc = 2 * qiov->nalloc + 1;
qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc);
}
qiov->iov[qiov->niov].iov_base = base;
qiov->iov[qiov->niov].iov_len = len;
qiov->size += len;
++qiov->niov;
}
/*
* Concatenates (partial) iovecs from src_iov to the end of dst.
* It starts copying after skipping `soffset' bytes at the
* beginning of src and adds individual vectors from src to
* dst copies up to `sbytes' bytes total, or up to the end
* of src_iov if it comes first. This way, it is okay to specify
* very large value for `sbytes' to indicate "up to the end
* of src".
* Only vector pointers are processed, not the actual data buffers.
*/
size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
struct iovec *src_iov, unsigned int src_cnt,
size_t soffset, size_t sbytes)
{
int i;
size_t done;
if (!sbytes) {
return 0;
}
assert(dst->nalloc != -1);
for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
if (soffset < src_iov[i].iov_len) {
size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
done += len;
soffset = 0;
} else {
soffset -= src_iov[i].iov_len;
}
}
assert(soffset == 0); /* offset beyond end of src */
return done;
}
/*
* Concatenates (partial) iovecs from src to the end of dst.
* It starts copying after skipping `soffset' bytes at the
* beginning of src and adds individual vectors from src to
* dst copies up to `sbytes' bytes total, or up to the end
* of src if it comes first. This way, it is okay to specify
* very large value for `sbytes' to indicate "up to the end
* of src".
* Only vector pointers are processed, not the actual data buffers.
*/
void qemu_iovec_concat(QEMUIOVector *dst,
QEMUIOVector *src, size_t soffset, size_t sbytes)
{
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;
}
/*
* 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).
*/
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;
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;
}
int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len)
{
size_t head, tail;
int niov;
qemu_iovec_slice(qiov, offset, len, &head, &tail, &niov);
return niov;
}
/*
* Check if the contents of subrange of qiov data is all zeroes.
*/
bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes)
{
struct iovec *iov;
size_t current_offset;
assert(offset + bytes <= qiov->size);
iov = iov_skip_offset(qiov->iov, offset, &current_offset);
while (bytes) {
uint8_t *base = (uint8_t *)iov->iov_base + current_offset;
size_t len = MIN(iov->iov_len - current_offset, bytes);
if (!buffer_is_zero(base, len)) {
return false;
}
current_offset = 0;
bytes -= len;
iov++;
}
return true;
}
void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
size_t offset, size_t len)
{
struct iovec *slice_iov;
int slice_niov;
size_t slice_head, slice_tail;
assert(source->size >= len);
assert(source->size - len >= offset);
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)
{
if (qiov->nalloc != -1) {
g_free(qiov->iov);
}
memset(qiov, 0, sizeof(*qiov));
}
void qemu_iovec_reset(QEMUIOVector *qiov)
{
assert(qiov->nalloc != -1);
qiov->niov = 0;
qiov->size = 0;
}
size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
void *buf, size_t bytes)
{
return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
}
size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
const void *buf, size_t bytes)
{
return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
}
size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
int fillc, size_t bytes)
{
return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
}
/**
* Check that I/O vector contents are identical
*
* The IO vectors must have the same structure (same length of all parts).
* A typical usage is to compare vectors created with qemu_iovec_clone().
*
* @a: I/O vector
* @b: I/O vector
* @ret: Offset to first mismatching byte or -1 if match
*/
ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
{
int i;
ssize_t offset = 0;
assert(a->niov == b->niov);
for (i = 0; i < a->niov; i++) {
size_t len = 0;
uint8_t *p = (uint8_t *)a->iov[i].iov_base;
uint8_t *q = (uint8_t *)b->iov[i].iov_base;
assert(a->iov[i].iov_len == b->iov[i].iov_len);
while (len < a->iov[i].iov_len && *p++ == *q++) {
len++;
}
offset += len;
if (len != a->iov[i].iov_len) {
return offset;
}
}
return -1;
}
typedef struct {
int src_index;
struct iovec *src_iov;
void *dest_base;
} IOVectorSortElem;
static int sortelem_cmp_src_base(const void *a, const void *b)
{
const IOVectorSortElem *elem_a = a;
const IOVectorSortElem *elem_b = b;
/* Don't overflow */
if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
return -1;
} else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
return 1;
} else {
return 0;
}
}
static int sortelem_cmp_src_index(const void *a, const void *b)
{
const IOVectorSortElem *elem_a = a;
const IOVectorSortElem *elem_b = b;
return elem_a->src_index - elem_b->src_index;
}
/**
* Copy contents of I/O vector
*
* The relative relationships of overlapping iovecs are preserved. This is
* necessary to ensure identical semantics in the cloned I/O vector.
*/
void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
{
IOVectorSortElem sortelems[src->niov];
void *last_end;
int i;
/* Sort by source iovecs by base address */
for (i = 0; i < src->niov; i++) {
sortelems[i].src_index = i;
sortelems[i].src_iov = &src->iov[i];
}
qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
/* Allocate buffer space taking into account overlapping iovecs */
last_end = NULL;
for (i = 0; i < src->niov; i++) {
struct iovec *cur = sortelems[i].src_iov;
ptrdiff_t rewind = 0;
/* Detect overlap */
if (last_end && last_end > cur->iov_base) {
rewind = last_end - cur->iov_base;
}
sortelems[i].dest_base = buf - rewind;
buf += cur->iov_len - MIN(rewind, cur->iov_len);
last_end = MAX(cur->iov_base + cur->iov_len, last_end);
}
/* Sort by source iovec index and build destination iovec */
qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
for (i = 0; i < src->niov; i++) {
qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
}
}
void iov_discard_undo(IOVDiscardUndo *undo)
{
/* Restore original iovec if it was modified */
if (undo->modified_iov) {
*undo->modified_iov = undo->orig;
}
}
size_t iov_discard_front_undoable(struct iovec **iov,
unsigned int *iov_cnt,
size_t bytes,
IOVDiscardUndo *undo)
{
size_t total = 0;
struct iovec *cur;
if (undo) {
undo->modified_iov = NULL;
}
for (cur = *iov; *iov_cnt > 0; cur++) {
if (cur->iov_len > bytes) {
if (undo) {
undo->modified_iov = cur;
undo->orig = *cur;
}
cur->iov_base += bytes;
cur->iov_len -= bytes;
total += bytes;
break;
}
bytes -= cur->iov_len;
total += cur->iov_len;
*iov_cnt -= 1;
}
*iov = cur;
return total;
}
size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
size_t bytes)
{
return iov_discard_front_undoable(iov, iov_cnt, bytes, NULL);
}
size_t iov_discard_back_undoable(struct iovec *iov,
unsigned int *iov_cnt,
size_t bytes,
IOVDiscardUndo *undo)
{
size_t total = 0;
struct iovec *cur;
if (undo) {
undo->modified_iov = NULL;
}
if (*iov_cnt == 0) {
return 0;
}
cur = iov + (*iov_cnt - 1);
while (*iov_cnt > 0) {
if (cur->iov_len > bytes) {
if (undo) {
undo->modified_iov = cur;
undo->orig = *cur;
}
cur->iov_len -= bytes;
total += bytes;
break;
}
bytes -= cur->iov_len;
total += cur->iov_len;
cur--;
*iov_cnt -= 1;
}
return total;
}
size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
size_t bytes)
{
return iov_discard_back_undoable(iov, iov_cnt, bytes, NULL);
}
void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
{
size_t total;
unsigned int niov = qiov->niov;
assert(qiov->size >= bytes);
total = iov_discard_back(qiov->iov, &niov, bytes);
assert(total == bytes);
qiov->niov = niov;
qiov->size -= bytes;
}