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migration/qemu-file: fix potential buf waste for extra buf_index adjustment

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In add_to_iovec(), qemu_fflush() will be called if iovec is full. If
this happens, buf_index is reset. Currently, this is not checked and
buf_index would always been adjust with buf size.

This is not harmful, but will waste some space in file buffer.

This patch make add_to_iovec() return 1 when it has flushed the file.
Then the caller could check the return value to see whether it is
necessary to adjust the buf_index any more.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Message-Id: <20190911132839.23336-3-richard.weiyang@gmail.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Wei Yang 2019-09-11 13:28:39 +00:00 committed by Dr. David Alan Gilbert
parent 89fe04b458
commit 1bf57fb3df
1 changed files with 26 additions and 17 deletions
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43
migration/qemu-file.c
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@ -381,8 +381,16 @@ int qemu_fclose(QEMUFile *f)
return ret;
}
static void add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
bool may_free)
/*
* Add buf to iovec. Do flush if iovec is full.
*
* Return values:
* 1 iovec is full and flushed
* 0 iovec is not flushed
*
*/
static int add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
bool may_free)
{
/* check for adjacent buffer and coalesce them */
if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base +
@ -400,6 +408,19 @@ static void add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
if (f->iovcnt >= MAX_IOV_SIZE) {
qemu_fflush(f);
return 1;
}
return 0;
}
static void add_buf_to_iovec(QEMUFile *f, size_t len)
{
if (!add_to_iovec(f, f->buf + f->buf_index, len, false)) {
f->buf_index += len;
if (f->buf_index == IO_BUF_SIZE) {
qemu_fflush(f);
}
}
}
@ -429,11 +450,7 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, size_t size)
}
memcpy(f->buf + f->buf_index, buf, l);
f->bytes_xfer += l;
add_to_iovec(f, f->buf + f->buf_index, l, false);
f->buf_index += l;
if (f->buf_index == IO_BUF_SIZE) {
qemu_fflush(f);
}
add_buf_to_iovec(f, l);
if (qemu_file_get_error(f)) {
break;
}
@ -450,11 +467,7 @@ void qemu_put_byte(QEMUFile *f, int v)
f->buf[f->buf_index] = v;
f->bytes_xfer++;
add_to_iovec(f, f->buf + f->buf_index, 1, false);
f->buf_index++;
if (f->buf_index == IO_BUF_SIZE) {
qemu_fflush(f);
}
add_buf_to_iovec(f, 1);
}
void qemu_file_skip(QEMUFile *f, int size)
@ -760,11 +773,7 @@ ssize_t qemu_put_compression_data(QEMUFile *f, z_stream *stream,
}
qemu_put_be32(f, blen);
add_to_iovec(f, f->buf + f->buf_index, blen, false);
f->buf_index += blen;
if (f->buf_index == IO_BUF_SIZE) {
qemu_fflush(f);
}
add_buf_to_iovec(f, blen);
return blen + sizeof(int32_t);
}