On 05/16/2017 10:04 AM, Michal Privoznik wrote:
> Basically, what is needed here is to introduce new message type
> for the messages passed between the event loop callbacks and the
> worker thread that does all the I/O. The idea is that instead of
> a queue of read buffers we will have a queue where "hole of size
> X" messages appear. That way the even loop callbacks can just
s/even/event/
> check the head of the queue and see if the worker thread is in
> data or a hole section and how long the section is.
>
> Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
> ---
> src/storage/storage_util.c | 4 +-
> src/util/virfdstream.c | 239
> ++++++++++++++++++++++++++++++++++++++++-----
> src/util/virfdstream.h | 1 +
> 3 files changed, 220 insertions(+), 24 deletions(-)
>
[...]
> diff --git a/src/util/virfdstream.c b/src/util/virfdstream.c
> index 4b42939e7..ba209025a 100644
> --- a/src/util/virfdstream.c
> +++ b/src/util/virfdstream.c
[...]
> static ssize_t
> virFDStreamThreadDoRead(virFDStreamDataPtr fdst,
> + bool sparse,
> const int fdin,
> const int fdout,
> const char *fdinname,
> const char *fdoutname,
> + size_t *dataLen,
> size_t buflen)
> {
> virFDStreamMsgPtr msg = NULL;
> + int inData = 0;
> + long long sectionLen = 0;
> char *buf = NULL;
> ssize_t got;
>
> + if (sparse && *dataLen == 0) {
> + if (virFileInData(fdin, &inData, §ionLen) < 0)
> + goto error;
> +
> + if (inData)
> + *dataLen = sectionLen;
> + }
> +
> if (VIR_ALLOC(msg) < 0)
> goto error;
>
> - if (VIR_ALLOC_N(buf, buflen) < 0)
> - goto error;
> -
> - if ((got = saferead(fdin, buf, buflen)) < 0) {
> - virReportSystemError(errno,
> - _("Unable to read %s"),
> - fdinname);
> - goto error;
> + if (sparse && *dataLen == 0) {
> + msg->type = VIR_FDSTREAM_MSG_TYPE_HOLE;
> + msg->stream.hole.len = sectionLen;
> + got = sectionLen;
> +
> + /* HACK. The message queue is one directional. So caller
HACK or "By design"
> + * cannot make us skip the hole. Do that for them instead. */
> + if (sectionLen &&
> + lseek(fdin, sectionLen, SEEK_CUR) == (off_t) -1) {
> + virReportSystemError(errno,
> + _("unable to seek in %s"),
> + fdinname);
> + goto error;
> + }
[...]
> +static int
> +virFDStreamSendHole(virStreamPtr st,
> + long long length,
> + unsigned int flags)
> +{
> + virFDStreamDataPtr fdst = st->privateData;
> + virFDStreamMsgPtr msg = NULL;
> + off_t off;
> + int ret = -1;
> +
> + virCheckFlags(0, -1);
> +
> + virObjectLock(fdst);
> + if (fdst->length) {
> + if (length > fdst->length - fdst->offset)
> + length = fdst->length - fdst->offset;
> + fdst->offset += length;
> + }
> +
> + if (fdst->thread) {
> + /* Things are a bit complicated here. But bear with me. If FDStream
> is
s/But bear with me.//
> + * in a read mode, then if the message at the queue head is HOLE,
> just
> + * pop it. The thread has lseek()-ed anyway. If however, the FDStream
However, if the FDStream
Reviewed-by: John Ferlan <jfer...@redhat.com>
John
> + * is in write mode, then tell the thread to do the lseek() for us.
> + * Under no circumstances we can do the lseek() ourselves here. We
> + * might mess up file position for the thread. */
> + if (fdst->threadDoRead) {
> + msg = fdst->msg;
> + if (msg->type != VIR_FDSTREAM_MSG_TYPE_HOLE) {
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> + _("Invalid stream hole"));
> + goto cleanup;
> + }
> +
> + virFDStreamMsgQueuePop(fdst, fdst->fd, "pipe");
> + } else {
> + if (VIR_ALLOC(msg) < 0)
> + goto cleanup;
> +
> + msg->type = VIR_FDSTREAM_MSG_TYPE_HOLE;
> + msg->stream.hole.len = length;
> + virFDStreamMsgQueuePush(fdst, msg, fdst->fd, "pipe");
> + msg = NULL;
> + }
[...]
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