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qemu: Use the end of QEMU log for reporting errors

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When QEMU dies, we read its output stored in a log file and use it for
reporting a hopefully useful error. However, virReportError will trim
the message to (VIR_ERROR_MAX_LENGTH - 1) characters, which means the
end of the log (which likely contains the error message we want to
report) may get lost. We should trim the beginning of the log instead.

https://bugzilla.redhat.com/show_bug.cgi?id=1335534

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
This commit is contained in:
Jiri Denemark 2017-11-22 13:12:00 +01:00
parent c88ce8ae74
commit 96f7a045e9
1 changed files with 30 additions and 4 deletions
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34
src/qemu/qemu_process.c
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@ -1827,17 +1827,24 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm, int asyncJob,
* qemuProcessReadLog: Read log file of a qemu VM * qemuProcessReadLog: Read log file of a qemu VM
* @logCtxt: the domain log context * @logCtxt: the domain log context
* @msg: pointer to buffer to store the read messages in * @msg: pointer to buffer to store the read messages in
* @max: maximum length of the message returned in @msg
* *
* Reads log of a qemu VM. Skips messages not produced by qemu or irrelevant * Reads log of a qemu VM. Skips messages not produced by qemu or irrelevant
* messages. Returns returns 0 on success or -1 on error * messages. If @max is not zero, @msg will contain at most @max characters
* from the end of the log and @msg will start after a new line if possible.
*
* Returns 0 on success or -1 on error
*/ */
static int static int
qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg) qemuProcessReadLog(qemuDomainLogContextPtr logCtxt,
char **msg,
size_t max)
{ {
char *buf; char *buf;
ssize_t got; ssize_t got;
char *eol; char *eol;
char *filter_next; char *filter_next;
size_t skip;
if ((got = qemuDomainLogContextRead(logCtxt, &buf)) < 0) if ((got = qemuDomainLogContextRead(logCtxt, &buf)) < 0)
return -1; return -1;
@ -1848,7 +1855,7 @@ qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg)
*eol = '\0'; *eol = '\0';
if (virLogProbablyLogMessage(filter_next) || if (virLogProbablyLogMessage(filter_next) ||
strstr(filter_next, "char device redirected to")) { strstr(filter_next, "char device redirected to")) {
size_t skip = (eol + 1) - filter_next; skip = (eol + 1) - filter_next;
memmove(filter_next, eol + 1, buf + got - eol); memmove(filter_next, eol + 1, buf + got - eol);
got -= skip; got -= skip;
} else { } else {
@ -1863,6 +1870,19 @@ qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg)
buf[got - 1] = '\0'; buf[got - 1] = '\0';
got--; got--;
} }
if (max > 0 && got > max) {
skip = got - max;
if (buf[skip - 1] != '\n' &&
(eol = strchr(buf + skip, '\n')) &&
!virStringIsEmpty(eol + 1))
skip = eol + 1 - buf;
memmove(buf, buf + skip, got - skip + 1);
got -= skip;
}
ignore_value(VIR_REALLOC_N_QUIET(buf, got + 1)); ignore_value(VIR_REALLOC_N_QUIET(buf, got + 1));
*msg = buf; *msg = buf;
return 0; return 0;
@ -1874,8 +1894,14 @@ qemuProcessReportLogError(qemuDomainLogContextPtr logCtxt,
const char *msgprefix) const char *msgprefix)
{ {
char *logmsg = NULL; char *logmsg = NULL;
size_t max;
if (qemuProcessReadLog(logCtxt, &logmsg) < 0) max = VIR_ERROR_MAX_LENGTH - 1;
max -= strlen(msgprefix);
/* The length of the formatting string minus two '%s' */
max -= strlen(_("%s: %s")) - 4;
if (qemuProcessReadLog(logCtxt, &logmsg, max) < 0)
return -1; return -1;
virResetLastError(); virResetLastError();