[libvirt] [PATCH 3/3] qemu: Use the end of QEMU log for reporting errors
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(a)redhat.com>
---
src/qemu/qemu_process.c | 34 ++++++++++++++++++++++++++++++----
1 file changed, 30 insertions(+), 4 deletions(-)
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 3da297c16f..214f41dd85 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -1827,17 +1827,24 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm,
int asyncJob,
* qemuProcessReadLog: Read log file of a qemu VM
* @logCtxt: the domain log context
* @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
- * 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
-qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg)
+qemuProcessReadLog(qemuDomainLogContextPtr logCtxt,
+ char **msg,
+ size_t max)
{
char *buf;
ssize_t got;
char *eol;
char *filter_next;
+ size_t skip;
if ((got = qemuDomainLogContextRead(logCtxt, &buf)) < 0)
return -1;
@@ -1848,7 +1855,7 @@ qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg)
*eol = '\0';
if (virLogProbablyLogMessage(filter_next) ||
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);
got -= skip;
} else {
@@ -1863,6 +1870,19 @@ qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg)
buf[got - 1] = '\0';
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));
*msg = buf;
return 0;
@@ -1874,8 +1894,14 @@ qemuProcessReportLogError(qemuDomainLogContextPtr logCtxt,
const char *msgprefix)
{
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;
virResetLastError();
--
2.15.0