From 59bde2137445b63c822720d069d91d38190c6540 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 8 Nov 2022 15:00:31 +0100 Subject: [PATCH] util/log: do not close and reopen log files when flags are turned off MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit log_append makes sure that if you turn off the logging (which clears log_flags and makes need_to_open_file false) the old log is not overwritten. The usecase is that if you remove or move the file QEMU will not keep writing to the old file. However, this is not always the desited behavior, in particular having log_append==1 after changing the file name makes little sense. When qemu_set_log_internal is called from the logfile monitor command, filename must be non-NULL and therefore changed_name must be true. Therefore, the only case where the file is closed and need_to_open_file == false is indeed when log_flags becomes zero. In this case, just flush the file and do not bother closing it, thus faking the same append behavior as previously. The behavioral change is that changing the logfile twice, for example log1 -> log2 -> log1, will cause log1 to be overwritten. This can simply be documented, since it is not a particularly surprising behavior. Suggested-by: Alex Bennée Signed-off-by: Paolo Bonzini Reviewed-by: Richard Henderson Reviewed-by: Greg Kurz Message-Id: <20221025092119.236224-1-pbonzini@redhat.com> [groug: nullify global_file before actually closing the file] Signed-off-by: Greg Kurz Message-Id: <20221108140032.1460307-2-groug@kaod.org> Signed-off-by: Paolo Bonzini --- util/log.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/util/log.c b/util/log.c index c2198badf2..fb843453dd 100644 --- a/util/log.c +++ b/util/log.c @@ -45,7 +45,6 @@ static __thread FILE *thread_file; static __thread Notifier qemu_log_thread_cleanup_notifier; int qemu_loglevel; -static bool log_append; static bool log_per_thread; static GArray *debug_regions; @@ -277,19 +276,20 @@ static bool qemu_set_log_internal(const char *filename, bool changed_name, daemonized = is_daemonized(); need_to_open_file = log_flags && !per_thread && (!daemonized || filename); - if (logfile && (!need_to_open_file || changed_name)) { - qatomic_rcu_set(&global_file, NULL); - if (logfile != stderr) { + if (logfile) { + fflush(logfile); + if (changed_name && logfile != stderr) { RCUCloseFILE *r = g_new0(RCUCloseFILE, 1); r->fd = logfile; + qatomic_rcu_set(&global_file, NULL); call_rcu(r, rcu_close_file, rcu); + logfile = NULL; } - logfile = NULL; } if (!logfile && need_to_open_file) { if (filename) { - logfile = fopen(filename, log_append ? "a" : "w"); + logfile = fopen(filename, "w"); if (!logfile) { error_setg_errno(errp, errno, "Error opening logfile %s", filename); @@ -308,8 +308,6 @@ static bool qemu_set_log_internal(const char *filename, bool changed_name, logfile = stderr; } - log_append = 1; - qatomic_rcu_set(&global_file, logfile); } return true;