[Virtio-fs] [PATCH] virtiofsd: add support to change log level on fly
Eryu Guan
eguan at linux.alibaba.com
Wed Aug 21 08:56:59 UTC 2019
Introduce a file which contains the target log level, and
current_log_level will be reloaded to the target log level on SIGHUP.
The file is set to "/run/virtiofsd/log_level.<pid>". Due to
sandboxing in virtiofsd, this file can only be read/write via
/proc/<pid>/fd/<fd> for now.
Example usage:
# view current log level
cat /proc/<pid>/fd/<fd>
# change log level to debug
echo debug > /proc/<pid>/fd/<fd>
kill -HUP <pid>
Signed-off-by: Eryu Guan <eguan at linux.alibaba.com>
---
contrib/virtiofsd/fuse_log.c | 144 +++++++++++++++++++++++++++++++++++++
contrib/virtiofsd/fuse_log.h | 4 ++
contrib/virtiofsd/fuse_signals.c | 4 +-
contrib/virtiofsd/passthrough_ll.c | 4 ++
4 files changed, 154 insertions(+), 2 deletions(-)
diff --git a/contrib/virtiofsd/fuse_log.c b/contrib/virtiofsd/fuse_log.c
index d54b64099a2b..adfcbb84bfb3 100644
--- a/contrib/virtiofsd/fuse_log.c
+++ b/contrib/virtiofsd/fuse_log.c
@@ -6,12 +6,24 @@
* See the COPYING.LIB file in the top-level directory.
*/
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
#include "fuse_log.h"
+#define FUSE_DYN_LOG_BASE "/run/virtiofsd"
+
static bool use_syslog;
+static char *dyn_log_file = NULL;
+static int dyn_log_fd = -1;
int current_log_level = LOG_INFO;
void fuse_log_enable_syslog(void)
@@ -71,3 +83,135 @@ void fuse_debug(const char *fmt, ...)
fuse_vlog(LOG_DEBUG, fmt, ap);
va_end(ap);
}
+
+static const char *fuse_log_level_str(int level)
+{
+ switch (level) {
+ case LOG_DEBUG:
+ return "debug";
+ case LOG_INFO:
+ return "info";
+ case LOG_WARNING:
+ return "warn";
+ case LOG_ERR:
+ return "err";
+ default:
+ return NULL;
+ }
+}
+
+void fuse_dyn_log_init(void)
+{
+ struct stat stbuf;
+ char buf[PATH_MAX];
+ const char *p;
+
+ /* Prepare FUSE_DYN_LOG_BASE */
+ if (mkdir(FUSE_DYN_LOG_BASE, 0755) == -1) {
+ if (errno != EEXIST) {
+ fuse_warning("Fail to mkdir(%s): %s\n", FUSE_DYN_LOG_BASE,
+ strerror(errno));
+ goto err;
+ }
+ }
+ if (stat(FUSE_DYN_LOG_BASE, &stbuf) == -1) {
+ fuse_warning("Fail to stat(%s): %s\n", FUSE_DYN_LOG_BASE,
+ strerror(errno));
+ goto err;
+ }
+ if (!S_ISDIR(stbuf.st_mode)) {
+ fuse_warning("%s is not a directory\n", FUSE_DYN_LOG_BASE);
+ goto err;
+ }
+ if (!(stbuf.st_mode & S_IRUSR) || !(stbuf.st_mode & S_IWUSR)) {
+ fuse_warning("Require rw permission on %s\n", FUSE_DYN_LOG_BASE);
+ goto err;
+ }
+
+ /* Prepare log level file */
+ snprintf(buf, sizeof(buf), FUSE_DYN_LOG_BASE "/log_level.%d",
+ getpid());
+ dyn_log_file = strdup(buf);
+ if (dyn_log_file == NULL) {
+ fuse_warning("Fail to duplicate str %s: %s\n", buf, strerror(errno));
+ goto err;
+ }
+ dyn_log_fd = open(dyn_log_file, O_CREAT | O_TRUNC | O_RDWR, 0644);
+ if (dyn_log_fd == -1) {
+ fuse_warning("Fail to open %s: %s\n", dyn_log_file, strerror(errno));
+ goto err;
+ }
+ /*
+ * TODO: Due to sandboxing, unlink won't work in
+ * fuse_dyn_log_fin(), we have to unlink log file here and access
+ * it via /proc/<pid>/fd/<fd>
+ */
+ if (unlink(dyn_log_file) == -1)
+ fuse_warning("Fail to unlink %s: %s\n", dyn_log_file, strerror(errno));
+
+ p = fuse_log_level_str(current_log_level);
+ if (p == NULL) {
+ fuse_warning("Unknown initial log level %d\n", current_log_level);
+ goto err;
+ }
+ if (write(dyn_log_fd, p, strlen(p)) == -1) {
+ fuse_warning("Fail to write (\"%s\") to %s: %s\n", p, dyn_log_file,
+ strerror(errno));
+ }
+
+ fuse_info("Dynamic log level adjustment is enabled, entry file %s\n",
+ dyn_log_file);
+ return;
+err:
+ fuse_warning("Dynamic log level adjustment is disabled\n");
+ return;
+}
+
+void fuse_dyn_log_fin(void)
+{
+ if (dyn_log_fd != -1) {
+ close(dyn_log_fd);
+ dyn_log_fd = -1;
+ }
+ if (dyn_log_file) {
+ free(dyn_log_file);
+ dyn_log_file = NULL;
+ }
+ return;
+}
+
+void fuse_log_handler(int sig)
+{
+ char buf[16] = { 0 };
+
+ /* FIXME: pread() causes read to hang, use lseek & read here */
+ if (lseek(dyn_log_fd, 0, SEEK_SET) == -1) {
+ fuse_warning("Fail to seek %s: %s\n", dyn_log_file, strerror(errno));
+ goto err;
+ }
+ if (read(dyn_log_fd, buf, 16) == -1 ) {
+ fuse_warning("Fail to read %s: %s\n", dyn_log_file, strerror(errno));
+ goto err;
+ }
+ buf[15] = '\0';
+ buf[strcspn(buf, "\n")] = '\0';
+
+ if (!strncmp(buf, "debug", 5)) {
+ current_log_level = LOG_DEBUG;
+ } else if (!strncmp(buf, "info", 4)) {
+ current_log_level = LOG_INFO;
+ } else if (!strncmp(buf, "warn", 4)) {
+ current_log_level = LOG_WARNING;
+ } else if (!strncmp(buf, "err", 3)) {
+ current_log_level = LOG_ERR;
+ } else {
+ fuse_warning("Unknown log level \"%s\"\n", buf);
+ goto err;
+ }
+
+ fuse_info("Changed current log level to %s(%d)\n", buf, current_log_level);
+ return;
+err:
+ fuse_warning("Reload log level failed\n");
+ return;
+}
diff --git a/contrib/virtiofsd/fuse_log.h b/contrib/virtiofsd/fuse_log.h
index c4dfc921b6d8..532a6d66e296 100644
--- a/contrib/virtiofsd/fuse_log.h
+++ b/contrib/virtiofsd/fuse_log.h
@@ -21,4 +21,8 @@ void fuse_warning(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
void fuse_info(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
void fuse_debug(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
+void fuse_dyn_log_init(void);
+void fuse_dyn_log_fin(void);
+void fuse_log_handler(int sig);
+
#endif /* FUSE_LOG_H */
diff --git a/contrib/virtiofsd/fuse_signals.c b/contrib/virtiofsd/fuse_signals.c
index 9d34f6b04025..862ba1852eff 100644
--- a/contrib/virtiofsd/fuse_signals.c
+++ b/contrib/virtiofsd/fuse_signals.c
@@ -69,7 +69,7 @@ int fuse_set_signal_handlers(struct fuse_session *se)
thus should reset to SIG_DFL in fuse_remove_signal_handlers)
or if it was already set to SIG_IGN (and should be left
untouched. */
- if (set_one_signal_handler(SIGHUP, exit_handler, 0) == -1 ||
+ if (set_one_signal_handler(SIGHUP, fuse_log_handler, 0) == -1 ||
set_one_signal_handler(SIGINT, exit_handler, 0) == -1 ||
set_one_signal_handler(SIGTERM, exit_handler, 0) == -1 ||
set_one_signal_handler(SIGPIPE, do_nothing, 0) == -1)
@@ -86,7 +86,7 @@ void fuse_remove_signal_handlers(struct fuse_session *se)
else
fuse_instance = NULL;
- set_one_signal_handler(SIGHUP, exit_handler, 1);
+ set_one_signal_handler(SIGHUP, fuse_log_handler, 1);
set_one_signal_handler(SIGINT, exit_handler, 1);
set_one_signal_handler(SIGTERM, exit_handler, 1);
set_one_signal_handler(SIGPIPE, do_nothing, 1);
diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
index ca11764feb88..5f32227a0712 100644
--- a/contrib/virtiofsd/passthrough_ll.c
+++ b/contrib/virtiofsd/passthrough_ll.c
@@ -2987,6 +2987,9 @@ int main(int argc, char *argv[])
get_shared(&lo, &lo.root);
}
+ /* Initialize dynamic log level infra, after SIGHUP handler is set. */
+ fuse_dyn_log_init();
+
/* Must be after daemonize to get the right /proc/self/fd */
setup_proc_self_fd(&lo);
@@ -2997,6 +3000,7 @@ int main(int argc, char *argv[])
/* Block until ctrl+c or fusermount -u */
ret = virtio_loop(se);
+ fuse_dyn_log_fin();
err_out4:
fuse_session_unmount(se);
err_out3:
--
2.14.4.44.g2045bb6
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