[PATCH 22/25] virtiofsd: set maximum RLIMIT_NOFILE limit

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: Stefan Hajnoczi <stefanha@redhat.com>

virtiofsd can exceed the default open file descriptor limit easily on
most systems.  Take advantage of the fact that it runs as root to set up
the maximum open file descriptor limit allowed on the system (the
nr_open sysctl).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 contrib/virtiofsd/passthrough_ll.c | 34 ++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
index fe46b25fb6..25f7ad854a 100644
--- a/contrib/virtiofsd/passthrough_ll.c
+++ b/contrib/virtiofsd/passthrough_ll.c
@@ -53,9 +53,11 @@
 #include <sys/xattr.h>
 #include <sys/capability.h>
 #include <sys/mount.h>
+#include <sys/resource.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
+#include <glib.h>
 #include "passthrough_helpers.h"
 #include "seccomp.h"
 
@@ -2110,6 +2112,36 @@ static void setup_sandbox(struct lo_data *lo)
 	setup_seccomp();
 }
 
+/* Raise the maximum number of open file descriptors to the system limit */
+static void setup_nofile_rlimit(void)
+{
+	gchar *nr_open = NULL;
+	struct rlimit rlim;
+	long long max;
+
+	if (!g_file_get_contents("/proc/sys/fs/nr_open", &nr_open, NULL, NULL)) {
+		fuse_log(FUSE_LOG_ERR, "unable to read /proc/sys/fs/nr_open\n");
+		exit(1);
+	}
+
+	errno = 0;
+	max = strtoll(nr_open, NULL, 0);
+	if (errno) {
+		fuse_log(FUSE_LOG_ERR, "strtoll(%s): %m\n", nr_open);
+		exit(1);
+	}
+
+	rlim.rlim_cur = max;
+	rlim.rlim_max = max;
+
+	if (setrlimit(RLIMIT_NOFILE, &rlim) < 0) {
+		fuse_log(FUSE_LOG_ERR, "setrlimit(RLIMIT_NOFILE): %m\n");
+		exit(1);
+	}
+
+	g_free(nr_open);
+}
+
 int main(int argc, char *argv[])
 {
 	struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
@@ -2125,6 +2157,8 @@ int main(int argc, char *argv[])
 	/* Don't mask creation mode, kernel already did that */
 	umask(0);
 
+	setup_nofile_rlimit();
+
 	pthread_mutex_init(&lo.mutex, NULL);
 	lo.root.next = lo.root.prev = &lo.root;
 	lo.root.fd = -1;
-- 
2.23.0