Re: [PATCH 054/104] virtiofsd: set maximum RLIMIT_NOFILE limit

[Philippe Mathieu-Daudé]

On 12/12/19 5:38 PM, Dr. David Alan Gilbert (git) wrote:
> From: Stefan Hajnoczi <address@hidden>
>
> virtiofsd can exceed the default open file descriptor limit easily on
> most systems.  Take advantage of the fact that it runs as root to raise
> the limit.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>   tools/virtiofsd/passthrough_ll.c | 32 ++++++++++++++++++++++++++++++++
>   1 file changed, 32 insertions(+)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index ab318a6f36..139bf08f4c 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -52,6 +52,7 @@
>   #include <sys/file.h>
>   #include <sys/mount.h>
>   #include <sys/prctl.h>
> +#include <sys/resource.h>
>   #include <sys/syscall.h>
>   #include <sys/types.h>
>   #include <sys/wait.h>
> @@ -2250,6 +2251,35 @@ static void setup_sandbox(struct lo_data *lo, struct 
> fuse_session *se)
>       setup_seccomp();
>   }
>   
> +/* Raise the maximum number of open file descriptors */
> +static void setup_nofile_rlimit(void)
> +{
> +    const rlim_t max_fds = 1000000;

'static const'?

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> +    struct rlimit rlim;
> +
> +    if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) {
> +        fuse_log(FUSE_LOG_ERR, "getrlimit(RLIMIT_NOFILE): %m\n");
> +        exit(1);
> +    }
> +
> +    if (rlim.rlim_cur >= max_fds) {
> +        return; /* nothing to do */
> +    }
> +
> +    rlim.rlim_cur = max_fds;
> +    rlim.rlim_max = max_fds;
> +
> +    if (setrlimit(RLIMIT_NOFILE, &rlim) < 0) {
> +        /* Ignore SELinux denials */
> +        if (errno == EPERM) {
> +            return;
> +        }
> +
> +        fuse_log(FUSE_LOG_ERR, "setrlimit(RLIMIT_NOFILE): %m\n");
> +        exit(1);
> +    }
> +}
> +
>   int main(int argc, char *argv[])
>   {
>       struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
> @@ -2371,6 +2401,8 @@ int main(int argc, char *argv[])
>   
>       fuse_daemonize(opts.foreground);
>   
> +    setup_nofile_rlimit();
> +
>       /* Must be before sandbox since it wants /proc */
>       setup_capng();
>