Implement shm_attach_to_open_removed() for OpenBSD

Add implementation which had been left by
0cfe2089 (Add runtime handlers for 97900ebf for FreeBSD/DragonFlyBSD).

This implementation is based on what
97900ebf (shm: have os remove shared memory if fio dies unexpectedly)
says. There seems to be no easy way to statically test versions like
KERNEL_VERSION() in Linux kernel.

The code assumes major/minor are both < 10. The minor has never been
10 or above. The major won't be 10 anytime soon based on the past
release cycle (current version is 6.1 after more than 2 decades).
https://en.wikipedia.org/wiki/OpenBSD_version_history

--
 # uname
 OpenBSD
 # uname -r
 6.1
 # cat ./test1.c
 #include <stdio.h>
 #include "./os/os.h"
 #include "./os/os-openbsd.h"
 int main(void) {
         printf("%d\n", shm_attach_to_open_removed());
         return 0;
 }
 # gcc -Wall -g ./test1.c
 # ./a.out
 1

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/os/os-openbsd.h b/os/os-openbsd.h
index 9c7092c8ef4908a682323b4065d18445430bc076..670892b44e2bc93dac3de3e4357cbcf0966d6087 100644 (file)
--- a/os/os-openbsd.h
+++ b/os/os-openbsd.h
@@ -9,6 +9,7 @@
 #include <sys/ioctl.h>
 #include <sys/dkio.h>
 #include <sys/disklabel.h>
+#include <sys/utsname.h>
 /* XXX hack to avoid conflicts between rbtree.h and <sys/tree.h> */
 #include <sys/sysctl.h>
 #undef RB_BLACK
@@ -90,9 +91,31 @@ static inline unsigned long long get_fs_free_size(const char *path)
 
 static inline int shm_attach_to_open_removed(void)
 {
+       struct utsname uts;
+       int major, minor;
+
+       if (uname(&uts) == -1)
+               return 0;
+
        /*
-        * XXX: Return 1 if >= OpenBSD 5.1 according to 97900ebf.
+        * Return 1 if >= OpenBSD 5.1 according to 97900ebf,
+        * assuming both major/minor versions are < 10.
         */
+       if (uts.release[0] > '9' || uts.release[0] < '0')
+               return 0;
+       if (uts.release[1] != '.')
+               return 0;
+       if (uts.release[2] > '9' || uts.release[2] < '0')
+               return 0;
+
+       major = uts.release[0] - '0';
+       minor = uts.release[2] - '0';
+
+       if (major > 5)
+               return 1;
+       if (major == 5 && minor >= 1)
+               return 1;
+
        return 0;
 }