utils:ping_pong: add a -c switch to check the lock before reading/writing

This is to verify that the fcntl F_GETLK call reports F_UNLCK if called
from a process already holding a lock. This is for example used by samba's
strict locking code in combination with "posix locking = true".

Signed-off-by: Michael Adam <obnox@samba.org>
(This used to be ctdb commit 4f42d17b74ce891691eee1cead498959cc8e4837)

diff --git a/ctdb/utils/ping_pong/ping_pong.c b/ctdb/utils/ping_pong/ping_pong.c
index 098dacd9c72b87f2ce3ba3950e57ae9436d06d30..0a49d6605bc56b424867aefca3960d1f37e5f5b5 100644 (file)
--- a/ctdb/utils/ping_pong/ping_pong.c
+++ b/ctdb/utils/ping_pong/ping_pong.c
@@ -2,6 +2,7 @@
    A ping-pong fcntl byte range lock test
 
    Copyright (C) Andrew Tridgell 2002
+   Copyright (C) Michael Adam 2012
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -41,7 +42,7 @@
 
 static struct timeval tp1,tp2;
 
-static int do_reads, do_writes, use_mmap;
+static int do_reads, do_writes, use_mmap, do_check;
 
 static void start_timer(void)
 {
@@ -69,6 +70,36 @@ static int lock_range(int fd, int offset, int len)
        return fcntl(fd,F_SETLKW,&lock);
 }
 
+/* check whether we could place a lock */
+int check_lock(int fd, int offset, int len)
+{
+       struct flock lock;
+       int ret;
+
+       lock.l_type = F_WRLCK;
+       lock.l_whence = SEEK_SET;
+       lock.l_start = offset;
+       lock.l_len = len;
+       lock.l_pid = 0;
+
+       ret = fcntl(fd, F_GETLK, &lock);
+       if (ret != 0) {
+               printf("error calling fcntl F_GETLCK: %s\n", strerror(errno));
+               return -1;
+       }
+
+       if (lock.l_type == F_UNLCK) {
+               /* we would be able to place the lock */
+               return 0;
+       }
+
+       /* we would not be able to place lock */
+       printf("check_lock failed: lock held: "
+              "pid='%d', type='%d', start='%d', len='%d'\n",
+              (int)lock.l_pid, (int)lock.l_type, (int)lock.l_start, (int)lock.l_len);
+       return 1;
+}
+
 /* unlock a byte range in a open file */
 static int unlock_range(int fd, int offset, int len)
 {
@@ -123,6 +154,9 @@ static void ping_pong(int fd, int num_locks)
                        printf("lock at %d failed! - %s\n",
                               (i+1) % num_locks, strerror(errno));
                }
+               if (do_check) {
+                       ret = check_lock(fd, i, 1);
+               }
                if (do_reads) {
                        unsigned char c;
                        if (use_mmap) {
@@ -169,7 +203,7 @@ int main(int argc, char *argv[])
        int fd, num_locks;
        int c;
 
-       while ((c = getopt(argc, argv, "rwm")) != -1) {
+       while ((c = getopt(argc, argv, "rwmc")) != -1) {
                switch (c){
                case 'w':
                        do_writes = 1;
@@ -180,6 +214,9 @@ int main(int argc, char *argv[])
                case 'm':
                        use_mmap = 1;
                        break;
+               case 'c':
+                       do_check = 1;
+                       break;
                default:
                        fprintf(stderr, "Unknown option '%c'\n", c);
                        exit(1);
@@ -194,6 +231,7 @@ int main(int argc, char *argv[])
                printf("           -r    do reads\n");
                printf("           -w    do writes\n");
                printf("           -m    use mmap\n");
+               printf("           -c    check locks\n");
                exit(1);
        }