src/enospc_unlink.c

   1 /*
   2  * Write a file until filesystem full is reached and then unlink it.
   3  * Demonstrates a particular deadlock that Kaz hit in testing.  Run
   4  * several iterations of this in parallel on a near-full filesystem.
   5  */
   6
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <unistd.h>
  13 #include <malloc.h>
  14 #include <sys/mman.h>
  15 #include <sys/stat.h>
  16
  17 int main(int argc, char **argv)
  18 {
  19         int                     fd, sz, done;
  20         void                    *ptr;
  21         size_t                  written;
  22         unsigned int            i, count = 0;
  23         unsigned long long      bytes = 0;
  24
  25         if (argc < 2) {
  26                 fprintf(stderr, "Insufficient arguments\n");
  27                 exit(1);
  28         }
  29         if (argc < 3) {
  30                 count = (unsigned int)atoi(argv[2]);
  31         }
  32
  33         sz = 1024 * 1024;
  34
  35         ptr = memalign(sz, sz);
  36         if (!ptr) {
  37                 perror("memalign");
  38                 exit(1);
  39         }
  40         memset(ptr, 0xffffffff, sz);
  41
  42         for (i = 0; i < count; i++) {
  43                 fd = open(argv[1], O_CREAT|O_WRONLY, 0666);
  44                 if (fd < 0) {
  45                         perror(argv[1]);
  46                         exit(1);
  47                 }
  48
  49                 done = 0;
  50                 while (!done) {
  51                         written = write(fd, ptr, sz);
  52                         if (written == -1) {
  53                                 if (errno == ENOSPC) {
  54                                         close(fd);
  55                                         unlink(argv[1]);
  56                                         printf("Unlinked %s\n", argv[1]);
  57                                         done = 1;
  58                                 }
  59                                 else {
  60                                         printf("Skipped unlink %s (%s)\n",
  61                                                 argv[1], strerror(errno));
  62                                         done = -1;
  63                                 }
  64                         }
  65                         if (written == 0) {
  66                                 printf("Wrote zero bytes?\n");
  67                                 done = -1;
  68                         }
  69                         bytes += written;
  70                 }
  71                 if (done > 0)
  72                         printf("Wrote %llu bytes total.\n", bytes);
  73                 else
  74                         exit(1);
  75         }
  76         printf("Completed %u iterations of unlink/out-of-space test.\n", i);
  77         exit(0);
  78 }