linux-tests/writebigsparse.c

   1 #define _LARGEFILE64_SOURCE
   2 #include<stdio.h>
   3 #include <sys/types.h>
   4 #include <sys/stat.h>
   5 #include <fcntl.h>
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8
   9 int handle;
  10
  11 #define N_WRITES 8000
  12 #define STRIDE   1000
  13
  14 #define BUFFER_N 2000
  15 unsigned  buffer[BUFFER_N];
  16
  17
  18 void set_buffer(int n)
  19 {
  20         int i;
  21         for(i = 0; i < BUFFER_N; i++)
  22                 buffer[i] = i + n;
  23 }
  24
  25 void write_big_sparse_file(int h)
  26 {
  27         int i;
  28         off64_t offset = 0;
  29         off64_t pos;
  30         int n = sizeof(buffer);
  31         int wrote;
  32
  33         for(i = 0; i < 4000; i++) {
  34                 set_buffer(i);
  35                 pos = lseek64(h, offset, SEEK_SET);
  36                 if(pos != offset) {
  37                         printf("mismatched seek pos %lld offset %lld\n",
  38                                 pos, offset);
  39                         exit(1);
  40                 }
  41                 wrote = write(h, buffer, n);
  42
  43                 if(wrote != n) {
  44                         printf("mismatched write wrote %d n %d\n", wrote, n);
  45                         exit(1);
  46                 }
  47
  48                 offset += (STRIDE * sizeof(buffer));
  49         }
  50 }
  51
  52
  53
  54
  55 void verify_big_sparse_file(int h)
  56 {
  57 }
  58
  59 int main(int argc, char *argv[])
  60 {
  61
  62         if(argc < 2) {
  63                 printf("Gimme a file name!\n");
  64                 exit(1);
  65         }
  66
  67         handle = open(argv[1], O_CREAT | O_RDWR | O_TRUNC, S_IREAD | S_IWRITE);
  68
  69         if(handle < 0) {
  70                 perror("opening file");
  71                 exit(1);
  72         }
  73
  74         write_big_sparse_file(handle);
  75         system("sudo echo 3 > /proc/sys/vm/drop_caches");
  76         verify_big_sparse_file(handle);
  77
  78         printf("Job done\n");
  79         return 0;
  80 }