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                         perror("lseek64");
  40                         exit(1);
  41                 }
  42                 wrote = write(h, buffer, n);
  43
  44                 if(wrote != n) {
  45                         printf("mismatched write wrote %d n %d\n", wrote, n);
  46                         exit(1);
  47                 }
  48
  49                 offset += (STRIDE * sizeof(buffer));
  50         }
  51 }
  52
  53
  54
  55
  56 void verify_big_sparse_file(int h)
  57 {
  58 }
  59
  60 int main(int argc, char *argv[])
  61 {
  62
  63         if(argc < 2) {
  64                 printf("Gimme a file name!\n");
  65                 exit(1);
  66         }
  67
  68         handle = open(argv[1], O_CREAT | O_RDWR | O_TRUNC, S_IREAD | S_IWRITE);
  69
  70         if(handle < 0) {
  71                 perror("opening file");
  72                 exit(1);
  73         }
  74
  75         write_big_sparse_file(handle);
  76         system("sudo echo 3 > /proc/sys/vm/drop_caches");
  77         verify_big_sparse_file(handle);
  78
  79         printf("Job done\n");
  80         return 0;
  81 }