as requested. like this?
---begin
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <linux/falloc.h>
#include <unistd.h>
#define BLOCKSIZE 4096
int main(int argc, char** argv) {
ssize_t rsize;
int fh, result;
char buff[BLOCKSIZE], ebuff[BLOCKSIZE];
off_t curpos, pstart, psize;
int freed;
if (argc < 2) {
printf("%s [file...]\n", argv[0]);
return 0;
}
memset(ebuff, 0, BLOCKSIZE); // prepare a block of 0's
for (int i = 1; i < argc; i++) {
char* file=argv[i];
curpos = 0;
pstart = 0;
psize = 0;
freed = 0;
fh = open(file, O_RDWR, O_NOATIME);
if (fh == -1) {
perror("open()");
return -1;
}
printf("sparseifying %s ", file);
fflush(stdout);
while ((rsize = read(fh, buff, BLOCKSIZE)) > 0) {
result = memcmp(buff, ebuff,rsize);
if (result == 0) { // block is empty
if (pstart == 0) { // previous block as not empty?
pstart = curpos;
psize = rsize; // save for later punching
} else {
psize += rsize; // previous block was empty too, add size
}
freed += rsize;
} else if (pstart) { // block is not empty and we have a block that we still need to punch
result = fallocate(fh, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, pstart, psize);
if (result == -1) {
perror("fallocate()");
return -1;
}
pstart = 0;
psize = 0;
}
curpos += rsize;
}
if (pstart) { // still a block to do ?
result = fallocate(fh, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, pstart, psize);
if (result == -1) {
perror("fallocate()");
return -1;
}
}
if (rsize == 0) {
printf("done. freed %i bytes\n", freed);
continue;
}
if (rsize == -1) {
perror("read()");
return -1;
}
}
return -1;
}
---end
Remco Hosman
On Nov 18, 2012, at 10:19 PM, Hugo Mills <hugo@xxxxxxxxxxxxx> wrote:
> On Sun, Nov 18, 2012 at 10:04:29PM +0100, Remco Hosman - Yerf IT wrote:
>> I wrote a little tool you can use to scan a file and punch holes, so make it sparse.
>>
>> Confirmed to work on 3.7.0-rc6
>> Feel free to use it in any way you like, and of course improve it.
>>
>> http://pastebin.com/8SjEsBLD
>
> For archival purposes, it's probably better to put the whole thing
> inline in the text of your mail. This also makes it far easier to make
> comments on it, should anyone feel moved to do so.
>
> Hugo.
>
> --
> === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
> PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
> --- In theory, theory and practice are the same. In ---
> practice, they're different.
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