* Re: does XFS supports hole punching ?
2008-10-22 21:20 ` Dave Chinner
@ 2008-10-27 11:57 ` Raz
2008-10-27 12:14 ` Dave Chinner
0 siblings, 1 reply; 4+ messages in thread
From: Raz @ 2008-10-27 11:57 UTC (permalink / raw)
To: Raz, linux-xfs; +Cc: Asaf Moses, Ofer Kruzel, yaronp
Dave Hello
I would be grateful if you help me here. man xfsctl was not clear enough.
I have written a small program that compares the behavior of FREESP
and UNRESERVE.
I create a file size 10M, each 1M is filled with aaa.. 2-nd MB filled with bbb
3-rd with ccc and so on. I am trying to punch a hole with the bellow program
and then inspect the file content, size and block map.
1. XFS_IOC_FREESP64 seems to be truncating the file and does not
create a hole.
2. XFS_IOC_UNRESERVE64 creates a hole and leaves the file size
unchanged. as the man
page says.
/d1/holely:
0: [0..14335]: 96..14431 14336 blocks
1: [14336..16383]: hole 2048 blocks
2: [16384..20479]: 16480..20575 4096 blocks
Do a hole blocks count as a the file-system free space ? "df" says it does.
1. prior to running
/dev/md1 374255616 1042116 373213500 1% /d1
2. create 10MB file
/dev/md1 374255616 1052416 373203200 1% /d1
3. create a hole
/dev/md1 374255616 1051332 373204284 1% /d1
1052416-1051332 = 1084k
kernel 2.6.18-8
On Wed, Oct 22, 2008 at 11:20 PM, Dave Chinner <david@fromorbit.com> wrote:
> On Wed, Oct 22, 2008 at 07:40:26PM +0200, Raz wrote:
>> I want to punch a hole in an exiting file.
>
> Yes. Check the man page for xfsctl(3) and read up on
> XFS_IOC_FREESP64.
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
>
#include <iostream>
using namespace std;
#include <xfs/libxfs.h>
#include <ctype.h>
#include <sys/unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <xfs/xfs_bmap.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int sizeB;
string exename;
int hole_offset;
int hole_size;
char* buf;
int xfs_create_file(string & filename){
int j=0;
int fd = open(filename.c_str(),O_RDWR | O_LARGEFILE | O_CREAT, 0666);
if (fd<0) {
perror("open:");
return -1;
}
buf = (char*) malloc(1048576);
for (int i=0;i<sizeB;i+=1048576,j++){
memset(buf,'A'+j,1048576);
if ( write(fd,buf,1048576) < 1048576)
perror("WRITE");
printf("[%d,%d]: %c%c%c ... %c%c%c\n",
i,
i+1048575,
buf[0],
buf[1],
buf[2],
buf[1048573],
buf[1048574],
buf[1048575]);
}
close(fd);
return 0;
}
int xfs_create_hole(string &filename)
{
int ret;
printf("PAUSE prior to set hole size at offset %d size %d\n",
hole_offset,hole_size);
getchar();
int fd = open(filename.c_str(),O_RDWR | O_LARGEFILE , 0666);
if (fd<0) {
perror("OPEN:");
return -1;
}
memset(buf,0,1048576);
lseek(fd,hole_offset,SEEK_SET);
ret = read(fd,buf,hole_size);
if (ret<0) {
perror("read offset :");
}
printf("Prior to hole :first 3 char in offset %d are %c%c%c\n",
hole_offset,
buf[0],
buf[1],
buf[2]);
xfs_flock64_t range;
range.l_len = hole_size;
range.l_start = hole_offset ;
range.l_whence = 0 ;
int CTL = XFS_IOC_FREESP64;
//CTL = XFS_IOC_UNRESVSP64;
if (ioctl(fd,CTL,&range)<0) {
perror("XFS_IOC_FREESP64:");
return -1;
}
close(fd);
fd = open(filename.c_str(),O_RDONLY | O_LARGEFILE, 0666);
if (fd<0) {
perror("OPEN:");
return -1;
}
for (int i=0;i<sizeB;i+=1048576){
memset(buf,0,1048576);
if ( read(fd,buf,1048576) < 1048576)
perror("READ");
printf("[%d,%d]: %c%c%c ... %c%c%c\n",
i,
i+1048575,
buf[0],
buf[1],
buf[2],
buf[1048573],
buf[1048574],
buf[1048575]);
}
close(fd);
}
int main (int argc, char *argv[])
{
exename = string(argv[0]);
if (argc<5) {
printf("%s <filename> <size MB> <hole offset MB> <hole size KB>\n",argv[0]);
return -1;
}
string fname(argv[1]);
sizeB = atoi(argv[2])<<20;
hole_offset = atoi(argv[3])<<20;
hole_size = atoi(argv[4])<<10;
if ( !xfs_create_file(fname) )
return xfs_create_hole(fname);
return(0);
}
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