Hello.
I found that running a sample program shown below on xfs filesystem
results in consuming extra disk space until close() is called.
Is this expected result?
I don't care if temporarily consumed extra disk space is trivial. But since
this amount as of returning from fsync() is as much as amount of written data,
I worry that there might be some bug.
---------- my_write_unlink.c ----------
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
static char buffer[1048576];
const char *filename = "my_testfile";
const int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
int i;
if (fd == EOF)
return 1;
printf("Before write().\n");
system("/bin/df -m .");
for (i = 0; i < 1024; i++)
if (write(fd, buffer, sizeof(buffer)) != sizeof(buffer))
return 1;
if (fsync(fd))
return 1;
printf("Before close().\n");
system("/bin/df -m .");
if (close(fd))
return 1;
printf("Before unlink().\n");
system("/bin/df -m .");
if (unlink(filename))
return 1;
printf("After unlink().\n");
system("/bin/df -m .");
return 0;
}
---------- my_write_unlink.c ----------
----------
$ uname -r
5.17.0
$ ./my_write_unlink
Before write().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 255875 130392 125483 51% /
Before close().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 255875 132443 123432 52% /
Before unlink().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 255875 131416 124459 52% /
After unlink().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 255875 130392 125483 51% /
$ grep sda /proc/mounts
/dev/sda1 / xfs rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
----------
----------
$ uname -r
4.18.0-365.el8.x86_64
$ ./my_write_unlink
Before write().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 2743 17727 14% /
Before close().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 4791 15679 24% /
Before unlink().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 3767 16703 19% /
After unlink().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 2743 17727 14% /
$ grep sda /proc/mounts
/dev/sda1 / xfs rw,seclabel,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
----------
----------
$ uname -r
3.10.0-1160.59.1.el7.x86_64
$ ./my_write_unlink
Before write().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 2310 18160 12% /
Before close().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 4358 16112 22% /
Before unlink().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 3334 17136 17% /
After unlink().
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda1 20469 2310 18160 12% /
$ grep sda /proc/mounts
/dev/sda1 / xfs rw,seclabel,relatime,attr2,inode64,noquota 0 0
----------
