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Bug #40633 disk_free_space returns a bad result on filesystems with negative free space
Submitted: 2007-02-26 00:55 UTC Modified: 2010-10-27 13:30 UTC
Avg. Score:5.0 ± 0.0
Reproduced:2 of 2 (100.0%)
Same Version:0 (0.0%)
Same OS:1 (50.0%)
From: adam-phpbugs at adam dot gs Assigned:
Status: Open Package: Filesystem function related
PHP Version: 5.2.1 OS: FreeBSD
Private report: No CVE-ID: None
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 [2007-02-26 00:55 UTC] adam-phpbugs at adam dot gs
on a filesystem with a negative amount of free space (this 
can happen on at least FreeBSD) disk_free_space returns 
unreasonable results.

-=[/some/path]=- -=[Sun Feb 25]=- -=[19:51:55]=-
[root@cube]# php -r 'print disk_free_space(".")."\n";'
-=[/some/path]=- -=[Sun Feb 25]=- -=[19:51:57]=-
[root@cube]# df -h .
Filesystem    Size    Used   Avail Capacity  Mounted on
/dev/ad7      289G    289G    -23G   109%    /some/path
-=[/some/path]=- -=[Sun Feb 25]=- -=[19:51:58]=-
[root@cube]# df .
Filesystem 1K-blocks      Used     Avail Capacity  Mounted 
/dev/ad7   302732078 302699550 -24186038   109%    /some/

Reproduce code:
php -r 'print disk_free_space(".")."\n";'

Expected result:

Actual result:


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 [2007-02-26 09:33 UTC]
What kind of BSD is that and don't you think that negative free space is a BSD bug?
 [2007-02-26 13:32 UTC] adam-phpbugs at adam dot gs
This was FreeBSD

if you look at the FreeBSD manpage for tunefs(8), this is 
the intended behaviour.

Basically, in FreeBSD (under UFS2 at least) avaliable space 
is calculated as total minus used minus reserved. A small % 
(8 by default) is reserved.

So, this is not really a bug, but actually an intended 
 [2007-02-26 13:33 UTC] adam-phpbugs at adam dot gs
changing OS to FreeBSD
 [2007-02-26 15:44 UTC]
Please provide an SSH account on a machine where I can reproduce it.
 [2007-04-10 20:58 UTC]
Funny thing is that PHP doesn't use any unsigned numbers on the way - it translates it directly from system call int64 to double. I guess version of the system and header file defining struct statvfs would be useful.
 [2007-04-26 23:18 UTC] adam-phpbugs at adam dot gs
For some reason I didn't get any notification of stas's message.

this is FreeBSD 6.2-STABLE
struct statvfs {
        fsblkcnt_t      f_bavail;       /* Number of blocks */
        fsblkcnt_t      f_bfree;
        fsblkcnt_t      f_blocks;
        fsfilcnt_t      f_favail;       /* Number of files (e.g., inodes) */
        fsfilcnt_t      f_ffree;
        fsfilcnt_t      f_files;
        unsigned long   f_bsize;        /* Size of blocks counted above */
        unsigned long   f_flag;
        unsigned long   f_frsize;       /* Size of fragments */
        unsigned long   f_fsid;         /* Not meaningful */
        unsigned long   f_namemax;      /* Same as pathconf(_PC_NAME_MAX) */
};</pre> for cvs/changelog (make sure your looking at 6.2-RELEASE) branch, there may be differences.
 [2009-10-16 04:29 UTC] perryc at gmail dot com
Remarkably on a completely different machine, version of FreeBSD, available disk space, etc I get the same return value from disk_free_space() (albeit with slightly better precision):

  Oct 15 2009 21:21:51 disk_free_space(): 3.7778931862952E+22

The reporter's remarks about negative free space are correct.
 [2010-10-27 13:30 UTC]
-Status: Suspended +Status: Open -Assigned To: tony2001 +Assigned To:
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