Re: 4.8.2: device/sysdep_LINUX.c

[Martin Pala]

Hi,

the blocks size is computed according to statvfs structure description 
(see 'man statvfs'):

--8<--
         struct statvfs {
           unsigned long  f_bsize;    /* file system block size */
           unsigned long  f_frsize;   /* fragment size */
           fsblkcnt_t     f_blocks;   /* size of fs in f_frsize units */
           fsblkcnt_t     f_bfree;    /* # free blocks */
           fsblkcnt_t     f_bavail;   /* # free blocks for non-root */
           fsfilcnt_t     f_files;    /* # inodes */
           fsfilcnt_t     f_ffree;    /* # free inodes */
           fsfilcnt_t     f_favail;   /* # free inodes for non-root */
           unsigned long  f_fsid;     /* file system ID */
           unsigned long  f_flag;     /* mount flags */
           unsigned long  f_namemax;  /* maximum filename length */
         };
--8<--

f_blocks has to be recomputed this way since it describes the number of 
fragments, not blocks (the f_bsize and f_frsize match on all linuxes 
which i ever saw even with different block sizes).

Martin


Aaron Scamehorn wrote:
> Hello,
>
> In device_usage_sysdep:
>
> I'm not quite sure what the following is supposed to be calculating:
>
> inf->f_blocks=          usage.f_blocks * usage.f_frsize / usage.f_bsize;
>
>
> I think you're incorrectly mixing block size & fragment sizes.  I don't
> think they have anything to do with each other.
>
> You're probably just getting lucky, because your f_frsize & f_bsize both
> = 4K.
>
> However, on large filesystems, where f_bsize might be 32K, you'll get
> crazy usage numbers.
>
> I think you just want:
>
> inf->f_blocks=          usage.f_blocks ;
>
>
> Thanks,
> Aaron 
>
>
> 25        if(statvfs( dir, &usage) != 0) {
> (gdb) n
> (gdb) print usage
> $1 = {f_bsize = 32768, f_frsize = 4096, f_blocks = 8811322, f_bfree =
> 8053030, f_bavail = 7605440,
>   f_files = 35815424, f_ffree = 35800806, f_favail = 35800806, f_fsid =
> 0, __f_unused = 0, f_flag = 0,
>     f_namemax = 255, __f_spare = {0, 0, 0, 0, 0, 0}}
>
>
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