bug#6331: [sshfs] df reports wrong disk space usage on solaris

[Miklos Szeredi]

On Thu, 03 Jun 2010, Jim Meyering wrote:
> Miklos Szeredi wrote:
> ...
> > Notice that the real statfs syscall does have an f_frsize field, but
> > for some historical reason it is not exported in the library API.
> >
> > Options to fix this behavior would be:
> >
> >  1) fix df and stat in coreutils to use statvfs
> >  2) make sshfs set f_bsize to f_frsize
> >  3) make sshfs set f_frsize to f_bsize and recalculate stats
> >  4) change both f_frsize and f_bsize to a common value and
> >     recalculate stats (this is what NFS appears to be doing)
> >
> > There is some difficulty with 1) as the libc implementation of statvfs
> > has problems:
> >
> >  "Do not use statvfs on systems with GNU libc on Linux, because that 
> > function
> >   stats all preceding entries in /proc/mounts, and that makes df hang if 
> > even
> >   one of the corresponding file systems is hard-mounted, but not available.
> >   statvfs in GNU libc on Hurd, BeOS, Haiku operates differently: it only 
> > makes
> >   a system call."
> >
> > This might have been fixed in libc since, so it's possible that
> > coreutils developers are willing to using statvfs on linux.
> 
> glibc's statvfs still appears to have this problem, so coreutils' df
> must not use that function.  To demonstrate, I recompiled fsusage.c
> with -DSTAT_STATVFS, relinked df, and ran this:
> 
>     $ strace -e open,stat ./df .
>     ...
>     open("/proc/mounts", O_RDONLY)          = 3
>     stat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
>     stat(".", {st_mode=S_IFDIR|0755, st_size=65536, ...}) = 0
>     stat("/", {st_mode=S_IFDIR|0555, st_size=4096, ...}) = 0
>     stat("/boot", {st_mode=S_IFDIR|0555, st_size=3072, ...}) = 0
>     stat("/full", {st_mode=S_IFDIR|0755, st_size=1024, ...}) = 0
>     stat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
> 
> It still opens /proc/mounts and stats mount point directories
> until it finds one with a matching dev/inode.  Note that it
> does limit its search, when possible, to file systems that are known
> to be of the same file system type, but that doesn't help when
> the target is NFS mounted.
> 

Hmm, actually "struct statfs" on linux does have f_frsize, only the
manpage doesn't document it.  So correct thing would be to use that,
no?

Thanks,
Miklos