Re: [Libguestfs] [PATCH] Correctly detect the size of a block device over SSH

On Wed, Aug 04, 2010 at 04:14:45PM +0100, Matthew Booth wrote: > When fetching a storage volume over SSH, we were detecting its size with a > simple 'stat -c %s'. While this works fine for files, it won't return the > correct size of a block device. > > This patch uses the output of 'blockdev --getsize64' for block devices, and stat > as before for regular files. > > Fixes RHBZ#620698 > --- > lib/Sys/VirtV2V/Transfer/SSH.pm | 16 +++++++++++++++- > 1 files changed, 15 insertions(+), 1 deletions(-) > > diff --git a/lib/Sys/VirtV2V/Transfer/SSH.pm b/lib/Sys/VirtV2V/Transfer/SSH.pm > index 66ec294..5f54f0e 100644 > --- a/lib/Sys/VirtV2V/Transfer/SSH.pm > +++ b/lib/Sys/VirtV2V/Transfer/SSH.pm > @@ -138,7 +138,21 @@ sub _connect > push(@command, 'ssh'); > push(@command, '-l', $username) if (defined($username)); > push(@command, $host); > - push(@command, "stat -c %s $path; cat $path"); > + > + # Return the size of the remote path on the first line, followed by its > + # contents. > + # The bit arithmetic with the output of stat is a translation into shell > + # of the S_ISBLK macro. If the remote device is a block device, stat > + # will simply return the size of the block device inode. In this case, > + # we use the output of blockdev --getsize64 instead. > + push(@command, > + "dev=$path; ". > + 'if [[ $(((0x$(stat -L -c %f $dev)&0170000)>>12)) == 6 ]]; then '. > + 'blockdev --getsize64 $dev; '. > + 'else '. > + 'stat -L -c %s $dev; '. > + 'fi; '. > + 'cat $dev'); > > # Close the ends of the pipes we don't need > close($stdin_write); Yikes. Not an easier way to ask if a filename is a block device? Like maybe: test -b $dev