Messages in this thread |  | | Date | Sun, 08 Dec 1996 15:53:14 +0100 | From | Gunther Mayer <> | Subject | Bug: loop-mount + sparse files |
| |
Hi,
this is a bugreport for linux-2.1.10 (others not yet tested): "loop mounting of an iso-image on an ext2-filesystem doesn't work for sparse files".
(sparse means a file containing a block full of nullbytes, ext2 has the capabilty to store such blocks without using diskspace.)
DETAILS (How to reproduce) ========================== mkdir looptest dd if=/dev/zero of=looptest/testfile bs=1024 count=100 echo Hi > looptest/hi mkisofs looptest >looptest.iso # this is not yet a sparse file cp looptest.iso looptest-cp.iso # cp knows how to create sparse files! mount -o loop -t iso9660 looptest-cp.iso /mnt strace cp /mnt/testfile /dev/null # this shows EIO on first read() # syslog shows "loop: block 63 not present" and so on. strace cat /mnt/hi # even this produces these errors! # the original file "looptest.iso" works OK; when you copy either image # to a FAT partition it will work OK (DOS doesn't know about sparse files)
DIAGNOSIS ========= linux/drivers/block/loop.c returns an error if it discovers such a "sparse" block (because it can't bmap it).
HELP ==== Either document this behaviour or correct it:-)
Sincerly, Gunther
|  |