• Paul Mackerras's avatar
    Fix thinko in iov_iter_single_seg_count · ad0eab92
    Paul Mackerras authored
    The branches of the if (i->type & ITER_BVEC) statement in
    iov_iter_single_seg_count() are the wrong way around; if ITER_BVEC is
    clear then we use i->bvec, when we should be using i->iov.  This fixes
    it.
    
    In my case, the symptom that this caused was that a KVM guest doing
    filesystem operations on a virtual disk would result in one of qemu's
    threads on the host going into an infinite loop in
    generic_perform_write().  The loop would hit the copied == 0 case and
    call iov_iter_single_seg_count() to reduce the number of bytes to try
    to process, but because of the error, iov_iter_single_seg_count()
    would just return i->count and the loop made no progress and continued
    forever.
    
    Cc: stable@vger.kernel.org # 3.16+
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    ad0eab92
iov_iter.c 21 KB