On Mon 17-03-14 10:21:18, Jan Kara wrote:
> On Fri 14-03-14 11:33:31, John Stultz wrote:
> > + for (;;) {
> > + unsigned long new_flags;
> > + pgoff_t pgoff;
> > + unsigned long tmp;
> > +
> > + if (!vma)
> > + goto out;
> > +
> > + if (vma->vm_flags & (VM_SPECIAL|VM_LOCKED|VM_MIXEDMAP|
> > + VM_HUGETLB))
> > + goto out;
> > +
> > + /* We don't support volatility on files for now */
> > + if (vma->vm_file) {
> > + ret = -EINVAL;
> > + goto out;
> > + }
> > +
> > + new_flags = vma->vm_flags;
> > +
> > + if (start < vma->vm_start) {
> > + start = vma->vm_start;
> > + if (start >= end)
> > + goto out;
> > + }
One more question: This seems to silently skip any holes between VMAs. Is
that really intended? I'd expect that marking unmapped range as volatile /
non-volatile should return error... In any case what happens should be
defined in the description.
Honza
> > + tmp = vma->vm_end;
> > + if (end < tmp)
> > + tmp = end;
> > +
> > + switch (mode) {
> > + case VRANGE_VOLATILE:
> > + new_flags |= VM_VOLATILE;
> > + break;
> > + case VRANGE_NONVOLATILE:
> > + new_flags &= ~VM_VOLATILE;
> > + }
> > +
> > + pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
> > + prev = vma_merge(mm, prev, start, tmp, new_flags,
> > + vma->anon_vma, vma->vm_file, pgoff,
> > + vma_policy(vma));
> > + if (prev)
> > + goto success;
> > +
> > + if (start != vma->vm_start) {
> > + ret = split_vma(mm, vma, start, 1);
> > + if (ret)
> > + goto out;
> > + }
> > +
> > + if (tmp != vma->vm_end) {
> > + ret = split_vma(mm, vma, tmp, 0);
> > + if (ret)
> > + goto out;
> > + }
> > +
> > + prev = vma;
> > +success:
> > + vma->vm_flags = new_flags;
> > + *purged = lpurged;
> > +
> > + /* update count to distance covered so far*/
> > + count = tmp - orig_start;
> > +
> > + if (prev && start < prev->vm_end)
> In which case 'prev' can be NULL? And when start >= prev->vm_end? In all
> the cases I can come up with this condition seems to be true...
>
> > + start = prev->vm_end;
> > + if (start >= end)
> > + goto out;
> > + if (prev)
> Ditto regarding 'prev'...
>
> > + vma = prev->vm_next;
> > + else /* madvise_remove dropped mmap_sem */
> > + vma = find_vma(mm, start);
> The comment regarding madvise_remove() looks bogus...
>
> > + }
> > +out:
> > + up_read(&mm->mmap_sem);
> > +
> > + /* report bytes successfully marked, even if we're exiting on error */
> > + if (count)
> > + return count;
> > +
> > + return ret;
> > +}
> > +
> > +SYSCALL_DEFINE4(vrange, unsigned long, start,
> > + size_t, len, int, mode, int __user *, purged)
> > +{
> > + unsigned long end;
> > + struct mm_struct *mm = current->mm;
> > + ssize_t ret = -EINVAL;
> > + int p = 0;
> > +
> > + if (start & ~PAGE_MASK)
> > + goto out;
> > +
> > + len &= PAGE_MASK;
> > + if (!len)
> > + goto out;
> > +
> > + end = start + len;
> > + if (end < start)
> > + goto out;
> > +
> > + if (start >= TASK_SIZE)
> > + goto out;
> > +
> > + if (purged) {
> > + /* Test pointer is valid before making any changes */
> > + if (put_user(p, purged))
> > + return -EFAULT;
> > + }
> > +
> > + ret = do_vrange(mm, start, end, mode, &p);
> > +
> > + if (purged) {
> > + if (put_user(p, purged)) {
> > + /*
> > + * This would be bad, since we've modified volatilty
> > + * and the change in purged state would be lost.
> > + */
> > + WARN_ONCE(1, "vrange: purge state possibly lost\n");
> > + }
> > + }
> > +
> > +out:
> > + return ret;
> > +}
> Honza
> --
> Jan Kara <j...@suse.cz>
> SUSE Labs, CR
--
Jan Kara <j...@suse.cz>
SUSE Labs, CR
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