On Fri, Sep 09, 2016 at 06:34:40PM +0200, Christoph Hellwig wrote:
> Very similar to the existing dax_fault function, but instead of using
> the get_block callback we rely on the iomap_ops vector from iomap.c.
> That also avoids having to do two calls into the file system for write
> faults.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Just noticed this on a quick initial browse...
> + if (vmf->cow_page) {
> + switch (iomap.type) {
> + case IOMAP_HOLE:
> + case IOMAP_UNWRITTEN:
> + clear_user_highpage(vmf->cow_page, vaddr);
> + break;
> + case IOMAP_MAPPED:
> + error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
> + vmf->cow_page, vaddr);
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + error = -EIO;
> + break;
> + }
> +
> + if (error)
> + goto unlock_entry;
> + if (!radix_tree_exceptional_entry(entry)) {
> + vmf->page = entry;
> + return VM_FAULT_LOCKED;
> + }
> + vmf->entry = entry;
> + return VM_FAULT_DAX_LOCKED;
> + }
> +
> + switch (iomap.type) {
> + case IOMAP_MAPPED:
> + if (iomap.flags & IOMAP_F_NEW) {
> + count_vm_event(PGMAJFAULT);
> + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
> + major = VM_FAULT_MAJOR;
> + }
> + break;
> + case IOMAP_UNWRITTEN:
> + case IOMAP_HOLE:
> + if (!(vmf->flags & FAULT_FLAG_WRITE))
> + return dax_load_hole(mapping, entry, vmf);
> + default:
> + WARN_ON_ONCE(1);
> + error = -EIO;
> + }
THe errors from the above two cases are not acted on. they are
immediately overwritten by:
> +
> + /* Filesystem should not return unwritten buffers to us! */
> + error = dax_insert_mapping(mapping, iomap.bdev, sector, PAGE_SIZE,
> + &entry, vma, vmf);
> +unlock_entry:
> + put_locked_mapping_entry(mapping, vmf->pgoff, entry);
> +out:
> + if (error == -ENOMEM)
> + return VM_FAULT_OOM | major;
> + /* -EBUSY is fine, somebody else faulted on the same PTE */
> + if (error < 0 && error != -EBUSY)
> + return VM_FAULT_SIGBUS | major;
> + return VM_FAULT_NOPAGE | major;
> +}
Is there a missing "if (error) goto out;" check somewhere here?
I'm also wondering if you've looked at supporting the PMD fault case
with iomap?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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