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    SubjectRe: [PATCH v2 5/5] dax: handle media errors in dax_do_io
    Date
    On Fri, 2016-04-15 at 12:11 -0400, Jeff Moyer wrote:
    > Vishal Verma <vishal.l.verma@intel.com> writes:
    >
    > >
    > > dax_do_io (called for read() or write() for a dax file system) may
    > > fail
    > > in the presence of bad blocks or media errors. Since we expect that
    > > a
    > > write should clear media errors on nvdimms, make dax_do_io fall
    > > back to
    > > the direct_IO path, which will send down a bio to the driver, which
    > > can
    > > then attempt to clear the error.
    > [snip]
    >
    > >
    > > + if (IS_DAX(inode)) {
    > > + ret = dax_do_io(iocb, inode, iter, offset,
    > > blkdev_get_block,
    > >   NULL, DIO_SKIP_DIO_COUNT);
    > > - return __blockdev_direct_IO(iocb, inode, I_BDEV(inode),
    > > iter, offset,
    > > + if (ret == -EIO && (iov_iter_rw(iter) == WRITE))
    > > + ret_saved = ret;
    > > + else
    > > + return ret;
    > > + }
    > > +
    > > + ret = __blockdev_direct_IO(iocb, inode, I_BDEV(inode),
    > > iter, offset,
    > >       blkdev_get_block, NULL, NULL,
    > >       DIO_SKIP_DIO_COUNT);
    > > + if (ret < 0 && ret_saved)
    > > + return ret_saved;
    > > +
    > Hmm, did you just break async DIO?  I think you did!  :)
    > __blockdev_direct_IO can return -EIOCBQUEUED, and you've now turned
    > that
    > into -EIO.  Really, I don't see a reason to save that first
    > -EIO.  The
    > same applies to all instances in this patch.

    The reason I saved it was if __blockdev_direct_IO fails for some
    reason, we should return the original cause o the error, which was an
    EIO.. i.e. we shouldn't be hiding the EIO if the direct_IO fails with
    something else..
    But, how does _EIOCBQUEUED work? Maybe we need an exception for it? 

    Thanks,
    -Vishal
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