On Fri, May 05, 2017 at 06:52:45PM +0200, David Sterba wrote:
> On Thu, Apr 13, 2017 at 06:11:56PM -0700, Liu Bo wrote:
> > With raid1 profile, dio read isn't tolerating IO errors if read length is
> > less than the stripe length (64K).
>
> Can you please write more details why this is true? Some pointers to
> code etc, I'm lost. Eg. where the errors is tolerated. Thanks.
Sure.
Our bio didn't get split in btrfs_submit_direct_hook() if (dip->flags &
BTRFS_DIO_ORIG_BIO_SUBMITTED) is true. If the underlying device returns error
somehow, bio->bi_error has recorded that error.
If we could recover the correct data from another copy in profile raid1/10/5/6,
with btrfs_subio_endio_read() returning 0, bio would have the correct data in
its vector, but bio->bi_error is not updated accordingly so that the following
dio_end_io(dio_bio, bio->bi_error) makes directIO think this read has failed.
Thanks,
-liubo
>
> > This fixes the problem by setting bio's error to 0 if a good copy has been
> > found.
> >
> > Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> > ---
> > fs/btrfs/inode.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index 632b616..4e1398e 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -8113,8 +8113,11 @@ static void btrfs_endio_direct_read(struct bio *bio)
> > struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
> > int err = bio->bi_error;
> >
> > - if (dip->flags & BTRFS_DIO_ORIG_BIO_SUBMITTED)
> > + if (dip->flags & BTRFS_DIO_ORIG_BIO_SUBMITTED) {
> > err = btrfs_subio_endio_read(inode, io_bio, err);
> > + if (!err)
> > + bio->bi_error = 0;
> > + }
> >
> > unlock_extent(&BTRFS_I(inode)->io_tree, dip->logical_offset,
> > dip->logical_offset + dip->bytes - 1);
> > --
> > 2.5.5
> >
> > --
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