On Thu, Oct 06, 2016 at 05:39:24PM +1100, NeilBrown wrote:
> On Thu, Aug 04 2016, NeilBrown wrote:
>
> >
> >
> > When nfsd calls fh_to_dentry, it expect ESTALE or ENOMEM as errors.
> > In particular it can be tempting to return ENOENT, but this is not
> > handled well by nfsd.
> >
> > Rather than requiring strict adherence to error code code filesystems,
> > treat all unexpected error codes the same as ESTALE. This is safest.
> >
> > Signed-off-by: NeilBrown <ne...@suse.com>
> > ---
> >
> > I didn't add a dprintk for unexpected error messages, partly
> > because dprintk isn't usable in exportfs. I could have used pr_debug()
> > but I really didn't see much value.
> >
> > This has been tested together with the btrfs change, and it restores
> > correct functionality.
> >
> > Thanks,
> > NeilBrown
>
>
> Hi Bruce,
> I notice that this patch isn't in -next, but the btrfs change which
> motivated it is.
> That means, unless there is some other work around somewhere, btrfs
> might start having problems with nfs export.
Whoops, I wonder what happened. Looking back.... Oh, I think I set it
aside pending a response from Christoph, but I don't think that's really
necessary.
> Can we get this patch into 4.9-rc??
>
> Or has someone fixed it a different way?
No, I'll just apply.
I need to send a pull request soon, I just have to make up my mind on
COPY first.
--b.
> Thanks,
> NeilBrown
>
>
> >
> > fs/exportfs/expfs.c | 10 ++++++----
> > include/linux/exportfs.h | 13 +++++++------
> > 2 files changed, 13 insertions(+), 10 deletions(-)
> >
> > diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> > index 207ba8d627ca..a4b531be9168 100644
> > --- a/fs/exportfs/expfs.c
> > +++ b/fs/exportfs/expfs.c
> > @@ -428,10 +428,10 @@ struct dentry *exportfs_decode_fh(struct vfsmount
> > *mnt, struct fid *fid,
> > if (!nop || !nop->fh_to_dentry)
> > return ERR_PTR(-ESTALE);
> > result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
> > - if (!result)
> > - result = ERR_PTR(-ESTALE);
> > - if (IS_ERR(result))
> > - return result;
> > + if (PTR_ERR(result) == -ENOMEM)
> > + return ERR_CAST(result);
> > + if (IS_ERR_OR_NULL(result))
> > + return ERR_PTR(-ESTALE);
> >
> > if (d_is_dir(result)) {
> > /*
> > @@ -541,6 +541,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt,
> > struct fid *fid,
> >
> > err_result:
> > dput(result);
> > + if (err != -ENOMEM)
> > + err = -ESTALE;
> > return ERR_PTR(err);
> > }
> > EXPORT_SYMBOL_GPL(exportfs_decode_fh);
> > diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> > index b03c0625fa6e..5ab958cdc50b 100644
> > --- a/include/linux/exportfs.h
> > +++ b/include/linux/exportfs.h
> > @@ -157,12 +157,13 @@ struct fid {
> > * @fh_to_dentry is given a &struct super_block (@sb) and a file handle
> > * fragment (@fh, @fh_len). It should return a &struct dentry which
> > refers
> > * to the same file that the file handle fragment refers to. If it
> > cannot,
> > - * it should return a %NULL pointer if the file was found but no
> > acceptable
> > - * &dentries were available, or an %ERR_PTR error code indicating why it
> > - * couldn't be found (e.g. %ENOENT or %ENOMEM). Any suitable dentry
> > can be
> > - * returned including, if necessary, a new dentry created with
> > d_alloc_root.
> > - * The caller can then find any other extant dentries by following the
> > - * d_alias links.
> > + * it should return a %NULL pointer if the file cannot be found, or an
> > + * %ERR_PTR error code of %ENOMEM if a memory allocation failure
> > occurred.
> > + * Any other error code is treated like %NULL, and will cause an
> > %ESTALE error
> > + * for callers of exportfs_decode_fh().
> > + * Any suitable dentry can be returned including, if necessary, a new
> > dentry
> > + * created with d_alloc_root. The caller can then find any other extant
> > + * dentries by following the d_alias links.
> > *
> > * fh_to_parent:
> > * Same as @fh_to_dentry, except that it returns a pointer to the parent
> > --
> > 2.9.2
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