Re: [PATCH 1/2] netfs: release the folio lock and put the folio before retrying

[Xiubo Li]

On 7/4/22 10:10 AM, Matthew Wilcox wrote:
> On Mon, Jul 04, 2022 at 09:13:44AM +0800, Xiubo Li wrote:
> > On 7/1/22 6:38 PM, Jeff Layton wrote:
> > > I don't know here... I think it might be better to just expect that when
> > > this function returns an error that the folio has already been unlocked.
> > > Doing it this way will mean that you will lock and unlock the folio a
> > > second time for no reason.
> > >
> > > Maybe something like this instead?
> > >
> > > diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
> > > index 42f892c5712e..8ae7b0f4c909 100644
> > > --- a/fs/netfs/buffered_read.c
> > > +++ b/fs/netfs/buffered_read.c
> > > @@ -353,7 +353,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
> > >                           trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
> > >                           if (ret == -EAGAIN)
> > >                                   goto retry;
> > > -                       goto error;
> > > +                       goto error_unlocked;
> > >                   }
> > >           }
> > > @@ -418,6 +418,7 @@ int netfs_write_begin(struct netfs_inode *ctx,
> > >    error:
> > >           folio_unlock(folio);
> > >           folio_put(folio);
> > > +error_unlocked:
> > >           _leave(" = %d", ret);
> > >           return ret;
> > >    }
> > Then the "afs" won't work correctly:
> >
> > 377 static int afs_check_write_begin(struct file *file, loff_t pos, unsigned
> > len,
> > 378                                  struct folio *folio, void **_fsdata)
> > 379 {
> > 380         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
> > 381
> > 382         return test_bit(AFS_VNODE_DELETED, &vnode->flags) ? -ESTALE : 0;
> > 383 }
> >
> > The "afs" does nothing with the folio lock.
> It's OK to fix AFS too.
Okay, will fix it. Thanks!

-- Xiubo