2022-03-31 03:45:38

by NeilBrown

[permalink] [raw]
Subject: Re: [PATCH] VFS: filename_create(): fix incorrect intent.

On Wed, 30 Mar 2022, David Disseldorp wrote:
> Hi Neil,
>
> I gave this a spin and was wondering why xfstests wouldn't start with
> this change...
>
> On Mon, 28 Mar 2022 11:56:48 +1100, NeilBrown wrote:
> ...
> >
> > diff --git a/fs/namei.c b/fs/namei.c
> > index 3f1829b3ab5b..3ffb42e56a8e 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -3676,7 +3676,6 @@ static struct dentry *filename_create(int dfd, struct filename *name,
> > int type;
> > int err2;
> > int error;
> > - bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
> >
> > /*
> > * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
> > @@ -3698,9 +3697,11 @@ static struct dentry *filename_create(int dfd, struct filename *name,
> > /* don't fail immediately if it's r/o, at least try to report other errors */
> > err2 = mnt_want_write(path->mnt);
> > /*
> > - * Do the final lookup.
> > + * Do the final lookup. Request 'create' only if there is no trailing
> > + * '/', or if directory is requested.
> > */
> > - lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
> > + if (!last.name[last.len] || (lookup_flags & LOOKUP_DIRECTORY))
> > + lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
>
> This doesn't look right, as any LOOKUP_DIRECTORY flag gets dropped via
> the prior "lookup_flags &= LOOKUP_REVAL;".

Arg.. thanks for testing - I clearly should have tested more broadly.

I could leave the "is_dir" variable there I guess.
Or maybe the masking statement should be
lookup_flags &= LOOKUP_REVAL | LOOKUP_DIRECTORY;
as that is a better match for the comment.

Thanks,
NeilBrown