[Devel] Re: [PATCH] checkpoint: discard const from struct cred * where appropriate

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> 
> 
> Nathan Lynch wrote:
> > Building the checkpoint tree results in enough build noise that
> > it's getting easy to miss new warnings added during development:
> > 
> > kernel/cred.c:737: warning: passing argument 2 of 'checkpoint_capabilities' discards qualifiers from pointer target type
> > checkpoint/process.c:146: warning: assignment discards qualifiers from pointer target type
> > checkpoint/process.c:147: warning: assignment discards qualifiers from pointer target type
> > checkpoint/files.c:154: warning: passing argument 2 of 'checkpoint_obj' discards qualifiers from pointer target type
> > 
> > The objhash code would require significant modification to properly
> > handle const objects, and only struct cred * is causing this kind of
> > warning, so just insert casts or drop const where it makes sense.
> > 
> > Signed-off-by: Nathan Lynch <ntl at pobox.com>
> 
> Looks good to me.
> 
> I vaguely recall that Serge had some issue with this approach ?

I don't.  This might be the best solution, and we do need to shut those
warnings up.  David Howells might have a problem with it though, so he
should be cc:d.

> Oren.
> 
> > ---
> >  checkpoint/files.c   |    4 +++-
> >  checkpoint/process.c |    4 ++--
> >  kernel/cred.c        |    2 +-
> >  3 files changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/checkpoint/files.c b/checkpoint/files.c
> > index 204055b..8f90c16 100644
> > --- a/checkpoint/files.c
> > +++ b/checkpoint/files.c
> > @@ -146,12 +146,14 @@ static int scan_fds(struct files_struct *files, int **fdtable)
> >  int checkpoint_file_common(struct ckpt_ctx *ctx, struct file *file,
> >  			   struct ckpt_hdr_file *h)
> >  {
> > +	struct cred *f_cred = (struct cred *)file->f_cred;
> > +
> >  	h->f_flags = file->f_flags;
> >  	h->f_mode = file->f_mode;
> >  	h->f_pos = file->f_pos;
> >  	h->f_version = file->f_version;
> >  
> > -	h->f_credref = checkpoint_obj(ctx, file->f_cred, CKPT_OBJ_CRED);
> > +	h->f_credref = checkpoint_obj(ctx, f_cred, CKPT_OBJ_CRED);
> >  	if (h->f_credref < 0)
> >  		return h->f_credref;
> >  
> > diff --git a/checkpoint/process.c b/checkpoint/process.c
> > index 40b2580..41566db 100644
> > --- a/checkpoint/process.c
> > +++ b/checkpoint/process.c
> > @@ -143,8 +143,8 @@ static int checkpoint_task_creds(struct ckpt_ctx *ctx, struct task_struct *t)
> >  	struct ckpt_hdr_task_creds *h;
> >  	int ret;
> >  
> > -	rcred = get_cred(t->real_cred);
> > -	ecred = get_cred(t->cred);
> > +	rcred = (struct cred *)get_cred(t->real_cred);
> > +	ecred = (struct cred *)get_cred(t->cred);
> >  
> >  	realcred_ref = checkpoint_obj(ctx, rcred, CKPT_OBJ_CRED);
> >  	if (realcred_ref < 0) {
> > diff --git a/kernel/cred.c b/kernel/cred.c
> > index 27e02ca..9710cae 100644
> > --- a/kernel/cred.c
> > +++ b/kernel/cred.c
> > @@ -706,7 +706,7 @@ int cred_setfsgid(struct cred *new, gid_t gid, gid_t *old_fsgid)
> >  }
> >  
> >  #ifdef CONFIG_CHECKPOINT
> > -static int do_checkpoint_cred(struct ckpt_ctx *ctx, const struct cred *cred)
> > +static int do_checkpoint_cred(struct ckpt_ctx *ctx, struct cred *cred)
> >  {
> >  	int ret;
> >  	int groupinfo_ref, user_ref;
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