Re: [PATCH v3] alloc_tag: check mem_profiling_support in alloc_tag_init

[Suren Baghdasaryan <surenb@google.com>]

On Mon, May 12, 2025 at 2:02 PM Casey Chen <cachen@purestorage.com> wrote:
>
> On Mon, May 12, 2025 at 1:53 PM Suren Baghdasaryan <surenb@google.com> wrote:
> >
> > On Mon, May 12, 2025 at 12:42 PM Casey Chen <cachen@purestorage.com> wrote:
> > >
> > > If mem_profiling_support is false, for example by
> > > sysctl.vm.mem_profiling=never, alloc_tag_init should skip
> > > module tags allocation, codetag type registration and
> > > procfs init.
> > >
> > > Signed-off-by: Casey Chen <cachen@purestorage.com>
> > > Reviewed-by: Yuanyuan Zhong <yzhong@purestorage.com>
> > > ---
> > >  lib/alloc_tag.c | 34 +++++++++++++++++++---------------
> > >  1 file changed, 19 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> > > index 25ecc1334b67..7c798778669c 100644
> > > --- a/lib/alloc_tag.c
> > > +++ b/lib/alloc_tag.c
> > > @@ -244,17 +244,6 @@ static void shutdown_mem_profiling(bool remove_file)
> > >         mem_profiling_support = false;
> > >  }
> > >
> > > -static void __init procfs_init(void)
> > > -{
> > > -       if (!mem_profiling_support)
> > > -               return;
> > > -
> > > -       if (!proc_create_seq(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_seq_op)) {
> > > -               pr_err("Failed to create %s file\n", ALLOCINFO_FILE_NAME);
> > > -               shutdown_mem_profiling(false);
> > > -       }
> > > -}
> > > -
> > >  void __init alloc_tag_sec_init(void)
> > >  {
> > >         struct alloc_tag *last_codetag;
> > > @@ -762,19 +751,34 @@ static int __init alloc_tag_init(void)
> > >         };
> > >         int res;
> > >
> > > +       sysctl_init();
> > > +
> > > +       if (!mem_profiling_support) {
> > > +               pr_info("Memory allocation profiling is not supported!\n");
> > > +               return 0;
> > > +       }
> > > +
> > > +       if (!proc_create_seq(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_seq_op)) {
> >
> > I suggest keeping file creation as the last step so that we don't have
> > to remove it if later steps fail.
> >
>
> If the file creation is the last step, how could it clean up codetag
> type registration ? As we miss codetag unregistration function, I
> think codetag type registration should be the last step.

I see. Ok, keeping it here sounds reasonable. Implementing
codetag_unregister_type() just for this failure case would not make
sense. Please go ahead and address the other nits and I think it will
be good to go.

>
> > > +               pr_err("Failed to create %s file\n", ALLOCINFO_FILE_NAME);
> > > +               shutdown_mem_profiling(false);
> > > +               return -EAGAIN;
> >
> > Why EAGAIN? I would just let it fall through returning 0 (after moving
> > this to the end as I suggested in my previous comment).
> >
>
> return 0 is fine to me if this fails. EAGAIN sounds fine too.
>
> > > +       }
> > > +
> > >         res = alloc_mod_tags_mem();
> > > -       if (res)
> > > +       if (res) {
> > > +               pr_err("Failed to allocate module tags\n");
> >
> > The error message is a bit misleading here since we are not allocating
> > module tags but reserving virtual space for them. Maybe:
> > "Failed to reserve address space for module tags"
> >
>
> Sounds good!
>
> > > +               shutdown_mem_profiling(true);
> > >                 return res;
> > > +       }
> > >
> > >         alloc_tag_cttype = codetag_register_type(&desc);
> > >         if (IS_ERR(alloc_tag_cttype)) {
> > > +               pr_err("Failed to register codetag type with desc %s\n", desc.section);
> >
> > pr_err("Allocation tags registration failed, errno = %d\n", ret);
> >
>
> Sounds good too.
>
> > >                 free_mod_tags_mem();
> > > +               shutdown_mem_profiling(true);
> > >                 return PTR_ERR(alloc_tag_cttype);
> > >         }
> > >
> > > -       sysctl_init();
> > > -       procfs_init();
> > > -
> > >         return 0;
> > >  }
> > >  module_init(alloc_tag_init);
> > > --
> > > 2.49.0
> > >