Re: [PATCH v6 05/37] fs: Convert alloc_inode_sb() to a macro

[Suren Baghdasaryan]

On Thu, Mar 21, 2024 at 1:31 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, 21 Mar 2024 09:36:27 -0700 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>
> > From: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> >
> > We're introducing alloc tagging, which tracks memory allocations by
> > callsite. Converting alloc_inode_sb() to a macro means allocations will
> > be tracked by its caller, which is a bit more useful.
>
> I'd have thought that there would be many similar
> inlines-which-allocate-memory.  Such as, I dunno, jbd2_alloc_inode().
> Do we have to go converting things to macros as people report
> misleading or less useful results, or is there some more general
> solution to this?

Yeah, that's unfortunately inevitable. Even if we had compiler support
we would have to add annotations for such inlined functions.
For the given example of jbd2_alloc_inode() it's not so bad since it's
used only from one location but in general yes, that's something we
will have to improve as we find more such cases.

>
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -3083,11 +3083,7 @@ int setattr_should_drop_sgid(struct mnt_idmap *idmap,
> >   * This must be used for allocating filesystems specific inodes to set
> >   * up the inode reclaim context correctly.
> >   */
> > -static inline void *
> > -alloc_inode_sb(struct super_block *sb, struct kmem_cache *cache, gfp_t gfp)
> > -{
> > -     return kmem_cache_alloc_lru(cache, &sb->s_inode_lru, gfp);
> > -}
> > +#define alloc_inode_sb(_sb, _cache, _gfp) kmem_cache_alloc_lru(_cache, &_sb->s_inode_lru, _gfp)
>
> Parenthesizing __sb seems sensible here?

Ack.
Let's wait for more comments and then I'll post fixes.
Thanks!