Re: [PATCH] gfs2: Use container_of() for gfs2_glock(aspace)
From: Christoph Hellwig
Date: Tue May 10 2022 - 03:32:56 EST
> +/* gfs2_glock_get(), "glock" must be first. */
> +struct glock_aspace {
> + struct gfs2_glock glock;
> + struct address_space mapping;
> +};
Why does glock need to be first? The whole point of using container_of
is that we don't have to make that assumption.
> static inline struct address_space *gfs2_glock2aspace(struct gfs2_glock *gl)
> {
> if (gl->gl_ops->go_flags & GLOF_ASPACE)
> - return (struct address_space *)(gl + 1);
> + return &(container_of(gl, struct glock_aspace, glock)->mapping);
Do we even need the braces here?
> struct inode *inode = mapping->host;
> if (mapping->a_ops == &gfs2_meta_aops)
> - return (((struct gfs2_glock *)mapping) - 1)->gl_name.ln_sbd;
> + return container_of(mapping, struct glock_aspace, mapping)->glock.gl_name.ln_sbd;
A local variable would be really nice for the reader here to decompose
this a bit:
struct glock_aspace *a =
container_of(mapping, struct glock_aspace, mapping);
return a->glock.gl_name.ln_sbd;