On Thu 29-08-19 15:47:19, Tejun Heo wrote:
> cgroup foreign inode handling has quite a bit of heuristics and
> internal states which sometimes makes it difficult to understand
> what's going on. Add tracepoints to improve visibility.
>
> Signed-off-by: Tejun Heo <t...@kernel.org>
...
> +TRACE_EVENT(track_foreign_dirty,
> +
> + TP_PROTO(struct page *page, struct bdi_writeback *wb),
> +
> + TP_ARGS(page, wb),
> +
> + TP_STRUCT__entry(
> + __array(char, name, 32)
> + __field(u64, bdi_id)
> + __field(unsigned long, ino)
> + __field(unsigned int, memcg_id)
> + __field(unsigned int, cgroup_ino)
> + __field(unsigned int, page_cgroup_ino)
> + ),
> +
> + TP_fast_assign(
> + strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
> + __entry->bdi_id = wb->bdi->id;
> + __entry->ino = page->mapping->host->i_ino;
> + __entry->memcg_id = wb->memcg_css->id;
> + __entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
> + __entry->page_cgroup_ino =
> page->mem_cgroup->css.cgroup->kn->id.ino;
> + ),
Are the page dereferences above safe? I suppose lock_page_memcg() protects
the page->mem_cgroup->css.cgroup->kn->id dereference? But page->mapping
does not seem to be protected by page lock?
Honza
--
Jan Kara <j...@suse.com>
SUSE Labs, CR
