Messages in this thread | | | Date | Mon, 8 Aug 2022 14:48:03 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH v5 22/32] mm/memcontrol.c: Convert to printbuf |
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On Mon 08-08-22 11:48:53, Michal Hocko wrote: > On Mon 08-08-22 03:41:18, Matthew Wilcox wrote: > > From: Kent Overstreet <kent.overstreet@gmail.com> > > > > This converts memory_stat_format() from seq_buf to printbuf. Printbuf is > > simalar to seq_buf except that it heap allocates the string buffer: > > here, we were already heap allocating the buffer with kmalloc() so the > > conversion is trivial. > > The changelog probably needs an update because the oom path doesn't > allocated and for somebody just reading this patch in isolation the > PRINTBUF_EXTERN doesn't really seem very obvious. > > > Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com> > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > Cc: Michal Hocko <mhocko@kernel.org> > > Cc: Roman Gushchin <roman.gushchin@linux.dev> > > > -static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) > > +static void memory_stat_format(struct printbuf *out, struct mem_cgroup *memcg) > > { > > - struct seq_buf s; > > int i; > > > > - seq_buf_init(&s, buf, bufsize); > > - > > When is the buffer cleared? > > > /* > > * Provide statistics on the state of the memory subsystem as > > * well as cumulative event counters that show past behavior. > [...] > > #define K(x) ((x) << (PAGE_SHIFT-10)) > > @@ -1573,7 +1570,8 @@ void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct * > > void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) > > { > > /* Use static buffer, for the caller is holding oom_lock. */ > > - static char buf[PAGE_SIZE]; > > + static char _buf[PAGE_SIZE]; > > + struct printbuf buf = PRINTBUF_EXTERN(_buf, sizeof(_buf)); > > > > lockdep_assert_held(&oom_lock); > > the buffer is static here!
And answering to myself. THere is an internal pos field which gets initialized by PRINTBUF_EXTERN even when not mentioned explicitly because it gets a default 0 initialization
Acked-by: Michal Hocko <mhocko@suse.com> -- Michal Hocko SUSE Labs
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