On 8/30/22 09:34, Michal Hocko wrote: > [Cc Dan] > Dan has brought up[1] that the use of gfp mask has confused his static > analyzer which assumes that GFP_HIGHUSER_MOVABLE implies a sleeping > allocation and that wouldn't be a great idea from the panic path. I > would add that most callers of this function would be really bad to > allocate. > > The report itself is a false positive but it made me think a bit about > this. Even if the check is too simplistic I guess it resembles how many > developers are thinking (including me). If I see GFP_HIGHUSER_MOVABLE or > GF_KERNEL I automatically assume a sleeping allocation down the road. > And who know somebody might add one in the future even into show_mem > because the gfp parameter would be too tempting to not (ab)use. > > My original intention was to use a natural allocation speak but this can > backfire so maybe it would be better to give the argument its real > meaning and that is the high_zone_idx. This is cryptic for code outside > of MM but that is not all that many callers and we can hide this fact > from them. In other words does the thing below looks better (incremental > for illustration, I will make it a proper patch if yes)? Yeah, looks better to me this way. Thanks! > > [1] https://lore.kernel.org/all/Yw2ugrlZ8bwE5/hh@kili/?q=http%3A%2F%2Flkml.kernel.org%2Fr%2FYw2ugrlZ8bwE5%2Fhh%40kili > > --- > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c > index 19b1a94b0c00..3d9782ea3fa7 100644 > --- a/arch/powerpc/xmon/xmon.c > +++ b/arch/powerpc/xmon/xmon.c > @@ -1086,7 +1086,7 @@ cmds(struct pt_regs *excp) > memzcan(); > break; > case 'i': > - show_mem(0, NULL, GFP_HIGHUSER_MOVABLE); > + show_mem(0, NULL); > break; > default: > termch = cmd; > diff --git a/arch/sparc/kernel/setup_32.c b/arch/sparc/kernel/setup_32.c > index 2a1e5641a7cc..c8e0dd99f370 100644 > --- a/arch/sparc/kernel/setup_32.c > +++ b/arch/sparc/kernel/setup_32.c > @@ -83,7 +83,7 @@ static void prom_sync_me(void) > "nop\n\t" : : "r" (&trapbase)); > > prom_printf("PROM SYNC COMMAND...\n"); > - show_free_areas(0, NULL, GFP_HIGHUSER_MOVABLE); > + show_free_areas(0, NULL); > if (!is_idle_task(current)) { > local_irq_enable(); > ksys_sync(); > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > index c6b2b42d2367..d2b2720db6ca 100644 > --- a/drivers/tty/sysrq.c > +++ b/drivers/tty/sysrq.c > @@ -342,7 +342,7 @@ static const struct sysrq_key_op sysrq_ftrace_dump_op = { > > static void sysrq_handle_showmem(int key) > { > - show_mem(0, NULL, GFP_HIGHUSER_MOVABLE); > + show_mem(0, NULL); > } > static const struct sysrq_key_op sysrq_showmem_op = { > .handler = sysrq_handle_showmem, > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c > index 9ceeea531cf6..be8313cdbac3 100644 > --- a/drivers/tty/vt/keyboard.c > +++ b/drivers/tty/vt/keyboard.c > @@ -606,7 +606,7 @@ static void fn_scroll_back(struct vc_data *vc) > > static void fn_show_mem(struct vc_data *vc) > { > - show_mem(0, NULL, GFP_HIGHUSER_MOVABLE); > + show_mem(0, NULL); > } > > static void fn_show_state(struct vc_data *vc) > diff --git a/include/linux/mm.h b/include/linux/mm.h > index e0d0ac52770c..0756798feaff 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1827,7 +1827,11 @@ extern void pagefault_out_of_memory(void); > */ > #define SHOW_MEM_FILTER_NODES (0x0001u) /* disallowed nodes */ > > -extern void show_free_areas(unsigned int flags, nodemask_t *nodemask, gfp_t gfp_mask); > +extern void __show_free_areas(unsigned int flags, nodemask_t *nodemask, int max_zone_idx); > +static void __maybe_unused show_free_areas(unsigned int flags, nodemask_t *nodemask) > +{ > + __show_free_areas(flags, nodemask, MAX_NR_ZONES - 1); > +} > > #ifdef CONFIG_MMU > extern bool can_do_mlock(void); > @@ -2563,7 +2567,12 @@ extern void calculate_min_free_kbytes(void); > extern int __meminit init_per_zone_wmark_min(void); > extern void mem_init(void); > extern void __init mmap_init(void); > -extern void show_mem(unsigned int flags, nodemask_t *nodemask, gfp_t gfp_mask); > + > +extern void __show_mem(unsigned int flags, nodemask_t *nodemask, int max_zone_idx); > +static inline void show_mem(unsigned int flags, nodemask_t *nodemask) > +{ > + __show_mem(flags, nodemask, MAX_NR_ZONES - 1); > +} > extern long si_mem_available(void); > extern void si_meminfo(struct sysinfo * val); > extern void si_meminfo_node(struct sysinfo *val, int nid); > diff --git a/init/initramfs.c b/init/initramfs.c > index ec966cb78363..18229cfe8906 100644 > --- a/init/initramfs.c > +++ b/init/initramfs.c > @@ -63,7 +63,7 @@ static void panic_show_mem(const char *fmt, ...) > { > va_list args; > > - show_mem(0, NULL, GFP_HIGHUSER_MOVABLE); > + show_mem(0, NULL); > va_start(args, fmt); > panic(fmt, args); > va_end(args); > diff --git a/kernel/panic.c b/kernel/panic.c > index ba5f7691d15c..a3308af28a21 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -187,7 +187,7 @@ static void panic_print_sys_info(bool console_flush) > show_state(); > > if (panic_print & PANIC_PRINT_MEM_INFO) > - show_mem(0, NULL, GFP_HIGHUSER_MOVABLE); > + show_mem(0, NULL); > > if (panic_print & PANIC_PRINT_TIMER_INFO) > sysrq_timer_list_show(); > diff --git a/lib/show_mem.c b/lib/show_mem.c > index b97461a6c4bb..ade71096e241 100644 > --- a/lib/show_mem.c > +++ b/lib/show_mem.c > @@ -8,13 +8,13 @@ > #include <linux/mm.h> > #include <linux/cma.h> > > -void show_mem(unsigned int filter, nodemask_t *nodemask, gfp_t gfp_mask) > +void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx) > { > pg_data_t *pgdat; > unsigned long total = 0, reserved = 0, highmem = 0; > > printk("Mem-Info:\n"); > - show_free_areas(filter, nodemask, gfp_mask); > + show_free_areas(filter, nodemask, max_zone_idx); > > for_each_online_pgdat(pgdat) { > int zoneid; > diff --git a/mm/nommu.c b/mm/nommu.c > index 46cff4a51fa0..9d7afc2d959e 100644 > --- a/mm/nommu.c > +++ b/mm/nommu.c > @@ -1047,7 +1047,7 @@ static int do_mmap_private(struct vm_area_struct *vma, > enomem: > pr_err("Allocation of length %lu from process %d (%s) failed\n", > len, current->pid, current->comm); > - show_free_areas(0, NULL, GFP_KERNEL); > + show_free_areas(0, NULL); > return -ENOMEM; > } > > @@ -1270,13 +1270,13 @@ unsigned long do_mmap(struct file *file, > kmem_cache_free(vm_region_jar, region); > pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n", > len, current->pid); > - show_free_areas(0, NULL, GFP_KERNEL); > + show_free_areas(0, NULL); > return -ENOMEM; > > error_getting_region: > pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n", > len, current->pid); > - show_free_areas(0, NULL, GFP_KERNEL); > + show_free_areas(0, NULL); > return -ENOMEM; > } > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index ffeaad3b348d..94804504be9c 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -461,7 +461,7 @@ static void dump_header(struct oom_control *oc, struct task_struct *p) > if (is_memcg_oom(oc)) > mem_cgroup_print_oom_meminfo(oc->memcg); > else { > - show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, oc->gfp_mask); > + __show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask)); > if (should_dump_unreclaim_slab()) > dump_unreclaimable_slab(); > } > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 208e3f8b38f8..110a16ea848a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4248,7 +4248,7 @@ static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask) > if (!in_task() || !(gfp_mask & __GFP_DIRECT_RECLAIM)) > filter &= ~SHOW_MEM_FILTER_NODES; > > - show_mem(filter, nodemask, gfp_mask); > + __show_mem(filter, nodemask, gfp_zone(gfp_mask)); > } > > void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...) > @@ -5944,10 +5944,9 @@ static bool node_has_managed_zones(pg_data_t *pgdat, int max_zone_idx) > * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's > * cpuset. > */ > -void show_free_areas(unsigned int filter, nodemask_t *nodemask, gfp_t gfp_mask) > +void __show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_zone_idx) > { > unsigned long free_pcp = 0; > - int max_zone_idx = gfp_zone(gfp_mask); > int cpu; > struct zone *zone; > pg_data_t *pgdat;
