mm, printk: introduce new format string for flags

In mm we use several kinds of flags bitfields that are sometimes printed
for debugging purposes, or exported to userspace via sysfs.  To make
them easier to interpret independently on kernel version and config, we
want to dump also the symbolic flag names.  So far this has been done
with repeated calls to pr_cont(), which is unreliable on SMP, and not
usable for e.g.  sysfs export.

To get a more reliable and universal solution, this patch extends
printk() format string for pointers to handle the page flags (%pGp),
gfp_flags (%pGg) and vma flags (%pGv).  Existing users of
dump_flag_names() are converted and simplified.

It would be possible to pass flags by value instead of pointer, but the
%p format string for pointers already has extensions for various kernel
structures, so it's a good fit, and the extra indirection in a
non-critical path is negligible.

[linux@rasmusvillemoes.dk: lots of good implementation suggestions]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 5d1128bf02824aaf2e16ef332e7cef014cccf7b6..5962949944fd7307530f26c54c65d783745a8a27 100644 (file)
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -298,6 +298,24 @@ bitmap and its derivatives such as cpumask and nodemask:
 
        Passed by reference.
 
+Flags bitfields such as page flags, gfp_flags:
+
+       %pGp    referenced|uptodate|lru|active|private
+       %pGg    GFP_USER|GFP_DMA32|GFP_NOWARN
+       %pGv    read|exec|mayread|maywrite|mayexec|denywrite
+
+       For printing flags bitfields as a collection of symbolic constants that
+       would construct the value. The type of flags is given by the third
+       character. Currently supported are [p]age flags, [v]ma_flags (both
+       expect unsigned long *) and [g]fp_flags (expects gfp_t *). The flag
+       names and print order depends on the particular type.
+
+       Note that this format should not be used directly in TP_printk() part
+       of a tracepoint. Instead, use the show_*_flags() functions from
+       <trace/events/mmflags.h>.
+
+       Passed by reference.
+
 Network device features:
 
        %pNF    0x000000000000c000

diff --git a/lib/test_printf.c b/lib/test_printf.c
index 4f6ae60433bc5d1e1d6df9b7c8d5d359512ad82a..563f10e6876aecf6e3932e0a2e955305f271b249 100644 (file)
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -17,6 +17,9 @@
 #include <linux/socket.h>
 #include <linux/in.h>
 
+#include <linux/gfp.h>
+#include <linux/mm.h>
+
 #define BUF_SIZE 256
 #define PAD_SIZE 16
 #define FILL_CHAR '$'
@@ -410,6 +413,55 @@ netdev_features(void)
 {
 }
 
+static void __init
+flags(void)
+{
+       unsigned long flags;
+       gfp_t gfp;
+       char *cmp_buffer;
+
+       flags = 0;
+       test("", "%pGp", &flags);
+
+       /* Page flags should filter the zone id */
+       flags = 1UL << NR_PAGEFLAGS;
+       test("", "%pGp", &flags);
+
+       flags |= 1UL << PG_uptodate | 1UL << PG_dirty | 1UL << PG_lru
+               | 1UL << PG_active | 1UL << PG_swapbacked;
+       test("uptodate|dirty|lru|active|swapbacked", "%pGp", &flags);
+
+
+       flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC
+                       | VM_DENYWRITE;
+       test("read|exec|mayread|maywrite|mayexec|denywrite", "%pGv", &flags);
+
+       gfp = GFP_TRANSHUGE;
+       test("GFP_TRANSHUGE", "%pGg", &gfp);
+
+       gfp = GFP_ATOMIC|__GFP_DMA;
+       test("GFP_ATOMIC|GFP_DMA", "%pGg", &gfp);
+
+       gfp = __GFP_ATOMIC;
+       test("__GFP_ATOMIC", "%pGg", &gfp);
+
+       cmp_buffer = kmalloc(BUF_SIZE, GFP_KERNEL);
+       if (!cmp_buffer)
+               return;
+
+       /* Any flags not translated by the table should remain numeric */
+       gfp = ~__GFP_BITS_MASK;
+       snprintf(cmp_buffer, BUF_SIZE, "%#lx", (unsigned long) gfp);
+       test(cmp_buffer, "%pGg", &gfp);
+
+       snprintf(cmp_buffer, BUF_SIZE, "__GFP_ATOMIC|%#lx",
+                                                       (unsigned long) gfp);
+       gfp |= __GFP_ATOMIC;
+       test(cmp_buffer, "%pGg", &gfp);
+
+       kfree(cmp_buffer);
+}
+
 static void __init
 test_pointer(void)
 {
@@ -428,6 +480,7 @@ test_pointer(void)
        struct_clk();
        bitmap();
        netdev_features();
+       flags();
 }
 
 static int __init

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index f44e178e6edec22e2f7c405f8cb433b2be935f83..525c8e19bda2b8a4e7398d7fc19064b2abc84b45 100644 (file)
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -35,6 +35,8 @@
 #include <linux/blkdev.h>
 #endif
 
+#include "../mm/internal.h"    /* For the trace_print_flags arrays */
+
 #include <asm/page.h>          /* for PAGE_SIZE */
 #include <asm/sections.h>      /* for dereference_function_descriptor() */
 #include <asm/byteorder.h>     /* cpu_to_le16 */
@@ -1407,6 +1409,72 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
        }
 }
 
+static
+char *format_flags(char *buf, char *end, unsigned long flags,
+                                       const struct trace_print_flags *names)
+{
+       unsigned long mask;
+       const struct printf_spec strspec = {
+               .field_width = -1,
+               .precision = -1,
+       };
+       const struct printf_spec numspec = {
+               .flags = SPECIAL|SMALL,
+               .field_width = -1,
+               .precision = -1,
+               .base = 16,
+       };
+
+       for ( ; flags && names->name; names++) {
+               mask = names->mask;
+               if ((flags & mask) != mask)
+                       continue;
+
+               buf = string(buf, end, names->name, strspec);
+
+               flags &= ~mask;
+               if (flags) {
+                       if (buf < end)
+                               *buf = '|';
+                       buf++;
+               }
+       }
+
+       if (flags)
+               buf = number(buf, end, flags, numspec);
+
+       return buf;
+}
+
+static noinline_for_stack
+char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
+{
+       unsigned long flags;
+       const struct trace_print_flags *names;
+
+       switch (fmt[1]) {
+       case 'p':
+               flags = *(unsigned long *)flags_ptr;
+               /* Remove zone id */
+               flags &= (1UL << NR_PAGEFLAGS) - 1;
+               names = pageflag_names;
+               break;
+       case 'v':
+               flags = *(unsigned long *)flags_ptr;
+               names = vmaflag_names;
+               break;
+       case 'g':
+               flags = *(gfp_t *)flags_ptr;
+               names = gfpflag_names;
+               break;
+       default:
+               WARN_ONCE(1, "Unsupported flags modifier: %c\n", fmt[1]);
+               return buf;
+       }
+
+       return format_flags(buf, end, flags, names);
+}
+
 int kptr_restrict __read_mostly;
 
 /*
@@ -1495,6 +1563,11 @@ int kptr_restrict __read_mostly;
  * - 'Cn' For a clock, it prints the name (Common Clock Framework) or address
  *        (legacy clock framework) of the clock
  * - 'Cr' For a clock, it prints the current rate of the clock
+ * - 'G' For flags to be printed as a collection of symbolic strings that would
+ *       construct the specific value. Supported flags given by option:
+ *       p page flags (see struct page) given as pointer to unsigned long
+ *       g gfp flags (GFP_* and __GFP_*) given as pointer to gfp_t
+ *       v vma flags (VM_*) given as pointer to unsigned long
  *
  * ** Please update also Documentation/printk-formats.txt when making changes **
  *
@@ -1648,6 +1721,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
                return bdev_name(buf, end, ptr, spec, fmt);
 #endif
 
+       case 'G':
+               return flags_string(buf, end, ptr, fmt);
        }
        spec.flags |= SMALL;
        if (spec.field_width == -1) {

diff --git a/mm/debug.c b/mm/debug.c
index 410af904a7d513a5fae5424458dcd70e39ce9e05..0328fd3775451670d5e454ed69b2548b184794d2 100644 (file)
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -11,12 +11,21 @@
 #include <linux/memcontrol.h>
 #include <trace/events/mmflags.h>
 
-static const struct trace_print_flags pageflag_names[] = {
-       __def_pageflag_names
+#include "internal.h"
+
+const struct trace_print_flags pageflag_names[] = {
+       __def_pageflag_names,
+       {0, NULL}
+};
+
+const struct trace_print_flags gfpflag_names[] = {
+       __def_gfpflag_names,
+       {0, NULL}
 };
 
-static const struct trace_print_flags gfpflag_names[] = {
-       __def_gfpflag_names
+const struct trace_print_flags vmaflag_names[] = {
+       __def_vmaflag_names,
+       {0, NULL}
 };
 
 static void dump_flags(unsigned long flags,
@@ -58,14 +67,15 @@ void dump_page_badflags(struct page *page, const char *reason,
        if (PageCompound(page))
                pr_cont(" compound_mapcount: %d", compound_mapcount(page));
        pr_cont("\n");
-       BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS);
-       dump_flags(page->flags, pageflag_names, ARRAY_SIZE(pageflag_names));
+       BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
+       dump_flags(page->flags, pageflag_names,
+                                       ARRAY_SIZE(pageflag_names) - 1);
        if (reason)
                pr_alert("page dumped because: %s\n", reason);
        if (page->flags & badflags) {
                pr_alert("bad because of flags:\n");
-               dump_flags(page->flags & badflags,
-                               pageflag_names, ARRAY_SIZE(pageflag_names));
+               dump_flags(page->flags & badflags, pageflag_names,
+                                       ARRAY_SIZE(pageflag_names) - 1);
        }
 #ifdef CONFIG_MEMCG
        if (page->mem_cgroup)
@@ -81,10 +91,6 @@ EXPORT_SYMBOL(dump_page);
 
 #ifdef CONFIG_DEBUG_VM
 
-static const struct trace_print_flags vmaflag_names[] = {
-       __def_vmaflag_names
-};
-
 void dump_vma(const struct vm_area_struct *vma)
 {
        pr_emerg("vma %p start %p end %p\n"
@@ -96,7 +102,7 @@ void dump_vma(const struct vm_area_struct *vma)
                (unsigned long)pgprot_val(vma->vm_page_prot),
                vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
                vma->vm_file, vma->vm_private_data);
-       dump_flags(vma->vm_flags, vmaflag_names, ARRAY_SIZE(vmaflag_names));
+       dump_flags(vma->vm_flags, vmaflag_names, ARRAY_SIZE(vmaflag_names) - 1);
 }
 EXPORT_SYMBOL(dump_vma);
 
@@ -168,7 +174,7 @@ void dump_mm(const struct mm_struct *mm)
                );
 
                dump_flags(mm->def_flags, vmaflag_names,
-                               ARRAY_SIZE(vmaflag_names));
+                               ARRAY_SIZE(vmaflag_names) - 1);
 }
 
 #endif         /* CONFIG_DEBUG_VM */

diff --git a/mm/internal.h b/mm/internal.h
index a38a21ebddb454540fc1dcae83be516ffc7cdf26..6636e1d3ecf0b53b52063eb1bc402a0e1648aa3b 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -14,6 +14,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
+#include <linux/tracepoint-defs.h>
 
 /*
  * The set of flags that only affect watermark checking and reclaim
@@ -466,4 +467,9 @@ static inline void try_to_unmap_flush_dirty(void)
 }
 
 #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
+
+extern const struct trace_print_flags pageflag_names[];
+extern const struct trace_print_flags vmaflag_names[];
+extern const struct trace_print_flags gfpflag_names[];
+
 #endif /* __MM_INTERNAL_H */