This lets us use regular string formatting code to dump MMs, use it
in VM_BUG_ON_MM instead of just printing it to screen as well.

Signed-off-by: Sasha Levin <sasha.le...@oracle.com>
---
 include/linux/mmdebug.h |    8 ++++++--
 lib/vsprintf.c          |    5 ++++-
 mm/debug.c              |   11 +++++++----
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 506e405..202ebdf 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -10,10 +10,10 @@ struct mm_struct;
 extern void dump_page(struct page *page, const char *reason);
 extern void dump_page_badflags(struct page *page, const char *reason,
                               unsigned long badflags);
-void dump_mm(const struct mm_struct *mm);
 
 #ifdef CONFIG_DEBUG_VM
 char *format_vma(const struct vm_area_struct *vma, char *buf, char *end);
+char *format_mm(const struct mm_struct *mm, char *buf, char *end);
 #define VM_BUG_ON(cond) BUG_ON(cond)
 #define VM_BUG_ON_PAGE(cond, page)                                     \
        do {                                                            \
@@ -32,7 +32,7 @@ char *format_vma(const struct vm_area_struct *vma, char *buf, 
char *end);
 #define VM_BUG_ON_MM(cond, mm)                                         \
        do {                                                            \
                if (unlikely(cond)) {                                   \
-                       dump_mm(mm);                                    \
+                       pr_emerg("%pZm", mm);                           \
                        BUG();                                          \
                }                                                       \
        } while (0)
@@ -44,6 +44,10 @@ static char *format_vma(const struct vm_area_struct *vma, 
char *buf, char *end)
 {
        return buf;
 }
+static char *format_mm(const struct mm_struct *mm, char *buf, char *end)
+{
+       return buf;
+}
 #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond)
 #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond)
 #define VM_BUG_ON_VMA(cond, vma) VM_BUG_ON(cond)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b4800c1..1ca3114 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1382,6 +1382,8 @@ char *mm_pointer(char *buf, char *end, const void *ptr,
        switch (fmt[1]) {
        case 'v':
                return format_vma(ptr, buf, end);
+       case 'm':
+               return format_mm(ptr, buf, end);
        }
 
        return buf;
@@ -1475,8 +1477,9 @@ int kptr_restrict __read_mostly;
  *        (legacy clock framework) of the clock
  * - 'Cr' For a clock, it prints the current rate of the clock
  * - 'T' task_struct->comm
- * - 'Z[v]' Outputs a readable version of a type of memory management struct:
+ * - 'Z[mv]' Outputs a readable version of a type of memory management struct:
  *             v struct vm_area_struct
+ *             m struct mm_struct
  *
  * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
  * function pointers are really function descriptors, which contain a
diff --git a/mm/debug.c b/mm/debug.c
index 82e2e1c..dff65ff 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -203,9 +203,10 @@ char *format_vma(const struct vm_area_struct *vma, char 
*buf, char *end)
                                buf, end);
 }
 
-void dump_mm(const struct mm_struct *mm)
+char *format_mm(const struct mm_struct *mm, char *buf, char *end)
 {
-       pr_emerg("mm %p mmap %p seqnum %d task_size %lu\n"
+       buf += snprintf(buf, buf > end ? 0 : end - buf,
+               "mm %p mmap %p seqnum %d task_size %lu\n"
 #ifdef CONFIG_MMU
                "get_unmapped_area %p\n"
 #endif
@@ -270,8 +271,10 @@ void dump_mm(const struct mm_struct *mm)
                ""              /* This is here to not have a comma! */
                );
 
-               dump_flags(mm->def_flags, vmaflags_names,
-                               ARRAY_SIZE(vmaflags_names));
+       buf = format_flags(mm->def_flags, vmaflags_names,
+                               ARRAY_SIZE(vmaflags_names), buf, end);
+
+       return buf;
 }
 
 #endif         /* CONFIG_DEBUG_VM */
-- 
1.7.10.4

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