[PATCH] mm: polish virtual memory accounting

Konstantin Khlebnikov
2016-01-28T09:45:54Z

* add VM_STACK as alias for VM_GROWSUP/DOWN depending on architecture
* always account VMAs with flag VM_STACK as stack (as it was before)
* cleanup classifying helpers
* update comments and documentation

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
---
Documentation/filesystems/proc.txt | 4 ++--
include/linux/mm.h | 6 ++++--
include/linux/mm_types.h | 6 +++---
mm/internal.h | 23 +++++++++++++++++++----
4 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index fde9fd06fa98..6a4da2a6d8c9 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -240,8 +240,8 @@ Table 1-2: Contents of the status files (as of 4.1)
RssFile size of resident file mappings
RssShmem size of resident shmem memory (includes SysV shm,
mapping of tmpfs and shared anonymous mappings)
- VmData size of data, stack, and text segments
- VmStk size of data, stack, and text segments
+ VmData size of private data segments
+ VmStk size of stack segments
VmExe size of text segment
VmLib size of shared library code
VmPTE size of page table entries
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f1cd22f2df1a..62fc828c7ec7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -201,11 +201,13 @@ extern unsigned int kobjsize(const void *objp);
#endif

#ifdef CONFIG_STACK_GROWSUP
-#define VM_STACK_FLAGS (VM_GROWSUP | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)
+#define VM_STACK VM_GROWSUP
#else
-#define VM_STACK_FLAGS (VM_GROWSDOWN | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)
+#define VM_STACK VM_GROWSDOWN
#endif

+#define VM_STACK_FLAGS (VM_STACK | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)
+
/*
* Special vmas that are non-mergable, non-mlock()able.
* Note: mm/huge_memory.c VM_NO_THP depends on this definition.
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index d3ebb9d21a53..624b78b848b8 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -424,9 +424,9 @@ struct mm_struct {
unsigned long total_vm; /* Total pages mapped */
unsigned long locked_vm; /* Pages that have PG_mlocked set */
unsigned long pinned_vm; /* Refcount permanently increased */
- unsigned long data_vm; /* VM_WRITE & ~VM_SHARED/GROWSDOWN */
- unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE */
- unsigned long stack_vm; /* VM_GROWSUP/DOWN */
+ unsigned long data_vm; /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
+ unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
+ unsigned long stack_vm; /* VM_STACK */
unsigned long def_flags;
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack;
diff --git a/mm/internal.h b/mm/internal.h
index 6e976302ddd8..a38a21ebddb4 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -216,20 +216,35 @@ static inline bool is_cow_mapping(vm_flags_t flags)
return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
}

+/*
+ * These three helpers classifies VMAs for virtual memory accounting.
+ */
+
+/*
+ * Executable code area - executable, not writable, not stack
+ */
static inline bool is_exec_mapping(vm_flags_t flags)
{
- return (flags & (VM_EXEC | VM_WRITE)) == VM_EXEC;
+ return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC;
}

+/*
+ * Stack area - atomatically grows in one direction
+ *
+ * VM_GROWSUP / VM_GROWSDOWN VMAs are always private anonymous:
+ * do_mmap() forbids all other combinations.
+ */
static inline bool is_stack_mapping(vm_flags_t flags)
{
- return (flags & (VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN))) != 0;
+ return (flags & VM_STACK) == VM_STACK;
}

+/*
+ * Data area - private, writable, not stack
+ */
static inline bool is_data_mapping(vm_flags_t flags)
{
- return (flags & ((VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)) |
- VM_WRITE | VM_SHARED)) == VM_WRITE;
+ return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
}

/* mm/util.c */