[PATCH] mm: add a note about partially hardcoded VM_* flags

[deliverable/linux.git] / include / linux / mm.h

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6eb7f48317f8f14a5493e234429697a0c9898d7d..097b3a3c693d58c924dd7409db1dd295ebfe8a23 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -136,6 +136,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_EXEC                0x00000004
 #define VM_SHARED      0x00000008
 
+/* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for r/w/x bits. */
 #define VM_MAYREAD     0x00000010      /* limits for mprotect() etc */
 #define VM_MAYWRITE    0x00000020
 #define VM_MAYEXEC     0x00000040
@@ -350,7 +351,8 @@ static inline void put_page(struct page *page)
  * only one copy in memory, at most, normally.
  *
  * For the non-reserved pages, page_count(page) denotes a reference count.
- *   page_count() == 0 means the page is free.
+ *   page_count() == 0 means the page is free. page->lru is then used for
+ *   freelist management in the buddy allocator.
  *   page_count() == 1 means the page is used for exactly one purpose
  *   (e.g. a private data page of one process).
  *
@@ -376,10 +378,8 @@ static inline void put_page(struct page *page)
  * attaches, plus 1 if `private' contains something, plus one for
  * the page cache itself.
  *
- * All pages belonging to an inode are in these doubly linked lists:
- * mapping->clean_pages, mapping->dirty_pages and mapping->locked_pages;
- * using the page->list list_head. These fields are also used for
- * freelist managemet (when page_count()==0).
+ * Instead of keeping dirty/clean pages in per address-space lists, we instead
+ * now tag pages as dirty/under writeback in the radix tree.
  *
  * There is also a per-mapping radix tree mapping index to the page
  * in memory if present. The tree is rooted at mapping->root.  
@@ -625,10 +625,16 @@ static inline int page_mapped(struct page *page)
  * Used to decide whether a process gets delivered SIGBUS or
  * just gets major/minor fault counters bumped up.
  */
-#define VM_FAULT_OOM   (-1)
-#define VM_FAULT_SIGBUS        0
-#define VM_FAULT_MINOR 1
-#define VM_FAULT_MAJOR 2
+#define VM_FAULT_OOM   0x00
+#define VM_FAULT_SIGBUS        0x01
+#define VM_FAULT_MINOR 0x02
+#define VM_FAULT_MAJOR 0x03
+
+/* 
+ * Special case for get_user_pages.
+ * Must be in a distinct bit from the above VM_FAULT_ flags.
+ */
+#define VM_FAULT_WRITE 0x10
 
 #define offset_in_page(p)      ((unsigned long)(p) & ~PAGE_MASK)
 
@@ -704,7 +710,13 @@ extern pte_t *FASTCALL(pte_alloc_kernel(struct mm_struct *mm, pmd_t *pmd, unsign
 extern pte_t *FASTCALL(pte_alloc_map(struct mm_struct *mm, pmd_t *pmd, unsigned long address));
 extern int install_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, struct page *page, pgprot_t prot);
 extern int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, unsigned long pgoff, pgprot_t prot);
-extern int handle_mm_fault(struct mm_struct *mm,struct vm_area_struct *vma, unsigned long address, int write_access);
+extern int __handle_mm_fault(struct mm_struct *mm,struct vm_area_struct *vma, unsigned long address, int write_access);
+
+static inline int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access)
+{
+       return __handle_mm_fault(mm, vma, address, write_access) & (~VM_FAULT_WRITE);
+}
+
 extern int make_pages_present(unsigned long addr, unsigned long end);
 extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write);
 void install_arg_page(struct vm_area_struct *, struct page *, unsigned long);