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authorNick Piggin <nickpiggin@yahoo.com.au>2005-08-03 20:24:01 +1000
committerLinus Torvalds <torvalds@g5.osdl.org>2005-08-03 09:12:05 -0700
commitf33ea7f404e592e4563b12101b7a4d17da6558d7 (patch)
tree1d587ad8a06cb6d2e3a187f0312c8a524ffefe53
parent5cb4cc0d8211c490537c8568001958fc76741312 (diff)
[PATCH] fix get_user_pages bug
Checking pte_dirty instead of pte_write in __follow_page is problematic for s390, and for copy_one_pte which leaves dirty when clearing write. So revert __follow_page to check pte_write as before, and make do_wp_page pass back a special extra VM_FAULT_WRITE bit to say it has done its full job: once get_user_pages receives this value, it no longer requires pte_write in __follow_page. But most callers of handle_mm_fault, in the various architectures, have switch statements which do not expect this new case. To avoid changing them all in a hurry, make an inline wrapper function (using the old name) that masks off the new bit, and use the extended interface with double underscores. Yes, we do have a call to do_wp_page from do_swap_page, but no need to change that: in rare case it's needed, another do_wp_page will follow. Signed-off-by: Hugh Dickins <hugh@veritas.com> [ Cleanups by Nick Piggin ] Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/linux/mm.h22
-rw-r--r--mm/memory.c31
2 files changed, 40 insertions, 13 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6eb7f48317f8..82d7024f0765 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -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);
diff --git a/mm/memory.c b/mm/memory.c
index 2405289dfdf8..81d7117aa58b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -811,15 +811,18 @@ static struct page *__follow_page(struct mm_struct *mm, unsigned long address,
pte = *ptep;
pte_unmap(ptep);
if (pte_present(pte)) {
- if (write && !pte_dirty(pte))
+ if (write && !pte_write(pte))
goto out;
if (read && !pte_read(pte))
goto out;
pfn = pte_pfn(pte);
if (pfn_valid(pfn)) {
page = pfn_to_page(pfn);
- if (accessed)
+ if (accessed) {
+ if (write && !pte_dirty(pte) &&!PageDirty(page))
+ set_page_dirty(page);
mark_page_accessed(page);
+ }
return page;
}
}
@@ -941,10 +944,11 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
}
spin_lock(&mm->page_table_lock);
do {
+ int write_access = write;
struct page *page;
cond_resched_lock(&mm->page_table_lock);
- while (!(page = follow_page(mm, start, write))) {
+ while (!(page = follow_page(mm, start, write_access))) {
/*
* Shortcut for anonymous pages. We don't want
* to force the creation of pages tables for
@@ -957,7 +961,16 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
break;
}
spin_unlock(&mm->page_table_lock);
- switch (handle_mm_fault(mm,vma,start,write)) {
+ switch (__handle_mm_fault(mm, vma, start,
+ write_access)) {
+ case VM_FAULT_WRITE:
+ /*
+ * do_wp_page has broken COW when
+ * necessary, even if maybe_mkwrite
+ * decided not to set pte_write
+ */
+ write_access = 0;
+ /* FALLTHRU */
case VM_FAULT_MINOR:
tsk->min_flt++;
break;
@@ -1220,6 +1233,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
struct page *old_page, *new_page;
unsigned long pfn = pte_pfn(pte);
pte_t entry;
+ int ret;
if (unlikely(!pfn_valid(pfn))) {
/*
@@ -1247,7 +1261,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
lazy_mmu_prot_update(entry);
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
- return VM_FAULT_MINOR;
+ return VM_FAULT_MINOR|VM_FAULT_WRITE;
}
}
pte_unmap(page_table);
@@ -1274,6 +1288,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
/*
* Re-check the pte - we dropped the lock
*/
+ ret = VM_FAULT_MINOR;
spin_lock(&mm->page_table_lock);
page_table = pte_offset_map(pmd, address);
if (likely(pte_same(*page_table, pte))) {
@@ -1290,12 +1305,13 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
/* Free the old page.. */
new_page = old_page;
+ ret |= VM_FAULT_WRITE;
}
pte_unmap(page_table);
page_cache_release(new_page);
page_cache_release(old_page);
spin_unlock(&mm->page_table_lock);
- return VM_FAULT_MINOR;
+ return ret;
no_new_page:
page_cache_release(old_page);
@@ -1987,7 +2003,6 @@ static inline int handle_pte_fault(struct mm_struct *mm,
if (write_access) {
if (!pte_write(entry))
return do_wp_page(mm, vma, address, pte, pmd, entry);
-
entry = pte_mkdirty(entry);
}
entry = pte_mkyoung(entry);
@@ -2002,7 +2017,7 @@ static inline int handle_pte_fault(struct mm_struct *mm,
/*
* By the time we get here, we already hold the mm semaphore
*/
-int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
+int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
unsigned long address, int write_access)
{
pgd_t *pgd;