The patch titled
mm: more rmap checking
has been removed from the -mm tree. Its filename was
mm-more-rmap-checking.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: mm: more rmap checking
From: Nick Piggin <npiggin@xxxxxxx>
Re-introduce rmap verification patches that Hugh removed when he removed
PG_map_lock. PG_map_lock actually isn't needed to synchronise access to
anonymous pages, because PG_locked and PTL together already do.
These checks were important in discovering and fixing a rare rmap corruption
in SLES9.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rmap.h | 13 +++------
mm/memory.c | 2 -
mm/rmap.c | 58 +++++++++++++++++++++++++++++++++++++++--
3 files changed, 62 insertions(+), 11 deletions(-)
diff -puN include/linux/rmap.h~mm-more-rmap-checking include/linux/rmap.h
--- a/include/linux/rmap.h~mm-more-rmap-checking
+++ a/include/linux/rmap.h
@@ -74,17 +74,14 @@ void page_add_new_anon_rmap(struct page
void page_add_file_rmap(struct page *);
void page_remove_rmap(struct page *, struct vm_area_struct *);
-/**
- * page_dup_rmap - duplicate pte mapping to a page
- * @page: the page to add the mapping to
- *
- * For copy_page_range only: minimal extract from page_add_rmap,
- * avoiding unnecessary tests (already checked) so it's quicker.
- */
-static inline void page_dup_rmap(struct page *page)
+#ifdef CONFIG_DEBUG_VM
+void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address);
+#else
+static inline void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
{
atomic_inc(&page->_mapcount);
}
+#endif
/*
* Called from mm/vmscan.c to handle paging out
diff -puN mm/memory.c~mm-more-rmap-checking mm/memory.c
--- a/mm/memory.c~mm-more-rmap-checking
+++ a/mm/memory.c
@@ -481,7 +481,7 @@ copy_one_pte(struct mm_struct *dst_mm, s
page = vm_normal_page(vma, addr, pte);
if (page) {
get_page(page);
- page_dup_rmap(page);
+ page_dup_rmap(page, vma, addr);
rss[!!PageAnon(page)]++;
}
diff -puN mm/rmap.c~mm-more-rmap-checking mm/rmap.c
--- a/mm/rmap.c~mm-more-rmap-checking
+++ a/mm/rmap.c
@@ -530,19 +530,51 @@ static void __page_set_anon_rmap(struct
}
/**
+ * page_set_anon_rmap - sanity check anonymous rmap addition
+ * @page: the page to add the mapping to
+ * @vma: the vm area in which the mapping is added
+ * @address: the user virtual address mapped
+ */
+static void __page_check_anon_rmap(struct page *page,
+ struct vm_area_struct *vma, unsigned long address)
+{
+#ifdef CONFIG_DEBUG_VM
+ /*
+ * The page's anon-rmap details (mapping and index) are guaranteed to
+ * be set up correctly at this point.
+ *
+ * We have exclusion against page_add_anon_rmap because the caller
+ * always holds the page locked, except if called from page_dup_rmap,
+ * in which case the page is already known to be setup.
+ *
+ * We have exclusion against page_add_new_anon_rmap because those pages
+ * are initially only visible via the pagetables, and the pte is locked
+ * over the call to page_add_new_anon_rmap.
+ */
+ struct anon_vma *anon_vma = vma->anon_vma;
+ anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+ BUG_ON(page->mapping != (struct address_space *)anon_vma);
+ BUG_ON(page->index != linear_page_index(vma, address));
+#endif
+}
+
+/**
* page_add_anon_rmap - add pte mapping to an anonymous page
* @page: the page to add the mapping to
* @vma: the vm area in which the mapping is added
* @address: the user virtual address mapped
*
- * The caller needs to hold the pte lock.
+ * The caller needs to hold the pte lock and the page must be locked.
*/
void page_add_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
+ VM_BUG_ON(!PageLocked(page));
+ VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
if (atomic_inc_and_test(&page->_mapcount))
__page_set_anon_rmap(page, vma, address);
- /* else checking page index and mapping is racy */
+ else
+ __page_check_anon_rmap(page, vma, address);
}
/*
@@ -553,10 +585,12 @@ void page_add_anon_rmap(struct page *pag
*
* Same as page_add_anon_rmap but must only be called on *new* pages.
* This means the inc-and-test can be bypassed.
+ * Page does not have to be locked.
*/
void page_add_new_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
+ BUG_ON(address < vma->vm_start || address >= vma->vm_end);
atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
__page_set_anon_rmap(page, vma, address);
}
@@ -573,6 +607,26 @@ void page_add_file_rmap(struct page *pag
__inc_zone_page_state(page, NR_FILE_MAPPED);
}
+#ifdef CONFIG_DEBUG_VM
+/**
+ * page_dup_rmap - duplicate pte mapping to a page
+ * @page: the page to add the mapping to
+ *
+ * For copy_page_range only: minimal extract from page_add_file_rmap /
+ * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
+ * quicker.
+ *
+ * The caller needs to hold the pte lock.
+ */
+void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
+{
+ BUG_ON(page_mapcount(page) == 0);
+ if (PageAnon(page))
+ __page_check_anon_rmap(page, vma, address);
+ atomic_inc(&page->_mapcount);
+}
+#endif
+
/**
* page_remove_rmap - take down pte mapping from a page
* @page: page to remove mapping from
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
origin.patch
mm-fix-fault-vs-invalidate-race-for-linear-mappings.patch
mm-merge-populate-and-nopage-into-fault-fixes-nonlinear.patch
mm-merge-nopfn-into-fault.patch
mm-remove-legacy-cruft.patch
mm-debug-check-for-the-fault-vs-invalidate-race.patch
mm-fix-clear_page_dirty_for_io-vs-fault-race.patch
mm-document-fault_data-and-flags.patch
fs-introduce-some-page-buffer-invariants.patch
-
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