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Subject[PATCH] [8/31] HWPOISON: abort on failed unmap
Date

From: Wu Fengguang <fengguang.wu@intel.com>

Don't try to isolate a still mapped page. Otherwise we will hit the
BUG_ON(page_mapped(page)) in __remove_from_page_cache().

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
mm/memory-failure.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

Index: linux/mm/memory-failure.c
===================================================================
--- linux.orig/mm/memory-failure.c
+++ linux/mm/memory-failure.c
@@ -657,7 +657,7 @@ static int page_action(struct page_state
* Do all that is necessary to remove user space mappings. Unmap
* the pages and send SIGBUS to the processes if the data was dirty.
*/
-static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
+static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
int trapno)
{
enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
@@ -667,15 +667,18 @@ static void hwpoison_user_mappings(struc
int i;
int kill = 1;

- if (PageReserved(p) || PageCompound(p) || PageSlab(p) || PageKsm(p))
- return;
+ if (PageReserved(p) || PageSlab(p))
+ return SWAP_SUCCESS;

/*
* This check implies we don't kill processes if their pages
* are in the swap cache early. Those are always late kills.
*/
if (!page_mapped(p))
- return;
+ return SWAP_SUCCESS;
+
+ if (PageCompound(p) || PageKsm(p))
+ return SWAP_FAIL;

if (PageSwapCache(p)) {
printk(KERN_ERR
@@ -737,6 +740,8 @@ static void hwpoison_user_mappings(struc
*/
kill_procs_ao(&tokill, !!PageDirty(p), trapno,
ret != SWAP_SUCCESS, pfn);
+
+ return ret;
}

int __memory_failure(unsigned long pfn, int trapno, int flags)
@@ -809,8 +814,13 @@ int __memory_failure(unsigned long pfn,

/*
* Now take care of user space mappings.
+ * Abort on fail: __remove_from_page_cache() assumes unmapped page.
*/
- hwpoison_user_mappings(p, pfn, trapno);
+ if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
+ printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
+ res = -EBUSY;
+ goto out;
+ }

/*
* Torn down by someone else?

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