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Subject[093/111] HWPOISON: abort on failed unmap
2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

commit 1668bfd5be9d8a52536c4865000fbbe065a3613b upstream.

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>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
mm/memory-failure.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -637,7 +637,7 @@ 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;
@@ -647,15 +647,18 @@ 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
@@ -717,6 +720,8 @@ 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 ref)
@@ -786,8 +791,13 @@ 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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