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Subject[PATCH 3.4 11/43] mm/memory-failure.c: dont let collect_procs() skip over processes for MF_ACTION_REQUIRED
Date
3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tony Luck <tony.luck@intel.com>

commit 74614de17db6fb472370c426d4f934d8d616edf2 upstream.

When Linux sees an "action optional" machine check (where h/w has reported
an error that is not in the current execution path) we generally do not
want to signal a process, since most processes do not have a SIGBUS
handler - we'd just prematurely terminate the process for a problem that
they might never actually see.

task_early_kill() decides whether to consider a process - and it checks
whether this specific process has been marked for early signals with
"prctl", or if the system administrator has requested early signals for
all processes using /proc/sys/vm/memory_failure_early_kill.

But for MF_ACTION_REQUIRED case we must not defer. The error is in the
execution path of the current thread so we must send the SIGBUS
immediatley.

Fix by passing a flag argument through collect_procs*() to
task_early_kill() so it knows whether we can defer or must take action.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Chen Gong <gong.chen@linux.jf.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/memory-failure.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -382,10 +382,12 @@ static void kill_procs(struct list_head
}
}

-static int task_early_kill(struct task_struct *tsk)
+static int task_early_kill(struct task_struct *tsk, int force_early)
{
if (!tsk->mm)
return 0;
+ if (force_early)
+ return 1;
if (tsk->flags & PF_MCE_PROCESS)
return !!(tsk->flags & PF_MCE_EARLY);
return sysctl_memory_failure_early_kill;
@@ -395,7 +397,7 @@ static int task_early_kill(struct task_s
* Collect processes when the error hit an anonymous page.
*/
static void collect_procs_anon(struct page *page, struct list_head *to_kill,
- struct to_kill **tkc)
+ struct to_kill **tkc, int force_early)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
@@ -409,7 +411,7 @@ static void collect_procs_anon(struct pa
for_each_process (tsk) {
struct anon_vma_chain *vmac;

- if (!task_early_kill(tsk))
+ if (!task_early_kill(tsk, force_early))
continue;
list_for_each_entry(vmac, &av->head, same_anon_vma) {
vma = vmac->vma;
@@ -427,7 +429,7 @@ static void collect_procs_anon(struct pa
* Collect processes when the error hit a file mapped page.
*/
static void collect_procs_file(struct page *page, struct list_head *to_kill,
- struct to_kill **tkc)
+ struct to_kill **tkc, int force_early)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
@@ -439,7 +441,7 @@ static void collect_procs_file(struct pa
for_each_process(tsk) {
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

- if (!task_early_kill(tsk))
+ if (!task_early_kill(tsk, force_early))
continue;

vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
@@ -465,7 +467,8 @@ static void collect_procs_file(struct pa
* First preallocate one tokill structure outside the spin locks,
* so that we can kill at least one process reasonably reliable.
*/
-static void collect_procs(struct page *page, struct list_head *tokill)
+static void collect_procs(struct page *page, struct list_head *tokill,
+ int force_early)
{
struct to_kill *tk;

@@ -476,9 +479,9 @@ static void collect_procs(struct page *p
if (!tk)
return;
if (PageAnon(page))
- collect_procs_anon(page, tokill, &tk);
+ collect_procs_anon(page, tokill, &tk, force_early);
else
- collect_procs_file(page, tokill, &tk);
+ collect_procs_file(page, tokill, &tk, force_early);
kfree(tk);
}

@@ -948,7 +951,7 @@ static int hwpoison_user_mappings(struct
* there's nothing that can be done.
*/
if (kill)
- collect_procs(ppage, &tokill);
+ collect_procs(ppage, &tokill, flags & MF_ACTION_REQUIRED);

if (hpage != ppage)
lock_page(ppage);



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