Subject: + x86-finish-user-fault-error-path-with-fatal-signal.patch added to -mm tree
To: hannes@xxxxxxxxxxx,azurit@xxxxxxxx,kamezawa.hiroyu@xxxxxxxxxxxxxx,kosaki.motohiro@xxxxxxxxxxxxxx,mhocko@xxxxxxx,rientjes@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Mon, 05 Aug 2013 15:05:56 -0700
The patch titled
Subject: x86: finish user fault error path with fatal signal
has been added to the -mm tree. Its filename is
x86-finish-user-fault-error-path-with-fatal-signal.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/x86-finish-user-fault-error-path-with-fatal-signal.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/x86-finish-user-fault-error-path-with-fatal-signal.patch
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: x86: finish user fault error path with fatal signal
The x86 fault handler bails in the middle of error handling when the task
has a fatal signal pending. For a subsequent patch this is a problem in
OOM situations because it relies on pagefault_out_of_memory() being called
even when the task has been killed, to perform proper per-task OOM state
unwinding.
Shortcutting the fault like this is a rather minor optimization that saves
a few instructions in rare cases. Just remove it for user-triggered
faults.
Use the opportunity to split the fault retry handling from actual fault
errors and add locking documentation that reads suprisingly similar to
ARM's.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: azurIt <azurit@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/fault.c | 35 +++++++++++++++++------------------
1 file changed, 17 insertions(+), 18 deletions(-)
diff -puN arch/x86/mm/fault.c~x86-finish-user-fault-error-path-with-fatal-signal arch/x86/mm/fault.c
--- a/arch/x86/mm/fault.c~x86-finish-user-fault-error-path-with-fatal-signal
+++ a/arch/x86/mm/fault.c
@@ -842,23 +842,15 @@ do_sigbus(struct pt_regs *regs, unsigned
force_sig_info_fault(SIGBUS, code, address, tsk, fault);
}
-static noinline int
+static noinline void
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
unsigned long address, unsigned int fault)
{
- /*
- * Pagefault was interrupted by SIGKILL. We have no reason to
- * continue pagefault.
- */
- if (fatal_signal_pending(current)) {
- if (!(fault & VM_FAULT_RETRY))
- up_read(¤t->mm->mmap_sem);
- if (!(error_code & PF_USER))
- no_context(regs, error_code, address, 0, 0);
- return 1;
+ if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
+ up_read(¤t->mm->mmap_sem);
+ no_context(regs, error_code, address, 0, 0);
+ return;
}
- if (!(fault & VM_FAULT_ERROR))
- return 0;
if (fault & VM_FAULT_OOM) {
/* Kernel mode? Handle exceptions or die: */
@@ -866,7 +858,7 @@ mm_fault_error(struct pt_regs *regs, uns
up_read(¤t->mm->mmap_sem);
no_context(regs, error_code, address,
SIGSEGV, SEGV_MAPERR);
- return 1;
+ return;
}
up_read(¤t->mm->mmap_sem);
@@ -884,7 +876,6 @@ mm_fault_error(struct pt_regs *regs, uns
else
BUG();
}
- return 1;
}
static int spurious_fault_check(unsigned long error_code, pte_t *pte)
@@ -1189,9 +1180,17 @@ good_area:
*/
fault = handle_mm_fault(mm, vma, address, flags);
- if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
- if (mm_fault_error(regs, error_code, address, fault))
- return;
+ /*
+ * If we need to retry but a fatal signal is pending, handle the
+ * signal first. We do not need to release the mmap_sem because it
+ * would already be released in __lock_page_or_retry in mm/filemap.c.
+ */
+ if (unlikely((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)))
+ return;
+
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ mm_fault_error(regs, error_code, address, fault);
+ return;
}
/*
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
memcg-dont-initialize-kmem-cache-destroying-work-for-root-caches.patch
mm-kill-one-if-loop-in-__free_pages_bootmem.patch
mm-vmscan-fix-numa-reclaim-balance-problem-in-kswapd.patch
mm-page_alloc-rearrange-watermark-checking-in-get_page_from_freelist.patch
mm-page_alloc-fair-zone-allocator-policy.patch
mm-revert-page-writebackc-subtract-min_free_kbytes-from-dirtyable-memory.patch
memcg-remove-redundant-code-in-mem_cgroup_force_empty_write.patch
memcg-vmscan-integrate-soft-reclaim-tighter-with-zone-shrinking-code.patch
memcg-get-rid-of-soft-limit-tree-infrastructure.patch
vmscan-memcg-do-softlimit-reclaim-also-for-targeted-reclaim.patch
memcg-enhance-memcg-iterator-to-support-predicates.patch
memcg-track-children-in-soft-limit-excess-to-improve-soft-limit.patch
memcg-vmscan-do-not-attempt-soft-limit-reclaim-if-it-would-not-scan-anything.patch
memcg-track-all-children-over-limit-in-the-root.patch
memcg-vmscan-do-not-fall-into-reclaim-all-pass-too-quickly.patch
arch-mm-remove-obsolete-init-oom-protection.patch
arch-mm-do-not-invoke-oom-killer-on-kernel-fault-oom.patch
arch-mm-pass-userspace-fault-flag-to-generic-fault-handler.patch
x86-finish-user-fault-error-path-with-fatal-signal.patch
mm-memcg-enable-memcg-oom-killer-only-for-user-faults.patch
mm-memcg-rework-and-document-oom-waiting-and-wakeup.patch
mm-memcg-do-not-trap-chargers-with-full-callstack-on-oom.patch
swap-add-a-simple-detector-for-inappropriate-swapin-readahead-fix.patch
debugging-keep-track-of-page-owners-fix-2-fix-fix-fix.patch
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