A few cleanups, given the munlock fix: the comment on ksm_test_exit()
no longer applies, and it can be made private to ksm.c; there's no
more reference to mmu_gather or tlb.h, and mmap.c doesn't need ksm.h.
Signed-off-by: Hugh Dickins <[email protected]>
---
include/linux/ksm.h | 20 --------------------
mm/ksm.c | 14 +++++++++++++-
mm/mmap.c | 1 -
3 files changed, 13 insertions(+), 22 deletions(-)
--- mmotm/include/linux/ksm.h 2009-09-05 14:40:16.000000000 +0100
+++ linux/include/linux/ksm.h 2009-09-05 16:41:55.000000000 +0100
@@ -12,8 +12,6 @@
#include <linux/sched.h>
#include <linux/vmstat.h>
-struct mmu_gather;
-
#ifdef CONFIG_KSM
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
unsigned long end, int advice, unsigned long *vm_flags);
@@ -27,19 +25,6 @@ static inline int ksm_fork(struct mm_str
return 0;
}
-/*
- * For KSM to handle OOM without deadlock when it's breaking COW in a
- * likely victim of the OOM killer, exit_mmap() has to serialize with
- * ksm_exit() after freeing mm's pages but before freeing its page tables.
- * That leaves a window in which KSM might refault pages which have just
- * been finally unmapped: guard against that with ksm_test_exit(), and
- * use it after getting mmap_sem in ksm.c, to check if mm is exiting.
- */
-static inline bool ksm_test_exit(struct mm_struct *mm)
-{
- return atomic_read(&mm->mm_users) == 0;
-}
-
static inline void ksm_exit(struct mm_struct *mm)
{
if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
@@ -78,11 +63,6 @@ static inline int ksm_fork(struct mm_str
{
return 0;
}
-
-static inline bool ksm_test_exit(struct mm_struct *mm)
-{
- return 0;
-}
static inline void ksm_exit(struct mm_struct *mm)
{
--- mmotm/mm/ksm.c 2009-09-05 14:40:16.000000000 +0100
+++ linux/mm/ksm.c 2009-09-05 16:41:55.000000000 +0100
@@ -32,7 +32,6 @@
#include <linux/mmu_notifier.h>
#include <linux/ksm.h>
-#include <asm/tlb.h>
#include <asm/tlbflush.h>
/*
@@ -285,6 +284,19 @@ static inline int in_stable_tree(struct
}
/*
+ * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's
+ * page tables after it has passed through ksm_exit() - which, if necessary,
+ * takes mmap_sem briefly to serialize against them. ksm_exit() does not set
+ * a special flag: they can just back out as soon as mm_users goes to zero.
+ * ksm_test_exit() is used throughout to make this test for exit: in some
+ * places for correctness, in some places just to avoid unnecessary work.
+ */
+static inline bool ksm_test_exit(struct mm_struct *mm)
+{
+ return atomic_read(&mm->mm_users) == 0;
+}
+
+/*
* We use break_ksm to break COW on a ksm page: it's a stripped down
*
* if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1)
--- mmotm/mm/mmap.c 2009-09-05 14:40:16.000000000 +0100
+++ linux/mm/mmap.c 2009-09-05 16:41:55.000000000 +0100
@@ -27,7 +27,6 @@
#include <linux/mount.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
-#include <linux/ksm.h>
#include <linux/mmu_notifier.h>
#include <linux/perf_counter.h>
#include <linux/hugetlb.h>
Just as the swapoff system call allocates many pages of RAM to various
processes, perhaps triggering OOM, so "echo 2 >/sys/kernel/mm/ksm/run"
(unmerge) is liable to allocate many pages of RAM to various processes,
perhaps triggering OOM; and each is normally run from a modest admin
process (swapoff or shell), easily repeated until it succeeds.
So treat unmerge_and_remove_all_rmap_items() in the same way that we
treat try_to_unuse(): generalize PF_SWAPOFF to PF_OOM_ORIGIN, and
bracket both with that, to ask the OOM killer to kill them first,
to prevent them from spawning more and more OOM kills.
Signed-off-by: Hugh Dickins <[email protected]>
---
include/linux/sched.h | 2 +-
mm/ksm.c | 2 ++
mm/oom_kill.c | 2 +-
mm/swapfile.c | 4 ++--
4 files changed, 6 insertions(+), 4 deletions(-)
--- mmotm/include/linux/sched.h 2009-09-05 14:40:16.000000000 +0100
+++ linux/include/linux/sched.h 2009-09-05 16:41:55.000000000 +0100
@@ -1755,7 +1755,7 @@ extern cputime_t task_gtime(struct task_
#define PF_FROZEN 0x00010000 /* frozen for system suspend */
#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
#define PF_KSWAPD 0x00040000 /* I am kswapd */
-#define PF_SWAPOFF 0x00080000 /* I am in swapoff */
+#define PF_OOM_ORIGIN 0x00080000 /* Allocating much memory to others */
#define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
--- mmotm/mm/ksm.c 2009-09-05 14:40:16.000000000 +0100
+++ linux/mm/ksm.c 2009-09-05 16:41:55.000000000 +0100
@@ -1564,7 +1564,9 @@ static ssize_t run_store(struct kobject
if (ksm_run != flags) {
ksm_run = flags;
if (flags & KSM_RUN_UNMERGE) {
+ current->flags |= PF_OOM_ORIGIN;
err = unmerge_and_remove_all_rmap_items();
+ current->flags &= ~PF_OOM_ORIGIN;
if (err) {
ksm_run = KSM_RUN_STOP;
count = err;
--- mmotm/mm/oom_kill.c 2009-09-05 14:40:16.000000000 +0100
+++ linux/mm/oom_kill.c 2009-09-05 16:41:55.000000000 +0100
@@ -103,7 +103,7 @@ unsigned long badness(struct task_struct
/*
* swapoff can easily use up all memory, so kill those first.
*/
- if (p->flags & PF_SWAPOFF)
+ if (p->flags & PF_OOM_ORIGIN)
return ULONG_MAX;
/*
--- mmotm/mm/swapfile.c 2009-09-05 14:40:16.000000000 +0100
+++ linux/mm/swapfile.c 2009-09-05 16:41:55.000000000 +0100
@@ -1573,9 +1573,9 @@ SYSCALL_DEFINE1(swapoff, const char __us
p->flags &= ~SWP_WRITEOK;
spin_unlock(&swap_lock);
- current->flags |= PF_SWAPOFF;
+ current->flags |= PF_OOM_ORIGIN;
err = try_to_unuse(type);
- current->flags &= ~PF_SWAPOFF;
+ current->flags &= ~PF_OOM_ORIGIN;
if (err) {
/* re-insert swap space back into swap_list */
mremap move's use of ksm_madvise() was assuming -ENOMEM on failure,
because ksm_madvise used to say -EAGAIN for that; but ksm_madvise now
says -ENOMEM (letting madvise convert that to -EAGAIN), and can also
say -ERESTARTSYS when signalled: so pass the error from ksm_madvise.
Signed-off-by: Hugh Dickins <[email protected]>
---
mm/mremap.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- mmotm/mm/mremap.c 2009-09-05 14:40:16.000000000 +0100
+++ linux/mm/mremap.c 2009-09-05 16:41:55.000000000 +0100
@@ -175,6 +175,7 @@ static unsigned long move_vma(struct vm_
unsigned long excess = 0;
unsigned long hiwater_vm;
int split = 0;
+ int err;
/*
* We'd prefer to avoid failure later on in do_munmap:
@@ -190,9 +191,10 @@ static unsigned long move_vma(struct vm_
* pages recently unmapped. But leave vma->vm_flags as it was,
* so KSM can come around to merge on vma and new_vma afterwards.
*/
- if (ksm_madvise(vma, old_addr, old_addr + old_len,
- MADV_UNMERGEABLE, &vm_flags))
- return -ENOMEM;
+ err = ksm_madvise(vma, old_addr, old_addr + old_len,
+ MADV_UNMERGEABLE, &vm_flags);
+ if (err)
+ return err;
new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
Hugh Dickins wrote:
> A few cleanups, given the munlock fix: the comment on ksm_test_exit()
> no longer applies, and it can be made private to ksm.c; there's no
> more reference to mmu_gather or tlb.h, and mmap.c doesn't need ksm.h.
>
> Signed-off-by: Hugh Dickins <[email protected]>
> ---
>
>
Acked-by: Izik Eidus <[email protected]>
Hugh Dickins wrote:
> Just as the swapoff system call allocates many pages of RAM to various
> processes, perhaps triggering OOM, so "echo 2 >/sys/kernel/mm/ksm/run"
> (unmerge) is liable to allocate many pages of RAM to various processes,
> perhaps triggering OOM; and each is normally run from a modest admin
> process (swapoff or shell), easily repeated until it succeeds.
>
> So treat unmerge_and_remove_all_rmap_items() in the same way that we
> treat try_to_unuse(): generalize PF_SWAPOFF to PF_OOM_ORIGIN, and
> bracket both with that, to ask the OOM killer to kill them first,
> to prevent them from spawning more and more OOM kills.
>
> Signed-off-by: Hugh Dickins <[email protected]>
> ---
>
Acked-by: Izik Eidus <[email protected]>
Hugh Dickins wrote:
> mremap move's use of ksm_madvise() was assuming -ENOMEM on failure,
> because ksm_madvise used to say -EAGAIN for that; but ksm_madvise now
> says -ENOMEM (letting madvise convert that to -EAGAIN), and can also
> say -ERESTARTSYS when signalled: so pass the error from ksm_madvise.
>
> Signed-off-by: Hugh Dickins <[email protected]>
> ---
>
Acked-by: Izik Eidus <[email protected]>