Change since V1: rebase on 3.2-rc1
Currently RSS rlimit is not enforced. We can not forbid a process to exceeds
its RSS limit and allow it swap out. That would hurts the performance of all
system, even when memory resources are plentiful.
Therefore, instead of enforcing a limit on rss usage alone, this patch enforces
a limit on rss+swap value. This is similar to memsw limits of cgroup.
If a process rss+swap usage exceeds RLIMIT_RSS max limit, he received a SIGBUS
signal.
My tests show that code in do_anonymous_page() and __do_fault() indeed prevents
processes to get more memory than the limit and I haven't seen any adverse
effect, but so far, I have no test coverage of the code in do_wp_page(). I'm
not sure how to test it.
Signed-off-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
---
include/linux/mm.h | 7 +++++++
mm/memory.c | 21 +++++++++++++++++++--
2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3dc3a8c..3b54ff1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1092,6 +1092,13 @@ static inline unsigned long get_mm_rss(struct mm_struct *mm)
get_mm_counter(mm, MM_ANONPAGES);
}
+static inline unsigned long get_mm_memsw(struct mm_struct *mm)
+{
+ return get_mm_counter(mm, MM_FILEPAGES) +
+ get_mm_counter(mm, MM_ANONPAGES) +
+ get_mm_counter(mm, MM_SWAPENTS);
+}
+
static inline unsigned long get_mm_hiwater_rss(struct mm_struct *mm)
{
return max(mm->hiwater_rss, get_mm_rss(mm));
diff --git a/mm/memory.c b/mm/memory.c
index 829d437..b0463c2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2661,8 +2661,14 @@ gotten:
dec_mm_counter_fast(mm, MM_FILEPAGES);
inc_mm_counter_fast(mm, MM_ANONPAGES);
}
- } else
+ } else {
+ if (get_mm_memsw(mm) >=
+ rlimit_max(RLIMIT_RSS) >> PAGE_SHIFT) {
+ ret |= VM_FAULT_SIGBUS;
+ goto release;
+ }
inc_mm_counter_fast(mm, MM_ANONPAGES);
+ }
flush_cache_page(vma, address, pte_pfn(orig_pte));
entry = mk_pte(new_page, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
@@ -2713,6 +2719,7 @@ gotten:
} else
mem_cgroup_uncharge_page(new_page);
+release:
if (new_page)
page_cache_release(new_page);
unlock:
@@ -3073,6 +3080,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page *page;
spinlock_t *ptl;
pte_t entry;
+ int ret = 0;
pte_unmap(page_table);
@@ -3109,6 +3117,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (!pte_none(*page_table))
goto release;
+ if (get_mm_memsw(mm) >= rlimit_max(RLIMIT_RSS) >> PAGE_SHIFT) {
+ ret = VM_FAULT_SIGBUS;
+ goto release;
+ }
inc_mm_counter_fast(mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, address);
setpte:
@@ -3118,7 +3130,7 @@ setpte:
update_mmu_cache(vma, address, page_table);
unlock:
pte_unmap_unlock(page_table, ptl);
- return 0;
+ return ret;
release:
mem_cgroup_uncharge_page(page);
page_cache_release(page);
@@ -3263,6 +3275,10 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
entry = mk_pte(page, vma->vm_page_prot);
if (flags & FAULT_FLAG_WRITE)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ if (get_mm_memsw(mm) >= rlimit_max(RLIMIT_RSS) >> PAGE_SHIFT) {
+ ret = VM_FAULT_SIGBUS;
+ goto unlock;
+ }
if (anon) {
inc_mm_counter_fast(mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, address);
@@ -3287,6 +3303,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
anon = 1; /* no anon but release faulted_page */
}
+unlock:
pte_unmap_unlock(page_table, ptl);
if (dirty_page) {
--
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