On Tue 24-05-16 12:01:42, Vladimir Davydov wrote:
> On Tue, May 24, 2016 at 10:47:37AM +0200, Michal Hocko wrote:
> > On Tue 24-05-16 11:43:19, Vladimir Davydov wrote:
> > > On Mon, May 23, 2016 at 07:44:43PM +0200, Michal Hocko wrote:
> > > > On Mon 23-05-16 19:02:10, Vladimir Davydov wrote:
> > > > > mem_cgroup_oom may be invoked multiple times while a process is
> > > > > handling
> > > > > a page fault, in which case current->memcg_in_oom will be overwritten
> > > > > leaking the previously taken css reference.
> > > >
> > > > Have you seen this happening? I was under impression that the page fault
> > > > paths that have oom enabled will not retry allocations.
> > >
> > > filemap_fault will, for readahead.
> >
> > I thought that the readahead is __GFP_NORETRY so we do not trigger OOM
> > killer.
>
> Hmm, interesting. We do allocate readahead pages with __GFP_NORETRY, but
> we add them to page cache and hence charge with GFP_KERNEL or GFP_NOFS
> mask, see __do_page_cache_readahaed -> read_pages.
I guess we do not want to trigger OOM just because of readahead. What do
you think about the following? I will cook up a full patch if this
(untested) looks ok.
---
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 97354102794d..81363b834900 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -209,10 +209,10 @@ static inline struct page *page_cache_alloc_cold(struct
address_space *x)
return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
}
-static inline struct page *page_cache_alloc_readahead(struct address_space *x)
+static inline gfp_t readahead_gfp_mask(struct address_space *x)
{
- return __page_cache_alloc(mapping_gfp_mask(x) |
- __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN);
+ return mapping_gfp_mask(x) |
+ __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN;
}
typedef int filler_t(void *, struct page *);
diff --git a/mm/readahead.c b/mm/readahead.c
index 40be3ae0afe3..7431fefe4ede 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -108,7 +108,7 @@ int read_cache_pages(struct address_space *mapping, struct
list_head *pages,
EXPORT_SYMBOL(read_cache_pages);
static int read_pages(struct address_space *mapping, struct file *filp,
- struct list_head *pages, unsigned nr_pages)
+ struct list_head *pages, unsigned nr_pages, gfp_t gfp_mask)
{
struct blk_plug plug;
unsigned page_idx;
@@ -126,8 +126,7 @@ static int read_pages(struct address_space *mapping, struct
file *filp,
for (page_idx = 0; page_idx < nr_pages; page_idx++) {
struct page *page = lru_to_page(pages);
list_del(&page->lru);
- if (!add_to_page_cache_lru(page, mapping, page->index,
- mapping_gfp_constraint(mapping, GFP_KERNEL))) {
+ if (!add_to_page_cache_lru(page, mapping, page->index,
gfp_mask)) {
mapping->a_ops->readpage(filp, page);
}
put_page(page);
@@ -159,6 +158,7 @@ int __do_page_cache_readahead(struct address_space
*mapping, struct file *filp,
int page_idx;
int ret = 0;
loff_t isize = i_size_read(inode);
+ gfp_t gfp_mask = readahead_gfp_mask(mapping);
if (isize == 0)
goto out;
@@ -180,7 +180,7 @@ int __do_page_cache_readahead(struct address_space
*mapping, struct file *filp,
if (page && !radix_tree_exceptional_entry(page))
continue;
- page = page_cache_alloc_readahead(mapping);
+ page = __page_cache_alloc(gfp_mask);
if (!page)
break;
page->index = page_offset;
@@ -196,7 +196,7 @@ int __do_page_cache_readahead(struct address_space
*mapping, struct file *filp,
* will then handle the error.
*/
if (ret)
- read_pages(mapping, filp, &page_pool, ret);
+ read_pages(mapping, filp, &page_pool, ret, gfp_mask);
BUG_ON(!list_empty(&page_pool));
out:
return ret;
--
Michal Hocko
SUSE Labs
