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Subject[PATCH] [11/31] HWPOISON: introduce delete_from_lru_cache()
Date

From: Wu Fengguang <fengguang.wu@intel.com>

Introduce delete_from_lru_cache() to
- clear PG_active, PG_unevictable to avoid complains at unpoison time
- move the isolate_lru_page() call back to the handlers instead of the
entrance of __memory_failure(), this is more hwpoison filter friendly

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
mm/memory-failure.c | 45 +++++++++++++++++++++++++++++++++++++--------
1 file changed, 37 insertions(+), 8 deletions(-)
Index: linux/mm/memory-failure.c
===================================================================
--- linux.orig/mm/memory-failure.c
+++ linux/mm/memory-failure.c
@@ -350,6 +350,30 @@ static const char *action_name[] = {
};

/*
+ * XXX: It is possible that a page is isolated from LRU cache,
+ * and then kept in swap cache or failed to remove from page cache.
+ * The page count will stop it from being freed by unpoison.
+ * Stress tests should be aware of this memory leak problem.
+ */
+static int delete_from_lru_cache(struct page *p)
+{
+ if (!isolate_lru_page(p)) {
+ /*
+ * Clear sensible page flags, so that the buddy system won't
+ * complain when the page is unpoison-and-freed.
+ */
+ ClearPageActive(p);
+ ClearPageUnevictable(p);
+ /*
+ * drop the page count elevated by isolate_lru_page()
+ */
+ page_cache_release(p);
+ return 0;
+ }
+ return -EIO;
+}
+
+/*
* Error hit kernel page.
* Do nothing, try to be lucky and not touch this instead. For a few cases we
* could be more sophisticated.
@@ -393,6 +417,8 @@ static int me_pagecache_clean(struct pag
int ret = FAILED;
struct address_space *mapping;

+ delete_from_lru_cache(p);
+
/*
* For anonymous pages we're done the only reference left
* should be the one m_f() holds.
@@ -522,14 +548,20 @@ static int me_swapcache_dirty(struct pag
/* Trigger EIO in shmem: */
ClearPageUptodate(p);

- return DELAYED;
+ if (!delete_from_lru_cache(p))
+ return DELAYED;
+ else
+ return FAILED;
}

static int me_swapcache_clean(struct page *p, unsigned long pfn)
{
delete_from_swap_cache(p);

- return RECOVERED;
+ if (!delete_from_lru_cache(p))
+ return RECOVERED;
+ else
+ return FAILED;
}

/*
@@ -748,7 +780,6 @@ static int hwpoison_user_mappings(struct

int __memory_failure(unsigned long pfn, int trapno, int flags)
{
- unsigned long lru_flag;
struct page_state *ps;
struct page *p;
int res;
@@ -798,13 +829,11 @@ int __memory_failure(unsigned long pfn,
*/
if (!PageLRU(p))
lru_add_drain_all();
- lru_flag = p->flags & lru;
- if (isolate_lru_page(p)) {
+ if (!PageLRU(p)) {
action_result(pfn, "non LRU", IGNORED);
put_page(p);
return -EBUSY;
}
- page_cache_release(p);

/*
* Lock the page and wait for writeback to finish.
@@ -827,7 +856,7 @@ int __memory_failure(unsigned long pfn,
/*
* Torn down by someone else?
*/
- if ((lru_flag & lru) && !PageSwapCache(p) && p->mapping == NULL) {
+ if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
action_result(pfn, "already truncated LRU", IGNORED);
res = 0;
goto out;
@@ -835,7 +864,7 @@ int __memory_failure(unsigned long pfn,

res = -EBUSY;
for (ps = error_states;; ps++) {
- if (((p->flags | lru_flag)& ps->mask) == ps->res) {
+ if ((p->flags & ps->mask) == ps->res) {
res = page_action(ps, p, pfn);
break;
}

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