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Subject[PATCH v2] z3fold: fix reclaim lock-ups
Date
In the processing of headless pages, there was a problem that the
zhdr pointed to another page or a page was alread released in
z3fold_free(). So, the wrong page is encoded in headless, or test_bit
does not work properly in z3fold_reclaim_page(). This patch fixed these
problems.

Signed-off-by: Jongseok Kim <ks77sj@gmail.com>
---
mm/z3fold.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index d5b3f49..a36ffa5ab 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -819,6 +819,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
{
int i, ret = 0;
+ bool is_headless;
struct z3fold_header *zhdr = NULL;
struct page *page = NULL;
struct list_head *pos;
@@ -836,11 +837,11 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
}
list_for_each_prev(pos, &pool->lru) {
page = list_entry(pos, struct page, lru);
+ zhdr = page_address(page);
if (test_bit(PAGE_HEADLESS, &page->private))
/* candidate found */
break;

- zhdr = page_address(page);
if (!z3fold_page_trylock(zhdr))
continue; /* can't evict at this point */
kref_get(&zhdr->refcount);
@@ -873,9 +874,11 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
* reference to this page
*/
z3fold_page_unlock(zhdr);
+ is_headless = false;
} else {
first_handle = encode_handle(zhdr, HEADLESS);
last_handle = middle_handle = 0;
+ is_headless = true;
}

/* Issue the eviction callback(s) */
@@ -895,11 +898,10 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
goto next;
}
next:
- if (test_bit(PAGE_HEADLESS, &page->private)) {
- if (ret == 0) {
- free_z3fold_page(page);
+ if (is_headless) {
+ if (ret == 0)
return 0;
- }
+
spin_lock(&pool->lock);
list_add(&page->lru, &pool->lru);
spin_unlock(&pool->lock);
--
2.7.4
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