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Subject[PATCH] z3fold: fix wrong handling of headless pages
Date
During the processing of headless pages in z3fold_reclaim_page(),
there was a problem that the zhdr pointed to another page
or a page was already 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 | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 4b366d1..201a8ac 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -746,6 +746,9 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
}

if (bud == HEADLESS) {
+ if (test_bit(UNDER_RECLAIM, &page->private))
+ return;
+
spin_lock(&pool->lock);
list_del(&page->lru);
spin_unlock(&pool->lock);
@@ -836,20 +839,20 @@ 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);
list_del_init(&zhdr->buddy);
zhdr->cpu = -1;
- set_bit(UNDER_RECLAIM, &page->private);
break;
}

+ set_bit(UNDER_RECLAIM, &page->private);
list_del_init(&page->lru);
spin_unlock(&pool->lock);

@@ -898,6 +901,7 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
if (test_bit(PAGE_HEADLESS, &page->private)) {
if (ret == 0) {
free_z3fold_page(page);
+ atomic64_dec(&pool->pages_nr);
return 0;
}
spin_lock(&pool->lock);
--
2.7.4
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