From: Vitaly Wool <vitalywool@gmail.com>
To: <linux-mm@kvack.org>, linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH 3/3] z3fold: protect handle reads
Date: Wed, 27 Nov 2019 15:23:45 +0100 [thread overview]
Message-ID: <20191127152345.8059852f60947686674d726d@gmail.com> (raw)
In-Reply-To: <20191127152012.17a4b35f9e7f6e50f9aaca9c@gmail.com>
We need to make sure slots are protected on reading a handle. Since
handles are modified by free_handle() which only takes slot rwlock,
that lock should be used when handles are read.
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
---
mm/z3fold.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index f2a75418e248..43754d8ebce8 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -486,8 +486,12 @@ static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
/* only for LAST bud, returns zero otherwise */
static unsigned short handle_to_chunks(unsigned long handle)
{
- unsigned long addr = *(unsigned long *)handle;
+ struct z3fold_buddy_slots *slots = handle_to_slots(handle);
+ unsigned long addr;
+ read_lock(&slots->lock);
+ addr = *(unsigned long *)handle;
+ read_unlock(&slots->lock);
return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
}
@@ -499,10 +503,13 @@ static unsigned short handle_to_chunks(unsigned long handle)
static enum buddy handle_to_buddy(unsigned long handle)
{
struct z3fold_header *zhdr;
+ struct z3fold_buddy_slots *slots = handle_to_slots(handle);
unsigned long addr;
+ read_lock(&slots->lock);
WARN_ON(handle & (1 << PAGE_HEADLESS));
addr = *(unsigned long *)handle;
+ read_unlock(&slots->lock);
zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
return (addr - zhdr->first_num) & BUDDY_MASK;
}
--
2.17.1
prev parent reply other threads:[~2019-11-27 14:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 14:20 [PATCH 0/3] z3fold fixes for intra-page compaction Vitaly Wool
2019-11-27 14:21 ` [PATCH 1/3] z3fold: avoid subtle race when freeing slots Vitaly Wool
2019-11-27 14:22 ` [PATCH 2/3] z3fold: compact objects more accurately Vitaly Wool
2019-11-27 14:23 ` Vitaly Wool [this message]
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