linux-kernel - [PATCH 3/3] f2fs: fix unlocked nat set cache operation

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Date:	Mon,  9 Mar 2015 11:00:55 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Jaegeuk Kim <jaegeuk@...nel.org>
Cc:	Changman Lee <cm224.lee@...sung.com>,
	Chao Yu <chao2.yu@...sung.com>,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: [PATCH 3/3] f2fs: fix unlocked nat set cache operation

nm_i->nat_tree_lock is used to sync both the operations of nat entry
cache tree and nat set cache tree, however, it isn't held when flush 
nat entries during checkpoint which lead to potential race, this patch 
fix it by holding the lock when gang lookup nat set cache and delete 
item from nat set cache.

Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
---
 fs/f2fs/node.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 8751375..14e4387 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1837,6 +1837,7 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 	struct f2fs_nat_block *nat_blk;
 	struct nat_entry *ne, *cur;
 	struct page *page = NULL;
+	struct f2fs_nm_info *nm_i = NM_I(sbi);
 
 	/*
 	 * there are two steps to flush nat entries:
@@ -1890,7 +1891,9 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 
 	f2fs_bug_on(sbi, set->entry_cnt);
 
+	down_write(&nm_i->nat_tree_lock);
 	radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
+	up_write(&nm_i->nat_tree_lock);
 	kmem_cache_free(nat_entry_set_slab, set);
 }
 
@@ -1918,6 +1921,7 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
 	if (!__has_cursum_space(sum, nm_i->dirty_nat_cnt, NAT_JOURNAL))
 		remove_nats_in_journal(sbi);
 
+	down_write(&nm_i->nat_tree_lock);
 	while ((found = __gang_lookup_nat_set(nm_i,
 					set_idx, SETVEC_SIZE, setvec))) {
 		unsigned idx;
@@ -1926,6 +1930,7 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
 			__adjust_nat_entry_set(setvec[idx], &sets,
 							MAX_NAT_JENTRIES(sum));
 	}
+	up_write(&nm_i->nat_tree_lock);
 
 	/* flush dirty nats in nat entry set */
 	list_for_each_entry_safe(set, tmp, &sets, set_list)
-- 
1.9.1

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