linux-kernel - [f2fs-dev] [PATCH] f2fs: validate before set/clear free nat bitmap

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Message-ID: <000101d359f7$77d1aae0$677500a0$@samsung.com>
Date:   Fri, 10 Nov 2017 15:41:42 +0800
From:   "LiFan" <fanofcode.li@...sung.com>
To:     "'Chao Yu'" <chao@...nel.org>, "'Chao Yu'" <yuchao0@...wei.com>,
        "'Jaegeuk Kim'" <jaegeuk@...nel.org>
Cc:     <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: [f2fs-dev] [PATCH] f2fs: validate before set/clear free nat bitmap

In flush_nat_entries, all dirty nats will be flushed and if
their new address isn't NULL_ADDR, their bitmaps will be updated,
the free_nid_count of the bitmaps will be increaced regardless
of whether the nats have already been occupied before.
This could lead to wrong free_nid_count.
So this patch checks the status of the bits beforeactually
set/clear them.

Signed-off-by: Fan li <fanofcode.li@...sung.com>
---
 fs/f2fs/node.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index d234c6e..b965a53 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1906,15 +1906,18 @@ static void update_free_nid_bitmap(struct
f2fs_sb_info *sbi, nid_t nid,
 	if (!test_bit_le(nat_ofs, nm_i->nat_block_bitmap))
 		return;
 
-	if (set)
+	if (set) {
+		if (test_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]))
+			return;
 		__set_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
-	else
-		__clear_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
-
-	if (set)
 		nm_i->free_nid_count[nat_ofs]++;
-	else if (!build)
-		nm_i->free_nid_count[nat_ofs]--;
+	} else {
+		if (!test_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]))
+			return;
+		__clear_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
+		if (!build)
+			nm_i->free_nid_count[nat_ofs]--;
+	}
 }
 
 static void scan_nat_page(struct f2fs_sb_info *sbi,
-- 
2.7.4