We need to calculate the max file size accurately if the total blocks
that can address by block tree exceed the upper_limit. But this check is
not correct now, it only compute the total data blocks but missing
metadata blocks are needed. So in the case of "data blocks < upper_limit
&& total blocks > upper_limit", we will get wrong result. Fortunately,
this case could not happen in reality, but it's confused and better to
correct the computing.
bits data blocks metadatablocks upper_limit
10 16843020 66051 2147483647
11 134480396 263171 1073741823
12 1074791436 1050627 536870911 (*)
13 8594130956 4198403 268435455 (*)
14 68736258060 16785411 134217727 (*)
15 549822930956 67125251 67108863 (*)
16 4398314962956 268468227 33554431 (*)
[*] Need to calculate in depth.
Fixes: 1c2d14212b15 ("ext2: Fix underflow in ext2_max_size()")
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
fs/ext2/super.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 94f1fbd7d3ac..6d4f5ef74766 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -753,8 +753,12 @@ static loff_t ext2_max_size(int bits)
res += 1LL << (bits-2);
res += 1LL << (2*(bits-2));
res += 1LL << (3*(bits-2));
+ /* Compute how many metadata blocks are needed */
+ meta_blocks = 1;
+ meta_blocks += 1 + ppb;
+ meta_blocks += 1 + ppb + ppb * ppb;
/* Does block tree limit file size? */
- if (res < upper_limit)
+ if (res + meta_blocks <= upper_limit)
goto check_lfs;
res = upper_limit;
--
2.31.1
