| Message ID | 20220212050532.179055-1-yi.zhang@huawei.com |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | ext2: correct max file size computing | expand |
On Sat 12-02-22 13:05:32, Zhang Yi wrote: > 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@huawei.com> Thanks for the cleanup! I've merged the patch to my tree. Honza > --- > 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 >
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;
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@huawei.com> --- fs/ext2/super.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)