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f2fs: avoid overflow when large directory feathure is enabled

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When large directory feathure is enable, We have one case which could cause
overflow in dir_buckets() as following:
special case: level + dir_level >= 32 and level < MAX_DIR_HASH_DEPTH / 2.

Here we define MAX_DIR_BUCKETS to limit the return value when the condition
could trigger potential overflow.

Changes from V1
 o modify description of calculation in f2fs.txt suggested by Changman Lee.

Suggested-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Chao Yu
2014-05-28 08:56:09 +08:00
committed by Jaegeuk Kim
parent d631abdac9
commit bfec07d0f8
3 changed files with 9 additions and 6 deletions
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Documentation/filesystems/f2fs.txt
+4 -4
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@@ -461,11 +461,11 @@ The number of blocks and buckets are determined by,
# of blocks in level #n = |
`- 4, Otherwise
,- 2^ (n + dir_level),
| if n < MAX_DIR_HASH_DEPTH / 2,
,- 2^(n + dir_level),
| if n + dir_level < MAX_DIR_HASH_DEPTH / 2,
# of buckets in level #n = |
`- 2^((MAX_DIR_HASH_DEPTH / 2 + dir_level) - 1),
Otherwise
`- 2^((MAX_DIR_HASH_DEPTH / 2) - 1),
Otherwise
When F2FS finds a file name in a directory, at first a hash value of the file
name is calculated. Then, F2FS scans the hash table in level #0 to find the