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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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3
include/linux/f2fs_fs.h
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@@ -394,6 +394,9 @@ typedef __le32 f2fs_hash_t;
/* MAX level for dir lookup */
#define MAX_DIR_HASH_DEPTH 63
/* MAX buckets in one level of dir */
#define MAX_DIR_BUCKETS (1 << ((MAX_DIR_HASH_DEPTH / 2) - 1))
#define SIZE_OF_DIR_ENTRY 11 /* by byte */
#define SIZE_OF_DENTRY_BITMAP ((NR_DENTRY_IN_BLOCK + BITS_PER_BYTE - 1) / \
BITS_PER_BYTE)