From: Chao Yu Date: Wed, 28 May 2014 00:56:09 +0000 (+0800) Subject: f2fs: avoid overflow when large directory feathure is enabled X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=bfec07d0f8ed78b10df3ca3bc23e27de1166ea45;p=openwrt%2Fstaging%2Fblogic.git f2fs: avoid overflow when large directory feathure is enabled 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 Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim --- diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt index 25311e113e75..51afba17bbae 100644 --- a/Documentation/filesystems/f2fs.txt +++ b/Documentation/filesystems/f2fs.txt @@ -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 diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index c3f148555c37..966acb039e3b 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -23,10 +23,10 @@ static unsigned long dir_blocks(struct inode *inode) static unsigned int dir_buckets(unsigned int level, int dir_level) { - if (level < MAX_DIR_HASH_DEPTH / 2) + if (level + dir_level < MAX_DIR_HASH_DEPTH / 2) return 1 << (level + dir_level); else - return 1 << ((MAX_DIR_HASH_DEPTH / 2 + dir_level) - 1); + return MAX_DIR_BUCKETS; } static unsigned int bucket_blocks(unsigned int level) diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h index 8c03f71307c6..ba6f3127738f 100644 --- a/include/linux/f2fs_fs.h +++ b/include/linux/f2fs_fs.h @@ -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)