f2fs: avoid overflow when large directory feathure is enabled
Subsystems (3)
PATCH v2 1/1 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 <[email protected]>
Signed-off-by Chao Yu <[email protected]>
--- Documentation/filesystems/f2fs.txt | 8 ++++---- fs/f2fs/dir.c | 4 ++-- include/linux/f2fs_fs.h | 3 +++ 3 files changed, 9 insertions(+), 6 deletions(-)
Documentation/filesystems/f2fs.txt +4 -4
@@ -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
fs/f2fs/dir.c +2 -2
@@ -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)
include/linux/f2fs_fs.h +3 -0
@@ -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)
Signature · 1 line
1.7.9.5