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@xxxxxxxxxxx>
Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
---
Documentation/filesystems/f2fs.txt | 8 ++++----
fs/f2fs/dir.c | 4 ++--
include/linux/f2fs_fs.h | 3 +++
3 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 25311e11..51afba1 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 c3f1485..966acb0 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 8c03f71..ba6f312 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)
--
1.7.9.5
--
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