fs/f2fs/hash.c

Source file repositories/reference/linux-study-clean/fs/f2fs/hash.c

File Facts

System
Linux kernel
Corpus path
fs/f2fs/hash.c
Extension
.c
Size
3085 bytes
Lines
138
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

if ((i % 4) == 3) {
			*buf++ = val;
			val = pad;
			num--;
		}
	}
	if (--num >= 0)
		*buf++ = val;
	while (--num >= 0)
		*buf++ = pad;
}

static u32 TEA_hash_name(const u8 *p, size_t len)
{
	__u32 in[8], buf[4];

	/* Initialize the default seed for the hash checksum functions */
	buf[0] = 0x67452301;
	buf[1] = 0xefcdab89;
	buf[2] = 0x98badcfe;
	buf[3] = 0x10325476;

	while (1) {
		str2hashbuf(p, len, in, 4);
		TEA_transform(buf, in);
		p += 16;
		if (len <= 16)
			break;
		len -= 16;
	}
	return buf[0] & ~F2FS_HASH_COL_BIT;
}

/*
 * Compute @fname->hash.  For all directories, @fname->disk_name must be set.
 * For casefolded directories, @fname->usr_fname must be set, and also
 * @fname->cf_name if the filename is valid Unicode and is not "." or "..".
 */
void f2fs_hash_filename(const struct inode *dir, struct f2fs_filename *fname)
{
	const u8 *name = fname->disk_name.name;
	size_t len = fname->disk_name.len;

	WARN_ON_ONCE(!name);

	if (name_is_dot_dotdot(name, len)) {
		fname->hash = 0;
		return;
	}

#if IS_ENABLED(CONFIG_UNICODE)
	if (IS_CASEFOLDED(dir)) {
		/*
		 * If the casefolded name is provided, hash it instead of the
		 * on-disk name.  If the casefolded name is *not* provided, that
		 * should only be because the name wasn't valid Unicode or was
		 * "." or "..", so fall back to treating the name as an opaque
		 * byte sequence.  Note that to handle encrypted directories,
		 * the fallback must use usr_fname (plaintext) rather than
		 * disk_name (ciphertext).
		 */
		WARN_ON_ONCE(!fname->usr_fname->name);
		if (fname->cf_name.name) {
			name = fname->cf_name.name;
			len = fname->cf_name.len;
		} else {
			name = fname->usr_fname->name;
			len = fname->usr_fname->len;
		}
		if (IS_ENCRYPTED(dir)) {
			struct qstr tmp = QSTR_INIT(name, len);

			fname->hash =
				cpu_to_le32(fscrypt_fname_siphash(dir, &tmp));
			return;
		}
	}
#endif
	fname->hash = cpu_to_le32(TEA_hash_name(name, len));
}

Annotation

Implementation Notes