[PATCH v5] fs: introduce is_dot_or_dotdot helper for cleanup

[Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>]

There exists many similar and duplicate codes to check "." and "..",
so introduce is_dot_or_dotdot helper to make the code more clean.

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---

v5:
  - remove "qname" variable in fscrypt_fname_disk_to_usr()
  - modify "len < 2" to "len == 1" in is_dot_or_dotdot()

v4:
  - rename is_dot_dotdot() to is_dot_or_dotdot()

v3:
  - use "name" and "len" as arguments instead of qstr
  - move is_dot_dotdot() to include/linux/namei.h

v2:
  - use the better performance implementation of is_dot_dotdot
  - make it static inline and move it to include/linux/fs.h

 fs/crypto/fname.c     | 17 +++--------------
 fs/ecryptfs/crypto.c  | 12 +-----------
 fs/f2fs/f2fs.h        | 11 -----------
 fs/f2fs/hash.c        |  3 ++-
 fs/namei.c            |  6 ++----
 include/linux/namei.h | 10 ++++++++++
 6 files changed, 18 insertions(+), 41 deletions(-)

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 3da3707..bb41f5d 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -11,21 +11,11 @@
  * This has not yet undergone a rigorous security audit.
  */
 
+#include <linux/namei.h>
 #include <linux/scatterlist.h>
 #include <crypto/skcipher.h>
 #include "fscrypt_private.h"
 
-static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
-{
-	if (str->len == 1 && str->name[0] == '.')
-		return true;
-
-	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
-		return true;
-
-	return false;
-}
-
 /**
  * fname_encrypt() - encrypt a filename
  *
@@ -252,10 +242,9 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
 			const struct fscrypt_str *iname,
 			struct fscrypt_str *oname)
 {
-	const struct qstr qname = FSTR_TO_QSTR(iname);
 	struct fscrypt_digested_name digested_name;
 
-	if (fscrypt_is_dot_dotdot(&qname)) {
+	if (is_dot_or_dotdot(iname->name, iname->len)) {
 		oname->name[0] = '.';
 		oname->name[iname->len - 1] = '.';
 		oname->len = iname->len;
@@ -323,7 +312,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 	memset(fname, 0, sizeof(struct fscrypt_name));
 	fname->usr_fname = iname;
 
-	if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
+	if (!IS_ENCRYPTED(dir) || is_dot_or_dotdot(iname->name, iname->len)) {
 		fname->disk_name.name = (unsigned char *)iname->name;
 		fname->disk_name.len = iname->len;
 		return 0;
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index f91db24..c3bcbf0 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1991,16 +1991,6 @@ int ecryptfs_encrypt_and_encode_filename(
 	return rc;
 }
 
-static bool is_dot_dotdot(const char *name, size_t name_size)
-{
-	if (name_size == 1 && name[0] == '.')
-		return true;
-	else if (name_size == 2 && name[0] == '.' && name[1] == '.')
-		return true;
-
-	return false;
-}
-
 /**
  * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
  * @plaintext_name: The plaintext name
@@ -2027,7 +2017,7 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
 
 	if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) &&
 	    !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)) {
-		if (is_dot_dotdot(name, name_size)) {
+		if (is_dot_or_dotdot(name, name_size)) {
 			rc = ecryptfs_copy_filename(plaintext_name,
 						    plaintext_name_size,
 						    name, name_size);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 5a888a0..3d5e684 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2767,17 +2767,6 @@ static inline bool f2fs_cp_error(struct f2fs_sb_info *sbi)
 	return is_set_ckpt_flags(sbi, CP_ERROR_FLAG);
 }
 
-static inline bool is_dot_dotdot(const struct qstr *str)
-{
-	if (str->len == 1 && str->name[0] == '.')
-		return true;
-
-	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
-		return true;
-
-	return false;
-}
-
 static inline bool f2fs_may_extent_tree(struct inode *inode)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
diff --git a/fs/f2fs/hash.c b/fs/f2fs/hash.c
index 5bc4dcd..ef155c2 100644
--- a/fs/f2fs/hash.c
+++ b/fs/f2fs/hash.c
@@ -15,6 +15,7 @@
 #include <linux/cryptohash.h>
 #include <linux/pagemap.h>
 #include <linux/unicode.h>
+#include <linux/namei.h>
 
 #include "f2fs.h"
 
@@ -82,7 +83,7 @@ static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
 	if (fname && !fname->disk_name.name)
 		return cpu_to_le32(fname->hash);
 
-	if (is_dot_dotdot(name_info))
+	if (is_dot_or_dotdot(name, len))
 		return 0;
 
 	/* Initialize the default seed for the hash checksum functions */
diff --git a/fs/namei.c b/fs/namei.c
index d6c91d1..f3a4439 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2451,10 +2451,8 @@ static int lookup_one_len_common(const char *name, struct dentry *base,
 	if (!len)
 		return -EACCES;
 
-	if (unlikely(name[0] == '.')) {
-		if (len < 2 || (len == 2 && name[1] == '.'))
-			return -EACCES;
-	}
+	if (is_dot_or_dotdot(name, len))
+		return -EACCES;
 
 	while (len--) {
 		unsigned int c = *(const unsigned char *)name++;
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 7fe7b87..0fd9315 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -92,4 +92,14 @@ retry_estale(const long error, const unsigned int flags)
 	return error == -ESTALE && !(flags & LOOKUP_REVAL);
 }
 
+static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
+{
+	if (unlikely(name[0] == '.')) {
+		if (len == 1 || (len == 2 && name[1] == '.'))
+			return true;
+	}
+
+	return false;
+}
+
 #endif /* _LINUX_NAMEI_H */
-- 
2.1.0