[PATCH v5 6/6] ceph: replace local base64 helpers with lib/base64

Guan-Chun Wu
2025-11-14T06:02:48Z

Remove the ceph_base64_encode() and ceph_base64_decode() functions and
replace their usage with the generic base64_encode() and base64_decode()
helpers from lib/base64.

This eliminates the custom implementation in Ceph, reduces code
duplication, and relies on the shared Base64 code in lib.
The helpers preserve RFC 3501-compliant Base64 encoding without padding,
so there are no functional changes.

This change also improves performance: encoding is about 2.7x faster and
decoding achieves 43-52x speedups compared to the previous local
implementation.

Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
---
fs/ceph/crypto.c | 60 ++++--------------------------------------------
fs/ceph/crypto.h | 6 +----
fs/ceph/dir.c | 5 ++--
fs/ceph/inode.c | 2 +-
4 files changed, 9 insertions(+), 64 deletions(-)

diff --git a/fs/ceph/crypto.c b/fs/ceph/crypto.c
index 7026e794813c..b6016dcffbb6 100644
--- a/fs/ceph/crypto.c
+++ b/fs/ceph/crypto.c
@@ -15,59 +15,6 @@
#include "mds_client.h"
#include "crypto.h"

-/*
- * The base64url encoding used by fscrypt includes the '_' character, which may
- * cause problems in snapshot names (which can not start with '_'). Thus, we
- * used the base64 encoding defined for IMAP mailbox names (RFC 3501) instead,
- * which replaces '-' and '_' by '+' and ','.
- */
-static const char base64_table[65] =
- "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
-
-int ceph_base64_encode(const u8 *src, int srclen, char *dst)
-{
- u32 ac = 0;
- int bits = 0;
- int i;
- char *cp = dst;
-
- for (i = 0; i < srclen; i++) {
- ac = (ac << 8) | src[i];
- bits += 8;
- do {
- bits -= 6;
- *cp++ = base64_table[(ac >> bits) & 0x3f];
- } while (bits >= 6);
- }
- if (bits)
- *cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
- return cp - dst;
-}
-
-int ceph_base64_decode(const char *src, int srclen, u8 *dst)
-{
- u32 ac = 0;
- int bits = 0;
- int i;
- u8 *bp = dst;
-
- for (i = 0; i < srclen; i++) {
- const char *p = strchr(base64_table, src[i]);
-
- if (p == NULL || src[i] == 0)
- return -1;
- ac = (ac << 6) | (p - base64_table);
- bits += 6;
- if (bits >= 8) {
- bits -= 8;
- *bp++ = (u8)(ac >> bits);
- }
- }
- if (ac & ((1 << bits) - 1))
- return -1;
- return bp - dst;
-}
-
static int ceph_crypt_get_context(struct inode *inode, void *ctx, size_t len)
{
struct ceph_inode_info *ci = ceph_inode(inode);
@@ -318,7 +265,7 @@ int ceph_encode_encrypted_dname(struct inode *parent, char *buf, int elen)
}

/* base64 encode the encrypted name */
- elen = ceph_base64_encode(cryptbuf, len, p);
+ elen = base64_encode(cryptbuf, len, p, false, BASE64_IMAP);
doutc(cl, "base64-encoded ciphertext name = %.*s\n", elen, p);

/* To understand the 240 limit, see CEPH_NOHASH_NAME_MAX comments */
@@ -412,7 +359,8 @@ int ceph_fname_to_usr(const struct ceph_fname *fname, struct fscrypt_str *tname,
tname = &_tname;
}

- declen = ceph_base64_decode(name, name_len, tname->name);
+ declen = base64_decode(name, name_len,
+ tname->name, false, BASE64_IMAP);
if (declen <= 0) {
ret = -EIO;
goto out;
@@ -426,7 +374,7 @@ int ceph_fname_to_usr(const struct ceph_fname *fname, struct fscrypt_str *tname,

ret = fscrypt_fname_disk_to_usr(dir, 0, 0, &iname, oname);
if (!ret && (dir != fname->dir)) {
- char tmp_buf[CEPH_BASE64_CHARS(NAME_MAX)];
+ char tmp_buf[BASE64_CHARS(NAME_MAX)];

name_len = snprintf(tmp_buf, sizeof(tmp_buf), "_%.*s_%ld",
oname->len, oname->name, dir->i_ino);
diff --git a/fs/ceph/crypto.h b/fs/ceph/crypto.h
index 23612b2e9837..b748e2060bc9 100644
--- a/fs/ceph/crypto.h
+++ b/fs/ceph/crypto.h
@@ -8,6 +8,7 @@

#include <crypto/sha2.h>
#include <linux/fscrypt.h>
+#include <linux/base64.h>

#define CEPH_FSCRYPT_BLOCK_SHIFT 12
#define CEPH_FSCRYPT_BLOCK_SIZE (_AC(1, UL) << CEPH_FSCRYPT_BLOCK_SHIFT)
@@ -89,11 +90,6 @@ static inline u32 ceph_fscrypt_auth_len(struct ceph_fscrypt_auth *fa)
*/
#define CEPH_NOHASH_NAME_MAX (180 - SHA256_DIGEST_SIZE)

-#define CEPH_BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
-
-int ceph_base64_encode(const u8 *src, int srclen, char *dst);
-int ceph_base64_decode(const char *src, int srclen, u8 *dst);
-
void ceph_fscrypt_set_ops(struct super_block *sb);

void ceph_fscrypt_free_dummy_policy(struct ceph_fs_client *fsc);
diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index d18c0eaef9b7..0fa7c7777242 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -998,13 +998,14 @@ static int prep_encrypted_symlink_target(struct ceph_mds_request *req,
if (err)
goto out;

- req->r_path2 = kmalloc(CEPH_BASE64_CHARS(osd_link.len) + 1, GFP_KERNEL);
+ req->r_path2 = kmalloc(BASE64_CHARS(osd_link.len) + 1, GFP_KERNEL);
if (!req->r_path2) {
err = -ENOMEM;
goto out;
}

- len = ceph_base64_encode(osd_link.name, osd_link.len, req->r_path2);
+ len = base64_encode(osd_link.name, osd_link.len,
+ req->r_path2, false, BASE64_IMAP);
req->r_path2[len] = '\0';
out:
fscrypt_fname_free_buffer(&osd_link);
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index a6e260d9e420..b691343cb7f1 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -958,7 +958,7 @@ static int decode_encrypted_symlink(struct ceph_mds_client *mdsc,
if (!sym)
return -ENOMEM;

- declen = ceph_base64_decode(encsym, enclen, sym);
+ declen = base64_decode(encsym, enclen, sym, false, BASE64_IMAP);
if (declen < 0) {
pr_err_client(cl,
"can't decode symlink (%d). Content: %.*s\n",
--
2.34.1