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

Viacheslav Dubeyko
2025-11-14T18:07:57Z

On Fri, 2025-11-14 at 14:02 +0800, Guan-Chun Wu wrote:
> 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",

Looks good!

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>

Have you run xfstests for this patchset?

Thanks,
Slava.