diff options
| author | Gao Xiang <hsiangkao@linux.alibaba.com> | 2024-12-12 10:39:48 +0800 |
|---|---|---|
| committer | Gao Xiang <hsiangkao@linux.alibaba.com> | 2025-01-17 03:17:32 +0800 |
| commit | 54ab25d03eab652a321c3d1566edc2b050d83f2f (patch) | |
| tree | b84e5397e39604ecb17459cc839403612a3dc013 /fs/erofs | |
| parent | a78c5c2269e39544fab4140105f55fca4502e915 (diff) | |
erofs: micro-optimize superblock checksum
Just verify the remaining unknown on-disk data instead of allocating a
temporary buffer for the whole superblock and zeroing out the checksum
field since .magic(EROFS_SUPER_MAGIC_V1) is verified and .checksum(0)
is fixed.
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241212023948.1143038-1-hsiangkao@linux.alibaba.com
Diffstat (limited to 'fs/erofs')
| -rw-r--r-- | fs/erofs/erofs_fs.h | 3 | ||||
| -rw-r--r-- | fs/erofs/super.c | 30 |
2 files changed, 13 insertions, 20 deletions
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h index c8f2ae845bd2..199395ed1c1f 100644 --- a/fs/erofs/erofs_fs.h +++ b/fs/erofs/erofs_fs.h @@ -9,6 +9,7 @@ #ifndef __EROFS_FS_H #define __EROFS_FS_H +/* to allow for x86 boot sectors and other oddities. */ #define EROFS_SUPER_OFFSET 1024 #define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001 @@ -54,7 +55,7 @@ struct erofs_deviceslot { /* erofs on-disk super block (currently 128 bytes) */ struct erofs_super_block { __le32 magic; /* file system magic number */ - __le32 checksum; /* crc32c(super_block) */ + __le32 checksum; /* crc32c to avoid unexpected on-disk overlap */ __le32 feature_compat; __u8 blkszbits; /* filesystem block size in bit shift */ __u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */ diff --git a/fs/erofs/super.c b/fs/erofs/super.c index f5956474bfde..1fc5623c3a4d 100644 --- a/fs/erofs/super.c +++ b/fs/erofs/super.c @@ -39,29 +39,21 @@ void _erofs_printk(struct super_block *sb, const char *fmt, ...) static int erofs_superblock_csum_verify(struct super_block *sb, void *sbdata) { - size_t len = 1 << EROFS_SB(sb)->blkszbits; - struct erofs_super_block *dsb; - u32 expected_crc, crc; + struct erofs_super_block *dsb = sbdata + EROFS_SUPER_OFFSET; + u32 len = 1 << EROFS_SB(sb)->blkszbits, crc; if (len > EROFS_SUPER_OFFSET) len -= EROFS_SUPER_OFFSET; + len -= offsetof(struct erofs_super_block, checksum) + + sizeof(dsb->checksum); - dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET, len, GFP_KERNEL); - if (!dsb) - return -ENOMEM; - - expected_crc = le32_to_cpu(dsb->checksum); - dsb->checksum = 0; - /* to allow for x86 boot sectors and other oddities. */ - crc = crc32c(~0, dsb, len); - kfree(dsb); - - if (crc != expected_crc) { - erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected", - crc, expected_crc); - return -EBADMSG; - } - return 0; + /* skip .magic(pre-verified) and .checksum(0) fields */ + crc = crc32c(0x5045B54A, (&dsb->checksum) + 1, len); + if (crc == le32_to_cpu(dsb->checksum)) + return 0; + erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected", + crc, le32_to_cpu(dsb->checksum)); + return -EBADMSG; } static void erofs_inode_init_once(void *ptr) |