Gh0st
/
linux
mirror of https://github.com/torvalds/linux.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

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
This commit is contained in:
Gao Xiang 2024-12-12 10:39:48 +08:00
parent a78c5c2269
commit 54ab25d03e
2 changed files with 13 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/erofs/erofs_fs.h
View File

@ -9,6 +9,7 @@
#ifndef __EROFS_FS_H #ifndef __EROFS_FS_H
#define __EROFS_FS_H #define __EROFS_FS_H
/* to allow for x86 boot sectors and other oddities. */
#define EROFS_SUPER_OFFSET 1024 #define EROFS_SUPER_OFFSET 1024
#define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001 #define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
@ -54,7 +55,7 @@ struct erofs_deviceslot {
/* erofs on-disk super block (currently 128 bytes) */ /* erofs on-disk super block (currently 128 bytes) */
struct erofs_super_block { struct erofs_super_block {
__le32 magic; /* file system magic number */ __le32 magic; /* file system magic number */
__le32 checksum; /* crc32c(super_block) */ __le32 checksum; /* crc32c to avoid unexpected on-disk overlap */
__le32 feature_compat; __le32 feature_compat;
__u8 blkszbits; /* filesystem block size in bit shift */ __u8 blkszbits; /* filesystem block size in bit shift */
__u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */ __u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */

30
fs/erofs/super.c
View File

@ -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) 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 = sbdata + EROFS_SUPER_OFFSET;
struct erofs_super_block *dsb; u32 len = 1 << EROFS_SB(sb)->blkszbits, crc;
u32 expected_crc, crc;
if (len > EROFS_SUPER_OFFSET) if (len > EROFS_SUPER_OFFSET)
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); /* skip .magic(pre-verified) and .checksum(0) fields */
if (!dsb) crc = crc32c(0x5045B54A, (&dsb->checksum) + 1, len);
return -ENOMEM; if (crc == le32_to_cpu(dsb->checksum))
return 0;
expected_crc = le32_to_cpu(dsb->checksum); erofs_err(sb, "invalid checksum 0x%08x, 0x%08x expected",
dsb->checksum = 0; crc, le32_to_cpu(dsb->checksum));
/* to allow for x86 boot sectors and other oddities. */ return -EBADMSG;
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;
} }
static void erofs_inode_init_once(void *ptr) static void erofs_inode_init_once(void *ptr)