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ext4: add checksums to the MMP block 

Compute and verify a checksum for the MMP block.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Darrick J. Wong 2012-04-29 18:47:10 -04:00 committed by Theodore Ts'o
parent feb0ab32a5
commit 5c359a47e7
2 changed files with 42 additions and 5 deletions
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3
fs/ext4/ext4.h
View File

@ -2413,6 +2413,9 @@ extern int ext4_bio_write_page(struct ext4_io_submit *io,
/* mmp.c */
extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);
extern void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp);
extern int ext4_mmp_csum_verify(struct super_block *sb,
struct mmp_struct *mmp);
/* BH_Uninit flag: blocks are allocated but uninitialized on disk */
enum ext4_state_bits {

44
fs/ext4/mmp.c
View File

@ -6,12 +6,45 @@
#include "ext4.h"
/* Checksumming functions */
static __u32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
int offset = offsetof(struct mmp_struct, mmp_checksum);
__u32 csum;
csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
return cpu_to_le32(csum);
}
int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
{
if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return 1;
return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
}
void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
{
if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return;
mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
}
/*
* Write the MMP block using WRITE_SYNC to try to get the block on-disk
* faster.
*/
static int write_mmp_block(struct buffer_head *bh)
static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
{
struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
ext4_mmp_csum_set(sb, mmp);
mark_buffer_dirty(bh);
lock_buffer(bh);
bh->b_end_io = end_buffer_write_sync;
@ -59,7 +92,8 @@ static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
}
mmp = (struct mmp_struct *)((*bh)->b_data);
if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC)
if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC ||
!ext4_mmp_csum_verify(sb, mmp))
return -EINVAL;
return 0;
@ -120,7 +154,7 @@ static int kmmpd(void *data)
mmp->mmp_time = cpu_to_le64(get_seconds());
last_update_time = jiffies;
retval = write_mmp_block(bh);
retval = write_mmp_block(sb, bh);
/*
* Don't spew too many error messages. Print one every
* (s_mmp_update_interval * 60) seconds.
@ -200,7 +234,7 @@ static int kmmpd(void *data)
mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
mmp->mmp_time = cpu_to_le64(get_seconds());
retval = write_mmp_block(bh);
retval = write_mmp_block(sb, bh);
failed:
kfree(data);
@ -299,7 +333,7 @@ skip:
seq = mmp_new_seq();
mmp->mmp_seq = cpu_to_le32(seq);
retval = write_mmp_block(bh);
retval = write_mmp_block(sb, bh);
if (retval)
goto failed;