Commit 5c359a47 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Theodore Ts'o
Browse files

ext4: add checksums to the MMP block 



Compute and verify a checksum for the MMP block.

Signed-off-by: default avatarDarrick J. Wong <djwong@us.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent feb0ab32

fs/ext4/ext4.h

+3 −0
Original line number Diff line number Diff line
@@ -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 {

fs/ext4/mmp.c

+39 −5
Original line number Diff line number Diff line
@@ -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 @@ int ext4_multi_mount_protect(struct super_block *sb, 
	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;