From: "Darrick J. Wong" Subject: [PATCH 14/23] ext4: Add checksums to the MMP block Date: Tue, 06 Mar 2012 12:49:30 -0800 Message-ID: <20120306204930.1663.41920.stgit@elm3b70.beaverton.ibm.com> References: <20120306204750.1663.96751.stgit@elm3b70.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Sunil Mushran , Martin K Petersen , Greg Freemyer , Amir Goldstein , linux-kernel , Andi Kleen , Mingming Cao , Joel Becker , linux-fsdevel , linux-ext4@vger.kernel.org, Coly Li To: Andreas Dilger , Theodore Tso , "Darrick J. Wong" Return-path: In-Reply-To: <20120306204750.1663.96751.stgit@elm3b70.beaverton.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Compute and verify a checksum for the MMP block. Signed-off-by: Darrick J. Wong --- fs/ext4/ext4.h | 3 +++ fs/ext4/mmp.c | 44 +++++++++++++++++++++++++++++++++++++++----- 2 files changed, 42 insertions(+), 5 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index ee7bac7..900d5c4 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2394,6 +2394,9 @@ 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 { diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c index 7ea4ba4..142e9d7 100644 --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -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;