Hi Ted,
As the corresponding kernel change has been merged, can this patch be
merged to the e2fsporgs also?
Thanks
Tao
On 06/24/2012 10:13 PM, Tao Ma wrote:
> From: Tao Ma <boyu.mt@xxxxxxxxxx>
>
> In xattr block operation, we use h_refcount to indicate whether the
> xattr block is shared among many inodes. And xattr block csum uses
> s_csum_seed if it is shared and i_csum_seed if it belongs to
> one inode. But this has a problem. So consider the block is shared
> first bewteen inode A and B, and B has some xattr update and CoW
> the xattr block. When it updates the *old* xattr block(because
> of the h_refcount change) and calls ext4_xattr_release_block, we
> has no idea that inode A is the real owner of the *old* xattr
> block and we can't use the i_csum_seed of inode A either in xattr
> block csum calculation. And I don't think we have an easy way to
> find inode A.
>
> So this patch just removes the tricky i_csum_seed and we now uses
> s_csum_seed every time for the xattr block csum. The corresponding
> patch for the e2fsprogs will be sent in another patch.
>
> This is spotted by xfstests 117.
>
> Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
> Cc: "Theodore Ts'o" <tytso@xxxxxxx>
> Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx>
> ---
> fs/ext4/xattr.c | 11 ++++-------
> 1 files changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index e56c9ed..2cdb98d 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c
> @@ -127,19 +127,16 @@ static __le32 ext4_xattr_block_csum(struct inode *inode,
> struct ext4_xattr_header *hdr)
> {
> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> - struct ext4_inode_info *ei = EXT4_I(inode);
> __u32 csum, old;
>
> old = hdr->h_checksum;
> hdr->h_checksum = 0;
> - if (le32_to_cpu(hdr->h_refcount) != 1) {
> - block_nr = cpu_to_le64(block_nr);
> - csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&block_nr,
> - sizeof(block_nr));
> - } else
> - csum = ei->i_csum_seed;
> + block_nr = cpu_to_le64(block_nr);
> + csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&block_nr,
> + sizeof(block_nr));
> csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
> EXT4_BLOCK_SIZE(inode->i_sb));
> +
> hdr->h_checksum = old;
> return cpu_to_le32(csum);
> }
>
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