Re: [PATCH 4/9] xfs: add CRC checks to the AGFL

Ben Myers
2013-02-27T22:37:53Z

Hi Dave,

On Tue, Jan 22, 2013 at 12:25:55AM +1100, Dave Chinner wrote:
> From: Christoph Hellwig <hch@lst.de>
>
> Add CRC checks, location information and a magic number to the AGFL.
> Previously the AGFL was just a block containing nothing but the
> free block pointers. The new AGFL has a real header with the usual
> boilerplate instead, so that we can verify it's not corrupted and
> written into the right place.
>
> [dchinner@redhat.com] Added LSN field, reworked significantly to fit
> into new verifier structure and growfs structure, enabled full
> verifier functionality now there is a header to verify and we can
> guarantee an initialised AGFL.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

I have a couple comments below.

-Ben

> ---
> fs/xfs/xfs_ag.h | 25 +++++++++-
> fs/xfs/xfs_alloc.c | 119 ++++++++++++++++++++++++++++++----------------
> fs/xfs/xfs_buf_item.h | 4 +-
> fs/xfs/xfs_fsops.c | 5 ++
> fs/xfs/xfs_log_recover.c | 7 +++
> 5 files changed, 116 insertions(+), 44 deletions(-)
>
> diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
> index b382703..813caea 100644
> --- a/fs/xfs/xfs_ag.h
> +++ b/fs/xfs/xfs_ag.h
> @@ -30,6 +30,7 @@ struct xfs_trans;
>
> #define XFS_AGF_MAGIC 0x58414746 /* 'XAGF' */
> #define XFS_AGI_MAGIC 0x58414749 /* 'XAGI' */
> +#define XFS_AGFL_MAGIC 0x5841464c /* 'XAFL' */
> #define XFS_AGF_VERSION 1
> #define XFS_AGI_VERSION 1
>
> @@ -190,11 +191,31 @@ extern const struct xfs_buf_ops xfs_agi_buf_ops;
> */
> #define XFS_AGFL_DADDR(mp) ((xfs_daddr_t)(3 << (mp)->m_sectbb_log))
> #define XFS_AGFL_BLOCK(mp) XFS_HDR_BLOCK(mp, XFS_AGFL_DADDR(mp))
> -#define XFS_AGFL_SIZE(mp) ((mp)->m_sb.sb_sectsize / sizeof(xfs_agblock_t))
> #define XFS_BUF_TO_AGFL(bp) ((xfs_agfl_t *)((bp)->b_addr))
>
> +#define XFS_BUF_TO_AGFL_BNO(mp, bp) \
> + (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \
> + &(XFS_BUF_TO_AGFL(bp)->agfl_bno[0]) : \
> + (__be32 *)(bp)->b_addr)
> +
> +/*
> + * Size of the AGFL. For CRC-enabled filesystes we steal a couple of
> + * slots in the beginning of the block for a proper header with the
> + * location information and CRC.
> + */
> +#define XFS_AGFL_SIZE(mp) \
> + (((mp)->m_sb.sb_sectsize - \
> + (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \
> + sizeof(struct xfs_agfl) : 0)) / \
> + sizeof(xfs_agblock_t))
> +
> typedef struct xfs_agfl {
> - __be32 agfl_bno[1]; /* actually XFS_AGFL_SIZE(mp) */
> + __be32 agfl_magicnum;
> + __be32 agfl_seqno;
> + uuid_t agfl_uuid;
> + __be64 agfl_lsn;
> + __be32 agfl_crc;
> + __be32 agfl_bno[]; /* actually XFS_AGFL_SIZE(mp) */
> } xfs_agfl_t;
>
> /*
> diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
> index 1d2e9c3..53e699e 100644
> --- a/fs/xfs/xfs_alloc.c
> +++ b/fs/xfs/xfs_alloc.c
> @@ -432,53 +432,84 @@ xfs_alloc_fixup_trees(
> return 0;
> }
>
> -static void
> +static bool
> xfs_agfl_verify(
> struct xfs_buf *bp)
> {
> -#ifdef WHEN_CRCS_COME_ALONG
> - /*
> - * we cannot actually do any verification of the AGFL because mkfs does
> - * not initialise the AGFL to zero or NULL. Hence the only valid part of
> - * the AGFL is what the AGF says is active. We can't get to the AGF, so
> - * we can't verify just those entries are valid.
> - *
> - * This problem goes away when the CRC format change comes along as that
> - * requires the AGFL to be initialised by mkfs. At that point, we can
> - * verify the blocks in the agfl -active or not- lie within the bounds
> - * of the AG. Until then, just leave this check ifdef'd out.
> - */
> struct xfs_mount *mp = bp->b_target->bt_mount;
> struct xfs_agfl *agfl = XFS_BUF_TO_AGFL(bp);
> - int agfl_ok = 1;
> -
> int i;
>
> + if (!uuid_equal(&agfl->agfl_uuid, &mp->m_sb.sb_uuid))
> + return false;
> + if (be32_to_cpu(agfl->agfl_magicnum) != XFS_AGFL_MAGIC)
> + return false;
> + /*
> + * during growfs operations, the perag is not fully initialised,
> + * so we can't use it for any useful checking. growfs ensures we can't
> + * use it by using uncached buffers that don't have the perag attached
> + * so we can detect and avoid this problem.
> + */
> + if (bp->b_pag && be32_to_cpu(agfl->agfl_seqno) != bp->b_pag->pag_agno)
> + return false;
> +
> for (i = 0; i < XFS_AGFL_SIZE(mp); i++) {
> - if (be32_to_cpu(agfl->agfl_bno[i]) == NULLAGBLOCK ||
> + if (be32_to_cpu(agfl->agfl_bno[i]) != NULLAGBLOCK &&
> be32_to_cpu(agfl->agfl_bno[i]) >= mp->m_sb.sb_agblocks)
<

Any non NULLAGBLOCK should be less than m_sb.sb_agblocks, correct?

> - agfl_ok = 0;
> + return false;
> }
> + return true;
> +}
> +
> +static void
> +xfs_agfl_read_verify(
> + struct xfs_buf *bp)
> +{
> + struct xfs_mount *mp = bp->b_target->bt_mount;
> + int agfl_ok = 1;
> +
> + /*
> + * There is no verification of non-crc AGFLs because mkfs does not
> + * initialise the AGFL to zero or NULL. Hence the only valid part of the
> + * AGFL is what the AGF says is active. We can't get to the AGF, so we
> + * can't verify just those entries are valid.
> + */
> + if (!xfs_sb_version_hascrc(&mp->m_sb))
> + return;
> +
> + agfl_ok = xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length),
> + offsetof(struct xfs_agfl, agfl_crc));
> +
> + agfl_ok = agfl_ok && xfs_agfl_verify(bp);
>
> if (!agfl_ok) {
> - XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, agfl);
> + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
> xfs_buf_ioerror(bp, EFSCORRUPTED);
> }
> -#endif
> }
>
> static void
> xfs_agfl_write_verify(
> struct xfs_buf *bp)
> {
> - xfs_agfl_verify(bp);
> -}
> + struct xfs_mount *mp = bp->b_target->bt_mount;
> + struct xfs_buf_log_item *bip = bp->b_fspriv;
>
> -static void
> -xfs_agfl_read_verify(
> - struct xfs_buf *bp)
> -{
> - xfs_agfl_verify(bp);
> + /* no verification of non-crc AGFLs */
> + if (!xfs_sb_version_hascrc(&mp->m_sb))
> + return;
> +
> + if (!xfs_agfl_verify(bp)) {
> + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
> + xfs_buf_ioerror(bp, EFSCORRUPTED);
> + return;
> + }
> +
> + if (bip)
> + XFS_BUF_TO_AGFL(bp)->agfl_lsn = cpu_to_be64(bip->bli_item.li_lsn);
> +
> + xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
> + offsetof(struct xfs_agfl, agfl_crc));
> }
>
> const struct xfs_buf_ops xfs_agfl_buf_ops = {
> @@ -1984,18 +2015,18 @@ xfs_alloc_get_freelist(
> int btreeblk) /* destination is a AGF btree */
> {
> xfs_agf_t *agf; /* a.g. freespace structure */
> - xfs_agfl_t *agfl; /* a.g. freelist structure */
> xfs_buf_t *agflbp;/* buffer for a.g. freelist structure */
> xfs_agblock_t bno; /* block number returned */
> + __be32 *agfl_bno;
> int error;
> int logflags;
> - xfs_mount_t *mp; /* mount structure */
> + xfs_mount_t *mp = tp->t_mountp;
> xfs_perag_t *pag; /* per allocation group data */
>
> - agf = XFS_BUF_TO_AGF(agbp);
> /*
> * Freelist is empty, give up.
> */
> + agf = XFS_BUF_TO_AGF(agbp);
> if (!agf->agf_flcount) {
> *bnop = NULLAGBLOCK;
> return 0;
> @@ -2003,15 +2034,17 @@ xfs_alloc_get_freelist(
> /*
> * Read the array of free blocks.
> */
> - mp = tp->t_mountp;
> - if ((error = xfs_alloc_read_agfl(mp, tp,
> - be32_to_cpu(agf->agf_seqno), &agflbp)))
> + error = xfs_alloc_read_agfl(mp, tp, be32_to_cpu(agf->agf_seqno),
> + &agflbp);
> + if (error)
> return error;
> - agfl = XFS_BUF_TO_AGFL(agflbp);
> +
> +
> /*
> * Get the block number and update the data structures.
> */
> - bno = be32_to_cpu(agfl->agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
> + agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
> + bno = be32_to_cpu(agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
> be32_add_cpu(&agf->agf_flfirst, 1);
> xfs_trans_brelse(tp, agflbp);
> if (be32_to_cpu(agf->agf_flfirst) == XFS_AGFL_SIZE(mp))
> @@ -2104,12 +2137,13 @@ xfs_alloc_put_freelist(
> int btreeblk) /* block came from a AGF btree */
> {
> xfs_agf_t *agf; /* a.g. freespace structure */
> - xfs_agfl_t *agfl; /* a.g. free block array */
> __be32 *blockp;/* pointer to array entry */
> int error;
> int logflags;
> xfs_mount_t *mp; /* mount structure */
> xfs_perag_t *pag; /* per allocation group data */
> + __be32 *agfl_bno;
> + int startoff;
>
> agf = XFS_BUF_TO_AGF(agbp);
> mp = tp->t_mountp;
> @@ -2117,7 +2151,6 @@ xfs_alloc_put_freelist(
> if (!agflbp && (error = xfs_alloc_read_agfl(mp, tp,
> be32_to_cpu(agf->agf_seqno), &agflbp)))
> return error;
> - agfl = XFS_BUF_TO_AGFL(agflbp);
> be32_add_cpu(&agf->agf_fllast, 1);
> if (be32_to_cpu(agf->agf_fllast) == XFS_AGFL_SIZE(mp))
> agf->agf_fllast = 0;
> @@ -2138,13 +2171,17 @@ xfs_alloc_put_freelist(
> xfs_alloc_log_agf(tp, agbp, logflags);
>
> ASSERT(be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp));
> - blockp = &agfl->agfl_bno[be32_to_cpu(agf->agf_fllast)];
> +
> + agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
> + blockp = &agfl_bno[be32_to_cpu(agf->agf_fllast)];
> *blockp = cpu_to_be32(bno);
> + startoff = (char *)blockp - (char *)agflbp->b_addr;
> +
> xfs_alloc_log_agf(tp, agbp, logflags);
> - xfs_trans_log_buf(tp, agflbp,
> - (int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl),
> - (int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl +
> - sizeof(xfs_agblock_t) - 1));
> +
> + xfs_trans_buf_set_type(tp, agflbp, XFS_BLF_AGFL_BUF);
> + xfs_trans_log_buf(tp, agflbp, startoff,
> + startoff + sizeof(xfs_agblock_t) - 1);
> return 0;
> }
>
> diff --git a/fs/xfs/xfs_buf_item.h b/fs/xfs/xfs_buf_item.h
> index 76bd7a1..067d5f0 100644
> --- a/fs/xfs/xfs_buf_item.h
> +++ b/fs/xfs/xfs_buf_item.h
> @@ -46,13 +46,15 @@ extern kmem_zone_t *xfs_buf_item_zone;
> */
> #define XFS_BLF_BTREE_BUF (1<<5)
> #define XFS_BLF_AGF_BUF (1<<6)
> +#define XFS_BLF_AGFL_BUF (1<<7)
>
> #define XFS_BLF_TYPE_MASK \
> (XFS_BLF_UDQUOT_BUF | \
> XFS_BLF_PDQUOT_BUF | \
> XFS_BLF_GDQUOT_BUF | \
> XFS_BLF_BTREE_BUF | \
> - XFS_BLF_AGF_BUF)
> + XFS_BLF_AGF_BUF | \
> + XFS_BLF_AGFL_BUF)
>
> #define XFS_BLF_CHUNK 128
> #define XFS_BLF_SHIFT 7
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 10ee0b8..1edfdf0 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -268,6 +268,11 @@ xfs_growfs_data_private(
> }
>
> agfl = XFS_BUF_TO_AGFL(bp);
> + if (xfs_sb_version_hascrc(&mp->m_sb)) {
> + agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
> + agfl->agfl_seqno = cpu_to_be32(agno);
> + uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_uuid);
> + }
> for (bucket = 0; bucket < XFS_AGFL_SIZE(mp); bucket++)
> agfl->agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);
>
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 65c35d5..81d3cc5a 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -1961,6 +1961,13 @@ xlog_recover_do_reg_buffer(
> }
> bp->b_ops = &xfs_agf_buf_ops;
> break;
> + case XFS_BLF_AGFL_BUF:
> + if (*(__be32 *)bp->b_addr != cpu_to_be32(XFS_AGFL_MAGIC)) {
> + xfs_warn(mp, "Bad AGFL block magic!");
> + ASSERT(0);
> + }
> + bp->b_ops = &xfs_agfl_buf_ops;
> + break;

Your changes for v2 in this section look good.

> default:
> break;
> }
> --
> 1.7.10
>
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs