xfs: add CRC checks to the AGFL

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>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

5 files changed, 119 insertions, 44 deletions

diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 9f4815e0c96f..272ef097e2be 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 c34f799aa92e..40d3d576f473 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)
-                        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 76bd7a167a70..067d5f0fc233 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 b6cca27e9132..a693a54799e5 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 dadf24566d16..da2a19e0554e 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -1961,6 +1961,16 @@ xlog_recover_do_reg_buffer(
                 }
                 bp->b_ops = &xfs_agf_buf_ops;
                 break;
+        case XFS_BLF_AGFL_BUF:
+                if (!xfs_sb_version_hascrc(&mp->m_sb))
+                        break;
+                if (*(__be32 *)bp->b_addr != cpu_to_be32(XFS_AGFL_MAGIC)) {
+                        xfs_warn(mp, "Bad AGFL block magic!");
+                        ASSERT(0);
+                        break;
+                }
+                bp->b_ops = &xfs_agfl_buf_ops;
+                break;
         default:
                 break;
         }