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[PATCH 7/9] Add CRC checks to the AGI

To: xfs@xxxxxxxxxxx
Subject: [PATCH 7/9] Add CRC checks to the AGI
From: Christoph Hellwig <hch@xxxxxx>
Date: Fri, 26 Sep 2008 00:56:42 +0200
Cc: Dave Chinner <dgc@xxxxxxx>
User-agent: Mutt/1.3.28i
From: Dave Chinner <dgc@xxxxxxx>

[hch: minor adaptions]


Signed-off-by: Dave Chinner <dgc@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Index: linux-2.6-xfs/fs/xfs/xfs_ag.h
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_ag.h  2008-09-26 00:34:27.000000000 +0200
+++ linux-2.6-xfs/fs/xfs/xfs_ag.h       2008-09-26 00:39:17.000000000 +0200
@@ -123,6 +123,8 @@ typedef struct xfs_agi {
         * still being referenced.
         */
        __be32          agi_unlinked[XFS_AGI_UNLINKED_BUCKETS];
+       __be32          agi_crc;        /* crc of agi sector */
+       uuid_t          agi_uuid;       /* uuid of filesystem */
 } xfs_agi_t;
 
 #define        XFS_AGI_MAGICNUM        0x00000001
@@ -136,6 +138,9 @@ typedef struct xfs_agi {
 #define        XFS_AGI_NEWINO          0x00000100
 #define        XFS_AGI_DIRINO          0x00000200
 #define        XFS_AGI_UNLINKED        0x00000400
+/*
+ * XXX(hch): update for the CRC additions?  It's unused anyway..
+ */
 #define        XFS_AGI_NUM_BITS        11
 #define        XFS_AGI_ALL_BITS        ((1 << XFS_AGI_NUM_BITS) - 1)
 
@@ -144,6 +149,7 @@ typedef struct xfs_agi {
 #define        XFS_AGI_BLOCK(mp)       XFS_HDR_BLOCK(mp, XFS_AGI_DADDR(mp))
 #define        XFS_BUF_TO_AGI(bp)      ((xfs_agi_t *)XFS_BUF_PTR(bp))
 
+extern void xfs_agi_calc_crc(struct xfs_buf *bp);
 extern int xfs_read_agi(struct xfs_mount *mp, struct xfs_trans *tp,
                                xfs_agnumber_t agno, struct xfs_buf **bpp);
 
Index: linux-2.6-xfs/fs/xfs/xfs_fsops.c
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_fsops.c       2008-09-26 00:34:27.000000000 
+0200
+++ linux-2.6-xfs/fs/xfs/xfs_fsops.c    2008-09-26 00:39:17.000000000 +0200
@@ -239,8 +239,10 @@ xfs_growfs_data_private(
                agi->agi_freecount = 0;
                agi->agi_newino = cpu_to_be32(NULLAGINO);
                agi->agi_dirino = cpu_to_be32(NULLAGINO);
+               uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
                for (bucket = 0; bucket < XFS_AGI_UNLINKED_BUCKETS; bucket++)
                        agi->agi_unlinked[bucket] = cpu_to_be32(NULLAGINO);
+               xfs_buf_set_io_callback(bp, xfs_agi_calc_crc);
                error = xfs_bwrite(mp, bp);
                if (error) {
                        goto error0;
Index: linux-2.6-xfs/fs/xfs/xfs_ialloc.c
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_ialloc.c      2008-09-26 00:34:27.000000000 
+0200
+++ linux-2.6-xfs/fs/xfs/xfs_ialloc.c   2008-09-26 00:39:17.000000000 +0200
@@ -40,6 +40,7 @@
 #include "xfs_rtalloc.h"
 #include "xfs_error.h"
 #include "xfs_bmap.h"
+#include "xfs_cksum.h"
 
 /*
  * Log specified fields for the inode given by bp and off.
@@ -1477,6 +1478,24 @@ xfs_check_agi_unlinked(
 #endif
 
 /*
+ * Calculate CRC on AGI and stuff it into the structure.
+ *
+ * We CRC the entire AGI sector, not just the bits we use so that changes
+ * in structure size as features are included do not invalidate CRCs.
+ *
+ * We get called here just before the AGI is written to disk. We should
+ * also do some validity checking here.
+ */
+void
+xfs_agi_calc_crc(
+       xfs_buf_t       *bp)
+{
+       xfs_update_cksum(XFS_BUF_PTR(bp), XFS_BUF_SIZE(bp),
+                        offsetof(struct xfs_agi, agi_crc));
+
+}
+
+/*
  * Read in the allocation group header (inode allocation section)
  */
 int
@@ -1486,6 +1505,7 @@ xfs_read_agi(
        xfs_agnumber_t          agno,   /* allocation group number */
        struct xfs_buf          **bpp)  /* allocation group hdr buf */
 {
+       struct xfs_buf          *bp;
        struct xfs_agi          *agi;   /* allocation group header */
        int                     agi_ok; /* agi is consistent */
        int                     error;
@@ -1494,12 +1514,28 @@ xfs_read_agi(
 
        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
-                       XFS_FSS_TO_BB(mp, 1), 0, bpp);
+                       XFS_FSS_TO_BB(mp, 1), 0, &bp);
        if (error)
                return error;
 
-       ASSERT(*bpp && !XFS_BUF_GETERROR(*bpp));
-       agi = XFS_BUF_TO_AGI(*bpp);
+       ASSERT(bp && !XFS_BUF_GETERROR(bp));
+       agi = XFS_BUF_TO_AGI(bp);
+
+       /*
+        * Validate the CRC of the AGI block only if the block is clean (i.e.
+        * it just came from disk) and we have CRCs enabled.
+        */
+       if (xfs_sb_version_hascrc(&mp->m_sb) &&
+           !(XFS_BUF_ISWRITE(bp) || XFS_BUF_ISDELAYWRITE(bp))) {
+               if (!xfs_verify_cksum(XFS_BUF_PTR(bp), XFS_BUF_SIZE(bp),
+                                     offsetof(struct xfs_agi, agi_crc)) ||
+                   !uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_uuid)) {
+                       XFS_CORRUPTION_ERROR("xfs_read_agi crc",
+                                       XFS_ERRLEVEL_LOW, mp, agi);
+                       xfs_trans_brelse(tp, bp);
+                       return XFS_ERROR(EFSCORRUPTED);
+               }
+       }
 
        /*
         * Validate the magic number of the agi block.
@@ -1511,13 +1547,18 @@ xfs_read_agi(
                        XFS_RANDOM_IALLOC_READ_AGI))) {
                XFS_CORRUPTION_ERROR("xfs_read_agi", XFS_ERRLEVEL_LOW,
                                     mp, agi);
-               xfs_trans_brelse(tp, *bpp);
+               xfs_trans_brelse(tp, bp);
                return XFS_ERROR(EFSCORRUPTED);
        }
 
-       XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_AGI, XFS_AGI_REF);
+       XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGI, XFS_AGI_REF);
 
        xfs_check_agi_unlinked(agi);
+
+       if (xfs_sb_version_hascrc(&mp->m_sb))
+               xfs_buf_set_io_callback(bp, xfs_agi_calc_crc);
+
+       *bpp = bp;
        return 0;
 }
 
Index: linux-2.6-xfs/fs/xfs/xfs_log_recover.c
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_log_recover.c 2008-09-26 00:38:00.000000000 
+0200
+++ linux-2.6-xfs/fs/xfs/xfs_log_recover.c      2008-09-26 00:39:40.000000000 
+0200
@@ -1944,6 +1944,9 @@ xlog_recover_do_reg_buffer(
        case XFS_SB_MAGIC:
                xfs_sb_calc_crc(bp);
                break;
+       case XFS_AGI_MAGIC:
+               xfs_agi_calc_crc(bp);
+               break;
        default:
                break;
        }

-- 

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