[XFS] factor out xfs_read_agi helper

Add a helper to read the AGI header and perform basic verification.
Based on hunks from a larger patch from Dave Chinner.

(First sent on Juli 23rd)

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Niv Sardi <xaiki@sgi.com>

1 files changed, 63 insertions, 38 deletions

diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c
index c8a56c529642..efb65fea203c 100644
--- a/fs/xfs/xfs_ialloc.c
+++ b/fs/xfs/xfs_ialloc.c
@@ -1462,70 +1462,95 @@ xfs_ialloc_log_agi(
         xfs_trans_log_buf(tp, bp, first, last);
 }
 
+#ifdef DEBUG
+STATIC void
+xfs_check_agi_unlinked(
+        struct xfs_agi          *agi)
+{
+        int                     i;
+
+        for (i = 0; i < XFS_AGI_UNLINKED_BUCKETS; i++)
+                ASSERT(agi->agi_unlinked[i]);
+}
+#else
+#define xfs_check_agi_unlinked(agi)
+#endif
+
 /*
  * Read in the allocation group header (inode allocation section)
  */
 int
-xfs_ialloc_read_agi(
-        xfs_mount_t     *mp,            /* file system mount structure */
-        xfs_trans_t     *tp,            /* transaction pointer */
-        xfs_agnumber_t  agno,           /* allocation group number */
-        xfs_buf_t       **bpp)          /* allocation group hdr buf */
+xfs_read_agi(
+        struct xfs_mount        *mp,    /* file system mount structure */
+        struct xfs_trans        *tp,    /* transaction pointer */
+        xfs_agnumber_t          agno,   /* allocation group number */
+        struct xfs_buf          **bpp)  /* allocation group hdr buf */
 {
-        xfs_agi_t       *agi;           /* allocation group header */
-        int             agi_ok;         /* agi is consistent */
-        xfs_buf_t       *bp;            /* allocation group hdr buf */
-        xfs_perag_t     *pag;           /* per allocation group data */
-        int             error;
+        struct xfs_agi          *agi;   /* allocation group header */
+        int                     agi_ok; /* agi is consistent */
+        int                     error;
 
         ASSERT(agno != NULLAGNUMBER);
-        error = xfs_trans_read_buf(
-                        mp, tp, mp->m_ddev_targp,
+
+        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, &bp);
+                        XFS_FSS_TO_BB(mp, 1), 0, bpp);
         if (error)
                 return error;
-        ASSERT(bp && !XFS_BUF_GETERROR(bp));
+
+        ASSERT(*bpp && !XFS_BUF_GETERROR(*bpp));
+        agi = XFS_BUF_TO_AGI(*bpp);
 
         /*
          * Validate the magic number of the agi block.
          */
-        agi = XFS_BUF_TO_AGI(bp);
-        agi_ok =
-                be32_to_cpu(agi->agi_magicnum) == XFS_AGI_MAGIC &&
-                XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum));
+        agi_ok = be32_to_cpu(agi->agi_magicnum) == XFS_AGI_MAGIC &&
+                XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum)) &&
+                be32_to_cpu(agi->agi_seqno) == agno;
         if (unlikely(XFS_TEST_ERROR(!agi_ok, mp, XFS_ERRTAG_IALLOC_READ_AGI,
                         XFS_RANDOM_IALLOC_READ_AGI))) {
-                XFS_CORRUPTION_ERROR("xfs_ialloc_read_agi", XFS_ERRLEVEL_LOW,
+                XFS_CORRUPTION_ERROR("xfs_read_agi", XFS_ERRLEVEL_LOW,
                                      mp, agi);
-                xfs_trans_brelse(tp, bp);
+                xfs_trans_brelse(tp, *bpp);
                 return XFS_ERROR(EFSCORRUPTED);
         }
+
+        XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_AGI, XFS_AGI_REF);
+
+        xfs_check_agi_unlinked(agi);
+        return 0;
+}
+
+int
+xfs_ialloc_read_agi(
+        struct xfs_mount        *mp,    /* file system mount structure */
+        struct xfs_trans        *tp,    /* transaction pointer */
+        xfs_agnumber_t          agno,   /* allocation group number */
+        struct xfs_buf          **bpp)  /* allocation group hdr buf */
+{
+        struct xfs_agi          *agi;   /* allocation group header */
+        struct xfs_perag        *pag;   /* per allocation group data */
+        int                     error;
+
+        error = xfs_read_agi(mp, tp, agno, bpp);
+        if (error)
+                return error;
+
+        agi = XFS_BUF_TO_AGI(*bpp);
         pag = &mp->m_perag[agno];
+
         if (!pag->pagi_init) {
                 pag->pagi_freecount = be32_to_cpu(agi->agi_freecount);
                 pag->pagi_count = be32_to_cpu(agi->agi_count);
                 pag->pagi_init = 1;
-        } else {
-                /*
-                 * It's possible for these to be out of sync if
-                 * we are in the middle of a forced shutdown.
-                 */
-                ASSERT(pag->pagi_freecount == be32_to_cpu(agi->agi_freecount) ||
-                        XFS_FORCED_SHUTDOWN(mp));
-        }
-
-#ifdef DEBUG
-        {
-                int     i;
-
-                for (i = 0; i < XFS_AGI_UNLINKED_BUCKETS; i++)
-                        ASSERT(agi->agi_unlinked[i]);
         }
-#endif
 
-        XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGI, XFS_AGI_REF);
-        *bpp = bp;
+        /*
+         * It's possible for these to be out of sync if
+         * we are in the middle of a forced shutdown.
+         */
+        ASSERT(pag->pagi_freecount == be32_to_cpu(agi->agi_freecount) ||
+                XFS_FORCED_SHUTDOWN(mp));
         return 0;
 }