[XFS] factor out xfs_read_agf helper

Add a helper to read the AGF 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, 48 insertions, 21 deletions

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index c47ce9075728..028e44e58ea9 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -2233,44 +2233,41 @@ xfs_alloc_put_freelist(
  * Read in the allocation group header (free/alloc section).
  */
 int                                     /* error */
-xfs_alloc_read_agf(
-        xfs_mount_t     *mp,            /* mount point structure */
-        xfs_trans_t     *tp,            /* transaction pointer */
-        xfs_agnumber_t  agno,           /* allocation group number */
-        int             flags,          /* XFS_ALLOC_FLAG_... */
-        xfs_buf_t       **bpp)          /* buffer for the ag freelist header */
+xfs_read_agf(
+        struct xfs_mount        *mp,    /* mount point structure */
+        struct xfs_trans        *tp,    /* transaction pointer */
+        xfs_agnumber_t          agno,   /* allocation group number */
+        int                     flags,  /* XFS_BUF_ */
+        struct xfs_buf          **bpp)  /* buffer for the ag freelist header */
 {
-        xfs_agf_t       *agf;           /* ag freelist header */
+        struct xfs_agf  *agf;           /* ag freelist header */
         int             agf_ok;         /* set if agf is consistent */
-        xfs_buf_t       *bp;            /* return value */
-        xfs_perag_t     *pag;           /* per allocation group data */
         int             error;
 
         ASSERT(agno != NULLAGNUMBER);
         error = xfs_trans_read_buf(
                         mp, tp, mp->m_ddev_targp,
                         XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
-                        XFS_FSS_TO_BB(mp, 1),
-                        (flags & XFS_ALLOC_FLAG_TRYLOCK) ? XFS_BUF_TRYLOCK : 0U,
-                        &bp);
+                        XFS_FSS_TO_BB(mp, 1), flags, bpp);
         if (error)
                 return error;
-        ASSERT(!bp || !XFS_BUF_GETERROR(bp));
-        if (!bp) {
-                *bpp = NULL;
+        if (!*bpp)
                 return 0;
-        }
+
+        ASSERT(!XFS_BUF_GETERROR(*bpp));
+        agf = XFS_BUF_TO_AGF(*bpp);
+
         /*
          * Validate the magic number of the agf block.
          */
-        agf = XFS_BUF_TO_AGF(bp);
         agf_ok =
                 be32_to_cpu(agf->agf_magicnum) == XFS_AGF_MAGIC &&
                 XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) &&
                 be32_to_cpu(agf->agf_freeblks) <= be32_to_cpu(agf->agf_length) &&
                 be32_to_cpu(agf->agf_flfirst) < XFS_AGFL_SIZE(mp) &&
                 be32_to_cpu(agf->agf_fllast) < XFS_AGFL_SIZE(mp) &&
-                be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp);
+                be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp) &&
+                be32_to_cpu(agf->agf_seqno) == agno;
         if (xfs_sb_version_haslazysbcount(&mp->m_sb))
                 agf_ok = agf_ok && be32_to_cpu(agf->agf_btreeblks) <=
                                                 be32_to_cpu(agf->agf_length);
@@ -2278,9 +2275,41 @@ xfs_alloc_read_agf(
                         XFS_RANDOM_ALLOC_READ_AGF))) {
                 XFS_CORRUPTION_ERROR("xfs_alloc_read_agf",
                                      XFS_ERRLEVEL_LOW, mp, agf);
-                xfs_trans_brelse(tp, bp);
+                xfs_trans_brelse(tp, *bpp);
                 return XFS_ERROR(EFSCORRUPTED);
         }
+
+        XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_AGF, XFS_AGF_REF);
+        return 0;
+}
+
+/*
+ * Read in the allocation group header (free/alloc section).
+ */
+int                                     /* error */
+xfs_alloc_read_agf(
+        struct xfs_mount        *mp,    /* mount point structure */
+        struct xfs_trans        *tp,    /* transaction pointer */
+        xfs_agnumber_t          agno,   /* allocation group number */
+        int                     flags,  /* XFS_ALLOC_FLAG_... */
+        struct xfs_buf          **bpp)  /* buffer for the ag freelist header */
+{
+        struct xfs_agf          *agf;           /* ag freelist header */
+        struct xfs_perag        *pag;           /* per allocation group data */
+        int                     error;
+
+        ASSERT(agno != NULLAGNUMBER);
+
+        error = xfs_read_agf(mp, tp, agno,
+                        (flags & XFS_ALLOC_FLAG_TRYLOCK) ? XFS_BUF_TRYLOCK : 0,
+                        bpp);
+        if (error)
+                return error;
+        if (!*bpp)
+                return 0;
+        ASSERT(!XFS_BUF_GETERROR(*bpp));
+
+        agf = XFS_BUF_TO_AGF(*bpp);
         pag = &mp->m_perag[agno];
         if (!pag->pagf_init) {
                 pag->pagf_freeblks = be32_to_cpu(agf->agf_freeblks);
@@ -2308,8 +2337,6 @@ xfs_alloc_read_agf(
                        be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]));
         }
 #endif
-        XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGF, XFS_AGF_REF);
-        *bpp = bp;
         return 0;
 }