[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 c8a56c52..efb65fe 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;
 }