[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;
 }