xfs: add CRC checks to the superblock

With the addition of CRCs, there is such a wide and varied change to
the on disk format that it makes sense to bump the superblock
version number rather than try to use feature bits for all the new
functionality.

This commit introduces all the new superblock fields needed for all
the new functionality: feature masks similar to ext4, separate
project quota inodes, a LSN field for recovery and the CRC field.

This commit does not bump the superblock version number, however.
That will be done as a separate commit at the end of the series
after all the new functionality is present so we switch it all on in
one commit. This means that we can slowly introduce the changes
without them being active and hence maintain bisectability of the
tree.

This patch is based on a patch originally written by myself back
from SGI days, which was subsequently modified by Christoph Hellwig.
There is relatively little of that patch remaining, but the history
of the patch still should be acknowledged here.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_log_recover.c

@@ -2040,6 +2040,14 @@ xlog_recovery_validate_buf_type(
 		}
 		bp->b_ops = &xfs_attr3_rmt_buf_ops;
 		break;
+	case XFS_BLFT_SB_BUF:
+		if (magic32 != XFS_SB_MAGIC) {
+			xfs_warn(mp, "Bad SB block magic!");
+			ASSERT(0);
+			break;
+		}
+		bp->b_ops = &xfs_sb_buf_ops;
+		break;
 	default:
 		xfs_warn(mp, "Unknown buffer type %d!",
 			 xfs_blft_from_flags(buf_f));

fs/xfs/xfs_mount.c

@@ -43,6 +43,8 @@
 #include "xfs_utils.h"
 #include "xfs_trace.h"
 #include "xfs_icache.h"
+#include "xfs_cksum.h"
+#include "xfs_buf_item.h"
 
 
 #ifdef HAVE_PERCPU_SB
@@ -109,6 +111,12 @@ static const struct {
     { offsetof(xfs_sb_t, sb_logsunit),	 0 },
     { offsetof(xfs_sb_t, sb_features2),	 0 },
     { offsetof(xfs_sb_t, sb_bad_features2), 0 },
+    { offsetof(xfs_sb_t, sb_features_compat), 0 },
+    { offsetof(xfs_sb_t, sb_features_ro_compat), 0 },
+    { offsetof(xfs_sb_t, sb_features_incompat), 0 },
+    { offsetof(xfs_sb_t, sb_crc),	 0 },
+    { offsetof(xfs_sb_t, sb_pquotino),	 0 },
+    { offsetof(xfs_sb_t, sb_lsn),	 0 },
     { sizeof(xfs_sb_t),			 0 }
 };
 
@@ -319,11 +327,23 @@ xfs_mount_validate_sb(
 		return XFS_ERROR(EWRONGFS);
 	}
 
+
 	if (!xfs_sb_good_version(sbp)) {
 		xfs_warn(mp, "bad version");
 		return XFS_ERROR(EWRONGFS);
 	}
 
+	/*
+	 * Do not allow Version 5 superblocks to mount right now, even though
+	 * support is in place. We need to implement the proper feature masks
+	 * first.
+	 */
+	if (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) {
+		xfs_alert(mp,
+	"Version 5 superblock detected. Experimental support not yet enabled!");
+		return XFS_ERROR(EINVAL);
+	}
+
 	if (unlikely(
 	    sbp->sb_logstart == 0 && mp->m_logdev_targp == mp->m_ddev_targp)) {
 		xfs_warn(mp,
@@ -557,6 +577,11 @@ xfs_sb_from_disk(
 	to->sb_logsunit = be32_to_cpu(from->sb_logsunit);
 	to->sb_features2 = be32_to_cpu(from->sb_features2);
 	to->sb_bad_features2 = be32_to_cpu(from->sb_bad_features2);
+	to->sb_features_compat = be32_to_cpu(from->sb_features_compat);
+	to->sb_features_ro_compat = be32_to_cpu(from->sb_features_ro_compat);
+	to->sb_features_incompat = be32_to_cpu(from->sb_features_incompat);
+	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
+	to->sb_lsn = be64_to_cpu(from->sb_lsn);
 }
 
 /*
@@ -612,30 +637,59 @@ xfs_sb_to_disk(
 	}
 }
 
-static void
+static int
 xfs_sb_verify(
 	struct xfs_buf	*bp)
 {
 	struct xfs_mount *mp = bp->b_target->bt_mount;
 	struct xfs_sb	sb;
-	int		error;
 
 	xfs_sb_from_disk(&sb, XFS_BUF_TO_SBP(bp));
 
 	/*
 	 * Only check the in progress field for the primary superblock as
 	 * mkfs.xfs doesn't clear it from secondary superblocks.
 	 */
-	error = xfs_mount_validate_sb(mp, &sb, bp->b_bn == XFS_SB_DADDR);
-	if (error)
-		xfs_buf_ioerror(bp, error);
+	return xfs_mount_validate_sb(mp, &sb, bp->b_bn == XFS_SB_DADDR);
 }
 
+/*
+ * If the superblock has the CRC feature bit set or the CRC field is non-null,
+ * check that the CRC is valid.  We check the CRC field is non-null because a
+ * single bit error could clear the feature bit and unused parts of the
+ * superblock are supposed to be zero. Hence a non-null crc field indicates that
+ * we've potentially lost a feature bit and we should check it anyway.
+ */
 static void
 xfs_sb_read_verify(
 	struct xfs_buf	*bp)
 {
-	xfs_sb_verify(bp);
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_dsb	*dsb = XFS_BUF_TO_SBP(bp);
+	int		error;
+
+	/*
+	 * open code the version check to avoid needing to convert the entire
+	 * superblock from disk order just to check the version number
+	 */
+	if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC) &&
+	    (((be16_to_cpu(dsb->sb_versionnum) & XFS_SB_VERSION_NUMBITS) ==
+						XFS_SB_VERSION_5) ||
+	     dsb->sb_crc != 0)) {
+
+		if (!xfs_verify_cksum(bp->b_addr, be16_to_cpu(dsb->sb_sectsize),
+				      offsetof(struct xfs_sb, sb_crc))) {
+			error = EFSCORRUPTED;
+			goto out_error;
+		}
+	}
+	error = xfs_sb_verify(bp);
+
+out_error:
+	if (error) {
+		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
+		xfs_buf_ioerror(bp, error);
+	}
 }
 
 /*
@@ -648,11 +702,10 @@ static void
 xfs_sb_quiet_read_verify(
 	struct xfs_buf	*bp)
 {
-	struct xfs_sb	sb;
+	struct xfs_dsb	*dsb = XFS_BUF_TO_SBP(bp);
 
-	xfs_sb_from_disk(&sb, XFS_BUF_TO_SBP(bp));
 
-	if (sb.sb_magicnum == XFS_SB_MAGIC) {
+	if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC)) {
 		/* XFS filesystem, verify noisily! */
 		xfs_sb_read_verify(bp);
 		return;
@@ -663,9 +716,27 @@ xfs_sb_quiet_read_verify(
 
 static void
 xfs_sb_write_verify(
-	struct xfs_buf	*bp)
+	struct xfs_buf		*bp)
 {
-	xfs_sb_verify(bp);
+	struct xfs_mount	*mp = bp->b_target->bt_mount;
+	struct xfs_buf_log_item	*bip = bp->b_fspriv;
+	int			error;
+
+	error = xfs_sb_verify(bp);
+	if (error) {
+		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
+		xfs_buf_ioerror(bp, error);
+		return;
+	}
+
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	if (bip)
+		XFS_BUF_TO_SBP(bp)->sb_lsn = cpu_to_be64(bip->bli_item.li_lsn);
+
+	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
+			 offsetof(struct xfs_sb, sb_crc));
 }
 
 const struct xfs_buf_ops xfs_sb_buf_ops = {
@@ -687,7 +758,8 @@ int
 xfs_readsb(xfs_mount_t *mp, int flags)
 {
 	unsigned int	sector_size;
-	xfs_buf_t	*bp;
+	struct xfs_buf	*bp;
+	struct xfs_sb	*sbp = &mp->m_sb;
 	int		error;
 	int		loud = !(flags & XFS_MFSI_QUIET);
 
@@ -726,10 +798,10 @@ xfs_readsb(xfs_mount_t *mp, int flags)
 	/*
 	 * We must be able to do sector-sized and sector-aligned IO.
 	 */
-	if (sector_size > mp->m_sb.sb_sectsize) {
+	if (sector_size > sbp->sb_sectsize) {
 		if (loud)
 			xfs_warn(mp, "device supports %u byte sectors (not %u)",
-				sector_size, mp->m_sb.sb_sectsize);
+				sector_size, sbp->sb_sectsize);
 		error = ENOSYS;
 		goto release_buf;
 	}
@@ -738,15 +810,18 @@ xfs_readsb(xfs_mount_t *mp, int flags)
 	 * If device sector size is smaller than the superblock size,
 	 * re-read the superblock so the buffer is correctly sized.
 	 */
-	if (sector_size < mp->m_sb.sb_sectsize) {
+	if (sector_size < sbp->sb_sectsize) {
 		xfs_buf_relse(bp);
-		sector_size = mp->m_sb.sb_sectsize;
+		sector_size = sbp->sb_sectsize;
 		goto reread;
 	}
 
 	/* Initialize per-cpu counters */
 	xfs_icsb_reinit_counters(mp);
 
+	/* no need to be quiet anymore, so reset the buf ops */
+	bp->b_ops = &xfs_sb_buf_ops;
+
 	mp->m_sb_bp = bp;
 	xfs_buf_unlock(bp);
 	return 0;
@@ -1633,6 +1708,7 @@ xfs_mod_sb(xfs_trans_t *tp, __int64_t fields)
 	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
 	first = xfs_sb_info[f].offset;
 
+	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
 	xfs_trans_log_buf(tp, bp, first, last);
 }
 

fs/xfs/xfs_mount.h

@@ -391,6 +391,7 @@ extern void	xfs_set_low_space_thresholds(struct xfs_mount *);
 
 #endif	/* __KERNEL__ */
 
+extern void	xfs_sb_calc_crc(struct xfs_buf	*);
 extern void	xfs_mod_sb(struct xfs_trans *, __int64_t);
 extern int	xfs_initialize_perag(struct xfs_mount *, xfs_agnumber_t,
 					xfs_agnumber_t *);