xfs: sanitise sb_bad_features2 handling

We currently have to ensure that every time we update sb_features2
that we update sb_bad_features2. Now that we log and format the
superblock in it's entirety we actually don't have to care because
we can simply update the sb_bad_features2 when we format it into the
buffer. This removes the need for anything but the mount and
superblock formatting code to care about sb_bad_features2, and
hence removes the possibility that we forget to update bad_features2
when necessary in the future.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

2 files changed, 14 insertions, 8 deletions

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index fbd6da263571..749c86102794 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -151,10 +151,13 @@ typedef struct xfs_sb {
 	__uint32_t	sb_features2;	/* additional feature bits */
 
 	/*
-	 * bad features2 field as a result of failing to pad the sb
-	 * structure to 64 bits. Some machines will be using this field
-	 * for features2 bits. Easiest just to mark it bad and not use
-	 * it for anything else.
+	 * bad features2 field as a result of failing to pad the sb structure to
+	 * 64 bits. Some machines will be using this field for features2 bits.
+	 * Easiest just to mark it bad and not use it for anything else.
+	 *
+	 * This is not kept up to date in memory; it is always overwritten by
+	 * the value in sb_features2 when formatting the incore superblock to
+	 * the disk buffer.
 	 */
 	__uint32_t	sb_bad_features2;
 
@@ -453,13 +456,11 @@ static inline void xfs_sb_version_addattr2(struct xfs_sb *sbp)
 {
 	sbp->sb_versionnum |= XFS_SB_VERSION_MOREBITSBIT;
 	sbp->sb_features2 |= XFS_SB_VERSION2_ATTR2BIT;
-	sbp->sb_bad_features2 |= XFS_SB_VERSION2_ATTR2BIT;
 }
 
 static inline void xfs_sb_version_removeattr2(struct xfs_sb *sbp)
 {
 	sbp->sb_features2 &= ~XFS_SB_VERSION2_ATTR2BIT;
-	sbp->sb_bad_features2 &= ~XFS_SB_VERSION2_ATTR2BIT;
 	if (!sbp->sb_features2)
 		sbp->sb_versionnum &= ~XFS_SB_VERSION_MOREBITSBIT;
 }
@@ -475,7 +476,6 @@ static inline void xfs_sb_version_addprojid32bit(struct xfs_sb *sbp)
 {
 	sbp->sb_versionnum |= XFS_SB_VERSION_MOREBITSBIT;
 	sbp->sb_features2 |= XFS_SB_VERSION2_PROJID32BIT;
-	sbp->sb_bad_features2 |= XFS_SB_VERSION2_PROJID32BIT;
 }
 
 /*
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 63f814872dfb..b0a5fe95a3e2 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -497,7 +497,6 @@ xfs_sb_to_disk(
 	to->sb_fdblocks = cpu_to_be64(from->sb_fdblocks);
 	to->sb_frextents = cpu_to_be64(from->sb_frextents);
 
-
 	to->sb_flags = from->sb_flags;
 	to->sb_shared_vn = from->sb_shared_vn;
 	to->sb_inoalignmt = cpu_to_be32(from->sb_inoalignmt);
@@ -507,6 +506,13 @@ xfs_sb_to_disk(
 	to->sb_logsectlog = from->sb_logsectlog;
 	to->sb_logsectsize = cpu_to_be16(from->sb_logsectsize);
 	to->sb_logsunit = cpu_to_be32(from->sb_logsunit);
+
+	/*
+	 * We need to ensure that bad_features2 always matches features2.
+	 * Hence we enforce that here rather than having to remember to do it
+	 * everywhere else that updates features2.
+	 */
+	from->sb_bad_features2 = from->sb_features2;
 	to->sb_features2 = cpu_to_be32(from->sb_features2);
 	to->sb_bad_features2 = cpu_to_be32(from->sb_bad_features2);