4 files changed, 31 insertions, 8 deletions
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 5e66807737c5..1a4e446194dd 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1200,6 +1200,12 @@ xfs_iread_extents(
 		goto out;
 	}
 	ASSERT(ir.loaded == xfs_iext_count(ifp));
+	/*
+	 * Use release semantics so that we can use acquire semantics in
+	 * xfs_need_iread_extents and be guaranteed to see a valid mapping tree
+	 * after that load.
+	 */
+	smp_store_release(&ifp->if_needextents, 0);
 	return 0;
 out:
 	xfs_iext_destroy(ifp);
diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index ff37eecec4b0..5a2e7ddfa76d 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -227,10 +227,15 @@ xfs_iformat_data_fork(
 
 	/*
 	 * Initialize the extent count early, as the per-format routines may
-	 * depend on it.
+	 * depend on it.  Use release semantics to set needextents /after/ we
+	 * set the format. This ensures that we can use acquire semantics on
+	 * needextents in xfs_need_iread_extents() and be guaranteed to see a
+	 * valid format value after that load.
 	 */
 	ip->i_df.if_format = dip->di_format;
 	ip->i_df.if_nextents = xfs_dfork_data_extents(dip);
+	smp_store_release(&ip->i_df.if_needextents,
+			   ip->i_df.if_format == XFS_DINODE_FMT_BTREE ? 1 : 0);
 
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFIFO:
@@ -283,8 +288,17 @@ xfs_ifork_init_attr(
 	enum xfs_dinode_fmt	format,
 	xfs_extnum_t		nextents)
 {
+	/*
+	 * Initialize the extent count early, as the per-format routines may
+	 * depend on it.  Use release semantics to set needextents /after/ we
+	 * set the format. This ensures that we can use acquire semantics on
+	 * needextents in xfs_need_iread_extents() and be guaranteed to see a
+	 * valid format value after that load.
+	 */
 	ip->i_af.if_format = format;
 	ip->i_af.if_nextents = nextents;
+	smp_store_release(&ip->i_af.if_needextents,
+			   ip->i_af.if_format == XFS_DINODE_FMT_BTREE ? 1 : 0);
 }
 
 void
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index d3943d6ad0b9..96d307784c85 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -24,6 +24,7 @@ struct xfs_ifork {
 	xfs_extnum_t		if_nextents;	/* # of extents in this fork */
 	short			if_broot_bytes;	/* bytes allocated for root */
 	int8_t			if_format;	/* format of this fork */
+	uint8_t			if_needextents;	/* extents have not been read */
 };
 
 /*
@@ -260,9 +261,10 @@ int xfs_iext_count_upgrade(struct xfs_trans *tp, struct xfs_inode *ip,
 		uint nr_to_add);
 
 /* returns true if the fork has extents but they are not read in yet. */
-static inline bool xfs_need_iread_extents(struct xfs_ifork *ifp)
+static inline bool xfs_need_iread_extents(const struct xfs_ifork *ifp)
 {
-	return ifp->if_format == XFS_DINODE_FMT_BTREE && ifp->if_height == 0;
+	/* see xfs_iformat_{data,attr}_fork() for needextents semantics */
+	return smp_load_acquire(&ifp->if_needextents) != 0;
 }
 
 #endif	/* __XFS_INODE_FORK_H__ */
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 99cc03a298e2..ba0f17bc1dc0 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -72,7 +72,8 @@ xfs_sb_validate_v5_features(
 }
 
 /*
- * We support all XFS versions newer than a v4 superblock with V2 directories.
+ * We current support XFS v5 formats with known features and v4 superblocks with
+ * at least V2 directories.
  */
 bool
 xfs_sb_good_version(
@@ -86,16 +87,16 @@ xfs_sb_good_version(
 	if (xfs_sb_is_v5(sbp))
 		return xfs_sb_validate_v5_features(sbp);
 
+	/* versions prior to v4 are not supported */
+	if (XFS_SB_VERSION_NUM(sbp) != XFS_SB_VERSION_4)
+		return false;
+
 	/* We must not have any unknown v4 feature bits set */
 	if ((sbp->sb_versionnum & ~XFS_SB_VERSION_OKBITS) ||
 	    ((sbp->sb_versionnum & XFS_SB_VERSION_MOREBITSBIT) &&
 	     (sbp->sb_features2 & ~XFS_SB_VERSION2_OKBITS)))
 		return false;
 
-	/* versions prior to v4 are not supported */
-	if (XFS_SB_VERSION_NUM(sbp) < XFS_SB_VERSION_4)
-		return false;
-
 	/* V4 filesystems need v2 directories and unwritten extents */
 	if (!(sbp->sb_versionnum & XFS_SB_VERSION_DIRV2BIT))
 		return false;