xfs: simplify validation of the unwritten extent bit

XFS only supports the unwritten extent bit in the data fork, and only if
the file system has a version 5 superblock or the unwritten extent
feature bit.

We currently have two routines that validate the invariant:
xfs_check_nostate_extents which return -EFSCORRUPTED when it's not met,
and xfs_validate_extent that triggers and assert in debug build.

Both of them iterate over all extents of an inode fork when called,
which isn't very efficient.

This patch instead adds a new helper that verifies the invariant one
extent at a time, and calls it from the places where we iterate over
all extents to converted them from or two the in-memory format.  The
callers then return -EFSCORRUPTED when reading invalid extents from
disk, or trigger an assert when writing them to disk.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -1231,7 +1231,6 @@ xfs_bmap_read_extents(
 	xfs_fsblock_t		bno;	/* block # of "block" */
 	xfs_buf_t		*bp;	/* buffer for "block" */
 	int			error;	/* error return value */
-	xfs_exntfmt_t		exntf;	/* XFS_EXTFMT_NOSTATE, if checking */
 	xfs_extnum_t		i, j;	/* index into the extents list */
 	xfs_ifork_t		*ifp;	/* fork structure */
 	int			level;	/* btree level, for checking */
@@ -1242,8 +1241,6 @@ xfs_bmap_read_extents(
 
 	mp = ip->i_mount;
 	ifp = XFS_IFORK_PTR(ip, whichfork);
-	exntf = (whichfork != XFS_DATA_FORK) ? XFS_EXTFMT_NOSTATE :
-					XFS_EXTFMT_INODE(ip);
 	block = ifp->if_broot;
 	/*
 	 * Root level must use BMAP_BROOT_PTR_ADDR macro to get ptr out.
@@ -1311,18 +1308,9 @@ xfs_bmap_read_extents(
 			xfs_bmbt_rec_host_t *trp = xfs_iext_get_ext(ifp, i);
 			trp->l0 = be64_to_cpu(frp->l0);
 			trp->l1 = be64_to_cpu(frp->l1);
-		}
+			if (!xfs_bmbt_validate_extent(mp, whichfork, trp)) {
-		if (exntf == XFS_EXTFMT_NOSTATE) {
-			/*
-			 * Check all attribute bmap btree records and
-			 * any "older" data bmap btree records for a
-			 * set bit in the "extent flag" position.
-			 */
-			if (unlikely(xfs_check_nostate_extents(ifp,
-					start, num_recs))) {
 				XFS_ERROR_REPORT("xfs_bmap_read_extents(2)",
-						 XFS_ERRLEVEL_LOW,
+						 XFS_ERRLEVEL_LOW, mp);
-						 ip->i_mount);
 				goto error0;
 			}
 		}

fs/xfs/libxfs/xfs_bmap.h

@@ -244,8 +244,6 @@ int	xfs_bmap_del_extent_delay(struct xfs_inode *ip, int whichfork,
 		struct xfs_bmbt_irec *del);
 void	xfs_bmap_del_extent_cow(struct xfs_inode *ip, xfs_extnum_t *idx,
 		struct xfs_bmbt_irec *got, struct xfs_bmbt_irec *del);
-int	xfs_check_nostate_extents(struct xfs_ifork *ifp, xfs_extnum_t idx,
-		xfs_extnum_t num);
 uint	xfs_default_attroffset(struct xfs_inode *ip);
 int	xfs_bmap_shift_extents(struct xfs_trans *tp, struct xfs_inode *ip,
 		xfs_fileoff_t *next_fsb, xfs_fileoff_t offset_shift_fsb,

fs/xfs/libxfs/xfs_bmap_btree.c

@@ -366,32 +366,6 @@ xfs_bmbt_to_bmdr(
 	memcpy(tpp, fpp, sizeof(*fpp) * dmxr);
 }
 
-/*
- * Check extent records, which have just been read, for
- * any bit in the extent flag field. ASSERT on debug
- * kernels, as this condition should not occur.
- * Return an error condition (1) if any flags found,
- * otherwise return 0.
- */
-
-int
-xfs_check_nostate_extents(
-	xfs_ifork_t		*ifp,
-	xfs_extnum_t		idx,
-	xfs_extnum_t		num)
-{
-	for (; num > 0; num--, idx++) {
-		xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, idx);
-		if ((ep->l0 >>
-		     (64 - BMBT_EXNTFLAG_BITLEN)) != 0) {
-			ASSERT(0);
-			return 1;
-		}
-	}
-	return 0;
-}
-
-
 STATIC struct xfs_btree_cur *
 xfs_bmbt_dup_cursor(
 	struct xfs_btree_cur	*cur)

fs/xfs/libxfs/xfs_bmap_btree.h

@@ -24,13 +24,6 @@ struct xfs_mount;
 struct xfs_inode;
 struct xfs_trans;
 
-/*
- * Extent state and extent format macros.
- */
-#define XFS_EXTFMT_INODE(x)	\
-	(xfs_sb_version_hasextflgbit(&((x)->i_mount->m_sb)) ? \
-		XFS_EXTFMT_HASSTATE : XFS_EXTFMT_NOSTATE)
-
 /*
  * Btree block header size depends on a superblock flag.
  */
@@ -139,4 +132,18 @@ extern int xfs_bmbt_change_owner(struct xfs_trans *tp, struct xfs_inode *ip,
 extern struct xfs_btree_cur *xfs_bmbt_init_cursor(struct xfs_mount *,
 		struct xfs_trans *, struct xfs_inode *, int);
 
+/*
+ * Check that the extent does not contain an invalid unwritten extent flag.
+ */
+static inline bool xfs_bmbt_validate_extent(struct xfs_mount *mp, int whichfork,
+		struct xfs_bmbt_rec_host *ep)
+{
+	if (ep->l0 >> (64 - BMBT_EXNTFLAG_BITLEN) == 0)
+		return true;
+	if (whichfork == XFS_DATA_FORK &&
+	    xfs_sb_version_hasextflgbit(&mp->m_sb))
+		return true;
+	return false;
+}
+
 #endif	/* __XFS_BMAP_BTREE_H__ */

fs/xfs/libxfs/xfs_format.h

@@ -1575,14 +1575,6 @@ static inline xfs_filblks_t startblockval(xfs_fsblock_t x)
 	return (xfs_filblks_t)((x) & ~STARTBLOCKMASK);
 }
 
-/*
- * Possible extent formats.
- */
-typedef enum {
-	XFS_EXTFMT_NOSTATE = 0,
-	XFS_EXTFMT_HASSTATE
-} xfs_exntfmt_t;
-
 /*
  * Possible extent states.
  */

fs/xfs/libxfs/xfs_inode_fork.c

@@ -42,35 +42,6 @@ STATIC int xfs_iformat_local(xfs_inode_t *, xfs_dinode_t *, int, int);
 STATIC int xfs_iformat_extents(xfs_inode_t *, xfs_dinode_t *, int);
 STATIC int xfs_iformat_btree(xfs_inode_t *, xfs_dinode_t *, int);
 
-#ifdef DEBUG
-/*
- * Make sure that the extents in the given memory buffer
- * are valid.
- */
-void
-xfs_validate_extents(
-	xfs_ifork_t		*ifp,
-	int			nrecs,
-	xfs_exntfmt_t		fmt)
-{
-	xfs_bmbt_irec_t		irec;
-	xfs_bmbt_rec_host_t	rec;
-	int			i;
-
-	for (i = 0; i < nrecs; i++) {
-		xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
-		rec.l0 = get_unaligned(&ep->l0);
-		rec.l1 = get_unaligned(&ep->l1);
-		xfs_bmbt_get_all(&rec, &irec);
-		if (fmt == XFS_EXTFMT_NOSTATE)
-			ASSERT(irec.br_state == XFS_EXT_NORM);
-	}
-}
-#else /* DEBUG */
-#define xfs_validate_extents(ifp, nrecs, fmt)
-#endif /* DEBUG */
-
-
 /*
  * Move inode type and inode format specific information from the
  * on-disk inode to the in-core inode.  For fifos, devs, and sockets
@@ -352,40 +323,33 @@ xfs_iformat_local(
 }
 
 /*
- * The file consists of a set of extents all
+ * The file consists of a set of extents all of which fit into the on-disk
- * of which fit into the on-disk inode.
+ * inode.  If there are few enough extents to fit into the if_inline_ext, then
- * If there are few enough extents to fit into
+ * copy them there.  Otherwise allocate a buffer for them and copy them into it.
- * the if_inline_ext, then copy them there.
+ * Either way, set if_extents to point at the extents.
- * Otherwise allocate a buffer for them and copy
- * them into it.  Either way, set if_extents
- * to point at the extents.
  */
 STATIC int
 xfs_iformat_extents(
-	xfs_inode_t	*ip,
+	struct xfs_inode	*ip,
-	xfs_dinode_t	*dip,
+	struct xfs_dinode	*dip,
-	int		whichfork)
+	int			whichfork)
 {
-	xfs_bmbt_rec_t	*dp;
+	struct xfs_mount	*mp = ip->i_mount;
-	xfs_ifork_t	*ifp;
+	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, whichfork);
-	int		nex;
+	int			nex = XFS_DFORK_NEXTENTS(dip, whichfork);
-	int		size;
+	int			size = nex * sizeof(xfs_bmbt_rec_t);
-	int		i;
+	struct xfs_bmbt_rec	*dp;
-
+	int			i;
-	ifp = XFS_IFORK_PTR(ip, whichfork);
-	nex = XFS_DFORK_NEXTENTS(dip, whichfork);
-	size = nex * (uint)sizeof(xfs_bmbt_rec_t);
 
 	/*
-	 * If the number of extents is unreasonable, then something
+	 * If the number of extents is unreasonable, then something is wrong and
-	 * is wrong and we just bail out rather than crash in
+	 * we just bail out rather than crash in kmem_alloc() or memcpy() below.
-	 * kmem_alloc() or memcpy() below.
 	 */
-	if (unlikely(size < 0 || size > XFS_DFORK_SIZE(dip, ip->i_mount, whichfork))) {
+	if (unlikely(size < 0 || size > XFS_DFORK_SIZE(dip, mp, whichfork))) {
 		xfs_warn(ip->i_mount, "corrupt inode %Lu ((a)extents = %d).",
 			(unsigned long long) ip->i_ino, nex);
 		XFS_CORRUPTION_ERROR("xfs_iformat_extents(1)", XFS_ERRLEVEL_LOW,
-				     ip->i_mount, dip);
+				     mp, dip);
 		return -EFSCORRUPTED;
 	}
 
@@ -400,22 +364,17 @@ xfs_iformat_extents(
 	ifp->if_bytes = size;
 	if (size) {
 		dp = (xfs_bmbt_rec_t *) XFS_DFORK_PTR(dip, whichfork);
-		xfs_validate_extents(ifp, nex, XFS_EXTFMT_INODE(ip));
 		for (i = 0; i < nex; i++, dp++) {
 			xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
 			ep->l0 = get_unaligned_be64(&dp->l0);
 			ep->l1 = get_unaligned_be64(&dp->l1);
+			if (!xfs_bmbt_validate_extent(mp, whichfork, ep)) {
+				XFS_ERROR_REPORT("xfs_iformat_extents(2)",
+						 XFS_ERRLEVEL_LOW, mp);
+				return -EFSCORRUPTED;
+			}
 		}
 		XFS_BMAP_TRACE_EXLIST(ip, nex, whichfork);
-		if (whichfork != XFS_DATA_FORK ||
-			XFS_EXTFMT_INODE(ip) == XFS_EXTFMT_NOSTATE)
-				if (unlikely(xfs_check_nostate_extents(
-				    ifp, 0, nex))) {
-					XFS_ERROR_REPORT("xfs_iformat_extents(2)",
-							 XFS_ERRLEVEL_LOW,
-							 ip->i_mount);
-					return -EFSCORRUPTED;
-				}
 	}
 	ifp->if_flags |= XFS_IFEXTENTS;
 	return 0;
@@ -518,7 +477,6 @@ xfs_iread_extents(
 		xfs_iext_destroy(ifp);
 		return error;
 	}
-	xfs_validate_extents(ifp, nextents, XFS_EXTFMT_INODE(ip));
 	ifp->if_flags |= XFS_IFEXTENTS;
 	return 0;
 }
@@ -837,6 +795,9 @@ xfs_iextents_copy(
 	copied = 0;
 	for (i = 0; i < nrecs; i++) {
 		xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
+
+		ASSERT(xfs_bmbt_validate_extent(ip->i_mount, whichfork, ep));
+
 		start_block = xfs_bmbt_get_startblock(ep);
 		if (isnullstartblock(start_block)) {
 			/*
@@ -852,7 +813,6 @@ xfs_iextents_copy(
 		copied++;
 	}
 	ASSERT(copied != 0);
-	xfs_validate_extents(ifp, copied, XFS_EXTFMT_INODE(ip));
 
 	return (copied * (uint)sizeof(xfs_bmbt_rec_t));
 }