xfs: check dirents have parent pointers

If the fs has parent pointers, we need to check that each child dirent
points to a file that has a parent pointer pointing back at us.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_parent.c

@@ -291,3 +291,25 @@ xfs_parent_from_attr(
 		*parent_gen = be32_to_cpu(rec->p_gen);
 	return 0;
 }
+
+/*
+ * Look up a parent pointer record (@parent_name -> @pptr) of @ip.
+ *
+ * Caller must hold at least ILOCK_SHARED.  The scratchpad need not be
+ * initialized.
+ *
+ * Returns 0 if the pointer is found, -ENOATTR if there is no match, or a
+ * negative errno.
+ */
+int
+xfs_parent_lookup(
+	struct xfs_trans		*tp,
+	struct xfs_inode		*ip,
+	const struct xfs_name		*parent_name,
+	struct xfs_parent_rec		*pptr,
+	struct xfs_da_args		*scratch)
+{
+	memset(scratch, 0, sizeof(struct xfs_da_args));
+	xfs_parent_da_args_init(scratch, tp, pptr, ip, ip->i_ino, parent_name);
+	return xfs_attr_get_ilocked(scratch);
+}

fs/xfs/libxfs/xfs_parent.h

@@ -96,4 +96,9 @@ int xfs_parent_from_attr(struct xfs_mount *mp, unsigned int attr_flags,
 		const void *value, unsigned int valuelen,
 		xfs_ino_t *parent_ino, uint32_t *parent_gen);
 
+/* Repair functions */
+int xfs_parent_lookup(struct xfs_trans *tp, struct xfs_inode *ip,
+		const struct xfs_name *name, struct xfs_parent_rec *pptr,
+		struct xfs_da_args *scratch);
+
 #endif /* __XFS_PARENT_H__ */

fs/xfs/scrub/dir.c

@@ -16,6 +16,8 @@
 #include "xfs_dir2.h"
 #include "xfs_dir2_priv.h"
 #include "xfs_health.h"
+#include "xfs_attr.h"
+#include "xfs_parent.h"
 #include "scrub/scrub.h"
 #include "scrub/common.h"
 #include "scrub/dabtree.h"
@@ -41,6 +43,14 @@ xchk_setup_directory(
 
 /* Directories */
 
+struct xchk_dir {
+	struct xfs_scrub	*sc;
+
+	/* information for parent pointer validation. */
+	struct xfs_parent_rec	pptr_rec;
+	struct xfs_da_args	pptr_args;
+};
+
 /* Scrub a directory entry. */
 
 /* Check that an inode's mode matches a given XFS_DIR3_FT_* type. */
@@ -63,6 +73,90 @@ xchk_dir_check_ftype(
 		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 }
 
+/*
+ * Try to lock a child file for checking parent pointers.  Returns the inode
+ * flags for the locks we now hold, or zero if we failed.
+ */
+STATIC unsigned int
+xchk_dir_lock_child(
+	struct xfs_scrub	*sc,
+	struct xfs_inode	*ip)
+{
+	if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
+		return 0;
+
+	if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
+		xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+		return 0;
+	}
+
+	if (!xfs_inode_has_attr_fork(ip) || !xfs_need_iread_extents(&ip->i_af))
+		return XFS_IOLOCK_SHARED | XFS_ILOCK_SHARED;
+
+	xfs_iunlock(ip, XFS_ILOCK_SHARED);
+
+	if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
+		xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+		return 0;
+	}
+
+	return XFS_IOLOCK_SHARED | XFS_ILOCK_EXCL;
+}
+
+/* Check the backwards link (parent pointer) associated with this dirent. */
+STATIC int
+xchk_dir_parent_pointer(
+	struct xchk_dir		*sd,
+	const struct xfs_name	*name,
+	struct xfs_inode	*ip)
+{
+	struct xfs_scrub	*sc = sd->sc;
+	int			error;
+
+	xfs_inode_to_parent_rec(&sd->pptr_rec, sc->ip);
+	error = xfs_parent_lookup(sc->tp, ip, name, &sd->pptr_rec,
+			&sd->pptr_args);
+	if (error == -ENOATTR)
+		xchk_fblock_xref_set_corrupt(sc, XFS_DATA_FORK, 0);
+
+	return 0;
+}
+
+/* Look for a parent pointer matching this dirent, if the child isn't busy. */
+STATIC int
+xchk_dir_check_pptr_fast(
+	struct xchk_dir		*sd,
+	xfs_dir2_dataptr_t	dapos,
+	const struct xfs_name	*name,
+	struct xfs_inode	*ip)
+{
+	struct xfs_scrub	*sc = sd->sc;
+	unsigned int		lockmode;
+	int			error;
+
+	/* dot and dotdot entries do not have parent pointers */
+	if (xfs_dir2_samename(name, &xfs_name_dot) ||
+	    xfs_dir2_samename(name, &xfs_name_dotdot))
+		return 0;
+
+	/* No self-referential non-dot or dotdot dirents. */
+	if (ip == sc->ip) {
+		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+		return -ECANCELED;
+	}
+
+	/* Try to lock the inode. */
+	lockmode = xchk_dir_lock_child(sc, ip);
+	if (!lockmode) {
+		xchk_set_incomplete(sc);
+		return -ECANCELED;
+	}
+
+	error = xchk_dir_parent_pointer(sd, name, ip);
+	xfs_iunlock(ip, lockmode);
+	return error;
+}
+
 /*
  * Scrub a single directory entry.
  *
@@ -80,6 +174,7 @@ xchk_dir_actor(
 {
 	struct xfs_mount	*mp = dp->i_mount;
 	struct xfs_inode	*ip;
+	struct xchk_dir		*sd = priv;
 	xfs_ino_t		lookup_ino;
 	xfs_dablk_t		offset;
 	int			error = 0;
@@ -146,6 +241,14 @@ xchk_dir_actor(
 		goto out;
 
 	xchk_dir_check_ftype(sc, offset, ip, name->type);
+
+	if (xfs_has_parent(mp)) {
+		error = xchk_dir_check_pptr_fast(sd, dapos, name, ip);
+		if (error)
+			goto out_rele;
+	}
+
+out_rele:
 	xchk_irele(sc, ip);
 out:
 	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
@@ -767,6 +870,7 @@ int
 xchk_directory(
 	struct xfs_scrub	*sc)
 {
+	struct xchk_dir		*sd;
 	int			error;
 
 	if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
@@ -799,8 +903,14 @@ xchk_directory(
 	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
 		return 0;
 
+	sd = kvzalloc(sizeof(struct xchk_dir), XCHK_GFP_FLAGS);
+	if (!sd)
+		return -ENOMEM;
+	sd->sc = sc;
+
 	/* Look up every name in this directory by hash. */
-	error = xchk_dir_walk(sc, sc->ip, xchk_dir_actor, NULL);
+	error = xchk_dir_walk(sc, sc->ip, xchk_dir_actor, sd);
+	kvfree(sd);
 	if (error && error != -ECANCELED)
 		return error;