[1/2] xfs: check dirents have parent pointers

Commit Message

Darrick J. Wong April 6, 2023, 7:28 p.m. UTC

From: Darrick J. Wong <[e-mail]>

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 <[e-mail]>
---
 fs/xfs/scrub/dir.c |  117 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+), 1 deletion(-)

Patch

diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
index e30624dc35b3..9ae3afc4661a 100644
--- a/fs/xfs/scrub/dir.c
+++ b/fs/xfs/scrub/dir.c
@@ -15,6 +15,8 @@ 
 #include "xfs_icache.h"
 #include "xfs_dir2.h"
 #include "xfs_dir2_priv.h"
+#include "xfs_attr.h"
+#include "xfs_parent.h"
 #include "scrub/scrub.h"
 #include "scrub/common.h"
 #include "scrub/dabtree.h"
@@ -39,6 +41,20 @@  xchk_setup_directory(
 
 /* Directories */
 
+struct xchk_dir {
+	struct xfs_scrub	*sc;
+
+	/* Scratch buffer for scanning pptr xattrs */
+	struct xfs_parent_name_irec pptr;
+
+	/* xattr key and da args for parent pointer validation. */
+	struct xfs_parent_scratch pptr_scratch;
+
+	/* Name buffer for dirent revalidation. */
+	uint8_t			namebuf[MAXNAMELEN];
+
+};
+
 /* Scrub a directory entry. */
 
 /* Check that an inode's mode matches a given XFS_DIR3_FT_* type. */
@@ -61,6 +77,88 @@  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;
+
+	sd->pptr.p_ino = sc->ip->i_ino;
+	sd->pptr.p_gen = VFS_I(sc->ip)->i_generation;
+	sd->pptr.p_namelen = name->len;
+	memcpy(sd->pptr.p_name, name->name, name->len);
+	xfs_parent_irec_hashname(sc->mp, &sd->pptr);
+
+	error = xfs_parent_lookup(sc->tp, ip, &sd->pptr, &sd->pptr_scratch);
+	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 (!strncmp(".", name->name, name->len) ||
+	    !strncmp("..", name->name, name->len))
+		return 0;
+
+	/* 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.
  *
@@ -78,6 +176,7 @@  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;
@@ -144,6 +243,14 @@  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)
@@ -759,6 +866,7 @@  int
 xchk_directory(
 	struct xfs_scrub	*sc)
 {
+	struct xchk_dir		*sd;
 	int			error;
 
 	if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
@@ -786,9 +894,16 @@  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);
 	if (error == -ECANCELED)
 		error = 0;
+
+	kvfree(sd);
 	return error;
 }