[PATCH 4/7] xfs: scrub parent pointers

Darrick J. Wong
2024-04-16T01:35:10Z

Actually check parent pointers now.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/scrub/parent.c | 371 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 371 insertions(+)

diff --git a/fs/xfs/scrub/parent.c b/fs/xfs/scrub/parent.c
index acb6282c3d148..6ebbb71041269 100644
--- a/fs/xfs/scrub/parent.c
+++ b/fs/xfs/scrub/parent.c
@@ -15,11 +15,15 @@
#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/readdir.h"
#include "scrub/tempfile.h"
#include "scrub/repair.h"
+#include "scrub/listxattr.h"
+#include "scrub/trace.h"

/* Set us up to scrub parents. */
int
@@ -197,6 +201,370 @@ xchk_parent_validate(
return error;
}

+/*
+ * Checking of Parent Pointers
+ * ===========================
+ *
+ * On filesystems with directory parent pointers, we check the referential
+ * integrity by visiting each parent pointer of a child file and checking that
+ * the directory referenced by the pointer actually has a dirent pointing
+ * forward to the child file.
+ */
+
+struct xchk_pptrs {
+ struct xfs_scrub *sc;
+
+ /* How many parent pointers did we find at the end? */
+ unsigned long long pptrs_found;
+
+ /* Parent of this directory. */
+ xfs_ino_t parent_ino;
+};
+
+/* Does this parent pointer match the dotdot entry? */
+STATIC int
+xchk_parent_scan_dotdot(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ unsigned int attr_flags,
+ const unsigned char *name,
+ unsigned int namelen,
+ const void *value,
+ unsigned int valuelen,
+ void *priv)
+{
+ struct xchk_pptrs *pp = priv;
+ xfs_ino_t parent_ino;
+ int error;
+
+ if (!(attr_flags & XFS_ATTR_PARENT))
+ return 0;
+
+ error = xfs_parent_from_attr(sc->mp, attr_flags, name, namelen, value,
+ valuelen, &parent_ino, NULL);
+ if (error)
+ return error;
+
+ if (pp->parent_ino == parent_ino)
+ return -ECANCELED;
+
+ return 0;
+}
+
+/* Look up the dotdot entry so that we can check it as we walk the pptrs. */
+STATIC int
+xchk_parent_pptr_and_dotdot(
+ struct xchk_pptrs *pp)
+{
+ struct xfs_scrub *sc = pp->sc;
+ int error;
+
+ /* Look up '..' */
+ error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot, &pp->parent_ino);
+ if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
+ return error;
+ if (!xfs_verify_dir_ino(sc->mp, pp->parent_ino)) {
+ xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ return 0;
+ }
+
+ /* Is this the root dir? Then '..' must point to itself. */
+ if (sc->ip == sc->mp->m_rootip) {
+ if (sc->ip->i_ino != pp->parent_ino)
+ xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
+ return 0;
+ }
+
+ /*
+ * If this is now an unlinked directory, the dotdot value is
+ * meaningless as long as it points to a valid inode.
+ */
+ if (VFS_I(sc->ip)->i_nlink == 0)
+ return 0;
+
+ if (pp->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+ return 0;
+
+ /* Otherwise, walk the pptrs again, and check. */
+ error = xchk_xattr_walk(sc, sc->ip, xchk_parent_scan_dotdot, pp);
+ if (error == -ECANCELED) {
+ /* Found a parent pointer that matches dotdot. */
+ return 0;
+ }
+ if (!error || error == -EFSCORRUPTED) {
+ /* Found a broken parent pointer or no match. */
+ xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return 0;
+ }
+ return error;
+}
+
+/*
+ * Try to lock a parent directory for checking dirents. Returns the inode
+ * flags for the locks we now hold, or zero if we failed.
+ */
+STATIC unsigned int
+xchk_parent_lock_dir(
+ struct xfs_scrub *sc,
+ struct xfs_inode *dp)
+{
+ if (!xfs_ilock_nowait(dp, XFS_IOLOCK_SHARED))
+ return 0;
+
+ if (!xfs_ilock_nowait(dp, XFS_ILOCK_SHARED)) {
+ xfs_iunlock(dp, XFS_IOLOCK_SHARED);
+ return 0;
+ }
+
+ if (!xfs_need_iread_extents(&dp->i_df))
+ return XFS_IOLOCK_SHARED | XFS_ILOCK_SHARED;
+
+ xfs_iunlock(dp, XFS_ILOCK_SHARED);
+
+ if (!xfs_ilock_nowait(dp, XFS_ILOCK_EXCL)) {
+ xfs_iunlock(dp, XFS_IOLOCK_SHARED);
+ return 0;
+ }
+
+ return XFS_IOLOCK_SHARED | XFS_ILOCK_EXCL;
+}
+
+/* Check the forward link (dirent) associated with this parent pointer. */
+STATIC int
+xchk_parent_dirent(
+ struct xchk_pptrs *pp,
+ const struct xfs_name *xname,
+ struct xfs_inode *dp)
+{
+ struct xfs_scrub *sc = pp->sc;
+ xfs_ino_t child_ino;
+ int error;
+
+ /*
+ * Use the name attached to this parent pointer to look up the
+ * directory entry in the alleged parent.
+ */
+ error = xchk_dir_lookup(sc, dp, xname, &child_ino);
+ if (error == -ENOENT) {
+ xchk_fblock_xref_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return 0;
+ }
+ if (!xchk_fblock_xref_process_error(sc, XFS_ATTR_FORK, 0, &error))
+ return error;
+
+ /* Does the inode number match? */
+ if (child_ino != sc->ip->i_ino) {
+ xchk_fblock_xref_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return 0;
+ }
+
+ return 0;
+}
+
+/* Try to grab a parent directory. */
+STATIC int
+xchk_parent_iget(
+ struct xchk_pptrs *pp,
+ const struct xfs_parent_rec *pptr,
+ struct xfs_inode **dpp)
+{
+ struct xfs_scrub *sc = pp->sc;
+ struct xfs_inode *ip;
+ xfs_ino_t parent_ino = be64_to_cpu(pptr->p_ino);
+ int error;
+
+ /* Validate inode number. */
+ error = xfs_dir_ino_validate(sc->mp, parent_ino);
+ if (error) {
+ xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return -ECANCELED;
+ }
+
+ error = xchk_iget(sc, parent_ino, &ip);
+ if (error == -EINVAL || error == -ENOENT) {
+ xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return -ECANCELED;
+ }
+ if (!xchk_fblock_xref_process_error(sc, XFS_ATTR_FORK, 0, &error))
+ return error;
+
+ /* The parent must be a directory. */
+ if (!S_ISDIR(VFS_I(ip)->i_mode)) {
+ xchk_fblock_xref_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ goto out_rele;
+ }
+
+ /* Validate generation number. */
+ if (VFS_I(ip)->i_generation != be32_to_cpu(pptr->p_gen)) {
+ xchk_fblock_xref_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ goto out_rele;
+ }
+
+ *dpp = ip;
+ return 0;
+out_rele:
+ xchk_irele(sc, ip);
+ return 0;
+}
+
+/*
+ * Walk an xattr of a file. If this xattr is a parent pointer, follow it up
+ * to a parent directory and check that the parent has a dirent pointing back
+ * to us.
+ */
+STATIC int
+xchk_parent_scan_attr(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ unsigned int attr_flags,
+ const unsigned char *name,
+ unsigned int namelen,
+ const void *value,
+ unsigned int valuelen,
+ void *priv)
+{
+ struct xfs_name xname = {
+ .name = name,
+ .len = namelen,
+ };
+ struct xchk_pptrs *pp = priv;
+ struct xfs_inode *dp = NULL;
+ const struct xfs_parent_rec *pptr_rec = value;
+ xfs_ino_t parent_ino;
+ unsigned int lockmode;
+ int error;
+
+ if (!(attr_flags & XFS_ATTR_PARENT))
+ return 0;
+
+ error = xfs_parent_from_attr(sc->mp, attr_flags, name, namelen, value,
+ valuelen, &parent_ino, NULL);
+ if (error) {
+ xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return error;
+ }
+
+ /* No self-referential parent pointers. */
+ if (parent_ino == sc->ip->i_ino) {
+ xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
+ return -ECANCELED;
+ }
+
+ pp->pptrs_found++;
+
+ error = xchk_parent_iget(pp, pptr_rec, &dp);
+ if (error)
+ return error;
+ if (!dp)
+ return 0;
+
+ /* Try to lock the inode. */
+ lockmode = xchk_parent_lock_dir(sc, dp);
+ if (!lockmode) {
+ xchk_set_incomplete(sc);
+ error = -ECANCELED;
+ goto out_rele;
+ }
+
+ error = xchk_parent_dirent(pp, &xname, dp);
+ if (error)
+ goto out_unlock;
+
+out_unlock:
+ xfs_iunlock(dp, lockmode);
+out_rele:
+ xchk_irele(sc, dp);
+ return error;
+}
+
+/*
+ * Compare the number of parent pointers to the link count. For
+ * non-directories these should be the same. For unlinked directories the
+ * count should be zero; for linked directories, it should be nonzero.
+ */
+STATIC int
+xchk_parent_count_pptrs(
+ struct xchk_pptrs *pp)
+{
+ struct xfs_scrub *sc = pp->sc;
+
+ if (S_ISDIR(VFS_I(sc->ip)->i_mode)) {
+ if (sc->ip == sc->mp->m_rootip)
+ pp->pptrs_found++;
+
+ if (VFS_I(sc->ip)->i_nlink == 0 && pp->pptrs_found > 0)
+ xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+ else if (VFS_I(sc->ip)->i_nlink > 0 &&
+ pp->pptrs_found == 0)
+ xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+ } else {
+ if (VFS_I(sc->ip)->i_nlink != pp->pptrs_found)
+ xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+ }
+
+ return 0;
+}
+
+/* Check parent pointers of a file. */
+STATIC int
+xchk_parent_pptr(
+ struct xfs_scrub *sc)
+{
+ struct xchk_pptrs *pp;
+ int error;
+
+ pp = kvzalloc(sizeof(struct xchk_pptrs), XCHK_GFP_FLAGS);
+ if (!pp)
+ return -ENOMEM;
+ pp->sc = sc;
+
+ error = xchk_xattr_walk(sc, sc->ip, xchk_parent_scan_attr, pp);
+ if (error == -ECANCELED) {
+ error = 0;
+ goto out_pp;
+ }
+ if (error)
+ goto out_pp;
+
+ if (pp->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+ goto out_pp;
+
+ /*
+ * For subdirectories, make sure the dotdot entry references the same
+ * inode as the parent pointers.
+ *
+ * If we're scanning a /consistent/ directory, there should only be
+ * one parent pointer, and it should point to the same directory as
+ * the dotdot entry.
+ *
+ * However, a corrupt directory tree might feature a subdirectory with
+ * multiple parents. The directory loop scanner is responsible for
+ * correcting that kind of problem, so for now we only validate that
+ * the dotdot entry matches /one/ of the parents.
+ */
+ if (S_ISDIR(VFS_I(sc->ip)->i_mode)) {
+ error = xchk_parent_pptr_and_dotdot(pp);
+ if (error)
+ goto out_pp;
+ }
+
+ if (pp->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+ goto out_pp;
+
+ /*
+ * Complain if the number of parent pointers doesn't match the link
+ * count. This could be a sign of missing parent pointers (or an
+ * incorrect link count).
+ */
+ error = xchk_parent_count_pptrs(pp);
+ if (error)
+ goto out_pp;
+
+out_pp:
+ kvfree(pp);
+ return error;
+}
+
/* Scrub a parent pointer. */
int
xchk_parent(
@@ -206,6 +574,9 @@ xchk_parent(
xfs_ino_t parent_ino;
int error = 0;

+ if (xfs_has_parent(mp))
+ return xchk_parent_pptr(sc);
+
/*
* If we're a directory, check that the '..' link points up to
* a directory that has one entry pointing to us.