drm/atomic-helper: document drm_atomic_helper_check() restrictions

[drm/drm-misc.git] / fs / xfs / scrub / parent.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2017-2023 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <djwong@kernel.org>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_inode.h"
#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/xfile.h"
#include "scrub/xfarray.h"
#include "scrub/xfblob.h"
#include "scrub/trace.h"

/* Set us up to scrub parents. */
int
xchk_setup_parent(
        struct xfs_scrub        *sc)
{
        int                     error;

        if (xchk_could_repair(sc)) {
                error = xrep_setup_parent(sc);
                if (error)
                        return error;
        }

        return xchk_setup_inode_contents(sc, 0);
}

/* Parent pointers */

/* Look for an entry in a parent pointing to this inode. */

struct xchk_parent_ctx {
        struct xfs_scrub        *sc;
        xfs_nlink_t             nlink;
};

/* Look for a single entry in a directory pointing to an inode. */
STATIC int
xchk_parent_actor(
        struct xfs_scrub        *sc,
        struct xfs_inode        *dp,
        xfs_dir2_dataptr_t      dapos,
        const struct xfs_name   *name,
        xfs_ino_t               ino,
        void                    *priv)
{
        struct xchk_parent_ctx  *spc = priv;
        int                     error = 0;

        /* Does this name make sense? */
        if (!xfs_dir2_namecheck(name->name, name->len))
                error = -EFSCORRUPTED;
        if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
                return error;

        if (sc->ip->i_ino == ino)
                spc->nlink++;

        if (xchk_should_terminate(spc->sc, &error))
                return error;

        return 0;
}

/*
 * 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_ilock_dir(
        struct xfs_inode        *dp)
{
        if (!xfs_ilock_nowait(dp, XFS_ILOCK_SHARED))
                return 0;

        if (!xfs_need_iread_extents(&dp->i_df))
                return XFS_ILOCK_SHARED;

        xfs_iunlock(dp, XFS_ILOCK_SHARED);

        if (!xfs_ilock_nowait(dp, XFS_ILOCK_EXCL))
                return 0;

        return XFS_ILOCK_EXCL;
}

/*
 * Given the inode number of the alleged parent of the inode being scrubbed,
 * try to validate that the parent has exactly one directory entry pointing
 * back to the inode being scrubbed.  Returns -EAGAIN if we need to revalidate
 * the dotdot entry.
 */
STATIC int
xchk_parent_validate(
        struct xfs_scrub        *sc,
        xfs_ino_t               parent_ino)
{
        struct xchk_parent_ctx  spc = {
                .sc             = sc,
                .nlink          = 0,
        };
        struct xfs_mount        *mp = sc->mp;
        struct xfs_inode        *dp = NULL;
        xfs_nlink_t             expected_nlink;
        unsigned int            lock_mode;
        int                     error = 0;

        /* Is this the root dir?  Then '..' must point to itself. */
        if (sc->ip == mp->m_rootip) {
                if (sc->ip->i_ino != mp->m_sb.sb_rootino ||
                    sc->ip->i_ino != parent_ino)
                        xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                return 0;
        }

        /* Is this the metadata root dir?  Then '..' must point to itself. */
        if (sc->ip == mp->m_metadirip) {
                if (sc->ip->i_ino != mp->m_sb.sb_metadirino ||
                    sc->ip->i_ino != parent_ino)
                        xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                return 0;
        }

        /* '..' must not point to ourselves. */
        if (sc->ip->i_ino == parent_ino) {
                xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                return 0;
        }

        /*
         * If we're an unlinked directory, the parent /won't/ have a link
         * to us.  Otherwise, it should have one link.
         */
        expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1;

        /*
         * Grab the parent directory inode.  This must be released before we
         * cancel the scrub transaction.
         *
         * If _iget returns -EINVAL or -ENOENT then the parent inode number is
         * garbage and the directory is corrupt.  If the _iget returns
         * -EFSCORRUPTED or -EFSBADCRC then the parent is corrupt which is a
         *  cross referencing error.  Any other error is an operational error.
         */
        error = xchk_iget(sc, parent_ino, &dp);
        if (error == -EINVAL || error == -ENOENT) {
                error = -EFSCORRUPTED;
                xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error);
                return error;
        }
        if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
                return error;
        if (dp == sc->ip || xrep_is_tempfile(dp) ||
            !S_ISDIR(VFS_I(dp)->i_mode)) {
                xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                goto out_rele;
        }

        lock_mode = xchk_parent_ilock_dir(dp);
        if (!lock_mode) {
                xchk_iunlock(sc, XFS_ILOCK_EXCL);
                xchk_ilock(sc, XFS_ILOCK_EXCL);
                error = -EAGAIN;
                goto out_rele;
        }

        /*
         * We cannot yet validate this parent pointer if the directory looks as
         * though it has been zapped by the inode record repair code.
         */
        if (xchk_dir_looks_zapped(dp)) {
                error = -EBUSY;
                xchk_set_incomplete(sc);
                goto out_unlock;
        }

        /* Metadata and regular inodes cannot cross trees. */
        if (xfs_is_metadir_inode(dp) != xfs_is_metadir_inode(sc->ip)) {
                xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                goto out_unlock;
        }

        /* Look for a directory entry in the parent pointing to the child. */
        error = xchk_dir_walk(sc, dp, xchk_parent_actor, &spc);
        if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error))
                goto out_unlock;

        /*
         * Ensure that the parent has as many links to the child as the child
         * thinks it has to the parent.
         */
        if (spc.nlink != expected_nlink)
                xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);

out_unlock:
        xfs_iunlock(dp, lock_mode);
out_rele:
        xchk_irele(sc, dp);
        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.
 */

/* Deferred parent pointer entry that we saved for later. */
struct xchk_pptr {
        /* Cookie for retrieval of the pptr name. */
        xfblob_cookie           name_cookie;

        /* Parent pointer record. */
        struct xfs_parent_rec   pptr_rec;

        /* Length of the pptr name. */
        uint8_t                 namelen;
};

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;

        /* Fixed-size array of xchk_pptr structures. */
        struct xfarray          *pptr_entries;

        /* Blobs containing parent pointer names. */
        struct xfblob           *pptr_names;

        /* Scratch buffer for scanning pptr xattrs */
        struct xfs_da_args      pptr_args;

        /* If we've cycled the ILOCK, we must revalidate all deferred pptrs. */
        bool                    need_revalidate;

        /* Name buffer */
        struct xfs_name         xname;
        char                    namebuf[MAXNAMELEN];
};

/* 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 (xchk_inode_is_dirtree_root(sc->ip)) {
                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, NULL, 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) {
                struct xchk_pptr        save_pp = {
                        .pptr_rec       = *pptr_rec, /* struct copy */
                        .namelen        = namelen,
                };

                /* Couldn't lock the inode, so save the pptr for later. */
                trace_xchk_parent_defer(sc->ip, &xname, dp->i_ino);

                error = xfblob_storename(pp->pptr_names, &save_pp.name_cookie,
                                &xname);
                if (!xchk_fblock_xref_process_error(sc, XFS_ATTR_FORK, 0,
                                        &error))
                        goto out_rele;

                error = xfarray_append(pp->pptr_entries, &save_pp);
                if (!xchk_fblock_xref_process_error(sc, XFS_ATTR_FORK, 0,
                                        &error))
                        goto out_rele;

                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;
}

/*
 * Revalidate a parent pointer that we collected in the past but couldn't check
 * because of lock contention.  Returns 0 if the parent pointer is still valid,
 * -ENOENT if it has gone away on us, or a negative errno.
 */
STATIC int
xchk_parent_revalidate_pptr(
        struct xchk_pptrs               *pp,
        const struct xfs_name           *xname,
        struct xfs_parent_rec           *pptr)
{
        struct xfs_scrub                *sc = pp->sc;
        int                             error;

        error = xfs_parent_lookup(sc->tp, sc->ip, xname, pptr, &pp->pptr_args);
        if (error == -ENOATTR) {
                /* Parent pointer went away, nothing to revalidate. */
                return -ENOENT;
        }

        return error;
}

/*
 * Check a parent pointer the slow way, which means we cycle locks a bunch
 * and put up with revalidation until we get it done.
 */
STATIC int
xchk_parent_slow_pptr(
        struct xchk_pptrs       *pp,
        const struct xfs_name   *xname,
        struct xfs_parent_rec   *pptr)
{
        struct xfs_scrub        *sc = pp->sc;
        struct xfs_inode        *dp = NULL;
        unsigned int            lockmode;
        int                     error;

        /* Check that the deferred parent pointer still exists. */
        if (pp->need_revalidate) {
                error = xchk_parent_revalidate_pptr(pp, xname, pptr);
                if (error == -ENOENT)
                        return 0;
                if (!xchk_fblock_xref_process_error(sc, XFS_ATTR_FORK, 0,
                                        &error))
                        return error;
        }

        error = xchk_parent_iget(pp, pptr, &dp);
        if (error)
                return error;
        if (!dp)
                return 0;

        /*
         * If we can grab both IOLOCK and ILOCK of the alleged parent, we
         * can proceed with the validation.
         */
        lockmode = xchk_parent_lock_dir(sc, dp);
        if (lockmode) {
                trace_xchk_parent_slowpath(sc->ip, xname, dp->i_ino);
                goto check_dirent;
        }

        /*
         * We couldn't lock the parent dir.  Drop all the locks and try to
         * get them again, one at a time.
         */
        xchk_iunlock(sc, sc->ilock_flags);
        pp->need_revalidate = true;

        trace_xchk_parent_ultraslowpath(sc->ip, xname, dp->i_ino);

        error = xchk_dir_trylock_for_pptrs(sc, dp, &lockmode);
        if (error)
                goto out_rele;

        /* Revalidate the parent pointer now that we cycled locks. */
        error = xchk_parent_revalidate_pptr(pp, xname, pptr);
        if (error == -ENOENT) {
                error = 0;
                goto out_unlock;
        }
        if (!xchk_fblock_xref_process_error(sc, XFS_ATTR_FORK, 0, &error))
                goto out_unlock;

check_dirent:
        error = xchk_parent_dirent(pp, xname, dp);
out_unlock:
        xfs_iunlock(dp, lockmode);
out_rele:
        xchk_irele(sc, dp);
        return error;
}

/* Check all the parent pointers that we deferred the first time around. */
STATIC int
xchk_parent_finish_slow_pptrs(
        struct xchk_pptrs       *pp)
{
        xfarray_idx_t           array_cur;
        int                     error;

        foreach_xfarray_idx(pp->pptr_entries, array_cur) {
                struct xchk_pptr        pptr;

                if (pp->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
                        return 0;

                error = xfarray_load(pp->pptr_entries, array_cur, &pptr);
                if (error)
                        return error;

                error = xfblob_loadname(pp->pptr_names, pptr.name_cookie,
                                &pp->xname, pptr.namelen);
                if (error)
                        return error;

                error = xchk_parent_slow_pptr(pp, &pp->xname, &pptr.pptr_rec);
                if (error)
                        return error;
        }

        /* Empty out both xfiles now that we've checked everything. */
        xfarray_truncate(pp->pptr_entries);
        xfblob_truncate(pp->pptr_names);
        return 0;
}

/* Count the number of parent pointers. */
STATIC int
xchk_parent_count_pptr(
        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;
        int                             error;

        if (!(attr_flags & XFS_ATTR_PARENT))
                return 0;

        error = xfs_parent_from_attr(sc->mp, attr_flags, name, namelen, value,
                        valuelen, NULL, NULL);
        if (error)
                return error;

        pp->pptrs_found++;
        return 0;
}

/*
 * 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;
        int                     error;

        /*
         * If we cycled the ILOCK while cross-checking parent pointers with
         * dirents, then we need to recalculate the number of parent pointers.
         */
        if (pp->need_revalidate) {
                pp->pptrs_found = 0;
                error = xchk_xattr_walk(sc, sc->ip, xchk_parent_count_pptr,
                                NULL, pp);
                if (error == -EFSCORRUPTED) {
                        /* Found a bad parent pointer */
                        xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
                        return 0;
                }
                if (error)
                        return error;
        }

        if (S_ISDIR(VFS_I(sc->ip)->i_mode)) {
                if (xchk_inode_is_dirtree_root(sc->ip))
                        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 {
                /*
                 * Starting with metadir, we allow checking of parent pointers
                 * of non-directory files that are children of the superblock.
                 * Pretend that we found a parent pointer attr.
                 */
                if (xfs_has_metadir(sc->mp) && xchk_inode_is_sb_rooted(sc->ip))
                        pp->pptrs_found++;

                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;
        char                    *descr;
        int                     error;

        pp = kvzalloc(sizeof(struct xchk_pptrs), XCHK_GFP_FLAGS);
        if (!pp)
                return -ENOMEM;
        pp->sc = sc;
        pp->xname.name = pp->namebuf;

        /*
         * Set up some staging memory for parent pointers that we can't check
         * due to locking contention.
         */
        descr = xchk_xfile_ino_descr(sc, "slow parent pointer entries");
        error = xfarray_create(descr, 0, sizeof(struct xchk_pptr),
                        &pp->pptr_entries);
        kfree(descr);
        if (error)
                goto out_pp;

        descr = xchk_xfile_ino_descr(sc, "slow parent pointer names");
        error = xfblob_create(descr, &pp->pptr_names);
        kfree(descr);
        if (error)
                goto out_entries;

        error = xchk_xattr_walk(sc, sc->ip, xchk_parent_scan_attr, NULL, pp);
        if (error == -ECANCELED) {
                error = 0;
                goto out_names;
        }
        if (error)
                goto out_names;

        error = xchk_parent_finish_slow_pptrs(pp);
        if (error == -ETIMEDOUT) {
                /* Couldn't grab a lock, scrub was marked incomplete */
                error = 0;
                goto out_names;
        }
        if (error)
                goto out_names;

        if (pp->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
                goto out_names;

        /*
         * 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_names;
        }

        if (pp->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
                goto out_names;

        /*
         * 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_names;

out_names:
        xfblob_destroy(pp->pptr_names);
out_entries:
        xfarray_destroy(pp->pptr_entries);
out_pp:
        kvfree(pp);
        return error;
}

/* Scrub a parent pointer. */
int
xchk_parent(
        struct xfs_scrub        *sc)
{
        struct xfs_mount        *mp = sc->mp;
        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.
         */
        if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
                return -ENOENT;

        /* We're not a special inode, are we? */
        if (!xfs_verify_dir_ino(mp, sc->ip->i_ino)) {
                xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                return 0;
        }

        do {
                if (xchk_should_terminate(sc, &error))
                        break;

                /* Look up '..' */
                error = xchk_dir_lookup(sc, sc->ip, &xfs_name_dotdot,
                                &parent_ino);
                if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
                        return error;
                if (!xfs_verify_dir_ino(mp, parent_ino)) {
                        xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0);
                        return 0;
                }

                /*
                 * Check that the dotdot entry points to a parent directory
                 * containing a dirent pointing to this subdirectory.
                 */
                error = xchk_parent_validate(sc, parent_ino);
        } while (error == -EAGAIN);
        if (error == -EBUSY) {
                /*
                 * We could not scan a directory, so we marked the check
                 * incomplete.  No further error return is necessary.
                 */
                return 0;
        }

        return error;
}

/*
 * Decide if this file's extended attributes (and therefore its parent
 * pointers) have been zapped to satisfy the inode and ifork verifiers.
 * Checking and repairing should be postponed until the extended attribute
 * structure is fixed.
 */
bool
xchk_pptr_looks_zapped(
        struct xfs_inode        *ip)
{
        struct inode            *inode = VFS_I(ip);

        ASSERT(xfs_has_parent(ip->i_mount));

        /*
         * Temporary files that cannot be linked into the directory tree do not
         * have attr forks because they cannot ever have parents.
         */
        if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
                return false;

        /*
         * Directory tree roots do not have parents, so the expected outcome
         * of a parent pointer scan is always the empty set.  It's safe to scan
         * them even if the attr fork was zapped.
         */
        if (xchk_inode_is_dirtree_root(ip))
                return false;

        /*
         * Metadata inodes that are rooted in the superblock do not have any
         * parents.  Hence the attr fork will not be initialized, but there are
         * no parent pointers that might have been zapped.
         */
        if (xchk_inode_is_sb_rooted(ip))
                return false;

        /*
         * Linked and linkable non-rootdir files should always have an
         * attribute fork because that is where parent pointers are
         * stored.  If the fork is absent, something is amiss.
         */
        if (!xfs_inode_has_attr_fork(ip))
                return true;

        /* Repair zapped this file's attr fork a short time ago */
        if (xfs_ifork_zapped(ip, XFS_ATTR_FORK))
                return true;

        /*
         * If the dinode repair found a bad attr fork, it will reset the fork
         * to extents format with zero records and wait for the bmapbta
         * scrubber to reconstruct the block mappings.  The extended attribute
         * structure always contain some content when parent pointers are
         * enabled, so this is a clear sign of a zapped attr fork.
         */
        return ip->i_af.if_format == XFS_DINODE_FMT_EXTENTS &&
               ip->i_af.if_nextents == 0;
}