drm/atomic-helper: document drm_atomic_helper_check() restrictions

[drm/drm-misc.git] / fs / xfs / scrub / scrub.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_quota.h"
#include "xfs_qm.h"
#include "xfs_scrub.h"
#include "xfs_buf_mem.h"
#include "xfs_rmap.h"
#include "xfs_exchrange.h"
#include "xfs_exchmaps.h"
#include "xfs_dir2.h"
#include "xfs_parent.h"
#include "xfs_icache.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"
#include "scrub/repair.h"
#include "scrub/health.h"
#include "scrub/stats.h"
#include "scrub/xfile.h"
#include "scrub/tempfile.h"
#include "scrub/orphanage.h"

/*
 * Online Scrub and Repair
 *
 * Traditionally, XFS (the kernel driver) did not know how to check or
 * repair on-disk data structures.  That task was left to the xfs_check
 * and xfs_repair tools, both of which require taking the filesystem
 * offline for a thorough but time consuming examination.  Online
 * scrub & repair, on the other hand, enables us to check the metadata
 * for obvious errors while carefully stepping around the filesystem's
 * ongoing operations, locking rules, etc.
 *
 * Given that most XFS metadata consist of records stored in a btree,
 * most of the checking functions iterate the btree blocks themselves
 * looking for irregularities.  When a record block is encountered, each
 * record can be checked for obviously bad values.  Record values can
 * also be cross-referenced against other btrees to look for potential
 * misunderstandings between pieces of metadata.
 *
 * It is expected that the checkers responsible for per-AG metadata
 * structures will lock the AG headers (AGI, AGF, AGFL), iterate the
 * metadata structure, and perform any relevant cross-referencing before
 * unlocking the AG and returning the results to userspace.  These
 * scrubbers must not keep an AG locked for too long to avoid tying up
 * the block and inode allocators.
 *
 * Block maps and b-trees rooted in an inode present a special challenge
 * because they can involve extents from any AG.  The general scrubber
 * structure of lock -> check -> xref -> unlock still holds, but AG
 * locking order rules /must/ be obeyed to avoid deadlocks.  The
 * ordering rule, of course, is that we must lock in increasing AG
 * order.  Helper functions are provided to track which AG headers we've
 * already locked.  If we detect an imminent locking order violation, we
 * can signal a potential deadlock, in which case the scrubber can jump
 * out to the top level, lock all the AGs in order, and retry the scrub.
 *
 * For file data (directories, extended attributes, symlinks) scrub, we
 * can simply lock the inode and walk the data.  For btree data
 * (directories and attributes) we follow the same btree-scrubbing
 * strategy outlined previously to check the records.
 *
 * We use a bit of trickery with transactions to avoid buffer deadlocks
 * if there is a cycle in the metadata.  The basic problem is that
 * travelling down a btree involves locking the current buffer at each
 * tree level.  If a pointer should somehow point back to a buffer that
 * we've already examined, we will deadlock due to the second buffer
 * locking attempt.  Note however that grabbing a buffer in transaction
 * context links the locked buffer to the transaction.  If we try to
 * re-grab the buffer in the context of the same transaction, we avoid
 * the second lock attempt and continue.  Between the verifier and the
 * scrubber, something will notice that something is amiss and report
 * the corruption.  Therefore, each scrubber will allocate an empty
 * transaction, attach buffers to it, and cancel the transaction at the
 * end of the scrub run.  Cancelling a non-dirty transaction simply
 * unlocks the buffers.
 *
 * There are four pieces of data that scrub can communicate to
 * userspace.  The first is the error code (errno), which can be used to
 * communicate operational errors in performing the scrub.  There are
 * also three flags that can be set in the scrub context.  If the data
 * structure itself is corrupt, the CORRUPT flag will be set.  If
 * the metadata is correct but otherwise suboptimal, the PREEN flag
 * will be set.
 *
 * We perform secondary validation of filesystem metadata by
 * cross-referencing every record with all other available metadata.
 * For example, for block mapping extents, we verify that there are no
 * records in the free space and inode btrees corresponding to that
 * space extent and that there is a corresponding entry in the reverse
 * mapping btree.  Inconsistent metadata is noted by setting the
 * XCORRUPT flag; btree query function errors are noted by setting the
 * XFAIL flag and deleting the cursor to prevent further attempts to
 * cross-reference with a defective btree.
 *
 * If a piece of metadata proves corrupt or suboptimal, the userspace
 * program can ask the kernel to apply some tender loving care (TLC) to
 * the metadata object by setting the REPAIR flag and re-calling the
 * scrub ioctl.  "Corruption" is defined by metadata violating the
 * on-disk specification; operations cannot continue if the violation is
 * left untreated.  It is possible for XFS to continue if an object is
 * "suboptimal", however performance may be degraded.  Repairs are
 * usually performed by rebuilding the metadata entirely out of
 * redundant metadata.  Optimizing, on the other hand, can sometimes be
 * done without rebuilding entire structures.
 *
 * Generally speaking, the repair code has the following code structure:
 * Lock -> scrub -> repair -> commit -> re-lock -> re-scrub -> unlock.
 * The first check helps us figure out if we need to rebuild or simply
 * optimize the structure so that the rebuild knows what to do.  The
 * second check evaluates the completeness of the repair; that is what
 * is reported to userspace.
 *
 * A quick note on symbol prefixes:
 * - "xfs_" are general XFS symbols.
 * - "xchk_" are symbols related to metadata checking.
 * - "xrep_" are symbols related to metadata repair.
 * - "xfs_scrub_" are symbols that tie online fsck to the rest of XFS.
 */

/*
 * Scrub probe -- userspace uses this to probe if we're willing to scrub
 * or repair a given mountpoint.  This will be used by xfs_scrub to
 * probe the kernel's abilities to scrub (and repair) the metadata.  We
 * do this by validating the ioctl inputs from userspace, preparing the
 * filesystem for a scrub (or a repair) operation, and immediately
 * returning to userspace.  Userspace can use the returned errno and
 * structure state to decide (in broad terms) if scrub/repair are
 * supported by the running kernel.
 */
static int
xchk_probe(
        struct xfs_scrub        *sc)
{
        int                     error = 0;

        if (xchk_should_terminate(sc, &error))
                return error;

        return 0;
}

/* Scrub setup and teardown */

static inline void
xchk_fsgates_disable(
        struct xfs_scrub        *sc)
{
        if (!(sc->flags & XCHK_FSGATES_ALL))
                return;

        trace_xchk_fsgates_disable(sc, sc->flags & XCHK_FSGATES_ALL);

        if (sc->flags & XCHK_FSGATES_DRAIN)
                xfs_drain_wait_disable();

        if (sc->flags & XCHK_FSGATES_QUOTA)
                xfs_dqtrx_hook_disable();

        if (sc->flags & XCHK_FSGATES_DIRENTS)
                xfs_dir_hook_disable();

        if (sc->flags & XCHK_FSGATES_RMAP)
                xfs_rmap_hook_disable();

        sc->flags &= ~XCHK_FSGATES_ALL;
}

/* Free the resources associated with a scrub subtype. */
void
xchk_scrub_free_subord(
        struct xfs_scrub_subord *sub)
{
        struct xfs_scrub        *sc = sub->parent_sc;

        ASSERT(sc->ip == sub->sc.ip);
        ASSERT(sc->orphanage == sub->sc.orphanage);
        ASSERT(sc->tempip == sub->sc.tempip);

        sc->sm->sm_type = sub->old_smtype;
        sc->sm->sm_flags = sub->old_smflags |
                                (sc->sm->sm_flags & XFS_SCRUB_FLAGS_OUT);
        sc->tp = sub->sc.tp;

        if (sub->sc.buf) {
                if (sub->sc.buf_cleanup)
                        sub->sc.buf_cleanup(sub->sc.buf);
                kvfree(sub->sc.buf);
        }
        if (sub->sc.xmbtp)
                xmbuf_free(sub->sc.xmbtp);
        if (sub->sc.xfile)
                xfile_destroy(sub->sc.xfile);

        sc->ilock_flags = sub->sc.ilock_flags;
        sc->orphanage_ilock_flags = sub->sc.orphanage_ilock_flags;
        sc->temp_ilock_flags = sub->sc.temp_ilock_flags;

        kfree(sub);
}

/* Free all the resources and finish the transactions. */
STATIC int
xchk_teardown(
        struct xfs_scrub        *sc,
        int                     error)
{
        xchk_ag_free(sc, &sc->sa);
        if (sc->tp) {
                if (error == 0 && (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
                        error = xfs_trans_commit(sc->tp);
                else
                        xfs_trans_cancel(sc->tp);
                sc->tp = NULL;
        }
        if (sc->sr.rtg)
                xchk_rtgroup_free(sc, &sc->sr);
        if (sc->ip) {
                if (sc->ilock_flags)
                        xchk_iunlock(sc, sc->ilock_flags);
                xchk_irele(sc, sc->ip);
                sc->ip = NULL;
        }
        if (sc->flags & XCHK_HAVE_FREEZE_PROT) {
                sc->flags &= ~XCHK_HAVE_FREEZE_PROT;
                mnt_drop_write_file(sc->file);
        }
        if (sc->xmbtp) {
                xmbuf_free(sc->xmbtp);
                sc->xmbtp = NULL;
        }
        if (sc->xfile) {
                xfile_destroy(sc->xfile);
                sc->xfile = NULL;
        }
        if (sc->buf) {
                if (sc->buf_cleanup)
                        sc->buf_cleanup(sc->buf);
                kvfree(sc->buf);
                sc->buf_cleanup = NULL;
                sc->buf = NULL;
        }

        xrep_tempfile_rele(sc);
        xrep_orphanage_rele(sc);
        xchk_fsgates_disable(sc);
        return error;
}

/* Scrubbing dispatch. */

static const struct xchk_meta_ops meta_scrub_ops[] = {
        [XFS_SCRUB_TYPE_PROBE] = {      /* ioctl presence test */
                .type   = ST_NONE,
                .setup  = xchk_setup_fs,
                .scrub  = xchk_probe,
                .repair = xrep_probe,
        },
        [XFS_SCRUB_TYPE_SB] = {         /* superblock */
                .type   = ST_PERAG,
                .setup  = xchk_setup_agheader,
                .scrub  = xchk_superblock,
                .repair = xrep_superblock,
        },
        [XFS_SCRUB_TYPE_AGF] = {        /* agf */
                .type   = ST_PERAG,
                .setup  = xchk_setup_agheader,
                .scrub  = xchk_agf,
                .repair = xrep_agf,
        },
        [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
                .type   = ST_PERAG,
                .setup  = xchk_setup_agheader,
                .scrub  = xchk_agfl,
                .repair = xrep_agfl,
        },
        [XFS_SCRUB_TYPE_AGI] = {        /* agi */
                .type   = ST_PERAG,
                .setup  = xchk_setup_agheader,
                .scrub  = xchk_agi,
                .repair = xrep_agi,
        },
        [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_allocbt,
                .scrub  = xchk_allocbt,
                .repair = xrep_allocbt,
                .repair_eval = xrep_revalidate_allocbt,
        },
        [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_allocbt,
                .scrub  = xchk_allocbt,
                .repair = xrep_allocbt,
                .repair_eval = xrep_revalidate_allocbt,
        },
        [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_iallocbt,
                .scrub  = xchk_iallocbt,
                .repair = xrep_iallocbt,
                .repair_eval = xrep_revalidate_iallocbt,
        },
        [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_iallocbt,
                .scrub  = xchk_iallocbt,
                .has    = xfs_has_finobt,
                .repair = xrep_iallocbt,
                .repair_eval = xrep_revalidate_iallocbt,
        },
        [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_rmapbt,
                .scrub  = xchk_rmapbt,
                .has    = xfs_has_rmapbt,
                .repair = xrep_rmapbt,
        },
        [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_refcountbt,
                .scrub  = xchk_refcountbt,
                .has    = xfs_has_reflink,
                .repair = xrep_refcountbt,
        },
        [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode,
                .scrub  = xchk_inode,
                .repair = xrep_inode,
        },
        [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode_bmap,
                .scrub  = xchk_bmap_data,
                .repair = xrep_bmap_data,
        },
        [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode_bmap,
                .scrub  = xchk_bmap_attr,
                .repair = xrep_bmap_attr,
        },
        [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode_bmap,
                .scrub  = xchk_bmap_cow,
                .repair = xrep_bmap_cow,
        },
        [XFS_SCRUB_TYPE_DIR] = {        /* directory */
                .type   = ST_INODE,
                .setup  = xchk_setup_directory,
                .scrub  = xchk_directory,
                .repair = xrep_directory,
        },
        [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
                .type   = ST_INODE,
                .setup  = xchk_setup_xattr,
                .scrub  = xchk_xattr,
                .repair = xrep_xattr,
        },
        [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
                .type   = ST_INODE,
                .setup  = xchk_setup_symlink,
                .scrub  = xchk_symlink,
                .repair = xrep_symlink,
        },
        [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
                .type   = ST_INODE,
                .setup  = xchk_setup_parent,
                .scrub  = xchk_parent,
                .repair = xrep_parent,
        },
        [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
                .type   = ST_RTGROUP,
                .setup  = xchk_setup_rtbitmap,
                .scrub  = xchk_rtbitmap,
                .repair = xrep_rtbitmap,
        },
        [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
                .type   = ST_RTGROUP,
                .setup  = xchk_setup_rtsummary,
                .scrub  = xchk_rtsummary,
                .repair = xrep_rtsummary,
        },
        [XFS_SCRUB_TYPE_UQUOTA] = {     /* user quota */
                .type   = ST_FS,
                .setup  = xchk_setup_quota,
                .scrub  = xchk_quota,
                .repair = xrep_quota,
        },
        [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
                .type   = ST_FS,
                .setup  = xchk_setup_quota,
                .scrub  = xchk_quota,
                .repair = xrep_quota,
        },
        [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
                .type   = ST_FS,
                .setup  = xchk_setup_quota,
                .scrub  = xchk_quota,
                .repair = xrep_quota,
        },
        [XFS_SCRUB_TYPE_FSCOUNTERS] = { /* fs summary counters */
                .type   = ST_FS,
                .setup  = xchk_setup_fscounters,
                .scrub  = xchk_fscounters,
                .repair = xrep_fscounters,
        },
        [XFS_SCRUB_TYPE_QUOTACHECK] = { /* quota counters */
                .type   = ST_FS,
                .setup  = xchk_setup_quotacheck,
                .scrub  = xchk_quotacheck,
                .repair = xrep_quotacheck,
        },
        [XFS_SCRUB_TYPE_NLINKS] = {     /* inode link counts */
                .type   = ST_FS,
                .setup  = xchk_setup_nlinks,
                .scrub  = xchk_nlinks,
                .repair = xrep_nlinks,
        },
        [XFS_SCRUB_TYPE_HEALTHY] = {    /* fs healthy; clean all reminders */
                .type   = ST_FS,
                .setup  = xchk_setup_fs,
                .scrub  = xchk_health_record,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_DIRTREE] = {    /* directory tree structure */
                .type   = ST_INODE,
                .setup  = xchk_setup_dirtree,
                .scrub  = xchk_dirtree,
                .has    = xfs_has_parent,
                .repair = xrep_dirtree,
        },
        [XFS_SCRUB_TYPE_METAPATH] = {   /* metadata directory tree path */
                .type   = ST_GENERIC,
                .setup  = xchk_setup_metapath,
                .scrub  = xchk_metapath,
                .has    = xfs_has_metadir,
                .repair = xrep_metapath,
        },
        [XFS_SCRUB_TYPE_RGSUPER] = {    /* realtime group superblock */
                .type   = ST_RTGROUP,
                .setup  = xchk_setup_rgsuperblock,
                .scrub  = xchk_rgsuperblock,
                .has    = xfs_has_rtsb,
                .repair = xrep_rgsuperblock,
        },
};

static int
xchk_validate_inputs(
        struct xfs_mount                *mp,
        struct xfs_scrub_metadata       *sm)
{
        int                             error;
        const struct xchk_meta_ops      *ops;

        error = -EINVAL;
        /* Check our inputs. */
        sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
        if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN)
                goto out;
        /* sm_reserved[] must be zero */
        if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved)))
                goto out;

        error = -ENOENT;
        /* Do we know about this type of metadata? */
        if (sm->sm_type >= XFS_SCRUB_TYPE_NR)
                goto out;
        ops = &meta_scrub_ops[sm->sm_type];
        if (ops->setup == NULL || ops->scrub == NULL)
                goto out;
        /* Does this fs even support this type of metadata? */
        if (ops->has && !ops->has(mp))
                goto out;

        error = -EINVAL;
        /* restricting fields must be appropriate for type */
        switch (ops->type) {
        case ST_NONE:
        case ST_FS:
                if (sm->sm_ino || sm->sm_gen || sm->sm_agno)
                        goto out;
                break;
        case ST_PERAG:
                if (sm->sm_ino || sm->sm_gen ||
                    sm->sm_agno >= mp->m_sb.sb_agcount)
                        goto out;
                break;
        case ST_INODE:
                if (sm->sm_agno || (sm->sm_gen && !sm->sm_ino))
                        goto out;
                break;
        case ST_GENERIC:
                break;
        case ST_RTGROUP:
                if (sm->sm_ino || sm->sm_gen)
                        goto out;
                if (xfs_has_rtgroups(mp)) {
                        /*
                         * On a rtgroups filesystem, there won't be an rtbitmap
                         * or rtsummary file for group 0 unless there's
                         * actually a realtime volume attached.  However, older
                         * xfs_scrub always calls the rtbitmap/rtsummary
                         * scrubbers with sm_agno==0 so transform the error
                         * code to ENOENT.
                         */
                        if (sm->sm_agno >= mp->m_sb.sb_rgcount) {
                                if (sm->sm_agno == 0)
                                        error = -ENOENT;
                                goto out;
                        }
                } else {
                        /*
                         * Prior to rtgroups, the rtbitmap/rtsummary scrubbers
                         * accepted sm_agno==0, so we still accept that for
                         * scrubbing pre-rtgroups filesystems.
                         */
                        if (sm->sm_agno != 0)
                                goto out;
                }
                break;
        default:
                goto out;
        }

        /* No rebuild without repair. */
        if ((sm->sm_flags & XFS_SCRUB_IFLAG_FORCE_REBUILD) &&
            !(sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
                return -EINVAL;

        /*
         * We only want to repair read-write v5+ filesystems.  Defer the check
         * for ops->repair until after our scrub confirms that we need to
         * perform repairs so that we avoid failing due to not supporting
         * repairing an object that doesn't need repairs.
         */
        if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
                error = -EOPNOTSUPP;
                if (!xfs_has_crc(mp))
                        goto out;

                error = -EROFS;
                if (xfs_is_readonly(mp))
                        goto out;
        }

        error = 0;
out:
        return error;
}

#ifdef CONFIG_XFS_ONLINE_REPAIR
static inline void xchk_postmortem(struct xfs_scrub *sc)
{
        /*
         * Userspace asked us to repair something, we repaired it, rescanned
         * it, and the rescan says it's still broken.  Scream about this in
         * the system logs.
         */
        if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
            (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
                                 XFS_SCRUB_OFLAG_XCORRUPT)))
                xrep_failure(sc->mp);
}
#else
static inline void xchk_postmortem(struct xfs_scrub *sc)
{
        /*
         * Userspace asked us to scrub something, it's broken, and we have no
         * way of fixing it.  Scream in the logs.
         */
        if (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
                                XFS_SCRUB_OFLAG_XCORRUPT))
                xfs_alert_ratelimited(sc->mp,
                                "Corruption detected during scrub.");
}
#endif /* CONFIG_XFS_ONLINE_REPAIR */

/*
 * Create a new scrub context from an existing one, but with a different scrub
 * type.
 */
struct xfs_scrub_subord *
xchk_scrub_create_subord(
        struct xfs_scrub        *sc,
        unsigned int            subtype)
{
        struct xfs_scrub_subord *sub;

        sub = kzalloc(sizeof(*sub), XCHK_GFP_FLAGS);
        if (!sub)
                return ERR_PTR(-ENOMEM);

        sub->old_smtype = sc->sm->sm_type;
        sub->old_smflags = sc->sm->sm_flags;
        sub->parent_sc = sc;
        memcpy(&sub->sc, sc, sizeof(struct xfs_scrub));
        sub->sc.ops = &meta_scrub_ops[subtype];
        sub->sc.sm->sm_type = subtype;
        sub->sc.sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
        sub->sc.buf = NULL;
        sub->sc.buf_cleanup = NULL;
        sub->sc.xfile = NULL;
        sub->sc.xmbtp = NULL;

        return sub;
}

/* Dispatch metadata scrubbing. */
STATIC int
xfs_scrub_metadata(
        struct file                     *file,
        struct xfs_scrub_metadata       *sm)
{
        struct xchk_stats_run           run = { };
        struct xfs_scrub                *sc;
        struct xfs_mount                *mp = XFS_I(file_inode(file))->i_mount;
        u64                             check_start;
        int                             error = 0;

        BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
                (sizeof(struct xchk_meta_ops) * XFS_SCRUB_TYPE_NR));

        trace_xchk_start(XFS_I(file_inode(file)), sm, error);

        /* Forbidden if we are shut down or mounted norecovery. */
        error = -ESHUTDOWN;
        if (xfs_is_shutdown(mp))
                goto out;
        error = -ENOTRECOVERABLE;
        if (xfs_has_norecovery(mp))
                goto out;

        error = xchk_validate_inputs(mp, sm);
        if (error)
                goto out;

        xfs_warn_experimental(mp, XFS_EXPERIMENTAL_SCRUB);

        sc = kzalloc(sizeof(struct xfs_scrub), XCHK_GFP_FLAGS);
        if (!sc) {
                error = -ENOMEM;
                goto out;
        }

        sc->mp = mp;
        sc->file = file;
        sc->sm = sm;
        sc->ops = &meta_scrub_ops[sm->sm_type];
        sc->sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
        sc->relax = INIT_XCHK_RELAX;
retry_op:
        /*
         * When repairs are allowed, prevent freezing or readonly remount while
         * scrub is running with a real transaction.
         */
        if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
                error = mnt_want_write_file(sc->file);
                if (error)
                        goto out_sc;

                sc->flags |= XCHK_HAVE_FREEZE_PROT;
        }

        /* Set up for the operation. */
        error = sc->ops->setup(sc);
        if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
                goto try_harder;
        if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
                goto need_drain;
        if (error)
                goto out_teardown;

        /* Scrub for errors. */
        check_start = xchk_stats_now();
        if ((sc->flags & XREP_ALREADY_FIXED) && sc->ops->repair_eval != NULL)
                error = sc->ops->repair_eval(sc);
        else
                error = sc->ops->scrub(sc);
        run.scrub_ns += xchk_stats_elapsed_ns(check_start);
        if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
                goto try_harder;
        if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
                goto need_drain;
        if (error || (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE))
                goto out_teardown;

        xchk_update_health(sc);

        if (xchk_could_repair(sc)) {
                /*
                 * If userspace asked for a repair but it wasn't necessary,
                 * report that back to userspace.
                 */
                if (!xrep_will_attempt(sc)) {
                        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
                        goto out_nofix;
                }

                /*
                 * If it's broken, userspace wants us to fix it, and we haven't
                 * already tried to fix it, then attempt a repair.
                 */
                error = xrep_attempt(sc, &run);
                if (error == -EAGAIN) {
                        /*
                         * Either the repair function succeeded or it couldn't
                         * get all the resources it needs; either way, we go
                         * back to the beginning and call the scrub function.
                         */
                        error = xchk_teardown(sc, 0);
                        if (error) {
                                xrep_failure(mp);
                                goto out_sc;
                        }
                        goto retry_op;
                }
        }

out_nofix:
        xchk_postmortem(sc);
out_teardown:
        error = xchk_teardown(sc, error);
out_sc:
        if (error != -ENOENT)
                xchk_stats_merge(mp, sm, &run);
        kfree(sc);
out:
        trace_xchk_done(XFS_I(file_inode(file)), sm, error);
        if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
                sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
                error = 0;
        }
        return error;
need_drain:
        error = xchk_teardown(sc, 0);
        if (error)
                goto out_sc;
        sc->flags |= XCHK_NEED_DRAIN;
        run.retries++;
        goto retry_op;
try_harder:
        /*
         * Scrubbers return -EDEADLOCK to mean 'try harder'.  Tear down
         * everything we hold, then set up again with preparation for
         * worst-case scenarios.
         */
        error = xchk_teardown(sc, 0);
        if (error)
                goto out_sc;
        sc->flags |= XCHK_TRY_HARDER;
        run.retries++;
        goto retry_op;
}

/* Scrub one aspect of one piece of metadata. */
int
xfs_ioc_scrub_metadata(
        struct file                     *file,
        void                            __user *arg)
{
        struct xfs_scrub_metadata       scrub;
        int                             error;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        if (copy_from_user(&scrub, arg, sizeof(scrub)))
                return -EFAULT;

        error = xfs_scrub_metadata(file, &scrub);
        if (error)
                return error;

        if (copy_to_user(arg, &scrub, sizeof(scrub)))
                return -EFAULT;

        return 0;
}

/* Decide if there have been any scrub failures up to this point. */
static inline int
xfs_scrubv_check_barrier(
        struct xfs_mount                *mp,
        const struct xfs_scrub_vec      *vectors,
        const struct xfs_scrub_vec      *stop_vec)
{
        const struct xfs_scrub_vec      *v;
        __u32                           failmask;

        failmask = stop_vec->sv_flags & XFS_SCRUB_FLAGS_OUT;

        for (v = vectors; v < stop_vec; v++) {
                if (v->sv_type == XFS_SCRUB_TYPE_BARRIER)
                        continue;

                /*
                 * Runtime errors count as a previous failure, except the ones
                 * used to ask userspace to retry.
                 */
                switch (v->sv_ret) {
                case -EBUSY:
                case -ENOENT:
                case -EUSERS:
                case 0:
                        break;
                default:
                        return -ECANCELED;
                }

                /*
                 * If any of the out-flags on the scrub vector match the mask
                 * that was set on the barrier vector, that's a previous fail.
                 */
                if (v->sv_flags & failmask)
                        return -ECANCELED;
        }

        return 0;
}

/*
 * If the caller provided us with a nonzero inode number that isn't the ioctl
 * file, try to grab a reference to it to eliminate all further untrusted inode
 * lookups.  If we can't get the inode, let each scrub function try again.
 */
STATIC struct xfs_inode *
xchk_scrubv_open_by_handle(
        struct xfs_mount                *mp,
        const struct xfs_scrub_vec_head *head)
{
        struct xfs_trans                *tp;
        struct xfs_inode                *ip;
        int                             error;

        error = xfs_trans_alloc_empty(mp, &tp);
        if (error)
                return NULL;

        error = xfs_iget(mp, tp, head->svh_ino, XCHK_IGET_FLAGS, 0, &ip);
        xfs_trans_cancel(tp);
        if (error)
                return NULL;

        if (VFS_I(ip)->i_generation != head->svh_gen) {
                xfs_irele(ip);
                return NULL;
        }

        return ip;
}

/* Vectored scrub implementation to reduce ioctl calls. */
int
xfs_ioc_scrubv_metadata(
        struct file                     *file,
        void                            __user *arg)
{
        struct xfs_scrub_vec_head       head;
        struct xfs_scrub_vec_head       __user *uhead = arg;
        struct xfs_scrub_vec            *vectors;
        struct xfs_scrub_vec            __user *uvectors;
        struct xfs_inode                *ip_in = XFS_I(file_inode(file));
        struct xfs_mount                *mp = ip_in->i_mount;
        struct xfs_inode                *handle_ip = NULL;
        struct xfs_scrub_vec            *v;
        size_t                          vec_bytes;
        unsigned int                    i;
        int                             error = 0;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        if (copy_from_user(&head, uhead, sizeof(head)))
                return -EFAULT;

        if (head.svh_reserved)
                return -EINVAL;
        if (head.svh_flags & ~XFS_SCRUB_VEC_FLAGS_ALL)
                return -EINVAL;
        if (head.svh_nr == 0)
                return 0;

        vec_bytes = array_size(head.svh_nr, sizeof(struct xfs_scrub_vec));
        if (vec_bytes > PAGE_SIZE)
                return -ENOMEM;

        uvectors = u64_to_user_ptr(head.svh_vectors);
        vectors = memdup_user(uvectors, vec_bytes);
        if (IS_ERR(vectors))
                return PTR_ERR(vectors);

        trace_xchk_scrubv_start(ip_in, &head);

        for (i = 0, v = vectors; i < head.svh_nr; i++, v++) {
                if (v->sv_reserved) {
                        error = -EINVAL;
                        goto out_free;
                }

                if (v->sv_type == XFS_SCRUB_TYPE_BARRIER &&
                    (v->sv_flags & ~XFS_SCRUB_FLAGS_OUT)) {
                        error = -EINVAL;
                        goto out_free;
                }

                trace_xchk_scrubv_item(mp, &head, i, v);
        }

        /*
         * If the caller wants us to do a scrub-by-handle and the file used to
         * call the ioctl is not the same file, load the incore inode and pin
         * it across all the scrubv actions to avoid repeated UNTRUSTED
         * lookups.  The reference is not passed to deeper layers of scrub
         * because each scrubber gets to decide its own strategy and return
         * values for getting an inode.
         */
        if (head.svh_ino && head.svh_ino != ip_in->i_ino)
                handle_ip = xchk_scrubv_open_by_handle(mp, &head);

        /* Run all the scrubbers. */
        for (i = 0, v = vectors; i < head.svh_nr; i++, v++) {
                struct xfs_scrub_metadata       sm = {
                        .sm_type                = v->sv_type,
                        .sm_flags               = v->sv_flags,
                        .sm_ino                 = head.svh_ino,
                        .sm_gen                 = head.svh_gen,
                        .sm_agno                = head.svh_agno,
                };

                if (v->sv_type == XFS_SCRUB_TYPE_BARRIER) {
                        v->sv_ret = xfs_scrubv_check_barrier(mp, vectors, v);
                        if (v->sv_ret) {
                                trace_xchk_scrubv_barrier_fail(mp, &head, i, v);
                                break;
                        }

                        continue;
                }

                v->sv_ret = xfs_scrub_metadata(file, &sm);
                v->sv_flags = sm.sm_flags;

                trace_xchk_scrubv_outcome(mp, &head, i, v);

                if (head.svh_rest_us) {
                        ktime_t         expires;

                        expires = ktime_add_ns(ktime_get(),
                                        head.svh_rest_us * 1000);
                        set_current_state(TASK_KILLABLE);
                        schedule_hrtimeout(&expires, HRTIMER_MODE_ABS);
                }

                if (fatal_signal_pending(current)) {
                        error = -EINTR;
                        goto out_free;
                }
        }

        if (copy_to_user(uvectors, vectors, vec_bytes) ||
            copy_to_user(uhead, &head, sizeof(head))) {
                error = -EFAULT;
                goto out_free;
        }

out_free:
        if (handle_ip)
                xfs_irele(handle_ip);
        kfree(vectors);
        return error;
}