WIP FPC-III support

[linux/fpc-iii.git] / fs / xfs / scrub / scrub.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 */
#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_errortag.h"
#include "xfs_error.h"
#include "xfs_scrub.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"
#include "scrub/repair.h"
#include "scrub/health.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 */

/* Free all the resources and finish the transactions. */
STATIC int
xchk_teardown(
        struct xfs_scrub        *sc,
        struct xfs_inode        *ip_in,
        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->ip) {
                if (sc->ilock_flags)
                        xfs_iunlock(sc->ip, sc->ilock_flags);
                if (sc->ip != ip_in &&
                    !xfs_internal_inum(sc->mp, sc->ip->i_ino))
                        xfs_irele(sc->ip);
                sc->ip = NULL;
        }
        sb_end_write(sc->mp->m_super);
        if (sc->flags & XCHK_REAPING_DISABLED)
                xchk_start_reaping(sc);
        if (sc->flags & XCHK_HAS_QUOTAOFFLOCK) {
                mutex_unlock(&sc->mp->m_quotainfo->qi_quotaofflock);
                sc->flags &= ~XCHK_HAS_QUOTAOFFLOCK;
        }
        if (sc->buf) {
                kmem_free(sc->buf);
                sc->buf = NULL;
        }
        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_fs,
                .scrub  = xchk_superblock,
                .repair = xrep_superblock,
        },
        [XFS_SCRUB_TYPE_AGF] = {        /* agf */
                .type   = ST_PERAG,
                .setup  = xchk_setup_fs,
                .scrub  = xchk_agf,
                .repair = xrep_agf,
        },
        [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
                .type   = ST_PERAG,
                .setup  = xchk_setup_fs,
                .scrub  = xchk_agfl,
                .repair = xrep_agfl,
        },
        [XFS_SCRUB_TYPE_AGI] = {        /* agi */
                .type   = ST_PERAG,
                .setup  = xchk_setup_fs,
                .scrub  = xchk_agi,
                .repair = xrep_agi,
        },
        [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_allocbt,
                .scrub  = xchk_bnobt,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_allocbt,
                .scrub  = xchk_cntbt,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_iallocbt,
                .scrub  = xchk_inobt,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_iallocbt,
                .scrub  = xchk_finobt,
                .has    = xfs_sb_version_hasfinobt,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_rmapbt,
                .scrub  = xchk_rmapbt,
                .has    = xfs_sb_version_hasrmapbt,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
                .type   = ST_PERAG,
                .setup  = xchk_setup_ag_refcountbt,
                .scrub  = xchk_refcountbt,
                .has    = xfs_sb_version_hasreflink,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode,
                .scrub  = xchk_inode,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode_bmap,
                .scrub  = xchk_bmap_data,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode_bmap,
                .scrub  = xchk_bmap_attr,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
                .type   = ST_INODE,
                .setup  = xchk_setup_inode_bmap,
                .scrub  = xchk_bmap_cow,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_DIR] = {        /* directory */
                .type   = ST_INODE,
                .setup  = xchk_setup_directory,
                .scrub  = xchk_directory,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
                .type   = ST_INODE,
                .setup  = xchk_setup_xattr,
                .scrub  = xchk_xattr,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
                .type   = ST_INODE,
                .setup  = xchk_setup_symlink,
                .scrub  = xchk_symlink,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
                .type   = ST_INODE,
                .setup  = xchk_setup_parent,
                .scrub  = xchk_parent,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
                .type   = ST_FS,
                .setup  = xchk_setup_rt,
                .scrub  = xchk_rtbitmap,
                .has    = xfs_sb_version_hasrealtime,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
                .type   = ST_FS,
                .setup  = xchk_setup_rt,
                .scrub  = xchk_rtsummary,
                .has    = xfs_sb_version_hasrealtime,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_UQUOTA] = {     /* user quota */
                .type   = ST_FS,
                .setup  = xchk_setup_quota,
                .scrub  = xchk_quota,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
                .type   = ST_FS,
                .setup  = xchk_setup_quota,
                .scrub  = xchk_quota,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
                .type   = ST_FS,
                .setup  = xchk_setup_quota,
                .scrub  = xchk_quota,
                .repair = xrep_notsupported,
        },
        [XFS_SCRUB_TYPE_FSCOUNTERS] = { /* fs summary counters */
                .type   = ST_FS,
                .setup  = xchk_setup_fscounters,
                .scrub  = xchk_fscounters,
                .repair = xrep_notsupported,
        },
};

/* This isn't a stable feature, warn once per day. */
static inline void
xchk_experimental_warning(
        struct xfs_mount        *mp)
{
        static struct ratelimit_state scrub_warning = RATELIMIT_STATE_INIT(
                        "xchk_warning", 86400 * HZ, 1);
        ratelimit_set_flags(&scrub_warning, RATELIMIT_MSG_ON_RELEASE);

        if (__ratelimit(&scrub_warning))
                xfs_alert(mp,
"EXPERIMENTAL online scrub feature in use. Use at your own risk!");
}

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->m_sb))
                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;
        default:
                goto out;
        }

        /*
         * 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_sb_version_hascrc(&mp->m_sb))
                        goto out;

                error = -EROFS;
                if (mp->m_flags & XFS_MOUNT_RDONLY)
                        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 */

/* Dispatch metadata scrubbing. */
int
xfs_scrub_metadata(
        struct xfs_inode                *ip,
        struct xfs_scrub_metadata       *sm)
{
        struct xfs_scrub                sc = {
                .mp                     = ip->i_mount,
                .sm                     = sm,
                .sa                     = {
                        .agno           = NULLAGNUMBER,
                },
        };
        struct xfs_mount                *mp = ip->i_mount;
        int                             error = 0;

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

        trace_xchk_start(ip, sm, error);

        /* Forbidden if we are shut down or mounted norecovery. */
        error = -ESHUTDOWN;
        if (XFS_FORCED_SHUTDOWN(mp))
                goto out;
        error = -ENOTRECOVERABLE;
        if (mp->m_flags & XFS_MOUNT_NORECOVERY)
                goto out;

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

        xchk_experimental_warning(mp);

        sc.ops = &meta_scrub_ops[sm->sm_type];
        sc.sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
retry_op:
        /*
         * If freeze runs concurrently with a scrub, the freeze can be delayed
         * indefinitely as we walk the filesystem and iterate over metadata
         * buffers.  Freeze quiesces the log (which waits for the buffer LRU to
         * be emptied) and that won't happen while checking is running.
         */
        sb_start_write(mp->m_super);

        /* Set up for the operation. */
        error = sc.ops->setup(&sc, ip);
        if (error)
                goto out_teardown;

        /* Scrub for errors. */
        error = sc.ops->scrub(&sc);
        if (!(sc.flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) {
                /*
                 * 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, ip, 0);
                if (error)
                        goto out;
                sc.flags |= XCHK_TRY_HARDER;
                goto retry_op;
        } else if (error)
                goto out_teardown;

        xchk_update_health(&sc);

        if ((sc.sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
            !(sc.flags & XREP_ALREADY_FIXED)) {
                bool needs_fix;

                /* Let debug users force us into the repair routines. */
                if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_FORCE_SCRUB_REPAIR))
                        sc.sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;

                needs_fix = (sc.sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
                                                XFS_SCRUB_OFLAG_XCORRUPT |
                                                XFS_SCRUB_OFLAG_PREEN));
                /*
                 * If userspace asked for a repair but it wasn't necessary,
                 * report that back to userspace.
                 */
                if (!needs_fix) {
                        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(ip, &sc);
                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, ip, 0);
                        if (error) {
                                xrep_failure(mp);
                                goto out;
                        }
                        goto retry_op;
                }
        }

out_nofix:
        xchk_postmortem(&sc);
out_teardown:
        error = xchk_teardown(&sc, ip, error);
out:
        trace_xchk_done(ip, sm, error);
        if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
                sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
                error = 0;
        }
        return error;
}