Merge tag 'xtensa-20180225' of git://github.com/jcmvbkbc/linux-xtensa

[cris-mirror.git] / fs / xfs / scrub / scrub.c

/*
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 *
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
 */
#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_defer.h"
#include "xfs_btree.h"
#include "xfs_bit.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_inode.h"
#include "xfs_icache.h"
#include "xfs_itable.h"
#include "xfs_alloc.h"
#include "xfs_alloc_btree.h"
#include "xfs_bmap.h"
#include "xfs_bmap_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_refcount.h"
#include "xfs_refcount_btree.h"
#include "xfs_rmap.h"
#include "xfs_rmap_btree.h"
#include "scrub/xfs_scrub.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"
#include "scrub/btree.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.
 */

/*
 * 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
xfs_scrub_probe(
        struct xfs_scrub_context        *sc)
{
        int                             error = 0;

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

        return 0;
}

/* Scrub setup and teardown */

/* Free all the resources and finish the transactions. */
STATIC int
xfs_scrub_teardown(
        struct xfs_scrub_context        *sc,
        struct xfs_inode                *ip_in,
        int                             error)
{
        xfs_scrub_ag_free(sc, &sc->sa);
        if (sc->tp) {
                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))
                        iput(VFS_I(sc->ip));
                sc->ip = NULL;
        }
        if (sc->buf) {
                kmem_free(sc->buf);
                sc->buf = NULL;
        }
        return error;
}

/* Scrubbing dispatch. */

static const struct xfs_scrub_meta_ops meta_scrub_ops[] = {
        [XFS_SCRUB_TYPE_PROBE] = {      /* ioctl presence test */
                .type   = ST_NONE,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_probe,
        },
        [XFS_SCRUB_TYPE_SB] = {         /* superblock */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_superblock,
        },
        [XFS_SCRUB_TYPE_AGF] = {        /* agf */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_agf,
        },
        [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_agfl,
        },
        [XFS_SCRUB_TYPE_AGI] = {        /* agi */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_agi,
        },
        [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_allocbt,
                .scrub  = xfs_scrub_bnobt,
        },
        [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_allocbt,
                .scrub  = xfs_scrub_cntbt,
        },
        [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_iallocbt,
                .scrub  = xfs_scrub_inobt,
        },
        [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_iallocbt,
                .scrub  = xfs_scrub_finobt,
                .has    = xfs_sb_version_hasfinobt,
        },
        [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_rmapbt,
                .scrub  = xfs_scrub_rmapbt,
                .has    = xfs_sb_version_hasrmapbt,
        },
        [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_refcountbt,
                .scrub  = xfs_scrub_refcountbt,
                .has    = xfs_sb_version_hasreflink,
        },
        [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode,
                .scrub  = xfs_scrub_inode,
        },
        [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode_bmap,
                .scrub  = xfs_scrub_bmap_data,
        },
        [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode_bmap,
                .scrub  = xfs_scrub_bmap_attr,
        },
        [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode_bmap,
                .scrub  = xfs_scrub_bmap_cow,
        },
        [XFS_SCRUB_TYPE_DIR] = {        /* directory */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_directory,
                .scrub  = xfs_scrub_directory,
        },
        [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_xattr,
                .scrub  = xfs_scrub_xattr,
        },
        [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_symlink,
                .scrub  = xfs_scrub_symlink,
        },
        [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_parent,
                .scrub  = xfs_scrub_parent,
        },
        [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_rt,
                .scrub  = xfs_scrub_rtbitmap,
                .has    = xfs_sb_version_hasrealtime,
        },
        [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_rt,
                .scrub  = xfs_scrub_rtsummary,
                .has    = xfs_sb_version_hasrealtime,
        },
        [XFS_SCRUB_TYPE_UQUOTA] = {     /* user quota */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_quota,
                .scrub  = xfs_scrub_quota,
        },
        [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_quota,
                .scrub  = xfs_scrub_quota,
        },
        [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_quota,
                .scrub  = xfs_scrub_quota,
        },
};

/* This isn't a stable feature, warn once per day. */
static inline void
xfs_scrub_experimental_warning(
        struct xfs_mount        *mp)
{
        static struct ratelimit_state scrub_warning = RATELIMIT_STATE_INIT(
                        "xfs_scrub_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
xfs_scrub_validate_inputs(
        struct xfs_mount                *mp,
        struct xfs_scrub_metadata       *sm)
{
        int                             error;
        const struct xfs_scrub_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;
        }

        error = -EOPNOTSUPP;
        /*
         * We won't scrub any filesystem that doesn't have the ability
         * to record unwritten extents.  The option was made default in
         * 2003, removed from mkfs in 2007, and cannot be disabled in
         * v5, so if we find a filesystem without this flag it's either
         * really old or totally unsupported.  Avoid it either way.
         * We also don't support v1-v3 filesystems, which aren't
         * mountable.
         */
        if (!xfs_sb_version_hasextflgbit(&mp->m_sb))
                goto out;

        /* We don't know how to repair anything yet. */
        if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
                goto out;

        error = 0;
out:
        return error;
}

/* Dispatch metadata scrubbing. */
int
xfs_scrub_metadata(
        struct xfs_inode                *ip,
        struct xfs_scrub_metadata       *sm)
{
        struct xfs_scrub_context        sc;
        struct xfs_mount                *mp = ip->i_mount;
        bool                            try_harder = false;
        int                             error = 0;

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

        trace_xfs_scrub_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 = xfs_scrub_validate_inputs(mp, sm);
        if (error)
                goto out;

        xfs_scrub_experimental_warning(mp);

retry_op:
        /* Set up for the operation. */
        memset(&sc, 0, sizeof(sc));
        sc.mp = ip->i_mount;
        sc.sm = sm;
        sc.ops = &meta_scrub_ops[sm->sm_type];
        sc.try_harder = try_harder;
        sc.sa.agno = NULLAGNUMBER;
        error = sc.ops->setup(&sc, ip);
        if (error)
                goto out_teardown;

        /* Scrub for errors. */
        error = sc.ops->scrub(&sc);
        if (!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 = xfs_scrub_teardown(&sc, ip, 0);
                if (error)
                        goto out;
                try_harder = true;
                goto retry_op;
        } else if (error)
                goto out_teardown;

        if (sc.sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
                               XFS_SCRUB_OFLAG_XCORRUPT))
                xfs_alert_ratelimited(mp, "Corruption detected during scrub.");

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