--- /dev/null
+/*
+ * Copyright (C) 2018 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_alloc.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_ialloc.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_rmap.h"
+#include "xfs_rmap_btree.h"
+#include "xfs_refcount.h"
+#include "xfs_refcount_btree.h"
+#include "xfs_extent_busy.h"
+#include "xfs_ag_resv.h"
+#include "xfs_trans_space.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+
+/*
+ * Attempt to repair some metadata, if the metadata is corrupt and userspace
+ * told us to fix it.  This function returns -EAGAIN to mean "re-run scrub",
+ * and will set *fixed to true if it thinks it repaired anything.
+ */
+int
+xfs_repair_attempt(
+       struct xfs_inode                *ip,
+       struct xfs_scrub_context        *sc,
+       bool                            *fixed)
+{
+       int                             error = 0;
+
+       trace_xfs_repair_attempt(ip, sc->sm, error);
+
+       xfs_scrub_ag_btcur_free(&sc->sa);
+
+       /* Repair whatever's broken. */
+       ASSERT(sc->ops->repair);
+       error = sc->ops->repair(sc);
+       trace_xfs_repair_done(ip, sc->sm, error);
+       switch (error) {
+       case 0:
+               /*
+                * Repair succeeded.  Commit the fixes and perform a second
+                * scrub so that we can tell userspace if we fixed the problem.
+                */
+               sc->sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
+               *fixed = true;
+               return -EAGAIN;
+       case -EDEADLOCK:
+       case -EAGAIN:
+               /* Tell the caller to try again having grabbed all the locks. */
+               if (!sc->try_harder) {
+                       sc->try_harder = true;
+                       return -EAGAIN;
+               }
+               /*
+                * We tried harder but still couldn't grab all the resources
+                * we needed to fix it.  The corruption has not been fixed,
+                * so report back to userspace.
+                */
+               return -EFSCORRUPTED;
+       default:
+               return error;
+       }
+}
+
+/*
+ * Complain about unfixable problems in the filesystem.  We don't log
+ * corruptions when IFLAG_REPAIR wasn't set on the assumption that the driver
+ * program is xfs_scrub, which will call back with IFLAG_REPAIR set if the
+ * administrator isn't running xfs_scrub in no-repairs mode.
+ *
+ * Use this helper function because _ratelimited silently declares a static
+ * structure to track rate limiting information.
+ */
+void
+xfs_repair_failure(
+       struct xfs_mount                *mp)
+{
+       xfs_alert_ratelimited(mp,
+"Corruption not fixed during online repair.  Unmount and run xfs_repair.");
+}
+
+/*
+ * Repair probe -- userspace uses this to probe if we're willing to repair a
+ * given mountpoint.
+ */
+int
+xfs_repair_probe(
+       struct xfs_scrub_context        *sc)
+{
+       int                             error = 0;
+
+       if (xfs_scrub_should_terminate(sc, &error))
+               return error;
+
+       return 0;
+}
 
 #include "xfs_rmap_btree.h"
 #include "xfs_quota.h"
 #include "xfs_qm.h"
+#include "xfs_errortag.h"
+#include "xfs_error.h"
+#include "xfs_log.h"
+#include "xfs_trans_priv.h"
 #include "scrub/xfs_scrub.h"
 #include "scrub/scrub.h"
 #include "scrub/common.h"
 #include "scrub/trace.h"
 #include "scrub/btree.h"
+#include "scrub/repair.h"
 
 /*
  * Online Scrub and Repair
  * 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.
  */
 
 /*
 {
        xfs_scrub_ag_free(sc, &sc->sa);
        if (sc->tp) {
-               xfs_trans_cancel(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) {
                .type   = ST_NONE,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_probe,
+               .repair = xfs_repair_probe,
        },
        [XFS_SCRUB_TYPE_SB] = {         /* superblock */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_superblock,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_AGF] = {        /* agf */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_agf,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_agfl,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_AGI] = {        /* agi */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_fs,
                .scrub  = xfs_scrub_agi,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_allocbt,
                .scrub  = xfs_scrub_bnobt,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_allocbt,
                .scrub  = xfs_scrub_cntbt,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_iallocbt,
                .scrub  = xfs_scrub_inobt,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_iallocbt,
                .scrub  = xfs_scrub_finobt,
                .has    = xfs_sb_version_hasfinobt,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_rmapbt,
                .scrub  = xfs_scrub_rmapbt,
                .has    = xfs_sb_version_hasrmapbt,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
                .type   = ST_PERAG,
                .setup  = xfs_scrub_setup_ag_refcountbt,
                .scrub  = xfs_scrub_refcountbt,
                .has    = xfs_sb_version_hasreflink,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode,
                .scrub  = xfs_scrub_inode,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode_bmap,
                .scrub  = xfs_scrub_bmap_data,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode_bmap,
                .scrub  = xfs_scrub_bmap_attr,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_inode_bmap,
                .scrub  = xfs_scrub_bmap_cow,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_DIR] = {        /* directory */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_directory,
                .scrub  = xfs_scrub_directory,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_xattr,
                .scrub  = xfs_scrub_xattr,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_symlink,
                .scrub  = xfs_scrub_symlink,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
                .type   = ST_INODE,
                .setup  = xfs_scrub_setup_parent,
                .scrub  = xfs_scrub_parent,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_rt,
                .scrub  = xfs_scrub_rtbitmap,
                .has    = xfs_sb_version_hasrealtime,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_rt,
                .scrub  = xfs_scrub_rtsummary,
                .has    = xfs_sb_version_hasrealtime,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_UQUOTA] = {     /* user quota */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_quota,
                .scrub  = xfs_scrub_quota,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_quota,
                .scrub  = xfs_scrub_quota,
+               .repair = xfs_repair_notsupported,
        },
        [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
                .type   = ST_FS,
                .setup  = xfs_scrub_setup_quota,
                .scrub  = xfs_scrub_quota,
+               .repair = xfs_repair_notsupported,
        },
 };
 
        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;
+       /*
+        * 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 xfs_scrub_postmortem(struct xfs_scrub_context *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)))
+               xfs_repair_failure(sc->mp);
+}
+#else
+static inline void xfs_scrub_postmortem(struct xfs_scrub_context *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_scrub_context        sc;
        struct xfs_mount                *mp = ip->i_mount;
        bool                            try_harder = false;
+       bool                            already_fixed = false;
        int                             error = 0;
 
        BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
        } else if (error)
                goto out_teardown;
 
-       if (sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
-                           XFS_SCRUB_OFLAG_XCORRUPT))
-               xfs_alert_ratelimited(mp, "Corruption detected during scrub.");
+       if ((sc.sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) && !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 = xfs_repair_attempt(ip, &sc, &already_fixed);
+               if (error == -EAGAIN) {
+                       if (sc.try_harder)
+                               try_harder = true;
+                       error = xfs_scrub_teardown(&sc, ip, 0);
+                       if (error) {
+                               xfs_repair_failure(mp);
+                               goto out;
+                       }
+                       goto retry_op;
+               }
+       }
 
+out_nofix:
+       xfs_scrub_postmortem(&sc);
 out_teardown:
        error = xfs_scrub_teardown(&sc, ip, error);
 out: