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linux/fs/xfs/scrub/scrub.c

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// 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 "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;
}
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:
/* 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;
}
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