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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_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 "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
*
* 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))
iput(VFS_I(sc->ip));
sc->ip = NULL;
}
if (sc->has_quotaofflock)
mutex_unlock(&sc->mp->m_quotainfo->qi_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_notsupported,
},
[XFS_SCRUB_TYPE_AGFL]= { /* agfl */
.type = ST_PERAG,
.setup = xchk_setup_fs,
.scrub = xchk_agfl,
.repair = xrep_notsupported,
},
[XFS_SCRUB_TYPE_AGI] = { /* agi */
.type = ST_PERAG,
.setup = xchk_setup_fs,
.scrub = xchk_agi,
.repair = xrep_notsupported,
},
[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_b
|