2 * Copyright (C) 2017 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version 2
9 * of the License, or (at your option) any later version.
11 * This program is distributed in the hope that it would be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
22 #include "xfs_shared.h"
23 #include "xfs_format.h"
24 #include "xfs_trans_resv.h"
25 #include "xfs_mount.h"
26 #include "xfs_defer.h"
27 #include "xfs_btree.h"
29 #include "xfs_log_format.h"
30 #include "xfs_trans.h"
32 #include "xfs_inode.h"
33 #include "xfs_alloc.h"
34 #include "xfs_alloc_btree.h"
36 #include "xfs_bmap_btree.h"
37 #include "xfs_ialloc.h"
38 #include "xfs_ialloc_btree.h"
39 #include "xfs_refcount.h"
40 #include "xfs_refcount_btree.h"
42 #include "xfs_rmap_btree.h"
43 #include "scrub/xfs_scrub.h"
44 #include "scrub/scrub.h"
45 #include "scrub/common.h"
46 #include "scrub/trace.h"
47 #include "scrub/scrub.h"
48 #include "scrub/btree.h"
51 * Online Scrub and Repair
53 * Traditionally, XFS (the kernel driver) did not know how to check or
54 * repair on-disk data structures. That task was left to the xfs_check
55 * and xfs_repair tools, both of which require taking the filesystem
56 * offline for a thorough but time consuming examination. Online
57 * scrub & repair, on the other hand, enables us to check the metadata
58 * for obvious errors while carefully stepping around the filesystem's
59 * ongoing operations, locking rules, etc.
61 * Given that most XFS metadata consist of records stored in a btree,
62 * most of the checking functions iterate the btree blocks themselves
63 * looking for irregularities. When a record block is encountered, each
64 * record can be checked for obviously bad values. Record values can
65 * also be cross-referenced against other btrees to look for potential
66 * misunderstandings between pieces of metadata.
68 * It is expected that the checkers responsible for per-AG metadata
69 * structures will lock the AG headers (AGI, AGF, AGFL), iterate the
70 * metadata structure, and perform any relevant cross-referencing before
71 * unlocking the AG and returning the results to userspace. These
72 * scrubbers must not keep an AG locked for too long to avoid tying up
73 * the block and inode allocators.
75 * Block maps and b-trees rooted in an inode present a special challenge
76 * because they can involve extents from any AG. The general scrubber
77 * structure of lock -> check -> xref -> unlock still holds, but AG
78 * locking order rules /must/ be obeyed to avoid deadlocks. The
79 * ordering rule, of course, is that we must lock in increasing AG
80 * order. Helper functions are provided to track which AG headers we've
81 * already locked. If we detect an imminent locking order violation, we
82 * can signal a potential deadlock, in which case the scrubber can jump
83 * out to the top level, lock all the AGs in order, and retry the scrub.
85 * For file data (directories, extended attributes, symlinks) scrub, we
86 * can simply lock the inode and walk the data. For btree data
87 * (directories and attributes) we follow the same btree-scrubbing
88 * strategy outlined previously to check the records.
90 * We use a bit of trickery with transactions to avoid buffer deadlocks
91 * if there is a cycle in the metadata. The basic problem is that
92 * travelling down a btree involves locking the current buffer at each
93 * tree level. If a pointer should somehow point back to a buffer that
94 * we've already examined, we will deadlock due to the second buffer
95 * locking attempt. Note however that grabbing a buffer in transaction
96 * context links the locked buffer to the transaction. If we try to
97 * re-grab the buffer in the context of the same transaction, we avoid
98 * the second lock attempt and continue. Between the verifier and the
99 * scrubber, something will notice that something is amiss and report
100 * the corruption. Therefore, each scrubber will allocate an empty
101 * transaction, attach buffers to it, and cancel the transaction at the
102 * end of the scrub run. Cancelling a non-dirty transaction simply
103 * unlocks the buffers.
105 * There are four pieces of data that scrub can communicate to
106 * userspace. The first is the error code (errno), which can be used to
107 * communicate operational errors in performing the scrub. There are
108 * also three flags that can be set in the scrub context. If the data
109 * structure itself is corrupt, the CORRUPT flag will be set. If
110 * the metadata is correct but otherwise suboptimal, the PREEN flag
115 * Scrub probe -- userspace uses this to probe if we're willing to scrub
116 * or repair a given mountpoint. This will be used by xfs_scrub to
117 * probe the kernel's abilities to scrub (and repair) the metadata. We
118 * do this by validating the ioctl inputs from userspace, preparing the
119 * filesystem for a scrub (or a repair) operation, and immediately
120 * returning to userspace. Userspace can use the returned errno and
121 * structure state to decide (in broad terms) if scrub/repair are
122 * supported by the running kernel.
126 struct xfs_scrub_context *sc)
130 if (sc->sm->sm_ino || sc->sm->sm_agno)
132 if (xfs_scrub_should_terminate(sc, &error))
138 /* Scrub setup and teardown */
140 /* Free all the resources and finish the transactions. */
143 struct xfs_scrub_context *sc,
146 xfs_scrub_ag_free(sc, &sc->sa);
148 xfs_trans_cancel(sc->tp);
154 /* Scrubbing dispatch. */
156 static const struct xfs_scrub_meta_ops meta_scrub_ops[] = {
157 { /* ioctl presence test */
158 .setup = xfs_scrub_setup_fs,
159 .scrub = xfs_scrub_probe,
162 .setup = xfs_scrub_setup_ag_header,
163 .scrub = xfs_scrub_superblock,
166 .setup = xfs_scrub_setup_ag_header,
167 .scrub = xfs_scrub_agf,
170 .setup = xfs_scrub_setup_ag_header,
171 .scrub = xfs_scrub_agfl,
174 .setup = xfs_scrub_setup_ag_header,
175 .scrub = xfs_scrub_agi,
178 .setup = xfs_scrub_setup_ag_allocbt,
179 .scrub = xfs_scrub_bnobt,
182 .setup = xfs_scrub_setup_ag_allocbt,
183 .scrub = xfs_scrub_cntbt,
186 .setup = xfs_scrub_setup_ag_iallocbt,
187 .scrub = xfs_scrub_inobt,
190 .setup = xfs_scrub_setup_ag_iallocbt,
191 .scrub = xfs_scrub_finobt,
192 .has = xfs_sb_version_hasfinobt,
195 .setup = xfs_scrub_setup_ag_rmapbt,
196 .scrub = xfs_scrub_rmapbt,
197 .has = xfs_sb_version_hasrmapbt,
200 .setup = xfs_scrub_setup_ag_refcountbt,
201 .scrub = xfs_scrub_refcountbt,
202 .has = xfs_sb_version_hasreflink,
206 /* This isn't a stable feature, warn once per day. */
208 xfs_scrub_experimental_warning(
209 struct xfs_mount *mp)
211 static struct ratelimit_state scrub_warning = RATELIMIT_STATE_INIT(
212 "xfs_scrub_warning", 86400 * HZ, 1);
213 ratelimit_set_flags(&scrub_warning, RATELIMIT_MSG_ON_RELEASE);
215 if (__ratelimit(&scrub_warning))
217 "EXPERIMENTAL online scrub feature in use. Use at your own risk!");
220 /* Dispatch metadata scrubbing. */
223 struct xfs_inode *ip,
224 struct xfs_scrub_metadata *sm)
226 struct xfs_scrub_context sc;
227 struct xfs_mount *mp = ip->i_mount;
228 const struct xfs_scrub_meta_ops *ops;
229 bool try_harder = false;
232 trace_xfs_scrub_start(ip, sm, error);
234 /* Forbidden if we are shut down or mounted norecovery. */
236 if (XFS_FORCED_SHUTDOWN(mp))
238 error = -ENOTRECOVERABLE;
239 if (mp->m_flags & XFS_MOUNT_NORECOVERY)
242 /* Check our inputs. */
244 sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
245 if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN)
247 if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved)))
250 /* Do we know about this type of metadata? */
252 if (sm->sm_type >= XFS_SCRUB_TYPE_NR)
254 ops = &meta_scrub_ops[sm->sm_type];
255 if (ops->scrub == NULL)
259 * We won't scrub any filesystem that doesn't have the ability
260 * to record unwritten extents. The option was made default in
261 * 2003, removed from mkfs in 2007, and cannot be disabled in
262 * v5, so if we find a filesystem without this flag it's either
263 * really old or totally unsupported. Avoid it either way.
264 * We also don't support v1-v3 filesystems, which aren't
268 if (!xfs_sb_version_hasextflgbit(&mp->m_sb))
271 /* Does this fs even support this type of metadata? */
273 if (ops->has && !ops->has(&mp->m_sb))
276 /* We don't know how to repair anything yet. */
278 if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
281 xfs_scrub_experimental_warning(mp);
284 /* Set up for the operation. */
285 memset(&sc, 0, sizeof(sc));
289 sc.try_harder = try_harder;
290 sc.sa.agno = NULLAGNUMBER;
291 error = sc.ops->setup(&sc, ip);
295 /* Scrub for errors. */
296 error = sc.ops->scrub(&sc);
297 if (!try_harder && error == -EDEADLOCK) {
299 * Scrubbers return -EDEADLOCK to mean 'try harder'.
300 * Tear down everything we hold, then set up again with
301 * preparation for worst-case scenarios.
303 error = xfs_scrub_teardown(&sc, 0);
311 if (sc.sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
312 XFS_SCRUB_OFLAG_XCORRUPT))
313 xfs_alert_ratelimited(mp, "Corruption detected during scrub.");
316 error = xfs_scrub_teardown(&sc, error);
318 trace_xfs_scrub_done(ip, sm, error);
319 if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
320 sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;