From a56371865e7870d953d3837aaa1d12230bba021d Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 17 Oct 2017 21:37:35 -0700 Subject: [PATCH] xfs: dispatch metadata scrub subcommands Create structures needed to hold scrubbing context and dispatch incoming commands to the individual scrubbers. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner --- fs/xfs/scrub/scrub.c | 196 ++++++++++++++++++++++++++++++++++++++++++- fs/xfs/scrub/scrub.h | 24 ++++++ fs/xfs/scrub/trace.h | 43 ++++++++++ 3 files changed, 262 insertions(+), 1 deletion(-) diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c index 5db2a6f10fb2..1fc8d3b43902 100644 --- a/fs/xfs/scrub/scrub.c +++ b/fs/xfs/scrub/scrub.c @@ -44,11 +44,205 @@ #include "scrub/scrub.h" #include "scrub/trace.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. + */ + +/* Scrub setup and teardown */ + +/* Free all the resources and finish the transactions. */ +STATIC int +xfs_scrub_teardown( + struct xfs_scrub_context *sc, + int error) +{ + if (sc->tp) { + xfs_trans_cancel(sc->tp); + sc->tp = NULL; + } + return error; +} + +/* Scrubbing dispatch. */ + +static const struct xfs_scrub_meta_ops meta_scrub_ops[] = { +}; + +/* 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!"); +} + /* Dispatch metadata scrubbing. */ int xfs_scrub_metadata( struct xfs_inode *ip, struct xfs_scrub_metadata *sm) { - return -EOPNOTSUPP; + struct xfs_scrub_context sc; + struct xfs_mount *mp = ip->i_mount; + const struct xfs_scrub_meta_ops *ops; + bool try_harder = false; + int error = 0; + + 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; + + /* Check our inputs. */ + error = -EINVAL; + sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT; + if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN) + goto out; + if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved))) + goto out; + + /* Do we know about this type of metadata? */ + error = -ENOENT; + if (sm->sm_type >= XFS_SCRUB_TYPE_NR) + goto out; + ops = &meta_scrub_ops[sm->sm_type]; + if (ops->scrub == NULL) + goto out; + + /* + * 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. + */ + error = -EOPNOTSUPP; + if (!xfs_sb_version_hasextflgbit(&mp->m_sb)) + goto out; + + /* Does this fs even support this type of metadata? */ + error = -ENOENT; + if (ops->has && !ops->has(&mp->m_sb)) + goto out; + + /* We don't know how to repair anything yet. */ + error = -EOPNOTSUPP; + if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) + 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 = ops; + sc.try_harder = try_harder; + 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, 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, 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; } diff --git a/fs/xfs/scrub/scrub.h b/fs/xfs/scrub/scrub.h index eb1cd9dde868..ef7b50e33c93 100644 --- a/fs/xfs/scrub/scrub.h +++ b/fs/xfs/scrub/scrub.h @@ -20,6 +20,30 @@ #ifndef __XFS_SCRUB_SCRUB_H__ #define __XFS_SCRUB_SCRUB_H__ +struct xfs_scrub_context; + +struct xfs_scrub_meta_ops { + /* Acquire whatever resources are needed for the operation. */ + int (*setup)(struct xfs_scrub_context *, + struct xfs_inode *); + + /* Examine metadata for errors. */ + int (*scrub)(struct xfs_scrub_context *); + + /* Decide if we even have this piece of metadata. */ + bool (*has)(struct xfs_sb *); +}; + +struct xfs_scrub_context { + /* General scrub state. */ + struct xfs_mount *mp; + struct xfs_scrub_metadata *sm; + const struct xfs_scrub_meta_ops *ops; + struct xfs_trans *tp; + struct xfs_inode *ip; + bool try_harder; +}; + /* Metadata scrubbers */ #endif /* __XFS_SCRUB_SCRUB_H__ */ diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h index a95a7c836dea..688517e0a0cb 100644 --- a/fs/xfs/scrub/trace.h +++ b/fs/xfs/scrub/trace.h @@ -25,6 +25,49 @@ #include +DECLARE_EVENT_CLASS(xfs_scrub_class, + TP_PROTO(struct xfs_inode *ip, struct xfs_scrub_metadata *sm, + int error), + TP_ARGS(ip, sm, error), + TP_STRUCT__entry( + __field(dev_t, dev) + __field(xfs_ino_t, ino) + __field(unsigned int, type) + __field(xfs_agnumber_t, agno) + __field(xfs_ino_t, inum) + __field(unsigned int, gen) + __field(unsigned int, flags) + __field(int, error) + ), + TP_fast_assign( + __entry->dev = ip->i_mount->m_super->s_dev; + __entry->ino = ip->i_ino; + __entry->type = sm->sm_type; + __entry->agno = sm->sm_agno; + __entry->inum = sm->sm_ino; + __entry->gen = sm->sm_gen; + __entry->flags = sm->sm_flags; + __entry->error = error; + ), + TP_printk("dev %d:%d ino %llu type %u agno %u inum %llu gen %u flags 0x%x error %d", + MAJOR(__entry->dev), MINOR(__entry->dev), + __entry->ino, + __entry->type, + __entry->agno, + __entry->inum, + __entry->gen, + __entry->flags, + __entry->error) +) +#define DEFINE_SCRUB_EVENT(name) \ +DEFINE_EVENT(xfs_scrub_class, name, \ + TP_PROTO(struct xfs_inode *ip, struct xfs_scrub_metadata *sm, \ + int error), \ + TP_ARGS(ip, sm, error)) + +DEFINE_SCRUB_EVENT(xfs_scrub_start); +DEFINE_SCRUB_EVENT(xfs_scrub_done); + #endif /* _TRACE_XFS_SCRUB_TRACE_H */ #undef TRACE_INCLUDE_PATH