Commit a5637186 authored by Darrick J. Wong's avatar Darrick J. Wong

xfs: dispatch metadata scrub subcommands

Create structures needed to hold scrubbing context and dispatch incoming
commands to the individual scrubbers.
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
parent 36fd6e86
......@@ -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;
}
......@@ -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__ */
......@@ -25,6 +25,49 @@
#include <linux/tracepoint.h>
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
......
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