Re: [PATCH 2/9] xfs: report ag header corruption errors to the health tracking system

Darrick J. Wong
2019-11-22T18:10:18Z

On Fri, Nov 22, 2019 at 06:57:00AM -0500, Brian Foster wrote:
> On Thu, Nov 21, 2019 at 04:53:13PM -0800, Darrick J. Wong wrote:
> > On Thu, Nov 21, 2019 at 08:26:03AM -0500, Brian Foster wrote:
> > > On Wed, Nov 20, 2019 at 08:43:23AM -0800, Darrick J. Wong wrote:
> > > > On Wed, Nov 20, 2019 at 09:20:47AM -0500, Brian Foster wrote:
> > > > > On Thu, Nov 14, 2019 at 10:19:26AM -0800, Darrick J. Wong wrote:
> > > > > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > > > >
> > > > > > Whenever we encounter a corrupt AG header, we should report that to the
> > > > > > health monitoring system for later reporting.
> > > > > >
> > > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > > > > ---
> > > > > > fs/xfs/libxfs/xfs_alloc.c | 6 ++++++
> > > > > > fs/xfs/libxfs/xfs_health.h | 6 ++++++
> > > > > > fs/xfs/libxfs/xfs_ialloc.c | 3 +++
> > > > > > fs/xfs/libxfs/xfs_refcount.c | 5 ++++-
> > > > > > fs/xfs/libxfs/xfs_rmap.c | 5 ++++-
> > > > > > fs/xfs/libxfs/xfs_sb.c | 2 ++
> > > > > > fs/xfs/xfs_health.c | 17 +++++++++++++++++
> > > > > > fs/xfs/xfs_inode.c | 9 +++++++++
> > > > > > 8 files changed, 51 insertions(+), 2 deletions(-)
> > > > > >
> > > > > >
> > > > > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> > > > > > index c284e10af491..e75e3ae6c912 100644
> > > > > > --- a/fs/xfs/libxfs/xfs_alloc.c
> > > > > > +++ b/fs/xfs/libxfs/xfs_alloc.c
> > > > > > @@ -26,6 +26,7 @@
> > > > > > #include "xfs_log.h"
> > > > > > #include "xfs_ag_resv.h"
> > > > > > #include "xfs_bmap.h"
> > > > > > +#include "xfs_health.h"
> > > > > >
> > > > > > extern kmem_zone_t *xfs_bmap_free_item_zone;
> > > > > >
> > > > > > @@ -699,6 +700,8 @@ xfs_alloc_read_agfl(
> > > > > > mp, tp, mp->m_ddev_targp,
> > > > > > XFS_AG_DADDR(mp, agno, XFS_AGFL_DADDR(mp)),
> > > > > > XFS_FSS_TO_BB(mp, 1), 0, &bp, &xfs_agfl_buf_ops);
> > > > > > + if (xfs_metadata_is_sick(error))
> > > > > > + xfs_agno_mark_sick(mp, agno, XFS_SICK_AG_AGFL);
> > > > >
> > > > > Any reason we couldn't do some of these in verifiers? I'm assuming we'd
> > > > > still need calls in various external corruption checks, but at least we
> > > > > wouldn't add a requirement to check all future buffer reads, etc.
> > > >
> > > > I thought about that. It would be wonderful if C had a syntactically
> > > > slick method to package a function + execution scope and pass that
> > > > through other functions to be called later. :)
> > > >
> > > > For the per-AG stuff it wouldn't be hard to make the verifier functions
> > > > derive the AG number and call xfs_agno_mark_sick directly in the
> > > > verifier. For per-inode metadata, we'd have to find a way to pass the
> > > > struct xfs_inode pointer to the verifier, which means that we'd have to
> > > > add that to struct xfs_buf.
> > > >
> > > > xfs_buf is ~384 bytes so maybe adding another pointer for read context
> > > > wouldn't be terrible? That would add a fair amount of ugly special
> > > > casing in the btree code to decide if we have an inode to pass through,
> > > > though it would solve the problem of the bmbt verifier not being able to
> > > > check the owner field in the btree block header.
> > > >
> > > > OTOH that's 8 bytes of overhead that we can never get rid of even though
> > > > we only really need it the first time the buffer gets read in from disk.
> > > >
> > > > Thoughts?
> > > >
> > >
> > > That doesn't seem too unreasonable, but I guess I'd have to think about
> > > it some more. Maybe it's worth defining a private pointer in the buffer
> > > that callers can use to pass specific context to verifiers for health
> > > processing. I suppose such a field could also be conditionally defined
> > > on scrub enabled kernels (at least initially), so the overhead would be
> > > opt-in.
> >
> > Looking further into this, what if we could did something like the
> > following:
> >
> > struct xfs_buf_verify {
> > const struct xfs_buf_ops *ops;
> > struct xfs_inode *ip;
> > unsigned int sick_flags;
> > /* whatever else */
> > };
> >
> > ...then we change the _read_buf and _trans_read_buf functions to take as
> > the final argument a (struct xfs_buf_verify *). In the xfs_buf_reverify
> > cases, we can pass this context straight through to the ->read_verify
> > function.
> >
> > To handle the !DONE case where the buffer read completion can happen
> > asynchronously, we change the b_ops field definition to:
> >
> > union {
> > struct xfs_buf_ops *b_ops;
> > struct xfs_buf_verify *b_vctx;
> > };
> >
> > Next we define a new XBF_HAVE_VERIFY_CTX flag that means b_vctx is
> > active and not ops. xfs_buf_read_map can set the flag and b_vctx for
> > any synchronous (!XBF_ASYNC) read because we know the caller will be
> > asleep waiting for b_iowait and therefore cannot kill the verifier
> > context structure. Once we get to xfs_buf_ioend we can set b_ops, drop
> > the XBF_H_V_C flag, and call ->verify_read.
> >
> > Now we actually /can/ pass the inode pointer into the verifier, along
> > with pretty much anything else we can think of.
> >
> > Does that sound reasonable? Or totally heinous? :)
> >
>
> That sounds reasonable to me and potentially a nice way to mitigate
> additional overhead. I suppose we'd also need a means to abstract the
> various contextual data fed into the type-specific verifiers (i.e., does
> the verifier care about inode health state? perag? both?).

For an initial RFC I think I could start with adding some trivial
helpers to initialize the xfs_buf_verify structure, so that it's a
little more obvious what the intended usage patterns are.

> Would you
> plan to do that with higher level wrappers and/or perhaps use similar
> union/flag magic in the xfs_buf_verify context to indicate which state
> an instance happens to provide? It might be worth a quick and dirty RFC
> to answer these questions with a couple examples and get any API
> feedback before running through the full set of verifiers..

Yeah. I think I'll do a quick RFC to implement the bmbt owner check or
something.

--D

> Brian
>
> > > Anyways, I think for this series it might be reasonable to push things
> > > down into verifiers opportunistically where we can do so without any
> > > core mechanism changes. We can follow up with changes to do the rest if
> > > we can come up with something elegant.
> >
> > Ok. I think I will try to implement such a beast for 5.6 and then put
> > this series after it.
> >
> > > > > > if (error)
> > > > > > return error;
> > > > > > xfs_buf_set_ref(bp, XFS_AGFL_REF);
> > > > > > @@ -722,6 +725,7 @@ xfs_alloc_update_counters(
> > > > > > if (unlikely(be32_to_cpu(agf->agf_freeblks) >
> > > > > > be32_to_cpu(agf->agf_length))) {
> > > > > > xfs_buf_corruption_error(agbp);
> > > > > > + xfs_ag_mark_sick(pag, XFS_SICK_AG_AGF);
> > > > > > return -EFSCORRUPTED;
> > > > > > }
> > > > > >
> > > > > > @@ -2952,6 +2956,8 @@ xfs_read_agf(
> > > > > > mp, tp, mp->m_ddev_targp,
> > > > > > XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
> > > > > > XFS_FSS_TO_BB(mp, 1), flags, bpp, &xfs_agf_buf_ops);
> > > > > > + if (xfs_metadata_is_sick(error))
> > > > > > + xfs_agno_mark_sick(mp, agno, XFS_SICK_AG_AGF);
> > > > > > if (error)
> > > > > > return error;
> > > > > > if (!*bpp)
> > > > > > diff --git a/fs/xfs/libxfs/xfs_health.h b/fs/xfs/libxfs/xfs_health.h
> > > > > > index 3657a9cb8490..ce8954a10c66 100644
> > > > > > --- a/fs/xfs/libxfs/xfs_health.h
> > > > > > +++ b/fs/xfs/libxfs/xfs_health.h
> > > > > > @@ -123,6 +123,8 @@ void xfs_rt_mark_healthy(struct xfs_mount *mp, unsigned int mask);
> > > > > > void xfs_rt_measure_sickness(struct xfs_mount *mp, unsigned int *sick,
> > > > > > unsigned int *checked);
> > > > > >
> > > > > > +void xfs_agno_mark_sick(struct xfs_mount *mp, xfs_agnumber_t agno,
> > > > > > + unsigned int mask);
> > > > > > void xfs_ag_mark_sick(struct xfs_perag *pag, unsigned int mask);
> > > > > > void xfs_ag_mark_checked(struct xfs_perag *pag, unsigned int mask);
> > > > > > void xfs_ag_mark_healthy(struct xfs_perag *pag, unsigned int mask);
> > > > > > @@ -203,4 +205,8 @@ void xfs_fsop_geom_health(struct xfs_mount *mp, struct xfs_fsop_geom *geo);
> > > > > > void xfs_ag_geom_health(struct xfs_perag *pag, struct xfs_ag_geometry *ageo);
> > > > > > void xfs_bulkstat_health(struct xfs_inode *ip, struct xfs_bulkstat *bs);
> > > > > >
> > > > > > +#define xfs_metadata_is_sick(error) \
> > > > > > + (unlikely((error) == -EFSCORRUPTED || (error) == -EIO || \
> > > > > > + (error) == -EFSBADCRC))
> > > > >
> > > > > Why is -EIO considered sick? My understanding is that once something is
> > > > > marked sick, scrub is the only way to clear that state. -EIO can be
> > > > > transient, so afaict that means we could mark a persistent in-core state
> > > > > based on a transient/resolved issue.
> > > >
> > > > I think it sounds reasonable that if the fs hits a metadata IO error
> > > > then the administrator should scrub that data structure to make sure
> > > > it's ok, and if so, clear the sick state.
> > > >
> > >
> > > I'm not totally convinced... I thought we had configurations where I/O
> > > errors can be reasonably expected and recovered from. For example,
> > > consider the thin provisioning + infinite metadata writeback error retry
> > > mechanism. IIRC, the whole purpose of that was to facilitate the use
> > > case where the thin pool runs out of space, but the admin wants some
> > > window of time to expand and keep the filesystem alive.
> >
> > Aha, I just realized that it's not clear from the macro definition that
> > I was only intending it to be called from the read path.
> >
> > Though I guess there's always the possibility that the PFY trips over
> > the PCIE cable in the datacenter and XFS hits an EIO, but the disk will
> > be fine a moment later when he shoves it back in. The disk media is
> > fine, and by that point either we returned read error to userspace or
> > the transaction got cancelled and it's too late to do anything anyway.
> >
> > I'll drop the EIO check for now and we'll see if I get around to
> > revisiting it.
> >
> > > I don't necessarily think it's a bad thing to suggest a scrub any time
> > > errors have occurred, but for something like the above where an
> > > environment may have been thoroughly tested and verified through that
> > > particular error->expand sequence, it seems that flagging bits as sick
> > > might be unnecessarily ominous.
> >
> > <shrug> Yeah, (sick && !checked) is a weird passive-aggressive state
> > like that.
> >
> > > > Though I realized just now that if scrub isn't enabled then it's an
> > > > unfixable dead end so the EIO check should be gated on
> > > > CONFIG_XFS_ONLINE_SCRUB=y.
> > > >
> > >
> > > Yeah, that was my initial concern..
> > >
> > > > > Along similar lines, what's the expected behavior in the event of any of
> > > > > these errors for a kernel that might not support
> > > > > CONFIG_XFS_ONLINE_[SCRUB|REPAIR]? Just set the states that are never
> > > > > used for anything? If so, that seems Ok I suppose.. but it's a little
> > > > > awkward if we'd see the tracepoints and such associated with the state
> > > > > changes.
> > > >
> > > > Even if scrub is disabled, the kernel will still set the sick state, and
> > > > later the administrator can query the filesystem with xfs_spaceman to
> > > > observe that sick state.
> > > >
> > >
> > > Ok, so it's intended to be a valid health state independent of scrub.
> > > That seems reasonable in principle and can always be used to indicate
> > > offline repair is necessary too.
> >
> > Yes.
> >
> > > > In the future, I will also use the per-AG sick states to steer
> > > > allocations away from known problematic AGs to try to avoid
> > > > unexpected shutdown in the middle of a transaction.
> > > >
> > >
> > > Hmm.. I'm a little curious about how much we should steer away from
> > > traditional behavior on kernels that might not support scrub. I suppose
> > > I could see arguments for going either way, but this is getting a bit
> > > ahead of this patch anyways. ;)
> >
> > Yeah. I /do/ have prototype patches buried in my dev tree but they are
> > too ugly not to let all the magic smoke out. What really happens is
> > that when we hit a corruption error, we mark the AG as offline. Then
> > the sysadmin can run xfs_scrub to fix it (which would set th AG back
> > online) or I guess we could have a spaceman -x command to force it back
> > online.
> >
> > I always build in /some/ kind of manual override somewhere... :)
> >
> > --D
> >
> > > Brian
> > >
> > > > --D
> > > >
> > > > >
> > > > > Brian
> > > > >
> > > > > > +
> > > > > > #endif /* __XFS_HEALTH_H__ */
> > > > > > diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> > > > > > index 988cde7744e6..c401512a4350 100644
> > > > > > --- a/fs/xfs/libxfs/xfs_ialloc.c
> > > > > > +++ b/fs/xfs/libxfs/xfs_ialloc.c
> > > > > > @@ -27,6 +27,7 @@
> > > > > > #include "xfs_trace.h"
> > > > > > #include "xfs_log.h"
> > > > > > #include "xfs_rmap.h"
> > > > > > +#include "xfs_health.h"
> > > > > >
> > > > > > /*
> > > > > > * Lookup a record by ino in the btree given by cur.
> > > > > > @@ -2635,6 +2636,8 @@ xfs_read_agi(
> > > > > > error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
> > > > > > XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
> > > > > > XFS_FSS_TO_BB(mp, 1), 0, bpp, &xfs_agi_buf_ops);
> > > > > > + if (xfs_metadata_is_sick(error))
> > > > > > + xfs_agno_mark_sick(mp, agno, XFS_SICK_AG_AGI);
> > > > > > if (error)
> > > > > > return error;
> > > > > > if (tp)
> > > > > > diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c
> > > > > > index d7d702ee4d1a..25c87834e42a 100644
> > > > > > --- a/fs/xfs/libxfs/xfs_refcount.c
> > > > > > +++ b/fs/xfs/libxfs/xfs_refcount.c
> > > > > > @@ -22,6 +22,7 @@
> > > > > > #include "xfs_bit.h"
> > > > > > #include "xfs_refcount.h"
> > > > > > #include "xfs_rmap.h"
> > > > > > +#include "xfs_health.h"
> > > > > >
> > > > > > /* Allowable refcount adjustment amounts. */
> > > > > > enum xfs_refc_adjust_op {
> > > > > > @@ -1177,8 +1178,10 @@ xfs_refcount_finish_one(
> > > > > > XFS_ALLOC_FLAG_FREEING, &agbp);
> > > > > > if (error)
> > > > > > return error;
> > > > > > - if (XFS_IS_CORRUPT(tp->t_mountp, !agbp))
> > > > > > + if (XFS_IS_CORRUPT(tp->t_mountp, !agbp)) {
> > > > > > + xfs_agno_mark_sick(tp->t_mountp, agno, XFS_SICK_AG_AGF);
> > > > > > return -EFSCORRUPTED;
> > > > > > + }
> > > > > >
> > > > > > rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno);
> > > > > > if (!rcur) {
> > > > > > diff --git a/fs/xfs/libxfs/xfs_rmap.c b/fs/xfs/libxfs/xfs_rmap.c
> > > > > > index ff9412f113c4..a54a3c129cce 100644
> > > > > > --- a/fs/xfs/libxfs/xfs_rmap.c
> > > > > > +++ b/fs/xfs/libxfs/xfs_rmap.c
> > > > > > @@ -21,6 +21,7 @@
> > > > > > #include "xfs_errortag.h"
> > > > > > #include "xfs_error.h"
> > > > > > #include "xfs_inode.h"
> > > > > > +#include "xfs_health.h"
> > > > > >
> > > > > > /*
> > > > > > * Lookup the first record less than or equal to [bno, len, owner, offset]
> > > > > > @@ -2400,8 +2401,10 @@ xfs_rmap_finish_one(
> > > > > > error = xfs_free_extent_fix_freelist(tp, agno, &agbp);
> > > > > > if (error)
> > > > > > return error;
> > > > > > - if (XFS_IS_CORRUPT(tp->t_mountp, !agbp))
> > > > > > + if (XFS_IS_CORRUPT(tp->t_mountp, !agbp)) {
> > > > > > + xfs_agno_mark_sick(tp->t_mountp, agno, XFS_SICK_AG_AGF);
> > > > > > return -EFSCORRUPTED;
> > > > > > + }
> > > > > >
> > > > > > rcur = xfs_rmapbt_init_cursor(mp, tp, agbp, agno);
> > > > > > if (!rcur) {
> > > > > > diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
> > > > > > index 0ac69751fe85..4a923545465d 100644
> > > > > > --- a/fs/xfs/libxfs/xfs_sb.c
> > > > > > +++ b/fs/xfs/libxfs/xfs_sb.c
> > > > > > @@ -1169,6 +1169,8 @@ xfs_sb_read_secondary(
> > > > > > error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
> > > > > > XFS_AG_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
> > > > > > XFS_FSS_TO_BB(mp, 1), 0, &bp, &xfs_sb_buf_ops);
> > > > > > + if (xfs_metadata_is_sick(error))
> > > > > > + xfs_agno_mark_sick(mp, agno, XFS_SICK_AG_SB);
> > > > > > if (error)
> > > > > > return error;
> > > > > > xfs_buf_set_ref(bp, XFS_SSB_REF);
> > > > > > diff --git a/fs/xfs/xfs_health.c b/fs/xfs/xfs_health.c
> > > > > > index 860dc70c99e7..36c32b108b39 100644
> > > > > > --- a/fs/xfs/xfs_health.c
> > > > > > +++ b/fs/xfs/xfs_health.c
> > > > > > @@ -200,6 +200,23 @@ xfs_rt_measure_sickness(
> > > > > > spin_unlock(&mp->m_sb_lock);
> > > > > > }
> > > > > >
> > > > > > +/* Mark unhealthy per-ag metadata given a raw AG number. */
> > > > > > +void
> > > > > > +xfs_agno_mark_sick(
> > > > > > + struct xfs_mount *mp,
> > > > > > + xfs_agnumber_t agno,
> > > > > > + unsigned int mask)
> > > > > > +{
> > > > > > + struct xfs_perag *pag = xfs_perag_get(mp, agno);
> > > > > > +
> > > > > > + /* per-ag structure not set up yet? */
> > > > > > + if (!pag)
> > > > > > + return;
> > > > > > +
> > > > > > + xfs_ag_mark_sick(pag, mask);
> > > > > > + xfs_perag_put(pag);
> > > > > > +}
> > > > > > +
> > > > > > /* Mark unhealthy per-ag metadata. */
> > > > > > void
> > > > > > xfs_ag_mark_sick(
> > > > > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > > > > > index 401da197f012..a2812cea748d 100644
> > > > > > --- a/fs/xfs/xfs_inode.c
> > > > > > +++ b/fs/xfs/xfs_inode.c
> > > > > > @@ -35,6 +35,7 @@
> > > > > > #include "xfs_log.h"
> > > > > > #include "xfs_bmap_btree.h"
> > > > > > #include "xfs_reflink.h"
> > > > > > +#include "xfs_health.h"
> > > > > >
> > > > > > kmem_zone_t *xfs_inode_zone;
> > > > > >
> > > > > > @@ -787,6 +788,8 @@ xfs_ialloc(
> > > > > > */
> > > > > > if ((pip && ino == pip->i_ino) || !xfs_verify_dir_ino(mp, ino)) {
> > > > > > xfs_alert(mp, "Allocated a known in-use inode 0x%llx!", ino);
> > > > > > + xfs_agno_mark_sick(mp, XFS_INO_TO_AGNO(mp, ino),
> > > > > > + XFS_SICK_AG_INOBT);
> > > > > > return -EFSCORRUPTED;
> > > > > > }
> > > > > >
> > > > > > @@ -2137,6 +2140,7 @@ xfs_iunlink_update_bucket(
> > > > > > */
> > > > > > if (old_value == new_agino) {
> > > > > > xfs_buf_corruption_error(agibp);
> > > > > > + xfs_agno_mark_sick(tp->t_mountp, agno, XFS_SICK_AG_AGI);
> > > > > > return -EFSCORRUPTED;
> > > > > > }
> > > > > >
> > > > > > @@ -2203,6 +2207,7 @@ xfs_iunlink_update_inode(
> > > > > > if (!xfs_verify_agino_or_null(mp, agno, old_value)) {
> > > > > > xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__, dip,
> > > > > > sizeof(*dip), __this_address);
> > > > > > + xfs_inode_mark_sick(ip, XFS_SICK_INO_CORE);
> > > > > > error = -EFSCORRUPTED;
> > > > > > goto out;
> > > > > > }
> > > > > > @@ -2217,6 +2222,7 @@ xfs_iunlink_update_inode(
> > > > > > if (next_agino != NULLAGINO) {
> > > > > > xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__,
> > > > > > dip, sizeof(*dip), __this_address);
> > > > > > + xfs_inode_mark_sick(ip, XFS_SICK_INO_CORE);
> > > > > > error = -EFSCORRUPTED;
> > > > > > }
> > > > > > goto out;
> > > > > > @@ -2271,6 +2277,7 @@ xfs_iunlink(
> > > > > > if (next_agino == agino ||
> > > > > > !xfs_verify_agino_or_null(mp, agno, next_agino)) {
> > > > > > xfs_buf_corruption_error(agibp);
> > > > > > + xfs_agno_mark_sick(mp, agno, XFS_SICK_AG_AGI);
> > > > > > return -EFSCORRUPTED;
> > > > > > }
> > > > > >
> > > > > > @@ -2408,6 +2415,7 @@ xfs_iunlink_map_prev(
> > > > > > XFS_CORRUPTION_ERROR(__func__,
> > > > > > XFS_ERRLEVEL_LOW, mp,
> > > > > > *dipp, sizeof(**dipp));
> > > > > > + xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI);
> > > > > > error = -EFSCORRUPTED;
> > > > > > return error;
> > > > > > }
> > > > > > @@ -2454,6 +2462,7 @@ xfs_iunlink_remove(
> > > > > > if (!xfs_verify_agino(mp, agno, head_agino)) {
> > > > > > XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
> > > > > > agi, sizeof(*agi));
> > > > > > + xfs_agno_mark_sick(mp, agno, XFS_SICK_AG_AGI);
> > > > > > return -EFSCORRUPTED;
> > > > > > }
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>