On Mon, Jul 30, 2018 at 10:22:16AM -0700, Darrick J. Wong wrote:
> On Mon, Jul 30, 2018 at 12:25:24PM -0400, Brian Foster wrote:
> > On Sun, Jul 29, 2018 at 10:48:08PM -0700, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > >
> > > Repair the AGFL from the rmap data.
> > >
> > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > ---
> >
> > FWIW, I tried tweaking a couple agfl values via xfs_db and xfs_scrub
> > seems to always dump a cross-referencing failed error and not want to
> > deal with it. Expected? Is there a good way to unit test some of this
> > stuff with simple/localized corruptions?
>
> I usually pick one of the corruptions from xfs/355...
>
> $ SCRATCH_XFS_LIST_FUZZ_VERBS=random \
> SCRATCH_XFS_LIST_METADATA_FIELDS=somefield \
> ./check xfs/355
>
It looks like similar behavior if I do that, but tbh I'm not sure if I'm
using this correctly. E.g., if I do:
# SCRATCH_XFS_LIST_FUZZ_VERBS=random SCRATCH_XFS_LIST_METADATA_FIELDS=bno[0] ./check xfs/355
FSTYP -- xfs (debug)
PLATFORM -- Linux/x86_64 localhost 4.18.0-rc4+
MKFS_OPTIONS -- -f -mrmapbt=1,reflink=1 /dev/mapper/test-scratch
MOUNT_OPTIONS -- -o context=system_u:object_r:root_t:s0 /dev/mapper/test-scratch /mnt/scratch
xfs/355 - output mismatch (see /root/xfstests-dev/results//xfs/355.out.bad)
...
(Run 'diff -u tests/xfs/355.out /root/xfstests-dev/results//xfs/355.out.bad' to see the entire diff)
Ran: xfs/355
Failures: xfs/355
Failed 1 of 1 tests
# diff -u tests/xfs/355.out /root/xfstests-dev/results//xfs/355.out.bad
--- tests/xfs/355.out 2018-07-25 07:47:23.739575416 -0400
+++ /root/xfstests-dev/results//xfs/355.out.bad 2018-07-31
10:55:18.466178944 -0400
@@ -1,6 +1,10 @@
QA output created by 355
Format and populate
Fuzz AGFL
+online re-scrub (1) with bno[0] = random.
Done fuzzing AGFL
Fuzz AGFL flfirst
+offline re-scrub (1) with bno[14] = random.
+online re-scrub (1) with bno[14] = random.
+re-repair failed (1) with bno[14] = random.
Done fuzzing AGFL flfirst
If I run xfs_scrub directly on the scratch mount after the test I get a
stream of inode cross-referencing errors and it doesn't seem to fix
anything up.
Brian
> > Otherwise this looks sane, a couple comments..
> >
> > > fs/xfs/scrub/agheader_repair.c | 276 ++++++++++++++++++++++++++++++++++++++++
> > > fs/xfs/scrub/bitmap.c | 92 +++++++++++++
> > > fs/xfs/scrub/bitmap.h | 4 +
> > > fs/xfs/scrub/scrub.c | 2
> > > 4 files changed, 373 insertions(+), 1 deletion(-)
> > >
> > >
> > > diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
> > > index 4842fc598c9b..bfef066c87c3 100644
> > > --- a/fs/xfs/scrub/agheader_repair.c
> > > +++ b/fs/xfs/scrub/agheader_repair.c
> > > @@ -424,3 +424,279 @@ xrep_agf(
> > > memcpy(agf, &old_agf, sizeof(old_agf));
> > > return error;
> > > }
> > > +
> > ...
> > > +/* Write out a totally new AGFL. */
> > > +STATIC void
> > > +xrep_agfl_init_header(
> > > + struct xfs_scrub *sc,
> > > + struct xfs_buf *agfl_bp,
> > > + struct xfs_bitmap *agfl_extents,
> > > + xfs_agblock_t flcount)
> > > +{
> > > + struct xfs_mount *mp = sc->mp;
> > > + __be32 *agfl_bno;
> > > + struct xfs_bitmap_range *br;
> > > + struct xfs_bitmap_range *n;
> > > + struct xfs_agfl *agfl;
> > > + xfs_agblock_t agbno;
> > > + unsigned int fl_off;
> > > +
> > > + ASSERT(flcount <= xfs_agfl_size(mp));
> > > +
> > > + /* Start rewriting the header. */
> > > + agfl = XFS_BUF_TO_AGFL(agfl_bp);
> > > + memset(agfl, 0xFF, BBTOB(agfl_bp->b_length));
> >
> > What's the purpose behind 0xFF? Related to NULLAGBLOCK/NULLCOMMITLSN..?
>
> Yes, it prepopulates the AGFL bno[] array with NULLAGBLOCK, then writes
> in the header fields.
>
> > > + agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
> > > + agfl->agfl_seqno = cpu_to_be32(sc->sa.agno);
> > > + uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
> > > +
> > > + /*
> > > + * Fill the AGFL with the remaining blocks. If agfl_extents has more
> > > + * blocks than fit in the AGFL, they will be freed in a subsequent
> > > + * step.
> > > + */
> > > + fl_off = 0;
> > > + agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agfl_bp);
> > > + for_each_xfs_bitmap_extent(br, n, agfl_extents) {
> > > + agbno = XFS_FSB_TO_AGBNO(mp, br->start);
> > > +
> > > + trace_xrep_agfl_insert(mp, sc->sa.agno, agbno, br->len);
> > > +
> > > + while (br->len > 0 && fl_off < flcount) {
> > > + agfl_bno[fl_off] = cpu_to_be32(agbno);
> > > + fl_off++;
> > > + agbno++;
> >
> > /* bump br so we don't reap blocks we've used */
> >
> > (i.e., took me a sec to realize why we bother with ->start)
> >
> > > + br->start++;
> > > + br->len--;
> > > + }
> > > +
> > > + if (br->len)
> > > + break;
> > > + list_del(&br->list);
> > > + kmem_free(br);
> > > + }
> > > +
> > > + /* Write new AGFL to disk. */
> > > + xfs_trans_buf_set_type(sc->tp, agfl_bp, XFS_BLFT_AGFL_BUF);
> > > + xfs_trans_log_buf(sc->tp, agfl_bp, 0, BBTOB(agfl_bp->b_length) - 1);
> > > +}
> > > +
> > ...
> > > diff --git a/fs/xfs/scrub/bitmap.c b/fs/xfs/scrub/bitmap.c
> > > index c770e2d0b6aa..fdadc9e1dc49 100644
> > > --- a/fs/xfs/scrub/bitmap.c
> > > +++ b/fs/xfs/scrub/bitmap.c
> > > @@ -9,6 +9,7 @@
> > > #include "xfs_format.h"
> > > #include "xfs_trans_resv.h"
> > > #include "xfs_mount.h"
> > > +#include "xfs_btree.h"
> > > #include "scrub/xfs_scrub.h"
> > > #include "scrub/scrub.h"
> > > #include "scrub/common.h"
> > > @@ -209,3 +210,94 @@ xfs_bitmap_disunion(
> > > }
> > > #undef LEFT_ALIGNED
> > > #undef RIGHT_ALIGNED
> > > +
> > > +/*
> > > + * Record all btree blocks seen while iterating all records of a btree.
> > > + *
> > > + * We know that the btree query_all function starts at the left edge and walks
> > > + * towards the right edge of the tree. Therefore, we know that we can walk up
> > > + * the btree cursor towards the root; if the pointer for a given level points
> > > + * to the first record/key in that block, we haven't seen this block before;
> > > + * and therefore we need to remember that we saw this block in the btree.
> > > + *
> > > + * So if our btree is:
> > > + *
> > > + * 4
> > > + * / | \
> > > + * 1 2 3
> > > + *
> > > + * Pretend for this example that each leaf block has 100 btree records. For
> > > + * the first btree record, we'll observe that bc_ptrs[0] == 1, so we record
> > > + * that we saw block 1. Then we observe that bc_ptrs[1] == 1, so we record
> > > + * block 4. The list is [1, 4].
> > > + *
> > > + * For the second btree record, we see that bc_ptrs[0] == 2, so we exit the
> > > + * loop. The list remains [1, 4].
> > > + *
> > > + * For the 101st btree record, we've moved onto leaf block 2. Now
> > > + * bc_ptrs[0] == 1 again, so we record that we saw block 2. We see that
> > > + * bc_ptrs[1] == 2, so we exit the loop. The list is now [1, 4, 2].
> > > + *
> > > + * For the 102nd record, bc_ptrs[0] == 2, so we continue.
> > > + *
> > > + * For the 201st record, we've moved on to leaf block 3. bc_ptrs[0] == 1, so
> > > + * we add 3 to the list. Now it is [1, 4, 2, 3].
> > > + *
> > > + * For the 300th record we just exit, with the list being [1, 4, 2, 3].
> > > + */
> > > +
> > > +/*
> > > + * Record all the buffers pointed to by the btree cursor. Callers already
> > > + * engaged in a btree walk should call this function to capture the list of
> > > + * blocks going from the leaf towards the root.
> > > + */
> > > +int
> > > +xfs_bitmap_set_btcur_path(
> > > + struct xfs_bitmap *bitmap,
> > > + struct xfs_btree_cur *cur)
> > > +{
> > > + struct xfs_buf *bp;
> > > + xfs_fsblock_t fsb;
> > > + int i;
> > > + int error;
> > > +
> > > + for (i = 0; i < cur->bc_nlevels && cur->bc_ptrs[i] == 1; i++) {
> > > + xfs_btree_get_block(cur, i, &bp);
> > > + if (!bp)
> > > + continue;
> > > + fsb = XFS_DADDR_TO_FSB(cur->bc_mp, bp->b_bn);
> > > + error = xfs_bitmap_set(bitmap, fsb, 1);
> >
> > Thanks for the comment. It helps explain the bc_ptrs == 1 check above,
> > but also highlights that xfs_bitmap_set() essentially allocates entries
> > for duplicate values if they exist. Is this handled by the broader
> > mechanism, for example, if the rmapbt was corrupted to have multiple
> > entries for a particular unused OWN_AG block? Or could we end up leaking
> > that corruption over to the agfl?
>
> Right now we're totally dependent on the rmapbt being sane to rebuild
> the space metadata.
>
> > I also wonder a bit about memory consumption on filesystems with large
> > metadata footprints. We essentially have to allocate one of these for
> > every allocation btree block before we can do the disunion and locate
> > the agfl-appropriate blocks. If we had a more lookup friendly structure,
> > perhaps this could be optimized by filtering out bnobt/cntbt blocks
> > during the associated btree walks..?
> >
> > Have you thought about reusing something like the new in-core extent
> > tree mechanism as a pure in-memory extent store? It's certainly not
> > worth reworking something like that right now, but I wonder if we could
> > save memory via the denser format (and perhaps benefit from code
> > flexibility, reuse, etc.).
>
> Yes, I was thinking about refactoring the iext btree into a more generic
> in-core index with 64-bit key so that I could adapt xfs_bitmap to use
> it. In the longer term I would /also/ like to use xfs_bitmap to detect
> xfs_buf cache aliasing when multi-block buffers are in use, but that's
> further off. :)
>
> As for the memory-intensive record lists in all the btree rebuilders, I
> have some ideas around that too -- either find a way to build an
> alternate btree and switch the roots over, or (once we gain the ability
> to mark an AG unavailable for new allocations) allocate an unlinked
> inode, store the records in the page cache pages for the file, and
> release it when we're done.
>
> But, that can wait until I've gotten more of this merged, or get bored.
> :)
>
> --D
>
> > Brian
> >
> > > + if (error)
> > > + return error;
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* Collect a btree's block in the bitmap. */
> > > +STATIC int
> > > +xfs_bitmap_collect_btblock(
> > > + struct xfs_btree_cur *cur,
> > > + int level,
> > > + void *priv)
> > > +{
> > > + struct xfs_bitmap *bitmap = priv;
> > > + struct xfs_buf *bp;
> > > + xfs_fsblock_t fsbno;
> > > +
> > > + xfs_btree_get_block(cur, level, &bp);
> > > + if (!bp)
> > > + return 0;
> > > +
> > > + fsbno = XFS_DADDR_TO_FSB(cur->bc_mp, bp->b_bn);
> > > + return xfs_bitmap_set(bitmap, fsbno, 1);
> > > +}
> > > +
> > > +/* Walk the btree and mark the bitmap wherever a btree block is found. */
> > > +int
> > > +xfs_bitmap_set_btblocks(
> > > + struct xfs_bitmap *bitmap,
> > > + struct xfs_btree_cur *cur)
> > > +{
> > > + return xfs_btree_visit_blocks(cur, xfs_bitmap_collect_btblock, bitmap);
> > > +}
> > > diff --git a/fs/xfs/scrub/bitmap.h b/fs/xfs/scrub/bitmap.h
> > > index dad652ee9177..ae8ecbce6fa6 100644
> > > --- a/fs/xfs/scrub/bitmap.h
> > > +++ b/fs/xfs/scrub/bitmap.h
> > > @@ -28,5 +28,9 @@ void xfs_bitmap_destroy(struct xfs_bitmap *bitmap);
> > >
> > > int xfs_bitmap_set(struct xfs_bitmap *bitmap, uint64_t start, uint64_t len);
> > > int xfs_bitmap_disunion(struct xfs_bitmap *bitmap, struct xfs_bitmap *sub);
> > > +int xfs_bitmap_set_btcur_path(struct xfs_bitmap *bitmap,
> > > + struct xfs_btree_cur *cur);
> > > +int xfs_bitmap_set_btblocks(struct xfs_bitmap *bitmap,
> > > + struct xfs_btree_cur *cur);
> > >
> > > #endif /* __XFS_SCRUB_BITMAP_H__ */
> > > diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
> > > index 1e8a17c8e2b9..2670f4cf62f4 100644
> > > --- a/fs/xfs/scrub/scrub.c
> > > +++ b/fs/xfs/scrub/scrub.c
> > > @@ -220,7 +220,7 @@ static const struct xchk_meta_ops meta_scrub_ops[] = {
> > > .type = ST_PERAG,
> > > .setup = xchk_setup_fs,
> > > .scrub = xchk_agfl,
> > > - .repair = xrep_notsupported,
> > > + .repair = xrep_agfl,
> > > },
> > > [XFS_SCRUB_TYPE_AGI] = { /* agi */
> > > .type = ST_PERAG,
> > >
> > > --
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