On Thu, Mar 22, 2018 at 10:33:58AM -0400, Brian Foster wrote:
> On Wed, Mar 21, 2018 at 11:02:18PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > When we're scanning an extent mapping inode fork, ensure that every rmap
> > record for this ifork has a corresponding bmbt record too. This
> > (mostly) provides the ability to cross-reference rmap records with bmap
> > data. The rmap scrubber cannot do the xref on its own because that
> > requires taking an ilock with the agf lock held, which violates our
> > locking order rules (inode, then agf).
> >
> > Note that we only do this for forks that are in btree format due to the
> > increased complexity; or forks that should have data but suspiciously
> > have zero extents because the inode could have just had its iforks
> > zapped by the inode repair code and now we need to reclaim the old
> > extents.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> > v2: enhance comments, fix XFS_BTREE_ERROR usage
> > ---
> > fs/xfs/scrub/bmap.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 169 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
> > index d002821..75ea2d6 100644
> > --- a/fs/xfs/scrub/bmap.c
> > +++ b/fs/xfs/scrub/bmap.c
> > @@ -37,6 +37,7 @@
> > #include "xfs_bmap_util.h"
> > #include "xfs_bmap_btree.h"
> > #include "xfs_rmap.h"
> > +#include "xfs_rmap_btree.h"
> > #include "xfs_refcount.h"
> > #include "scrub/xfs_scrub.h"
> > #include "scrub/scrub.h"
> > @@ -423,6 +424,169 @@ xfs_scrub_bmap_btree(
> > return error;
> > }
> >
> ...
> > +/* Make sure each rmap has a corresponding bmbt entry. */
> > +STATIC int
> > +xfs_scrub_bmap_check_ag_rmaps(
> > + struct xfs_scrub_context *sc,
> > + int whichfork,
> > + xfs_agnumber_t agno)
> > +{
> > + struct xfs_scrub_bmap_check_rmap_info sbcri;
> > + struct xfs_btree_cur *cur;
> > + struct xfs_buf *agf;
> > + int error;
> > +
> > + error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf);
> > + if (error)
> > + return error;
> > +
> > + cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf, agno);
> > + if (!cur) {
> > + error = -ENOMEM;
> > + goto out_agf;
> > + }
> > +
> > + sbcri.sc = sc;
> > + sbcri.whichfork = whichfork;
> > + error = xfs_rmap_query_all(cur, xfs_scrub_bmap_check_rmap, &sbcri);
> > + if (error == XFS_BTREE_QUERY_RANGE_ABORT)
> > + error = 0;
> > +
> > + xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
>
> So I assume it's intentional that we don't care about _QUERY_RANGE_ABORT
> here? Otherwise looks fine.
Yes. The only difference between XFS_BTREE_ERROR and XFS_BTREE_NOERROR
is that _ERROR forces _del_cursor to scan every bc_bufs entry for
buffers to release, whereas _NOERROR stops after the first NULL it finds
while going from level 0 to level n. I've had half a mind to remove
that parameter since it clutters up the callsites and most of the time
all the btree pointers fit in a single cacheline.
That said, the btree query_range/query_all functions only return
_QUERY_RANGE_ABORT if the helper function (i.e. xfs_scrub_bmap_check_rmap)
returns _ABORT. The helper only gets called if we find a record in the
btree which means that we can use _NOERROR since bc_bufs[0] is set.
--D
> Brian
>
> > +out_agf:
> > + xfs_trans_brelse(sc->tp, agf);
> > + return error;
> > +}
> > +
> > +/* Make sure each rmap has a corresponding bmbt entry. */
> > +STATIC int
> > +xfs_scrub_bmap_check_rmaps(
> > + struct xfs_scrub_context *sc,
> > + int whichfork)
> > +{
> > + loff_t size;
> > + xfs_agnumber_t agno;
> > + int error;
> > +
> > + if (!xfs_sb_version_hasrmapbt(&sc->mp->m_sb) ||
> > + whichfork == XFS_COW_FORK ||
> > + (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
> > + return 0;
> > +
> > + /* Don't support realtime rmap checks yet. */
> > + if (XFS_IS_REALTIME_INODE(sc->ip) && whichfork == XFS_DATA_FORK)
> > + return 0;
> > +
> > + /*
> > + * Only do this for complex maps that are in btree format, or for
> > + * situations where we would seem to have a size but zero extents.
> > + * The inode repair code can zap broken iforks, which means we have
> > + * to flag this bmap as corrupt if there are rmaps that need to be
> > + * reattached.
> > + */
> > + switch (whichfork) {
> > + case XFS_DATA_FORK:
> > + size = i_size_read(VFS_I(sc->ip));
> > + break;
> > + case XFS_ATTR_FORK:
> > + size = XFS_IFORK_Q(sc->ip);
> > + break;
> > + default:
> > + size = 0;
> > + break;
> > + }
> > + if (XFS_IFORK_FORMAT(sc->ip, whichfork) != XFS_DINODE_FMT_BTREE &&
> > + (size == 0 || XFS_IFORK_NEXTENTS(sc->ip, whichfork) > 0))
> > + return 0;
> > +
> > + for (agno = 0; agno < sc->mp->m_sb.sb_agcount; agno++) {
> > + error = xfs_scrub_bmap_check_ag_rmaps(sc, whichfork, agno);
> > + if (error)
> > + return error;
> > + if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
> > + break;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > /*
> > * Scrub an inode fork's block mappings.
> > *
> > @@ -463,7 +627,7 @@ xfs_scrub_bmap(
> > break;
> > case XFS_ATTR_FORK:
> > if (!ifp)
> > - goto out;
> > + goto out_check_rmap;
> > if (!xfs_sb_version_hasattr(&mp->m_sb) &&
> > !xfs_sb_version_hasattr2(&mp->m_sb))
> > xfs_scrub_ino_set_corrupt(sc, sc->ip->i_ino, NULL);
> > @@ -534,6 +698,10 @@ xfs_scrub_bmap(
> > goto out;
> > }
> >
> > +out_check_rmap:
> > + error = xfs_scrub_bmap_check_rmaps(sc, whichfork);
> > + if (!xfs_scrub_fblock_xref_process_error(sc, whichfork, 0, &error))
> > + goto out;
> > out:
> > return error;
> > }
> > --
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