Adapt the repair code so that we can stage a new btree in the data fork
area of a metadir inode and reap the old blocks. We already have nearly
all of the infrastructure; the only parts that were missing were the
metadata inode reservation handling.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Rebuild the reverse mapping btree from all primary metadata. This first
patch establishes the bare mechanics of finding records and putting
together a new ondisk tree; more complex pieces are needed to make it
work properly.
Link: Documentation/filesystems/xfs-online-fsck-design.rst
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Rebuild the free space btrees from the gaps in the rmap btree. Refer to
the case study in Documentation/filesystems/xfs-online-fsck-design.rst
for more details.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
We need to log EFIs for every extent that we allocate for the purpose of
staging a new btree so that if we fail then the blocks will be freed
during log recovery. Use the autoreaping mechanism provided by the
previous patch to attach paused freeing work to the scrub transaction.
We can then mark the EFIs stale if we decide to commit the new btree, or
we can unpause the EFIs if we decide to abort the repair.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Create a new xrep_newbt structure to encapsulate a fake root for
creating a staged btree cursor as well as to track all the blocks that
we need to reserve in order to build that btree.
As for the particular choice of lowspace thresholds and btree block
slack factors -- at this point one could say that the thresholds in
online repair come from bulkload_estimate_ag_slack in xfs_repair[1].
But that's not the entire story, since the offline btree rebuilding
code in xfs_repair was merged as a retroport of the online btree code
in this patchset!
Before xfs_btree_staging.[ch] came along, xfs_repair determined the
slack factor (aka the number of slots to leave unfilled in each new
btree block) via open-coded logic in repair/phase5.c[2]. At that point
the slack factors were arbitrary quantities per btree. The rmapbt
automatically left 10 slots free; everything else left zero.
That had a noticeable effect on performance straight after mounting
because adding records to /any/ btree would result in splits. A few
years ago when this patch was first written, Dave and I decided that
repair should generate btree blocks that were 75% full unless space was
tight, in which case it should try to fill the blocks to nearly full.
We defined tight as ~10% free to avoid repair failures but settled on
3/32 (~9%) to avoid div64.
IOWs, we mostly pulled the thresholds out of thin air. We've been
QAing with those geometry numbers ever since. ;)
Link: https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/tree/repair/bulkload.c?h=v6.5.0#n114
Link: https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/tree/repair/phase5.c?h=v4.19.0#n1349
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
