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Robert Evans
460858dfd6
This changes the basic search algorithm from a single search up and down
the tree to a full depth-first traversal to handle conditions where the
tree matches at a higher level but not a lower level.
Normally higher level blocks always point to matching blocks, but there
are cases where this does not happen:
1. Racing block pointer updates from dbuf_write_ready.
Before f664f1ee7f (#8946), both dbuf_write_ready and
dnode_next_offset held dn_struct_rwlock which protected against
pointer writes from concurrent syncs.
This no longer applies, so sync context can f.e. clear or fill all
L1->L0 BPs before the L2->L1 BP and higher BP's are updated.
dnode_free_range in particular can reach this case and skip over L1
blocks that need to be dirtied. Later, sync will panic in
free_children when trying to clear a non-dirty indirect block.
This case was found with ztest.
2. txg > 0, non-hole case. This is #11196.
Freeing blocks/dnodes breaks the assumption that a match at a higher
level implies a match at a lower level when filtering txg > 0.
Whenever some but not all L0 blocks are freed, the parent L1 block is
rewritten. Its updated L2->L1 BP reflects a newer birth txg.
Later when searching by txg, if the L1 block matches since the txg is
newer, it is possible that none of the remaining L1->L0 BPs match if
none have been updated.
The same behavior is possible with dnode search at L0.
This is reachable from dsl_destroy_head for synchronous freeing.
When this happens open context fails to free objects leaving sync
context stuck freeing potentially many objects.
This is also reachable from traverse_pool for extreme rewind where it
is theoretically possible that datasets not dirtied after txg are
skipped if the MOS has high enough indirection to trigger this case.
In both of these cases, without backtracking the search ends prematurely
as ESRCH result implies no more matches in the entire object.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Akash B <akash-b@hpe.com>
Signed-off-by: Robert Evans <evansr@google.com>
Closes #16025
Closes #11196
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
Official Resources
- Documentation - for using and developing this repo
- ZoL Site - Linux release info & links
- Mailing lists
- OpenZFS site - for conference videos and info on other platforms (illumos, OSX, Windows, etc)
Installation
Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.
Contribute & Develop
We have a separate document with contribution guidelines.
We have a Code of Conduct.
Release
OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are any supported branches and releases starting from 13.0-RELEASE.