OpenZFS 7614, 9064 - zfs device evacuation/removal

OpenZFS 7614 - zfs device evacuation/removal
OpenZFS 9064 - remove_mirror should wait for device removal to complete

This project allows top-level vdevs to be removed from the storage pool
with "zpool remove", reducing the total amount of storage in the pool.
This operation copies all allocated regions of the device to be removed
onto other devices, recording the mapping from old to new location.
After the removal is complete, read and free operations to the removed
(now "indirect") vdev must be remapped and performed at the new location
on disk.  The indirect mapping table is kept in memory whenever the pool
is loaded, so there is minimal performance overhead when doing operations
on the indirect vdev.

The size of the in-memory mapping table will be reduced when its entries
become "obsolete" because they are no longer used by any block pointers
in the pool.  An entry becomes obsolete when all the blocks that use
it are freed.  An entry can also become obsolete when all the snapshots
that reference it are deleted, and the block pointers that reference it
have been "remapped" in all filesystems/zvols (and clones).  Whenever an
indirect block is written, all the block pointers in it will be "remapped"
to their new (concrete) locations if possible.  This process can be
accelerated by using the "zfs remap" command to proactively rewrite all
indirect blocks that reference indirect (removed) vdevs.

Note that when a device is removed, we do not verify the checksum of
the data that is copied.  This makes the process much faster, but if it
were used on redundant vdevs (i.e. mirror or raidz vdevs), it would be
possible to copy the wrong data, when we have the correct data on e.g.
the other side of the mirror.

At the moment, only mirrors and simple top-level vdevs can be removed
and no removal is allowed if any of the top-level vdevs are raidz.

Porting Notes:

* Avoid zero-sized kmem_alloc() in vdev_compact_children().

    The device evacuation code adds a dependency that
    vdev_compact_children() be able to properly empty the vdev_child
    array by setting it to NULL and zeroing vdev_children.  Under Linux,
    kmem_alloc() and related functions return a sentinel pointer rather
    than NULL for zero-sized allocations.

* Remove comment regarding "mpt" driver where zfs_remove_max_segment
  is initialized to SPA_MAXBLOCKSIZE.

  Change zfs_condense_indirect_commit_entry_delay_ticks to
  zfs_condense_indirect_commit_entry_delay_ms for consistency with
  most other tunables in which delays are specified in ms.

* ZTS changes:

    Use set_tunable rather than mdb
    Use zpool sync as appropriate
    Use sync_pool instead of sync
    Kill jobs during test_removal_with_operation to allow unmount/export
    Don't add non-disk names such as "mirror" or "raidz" to $DISKS
    Use $TEST_BASE_DIR instead of /tmp
    Increase HZ from 100 to 1000 which is more common on Linux

    removal_multiple_indirection.ksh
        Reduce iterations in order to not time out on the code
        coverage builders.

    removal_resume_export:
        Functionally, the test case is correct but there exists a race
        where the kernel thread hasn't been fully started yet and is
        not visible.  Wait for up to 1 second for the removal thread
        to be started before giving up on it.  Also, increase the
        amount of data copied in order that the removal not finish
        before the export has a chance to fail.

* MMP compatibility, the concept of concrete versus non-concrete devices
  has slightly changed the semantics of vdev_writeable().  Update
  mmp_random_leaf_impl() accordingly.

* Updated dbuf_remap() to handle the org.zfsonlinux:large_dnode pool
  feature which is not supported by OpenZFS.

* Added support for new vdev removal tracepoints.

* Test cases removal_with_zdb and removal_condense_export have been
  intentionally disabled.  When run manually they pass as intended,
  but when running in the automated test environment they produce
  unreliable results on the latest Fedora release.

  They may work better once the upstream pool import refectoring is
  merged into ZoL at which point they will be re-enabled.

Authored by: Matthew Ahrens <[email protected]>
Reviewed-by: Alex Reece <[email protected]>
Reviewed-by: George Wilson <[email protected]>
Reviewed-by: John Kennedy <[email protected]>
Reviewed-by: Prakash Surya <[email protected]>
Reviewed by: Richard Laager <[email protected]>
Reviewed by: Tim Chase <[email protected]>
Reviewed by: Brian Behlendorf <[email protected]>
Approved by: Garrett D'Amore <[email protected]>
Ported-by: Tim Chase <[email protected]>
Signed-off-by: Tim Chase <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/7614
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f539f1eb
Closes #6900

1 files changed, 30 insertions, 0 deletions

diff --git a/include/sys/dsl_dataset.h b/include/sys/dsl_dataset.h
index 0030fca24..abd178e30 100644
--- a/include/sys/dsl_dataset.h
+++ b/include/sys/dsl_dataset.h
@@ -109,6 +109,11 @@ struct dsl_crypto_params;
 #define	DS_FIELD_RESUME_RAWOK "com.datto:resume_rawok"
 
 /*
+ * This field is set to the object number of the remap deadlist if one exists.
+ */
+#define	DS_FIELD_REMAP_DEADLIST	"com.delphix:remap_deadlist"
+
+/*
  * DS_FLAG_CI_DATASET is set if the dataset contains a file system whose
  * name lookups should be performed case-insensitively.
  */
@@ -169,6 +174,24 @@ typedef struct dsl_dataset {
 	dsl_deadlist_t ds_deadlist;
 	bplist_t ds_pending_deadlist;
 
+	/*
+	 * The remap deadlist contains blocks (DVA's, really) that are
+	 * referenced by the previous snapshot and point to indirect vdevs,
+	 * but in this dataset they have been remapped to point to concrete
+	 * (or at least, less-indirect) vdevs.  In other words, the
+	 * physical DVA is referenced by the previous snapshot but not by
+	 * this dataset.  Logically, the DVA continues to be referenced,
+	 * but we are using a different (less indirect) physical DVA.
+	 * This deadlist is used to determine when physical DVAs that
+	 * point to indirect vdevs are no longer referenced anywhere,
+	 * and thus should be marked obsolete.
+	 *
+	 * This is only used if SPA_FEATURE_OBSOLETE_COUNTS is enabled.
+	 */
+	dsl_deadlist_t ds_remap_deadlist;
+	/* protects creation of the ds_remap_deadlist */
+	kmutex_t ds_remap_deadlist_lock;
+
 	/* protected by lock on pool's dp_dirty_datasets list */
 	txg_node_t ds_dirty_link;
 	list_node_t ds_synced_link;
@@ -328,6 +351,8 @@ void dsl_dataset_block_born(dsl_dataset_t *ds, const blkptr_t *bp,
     dmu_tx_t *tx);
 int dsl_dataset_block_kill(dsl_dataset_t *ds, const blkptr_t *bp,
     dmu_tx_t *tx, boolean_t async);
+void dsl_dataset_block_remapped(dsl_dataset_t *ds, uint64_t vdev,
+    uint64_t offset, uint64_t size, uint64_t birth, dmu_tx_t *tx);
 int dsl_dataset_snap_lookup(dsl_dataset_t *ds, const char *name,
     uint64_t *value);
 
@@ -416,6 +441,11 @@ void dsl_dataset_rollback_sync(void *arg, dmu_tx_t *tx);
 int dsl_dataset_rollback(const char *fsname, const char *tosnap, void *owner,
     nvlist_t *result);
 
+uint64_t dsl_dataset_get_remap_deadlist_object(dsl_dataset_t *ds);
+void dsl_dataset_create_remap_deadlist(dsl_dataset_t *ds, dmu_tx_t *tx);
+boolean_t dsl_dataset_remap_deadlist_exists(dsl_dataset_t *ds);
+void dsl_dataset_destroy_remap_deadlist(dsl_dataset_t *ds, dmu_tx_t *tx);
+
 void dsl_dataset_activate_feature(uint64_t dsobj,
     spa_feature_t f, dmu_tx_t *tx);
 void dsl_dataset_deactivate_feature(uint64_t dsobj,