Improved zpool status output, list all affected datasets

Currently, determining which datasets are affected by corruption is
a manual process.

The primary difficulty in reporting the list of affected snapshots is
that since the error was initially found, the snapshot where the error
originally occurred in, may have been deleted. To solve this issue, we
add the ID of the head dataset of the original snapshot which the error
was detected in, to the stored error report. Then any time a filesystem
is deleted, the errors associated with it are deleted as well. Any time
a clone promote occurs, we modify reports associated with the original
head to refer to the new head. The stored error reports are identified
by this head ID, the birth time of the block which the error occurred
in, as well as some information about the error itself are also stored.

Once this information is stored, we can find the set of datasets
affected by an error by walking back the list of snapshots in the given
head until we find one with the appropriate birth txg, and then traverse
through the snapshots of the clone family, terminating a branch if the
block was replaced in a given snapshot. Then we report this information
back to libzfs, and to the zpool status command, where it is displayed
as follows:

 pool: test
 state: ONLINE
status: One or more devices has experienced an error resulting in data
        corruption.  Applications may be affected.
action: Restore the file in question if possible.  Otherwise restore the
        entire pool from backup.
   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-8A
  scan: scrub repaired 0B in 00:00:00 with 800 errors on Fri Dec  3
08:27:57 2021
config:

        NAME        STATE     READ WRITE CKSUM
        test        ONLINE       0     0     0
          sdb       ONLINE       0     0 1.58K

errors: Permanent errors have been detected in the following files:

        test@1:/test.0.0
        /test/test.0.0
        /test/1clone/test.0.0

A new feature flag is introduced to mark the presence of this change, as
well as promotion and backwards compatibility logic. This is an updated
version of openzfs#9175. Rebase required fixing the tests, updating the ABI of
libzfs, and updating the man pages.

Signed-off-by: TulsiJain <tulsi.jain@delphix.com>
Signed-off-by: George Amanakis <gamanakis@gmail.com>

include/sys/spa.h

@@ -1144,11 +1144,14 @@ extern void zfs_post_remove(spa_t *spa, vdev_t *vd);
 extern void zfs_post_state_change(spa_t *spa, vdev_t *vd, uint64_t laststate);
 extern void zfs_post_autoreplace(spa_t *spa, vdev_t *vd);
 extern uint64_t spa_get_errlog_size(spa_t *spa);
-extern int spa_get_errlog(spa_t *spa, void *uaddr, size_t *count);
+extern int spa_get_errlog(spa_t *spa, void *uaddr, uint64_t *count);
 extern void spa_errlog_rotate(spa_t *spa);
 extern void spa_errlog_drain(spa_t *spa);
 extern void spa_errlog_sync(spa_t *spa, uint64_t txg);
 extern void spa_get_errlists(spa_t *spa, avl_tree_t *last, avl_tree_t *scrub);
+extern void spa_delete_dataset_errlog(spa_t *spa, uint64_t ds, dmu_tx_t *tx);
+extern void spa_swap_errlog(spa_t *spa, uint64_t new_head_ds,
+    uint64_t old_head_ds, dmu_tx_t *tx);
 
 /* vdev cache */
 extern void vdev_cache_stat_init(void);

include/sys/zio.h

@@ -291,6 +291,13 @@ struct zbookmark_phys {
 	uint64_t	zb_blkid;
 };
 
+typedef struct zbookmark_err_phys {
+	uint64_t	zb_object;
+	int64_t		zb_level;
+	uint64_t	zb_blkid;
+	uint64_t	zb_birth;
+} zbookmark_err_phys_t;
+
 #define	SET_BOOKMARK(zb, objset, object, level, blkid)  \
 {                                                       \
 	(zb)->zb_objset = objset;                       \

include/zfeature_common.h

@@ -75,6 +75,7 @@ typedef enum spa_feature {
 	SPA_FEATURE_DEVICE_REBUILD,
 	SPA_FEATURE_ZSTD_COMPRESS,
 	SPA_FEATURE_DRAID,
+	SPA_FEATURE_HEAD_ERRLOG,
 	SPA_FEATURES
 } spa_feature_t;
 

lib/libzfs/libzfs.abi

@@ -599,7 +599,7 @@
     <elf-symbol name='fletcher_4_superscalar_ops' size='64' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='libspl_assert_ok' size='4' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='libzfs_config_ops' size='16' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
-    <elf-symbol name='spa_feature_table' size='1904' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
+    <elf-symbol name='spa_feature_table' size='1960' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfeature_checks_disable' size='4' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_deleg_perm_tab' size='512' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_history_event_names' size='328' type='object-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
@@ -1862,8 +1862,8 @@
     </function-decl>
   </abi-instr>
   <abi-instr address-size='64' path='../../module/zcommon/zfeature_common.c' language='LANG_C99'>
-    <array-type-def dimensions='1' type-id='83f29ca2' size-in-bits='15232' id='d96379d0'>
-      <subrange length='34' type-id='7359adad' id='6a6a7e00'/>
+    <array-type-def dimensions='1' type-id='83f29ca2' size-in-bits='15680' id='9d60dcc5'>
+      <subrange length='35' type-id='7359adad' id='6e6845b5'/>
     </array-type-def>
     <enum-decl name='spa_feature' id='33ecb627'>
       <underlying-type type-id='9cac1fee'/>
@@ -1902,7 +1902,8 @@
       <enumerator name='SPA_FEATURE_DEVICE_REBUILD' value='31'/>
       <enumerator name='SPA_FEATURE_ZSTD_COMPRESS' value='32'/>
       <enumerator name='SPA_FEATURE_DRAID' value='33'/>
-      <enumerator name='SPA_FEATURES' value='34'/>
+      <enumerator name='SPA_FEATURE_HEAD_ERRLOG' value='34'/>
+      <enumerator name='SPA_FEATURES' value='35'/>
     </enum-decl>
     <typedef-decl name='spa_feature_t' type-id='33ecb627' id='d6618c78'/>
     <enum-decl name='zfeature_flags' id='6db816a4'>
@@ -1950,7 +1951,7 @@
     <qualified-type-def type-id='d6618c78' const='yes' id='81a65028'/>
     <pointer-type-def type-id='81a65028' size-in-bits='64' id='1acff326'/>
     <pointer-type-def type-id='d6618c78' size-in-bits='64' id='a8425263'/>
-    <var-decl name='spa_feature_table' type-id='d96379d0' mangled-name='spa_feature_table' visibility='default' elf-symbol-id='spa_feature_table'/>
+    <var-decl name='spa_feature_table' type-id='9d60dcc5' mangled-name='spa_feature_table' visibility='default' elf-symbol-id='spa_feature_table'/>
     <var-decl name='zfeature_checks_disable' type-id='c19b74c3' mangled-name='zfeature_checks_disable' visibility='default' elf-symbol-id='zfeature_checks_disable'/>
     <function-decl name='zfeature_is_valid_guid' mangled-name='zfeature_is_valid_guid' visibility='default' binding='global' size-in-bits='64' elf-symbol-id='zfeature_is_valid_guid'>
       <parameter type-id='80f4b756' name='name'/>

man/man7/zpool-features.7

@@ -832,7 +832,15 @@ once all filesystems that have ever had their
 property set to
 .Sy zstd
 are destroyed.
+.feature com.delphix head_errlog no
+This feature enables the upgraded version of errlog.
+This required an on-disk error format change.
+Now the errorlog of each head dataset is stored separately
+in the zap object and keyed by the head id.
+With this feature enabled, every dataset affected by an error block is listed
+in the output of
+.Nm zpool Cm status .
+This feature can only be enabled at pool creation time.
 .El
-.
 .Sh SEE ALSO
 .Xr zpool 8

module/zcommon/zfeature_common.c

@@ -594,6 +594,11 @@ zpool_feature_init(void)
 	zfeature_register(SPA_FEATURE_DRAID,
 	    "org.openzfs:draid", "draid", "Support for distributed spare RAID",
 	    ZFEATURE_FLAG_MOS, ZFEATURE_TYPE_BOOLEAN, NULL);
+
+	zfeature_register(SPA_FEATURE_HEAD_ERRLOG,
+	    "com.delphix:head_errlog", "head_errlog",
+	    "Introduce an on-disk block error log.",
+	    ZFEATURE_FLAG_ACTIVATE_ON_ENABLE, ZFEATURE_TYPE_BOOLEAN, NULL);
 }
 
 #if defined(_KERNEL)

module/zfs/dsl_dataset.c

@@ -3741,6 +3741,15 @@ dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx)
 
 	dsl_dir_rele(odd, FTAG);
 	promote_rele(ddpa, FTAG);
+
+	/*
+	 * Transfer common error blocks from old head to new head.
+	 */
+	if (spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_HEAD_ERRLOG)) {
+		uint64_t old_head = origin_head->ds_object;
+		uint64_t new_head = hds->ds_object;
+		spa_swap_errlog(dp->dp_spa, new_head, old_head, tx);
+	}
 }
 
 /*

module/zfs/dsl_destroy.c

@@ -1153,6 +1153,9 @@ dsl_destroy_head_sync_impl(dsl_dataset_t *ds, dmu_tx_t *tx)
 		dsl_destroy_snapshot_sync_impl(prev, B_FALSE, tx);
 		dsl_dataset_rele(prev, FTAG);
 	}
+	/* Delete errlog. */
+	if (spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_HEAD_ERRLOG))
+		spa_delete_dataset_errlog(dp->dp_spa, ds->ds_object, tx);
 }
 
 void