From 6e91a72fe3ff8bb282490773bd687632f3e8c79d Mon Sep 17 00:00:00 2001 From: Brian Behlendorf Date: Tue, 15 Jan 2019 15:46:58 -0800 Subject: [PATCH] Disable 'zfs remap' command The implementation of 'zfs remap' has proven to be problematic since it modifies the objset (but not its logical contents) by dirtying metadata without owning it. The consequence of which is that dmu_objset_remap_indirects() is vulnerable to certain races. For example, if we are in the middle of receiving into the filesystem while it is being remapped. Then it is possible we could evict the objset when the receive completes (see dsl_dataset_clone_swap_sync_impl, or dmu_recv_end_sync), but dmu_objset_remap_indirects() may be still using the objset. The result of which would be a panic. Extended runs of ztest(8) have exposed other possible races which can occur when using 'zfs remap'. Several of these have been fixed but there may be others which have not yet been encountered and diagnosed. Furthermore, the ability to manually remap a filesystem is no longer particularly useful now that the removal code can map large chunks. Coupled with the fact that explaining what this command does and why it may be useful requires a detailed understanding of the internals of device removal. These are details users should not be bothered with. Therefore, the 'zfs remap' command is being disabled but not entirely removed. It may be removed in the future or potentially reworked to address the issues described above. Since 'zfs remap' has never been part of a tagged release its removal is expected to have minimal impact. The ZTS tests have been updated to continue to exercise the command to prevent atrophy, but it has been removed entirely from ztest(8). Reviewed by: Matt Ahrens Reviewed by: Tom Caputi Signed-off-by: Brian Behlendorf Closes #8238 --- cmd/zfs/zfs_main.c | 39 ++++++++++++++++++- cmd/ztest/ztest.c | 23 ----------- man/man5/zpool-features.5 | 3 +- man/man8/zfs.8 | 13 ------- .../alloc_class/alloc_class_012_pos.ksh | 3 ++ .../cli_root/zfs_remap/zfs_remap_cliargs.ksh | 3 ++ .../zfs_remap/zfs_remap_obsolete_counts.ksh | 3 ++ .../functional/removal/removal_remap.ksh | 3 ++ .../removal/removal_remap_deadlists.ksh | 3 ++ .../functional/removal/removal_with_remap.ksh | 3 ++ 10 files changed, 57 insertions(+), 39 deletions(-) diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c index 6b08bb115e..b8258a9cf5 100644 --- a/cmd/zfs/zfs_main.c +++ b/cmd/zfs/zfs_main.c @@ -7083,6 +7083,21 @@ zfs_do_unshare(int argc, char **argv) return (unshare_unmount(OP_SHARE, argc, argv)); } +static int +disable_command_idx(char *command) +{ + for (int i = 0; i < NCOMMAND; i++) { + if (command_table[i].name == NULL) + continue; + + if (strcmp(command, command_table[i].name) == 0) { + command_table[i].name = NULL; + return (0); + } + } + return (1); +} + static int find_command_idx(char *command, int *idx) { @@ -7180,7 +7195,22 @@ zfs_do_diff(int argc, char **argv) /* * zfs remap * - * Remap the indirect blocks in the given fileystem or volume. + * N.B. The remap command has been disabled and may be removed in the future. + * + * Remap the indirect blocks in the given filesystem or volume so that they no + * longer reference blocks on previously removed vdevs and we can eventually + * shrink the size of the indirect mapping objects for the previously removed + * vdevs. Note that remapping all blocks might not be possible and that + * references from snapshots will still exist and cannot be remapped. + * + * This functionality is no longer particularly useful now that the removal + * code can map large chunks. Furthermore, explaining what this command + * does and why it may be useful requires a detailed understanding of the + * internals of device removal. These are details users should not be + * bothered with. If required, the remap command can be re-enabled by + * setting the ZFS_REMAP_ENABLED environment variable. + * + * > ZFS_REMAP_ENABLED=yes zfs remap */ static int zfs_do_remap(int argc, char **argv) @@ -8006,6 +8036,13 @@ main(int argc, char **argv) if (strcmp(cmdname, "snap") == 0) cmdname = "snapshot"; + /* + * The 'remap' command has been disabled and may be removed in the + * future. See the comment above zfs_do_remap() for details. + */ + if (!libzfs_envvar_is_set("ZFS_REMAP_ENABLED")) + disable_command_idx("remap"); + /* * Special case '-?' */ diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c index f7f584358c..678e29ff66 100644 --- a/cmd/ztest/ztest.c +++ b/cmd/ztest/ztest.c @@ -216,7 +216,6 @@ extern int dmu_object_alloc_chunk_shift; extern boolean_t zfs_force_some_double_word_sm_entries; extern unsigned long zio_decompress_fail_fraction; extern unsigned long zfs_reconstruct_indirect_damage_fraction; -extern int zfs_object_remap_one_indirect_delay_ms; static ztest_shared_opts_t *ztest_shared_opts; @@ -373,7 +372,6 @@ ztest_func_t ztest_split_pool; ztest_func_t ztest_reguid; ztest_func_t ztest_spa_upgrade; ztest_func_t ztest_device_removal; -ztest_func_t ztest_remap_blocks; ztest_func_t ztest_spa_checkpoint_create_discard; ztest_func_t ztest_initialize; ztest_func_t ztest_fletcher; @@ -427,7 +425,6 @@ ztest_info_t ztest_info[] = { ZTI_INIT(ztest_vdev_class_add, 1, &ztest_opts.zo_vdevtime), ZTI_INIT(ztest_vdev_aux_add_remove, 1, &ztest_opts.zo_vdevtime), ZTI_INIT(ztest_device_removal, 1, &zopt_sometimes), - ZTI_INIT(ztest_remap_blocks, 1, &zopt_sometimes), ZTI_INIT(ztest_spa_checkpoint_create_discard, 1, &zopt_rarely), ZTI_INIT(ztest_initialize, 1, &zopt_sometimes), ZTI_INIT(ztest_fletcher, 1, &zopt_rarely), @@ -5550,20 +5547,6 @@ ztest_dsl_prop_get_set(ztest_ds_t *zd, uint64_t id) (void) pthread_rwlock_unlock(&ztest_name_lock); } -/* ARGSUSED */ -void -ztest_remap_blocks(ztest_ds_t *zd, uint64_t id) -{ - (void) pthread_rwlock_rdlock(&ztest_name_lock); - - int error = dmu_objset_remap_indirects(zd->zd_name); - if (error == ENOSPC) - error = 0; - ASSERT0(error); - - (void) pthread_rwlock_unlock(&ztest_name_lock); -} - /* ARGSUSED */ void ztest_spa_prop_get_set(ztest_ds_t *zd, uint64_t id) @@ -6629,12 +6612,6 @@ ztest_resume_thread(void *arg) */ if (ztest_random(10) == 0) zfs_abd_scatter_enabled = ztest_random(2); - - /* - * Periodically inject remapping delays (10% of the time). - */ - zfs_object_remap_one_indirect_delay_ms = - ztest_random(10) == 0 ? ztest_random(1000) + 1 : 0; } thread_exit(); diff --git a/man/man5/zpool-features.5 b/man/man5/zpool-features.5 index c1f6ee6e4e..4769c4eac3 100644 --- a/man/man5/zpool-features.5 +++ b/man/man5/zpool-features.5 @@ -475,8 +475,7 @@ DEPENDENCIES device_removal This feature is an enhancement of device_removal, which will over time reduce the memory used to track removed devices. When indirect blocks are freed or remapped, we note that their part of the indirect mapping -is "obsolete", i.e. no longer needed. See also the \fBzfs remap\fR -subcommand in \fBzfs\fR(1M). +is "obsolete", i.e. no longer needed. This feature becomes \fBactive\fR when the "zpool remove" command is used on a top-level vdev, and will never return to being \fBenabled\fR. diff --git a/man/man8/zfs.8 b/man/man8/zfs.8 index df904d0bdb..be28f2b62a 100644 --- a/man/man8/zfs.8 +++ b/man/man8/zfs.8 @@ -103,9 +103,6 @@ .Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc .Oo Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Oc Ns ... .Nm -.Cm remap -.Ar filesystem Ns | Ns Ar volume -.Nm .Cm set .Ar property Ns = Ns Ar value Oo Ar property Ns = Ns Ar value Oc Ns ... .Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns ... @@ -3037,16 +3034,6 @@ option was not specified. .El .It Xo .Nm -.Cm remap -.Ar filesystem Ns | Ns Ar volume -.Xc -Remap the indirect blocks in the given fileystem or volume so that they no -longer reference blocks on previously removed vdevs and we can eventually -shrink the size of the indirect mapping objects for the previously removed -vdevs. Note that remapping all blocks might not be possible and that -references from snapshots will still exist and cannot be remapped. -.It Xo -.Nm .Cm upgrade .Xc Displays a list of file systems that are not the most recent version. diff --git a/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh b/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh index b03a8b4c87..2371c5a268 100755 --- a/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh +++ b/tests/zfs-tests/tests/functional/alloc_class/alloc_class_012_pos.ksh @@ -55,7 +55,10 @@ log_must zpool list -v $TESTPOOL # # remove a special allocation vdev and force a remapping +# N.B. The 'zfs remap' command has been disabled and may be removed. # +export ZFS_REMAP_ENABLED=YES + log_must zpool remove $TESTPOOL $CLASS_DISK0 log_must zfs remap $TESTPOOL/$TESTFS diff --git a/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_cliargs.ksh b/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_cliargs.ksh index 9a0b7d6192..80a5e6e0d9 100755 --- a/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_cliargs.ksh +++ b/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_cliargs.ksh @@ -27,6 +27,9 @@ # 3. Verify other unsupported parameters raise an error # +# The 'zfs remap' command has been disabled and may be removed. +export ZFS_REMAP_ENABLED=YES + verify_runnable "both" function cleanup diff --git a/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_obsolete_counts.ksh b/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_obsolete_counts.ksh index 15d3ae493e..1f0e0e85d8 100755 --- a/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_obsolete_counts.ksh +++ b/tests/zfs-tests/tests/functional/cli_root/zfs_remap/zfs_remap_obsolete_counts.ksh @@ -29,6 +29,9 @@ # feature@obsolete_counts is enabled # +# N.B. The 'zfs remap' command has been disabled and may be removed. +export ZFS_REMAP_ENABLED=YES + verify_runnable "both" function cleanup diff --git a/tests/zfs-tests/tests/functional/removal/removal_remap.ksh b/tests/zfs-tests/tests/functional/removal/removal_remap.ksh index 04d0c50e48..5239ef3a5e 100755 --- a/tests/zfs-tests/tests/functional/removal/removal_remap.ksh +++ b/tests/zfs-tests/tests/functional/removal/removal_remap.ksh @@ -21,6 +21,9 @@ . $STF_SUITE/include/libtest.shlib . $STF_SUITE/tests/functional/removal/removal.kshlib +# N.B. The 'zfs remap' command has been disabled and may be removed. +export ZFS_REMAP_ENABLED=YES + default_setup_noexit "$DISKS" diff --git a/tests/zfs-tests/tests/functional/removal/removal_remap_deadlists.ksh b/tests/zfs-tests/tests/functional/removal/removal_remap_deadlists.ksh index 6c630f2f53..a2f6580b4f 100755 --- a/tests/zfs-tests/tests/functional/removal/removal_remap_deadlists.ksh +++ b/tests/zfs-tests/tests/functional/removal/removal_remap_deadlists.ksh @@ -21,6 +21,9 @@ . $STF_SUITE/include/libtest.shlib . $STF_SUITE/tests/functional/removal/removal.kshlib +# N.B. The 'zfs remap' command has been disabled and may be removed. +export ZFS_REMAP_ENABLED=YES + default_setup_noexit "$DISKS" log_onexit default_cleanup_noexit diff --git a/tests/zfs-tests/tests/functional/removal/removal_with_remap.ksh b/tests/zfs-tests/tests/functional/removal/removal_with_remap.ksh index d3a53e40b3..6f56740b82 100755 --- a/tests/zfs-tests/tests/functional/removal/removal_with_remap.ksh +++ b/tests/zfs-tests/tests/functional/removal/removal_with_remap.ksh @@ -21,6 +21,9 @@ . $STF_SUITE/include/libtest.shlib . $STF_SUITE/tests/functional/removal/removal.kshlib +# N.B. The 'zfs remap' command has been disabled and may be removed. +export ZFS_REMAP_ENABLED=YES + default_setup_noexit "$DISKS" log_onexit default_cleanup_noexit