From 30b3688e1f6c8cca8e0c6c74f88368497f081c9f Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Thu, 23 Jan 2020 15:44:50 +0800 Subject: btrfs: Add overview of device replace The overview of btrfs dev-replace. It mentions some corner cases caused by the write duplication and scrub based data copy. Reviewed-by: Anand Jain Signed-off-by: Qu Wenruo Reviewed-by: David Sterba [ adjust wording ] Signed-off-by: David Sterba --- fs/btrfs/dev-replace.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'fs/btrfs/dev-replace.c') diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 2ca2a09d0e23..2aad07cdaea8 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -22,6 +22,46 @@ #include "dev-replace.h" #include "sysfs.h" +/* + * Device replace overview + * + * [Objective] + * To copy all extents (both new and on-disk) from source device to target + * device, while still keeping the filesystem read-write. + * + * [Method] + * There are two main methods involved: + * + * - Write duplication + * + * All new writes will be written to both target and source devices, so even + * if replace gets canceled, sources device still contans up-to-date data. + * + * Location: handle_ops_on_dev_replace() from __btrfs_map_block() + * Start: btrfs_dev_replace_start() + * End: btrfs_dev_replace_finishing() + * Content: Latest data/metadata + * + * - Copy existing extents + * + * This happens by re-using scrub facility, as scrub also iterates through + * existing extents from commit root. + * + * Location: scrub_write_block_to_dev_replace() from + * scrub_block_complete() + * Content: Data/meta from commit root. + * + * Due to the content difference, we need to avoid nocow write when dev-replace + * is happening. This is done by marking the block group read-only and waiting + * for NOCOW writes. + * + * After replace is done, the finishing part is done by swapping the target and + * source devices. + * + * Location: btrfs_dev_replace_update_device_in_mapping_tree() from + * btrfs_dev_replace_finishing() + */ + static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, int scrub_ret); static void btrfs_dev_replace_update_device_in_mapping_tree( -- cgit v1.2.3 From f3cd2c58110dad14ee37cc47fd1473d90ee68ccb Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Wed, 12 Feb 2020 17:28:13 +0800 Subject: btrfs: sysfs, rename device_link add/remove functions Since commit 668e48af7a94 ("btrfs: sysfs, add devid/dev_state kobject and device attributes"), the functions btrfs_sysfs_add_device_link() and btrfs_sysfs_rm_device_link() do more than just adding and removing the device link as its name indicated. Rename them to be more specific that's about the directory with the attirbutes Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/dev-replace.c | 4 ++-- fs/btrfs/sysfs.c | 10 +++++----- fs/btrfs/sysfs.h | 4 ++-- fs/btrfs/volumes.c | 8 ++++---- 4 files changed, 13 insertions(+), 13 deletions(-) (limited to 'fs/btrfs/dev-replace.c') diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 2aad07cdaea8..db93909b25e0 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -512,7 +512,7 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info, atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0); up_write(&dev_replace->rwsem); - ret = btrfs_sysfs_add_device_link(tgt_device->fs_devices, tgt_device); + ret = btrfs_sysfs_add_devices_dir(tgt_device->fs_devices, tgt_device); if (ret) btrfs_err(fs_info, "kobj add dev failed %d", ret); @@ -743,7 +743,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, mutex_unlock(&fs_info->fs_devices->device_list_mutex); /* replace the sysfs entry */ - btrfs_sysfs_rm_device_link(fs_info->fs_devices, src_device); + btrfs_sysfs_remove_devices_dir(fs_info->fs_devices, src_device); btrfs_sysfs_update_devid(tgt_device); btrfs_rm_dev_replace_free_srcdev(src_device); diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 119edd4341d6..651aa65b1f3f 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -960,7 +960,7 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info) addrm_unknown_feature_attrs(fs_info, false); sysfs_remove_group(&fs_info->fs_devices->fsid_kobj, &btrfs_feature_attr_group); sysfs_remove_files(&fs_info->fs_devices->fsid_kobj, btrfs_attrs); - btrfs_sysfs_rm_device_link(fs_info->fs_devices, NULL); + btrfs_sysfs_remove_devices_dir(fs_info->fs_devices, NULL); } static const char * const btrfs_feature_set_names[FEAT_MAX] = { @@ -1149,7 +1149,7 @@ int btrfs_sysfs_add_space_info_type(struct btrfs_fs_info *fs_info, /* when one_device is NULL, it removes all device links */ -int btrfs_sysfs_rm_device_link(struct btrfs_fs_devices *fs_devices, +int btrfs_sysfs_remove_devices_dir(struct btrfs_fs_devices *fs_devices, struct btrfs_device *one_device) { struct hd_struct *disk; @@ -1269,7 +1269,7 @@ static struct kobj_type devid_ktype = { .release = btrfs_release_devid_kobj, }; -int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices, +int btrfs_sysfs_add_devices_dir(struct btrfs_fs_devices *fs_devices, struct btrfs_device *one_device) { int error = 0; @@ -1395,13 +1395,13 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info) btrfs_set_fs_info_ptr(fs_info); - error = btrfs_sysfs_add_device_link(fs_devs, NULL); + error = btrfs_sysfs_add_devices_dir(fs_devs, NULL); if (error) return error; error = sysfs_create_files(fsid_kobj, btrfs_attrs); if (error) { - btrfs_sysfs_rm_device_link(fs_devs, NULL); + btrfs_sysfs_remove_devices_dir(fs_devs, NULL); return error; } diff --git a/fs/btrfs/sysfs.h b/fs/btrfs/sysfs.h index c68582add92e..718a26c97833 100644 --- a/fs/btrfs/sysfs.h +++ b/fs/btrfs/sysfs.h @@ -14,9 +14,9 @@ enum btrfs_feature_set { char *btrfs_printable_features(enum btrfs_feature_set set, u64 flags); const char * const btrfs_feature_set_name(enum btrfs_feature_set set); -int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices, +int btrfs_sysfs_add_devices_dir(struct btrfs_fs_devices *fs_devices, struct btrfs_device *one_device); -int btrfs_sysfs_rm_device_link(struct btrfs_fs_devices *fs_devices, +int btrfs_sysfs_remove_devices_dir(struct btrfs_fs_devices *fs_devices, struct btrfs_device *one_device); int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs); void btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs); diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index b092021e41e9..387f80656476 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2054,7 +2054,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, if (device->bdev) { cur_devices->open_devices--; /* remove sysfs entry */ - btrfs_sysfs_rm_device_link(fs_devices, device); + btrfs_sysfs_remove_devices_dir(fs_devices, device); } num_devices = btrfs_super_num_devices(fs_info->super_copy) - 1; @@ -2174,7 +2174,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev) mutex_lock(&fs_devices->device_list_mutex); - btrfs_sysfs_rm_device_link(fs_devices, tgtdev); + btrfs_sysfs_remove_devices_dir(fs_devices, tgtdev); if (tgtdev->bdev) fs_devices->open_devices--; @@ -2522,7 +2522,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path orig_super_num_devices + 1); /* add sysfs device entry */ - btrfs_sysfs_add_device_link(fs_devices, device); + btrfs_sysfs_add_devices_dir(fs_devices, device); /* * we've got more storage, clear any full flags on the space @@ -2590,7 +2590,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path return ret; error_sysfs: - btrfs_sysfs_rm_device_link(fs_devices, device); + btrfs_sysfs_remove_devices_dir(fs_devices, device); mutex_lock(&fs_info->fs_devices->device_list_mutex); mutex_lock(&fs_info->chunk_mutex); list_del_rcu(&device->dev_list); -- cgit v1.2.3