[PATCH v4 3/9] btrfs: introduce dedicated helper to scrub simple-mirror based range

Qu Wenruo
2022-03-11T07:39:17Z

The new helper, scrub_simple_mirror(), will scrub all extents inside a range
which only has simple mirror based duplication.

This covers every range of SINGLE/DUP/RAID1/RAID1C*, and inside each
data stripe for RAID0/RAID10.

Currently we will use this function to scrub SINGLE/DUP/RAID1/RAID1C*
profiles.
As one can see, the new entrance for those simple-mirror based profiles
can be small enough (with comments, just reach 100 lines).

This function will be the basis for the incoming scrub refactor.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/scrub.c | 190 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 190 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index ce33cd4aa54d..f2c18acbe497 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2990,6 +2990,26 @@ static int find_first_extent_item(struct btrfs_root *extent_root,
return 1;
}

+static void get_extent_info(struct btrfs_path *path, u64 *extent_start_ret,
+ u64 *size_ret, u64 *flags_ret, u64 *generation_ret)
+{
+ struct btrfs_key key;
+ struct btrfs_extent_item *ei;
+
+ btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+ ASSERT(key.type == BTRFS_METADATA_ITEM_KEY ||
+ key.type == BTRFS_EXTENT_ITEM_KEY);
+ *extent_start_ret = key.objectid;
+ if (key.type == BTRFS_METADATA_ITEM_KEY)
+ *size_ret = path->nodes[0]->fs_info->nodesize;
+ else
+ *size_ret = key.offset;
+ ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+ struct btrfs_extent_item);
+ *flags_ret = btrfs_extent_flags(path->nodes[0], ei);
+ *generation_ret = btrfs_extent_generation(path->nodes[0], ei);
+}
+
static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
struct map_lookup *map,
struct btrfs_device *sdev,
@@ -3273,6 +3293,152 @@ static int sync_write_pointer_for_zoned(struct scrub_ctx *sctx, u64 logical,
return ret;
}

+static bool does_range_cross_boundary(u64 extent_start, u64 extent_len,
+ u64 boundary_start, u64 boudary_len)
+{
+ return (extent_start < boundary_start &&
+ extent_start + extent_len > boundary_start) ||
+ (extent_start < boundary_start + boudary_len &&
+ extent_start + extent_len > boundary_start + boudary_len);
+}
+
+/*
+ * Scrub one range which can only has simple mirror based profile.
+ * (Including all range in SINGLE/DUP/RAID1/RAID1C*, and each stripe in
+ * RAID0/RAID10).
+ *
+ * Since we may need to handle a subset of block group, we need @logical_start
+ * and @logical_length parameter.
+ */
+static int scrub_simple_mirror(struct scrub_ctx *sctx,
+ struct btrfs_root *extent_root,
+ struct btrfs_root *csum_root,
+ struct btrfs_block_group *bg,
+ struct map_lookup *map,
+ u64 logical_start, u64 logical_length,
+ struct btrfs_device *device,
+ u64 physical, int mirror_num)
+{
+ struct btrfs_fs_info *fs_info = sctx->fs_info;
+ const u64 logical_end = logical_start + logical_length;
+ /* An artificial limit, inherit from old scrub behavior */
+ const u32 max_length = SZ_64K;
+ struct btrfs_path path = {};
+ u64 cur_logical = logical_start;
+ int ret;
+
+ /* The range must be inside the bg */
+ ASSERT(logical_start >= bg->start &&
+ logical_end <= bg->start + bg->length);
+
+ path.search_commit_root = 1;
+ path.skip_locking = 1;
+ /* Go through each extent items inside the logical range */
+ while (cur_logical < logical_end) {
+ int cur_mirror = mirror_num;
+ struct btrfs_device *target_dev = device;
+ u64 extent_start;
+ u64 extent_len;
+ u64 extent_flags;
+ u64 extent_gen;
+ u64 scrub_len;
+ u64 cur_physical;
+
+ /* Canceled ? */
+ if (atomic_read(&fs_info->scrub_cancel_req) ||
+ atomic_read(&sctx->cancel_req)) {
+ ret = -ECANCELED;
+ break;
+ }
+ /* Paused ? */
+ if (atomic_read(&fs_info->scrub_pause_req)) {
+ /* Push queued extents */
+ sctx->flush_all_writes = true;
+ scrub_submit(sctx);
+ mutex_lock(&sctx->wr_lock);
+ scrub_wr_submit(sctx);
+ mutex_unlock(&sctx->wr_lock);
+ wait_event(sctx->list_wait,
+ atomic_read(&sctx->bios_in_flight) == 0);
+ sctx->flush_all_writes = false;
+ scrub_blocked_if_needed(fs_info);
+ }
+ /* Block group removed? */
+ spin_lock(&bg->lock);
+ if (bg->removed) {
+ spin_unlock(&bg->lock);
+ ret = 0;
+ break;
+ }
+ spin_unlock(&bg->lock);
+
+ ret = find_first_extent_item(extent_root, &path, cur_logical,
+ logical_end - cur_logical);
+ if (ret > 0) {
+ /* No more extent, just update the accounting */
+ sctx->stat.last_physical = physical + logical_length;
+ ret = 0;
+ break;
+ }
+ if (ret < 0)
+ break;
+ get_extent_info(&path, &extent_start, &extent_len,
+ &extent_flags, &extent_gen);
+ /* Skip hole range which doesn't have any extent */
+ cur_logical = max(extent_start, cur_logical);
+
+ /*
+ * Scrub len has three limits:
+ * - Extent size limit
+ * - Scrub range limit
+ * This is especially imporatant for RAID0/RAID10 to reuse
+ * this function
+ * - Max scrub size limit
+ */
+ scrub_len = min(min(extent_start + extent_len,
+ logical_end), cur_logical + max_length) -
+ cur_logical;
+ cur_physical = cur_logical - logical_start + physical;
+
+ if (sctx->is_dev_replace)
+ scrub_remap_extent(fs_info, cur_logical, scrub_len,
+ &cur_physical, &target_dev, &cur_mirror);
+ if (extent_flags & BTRFS_EXTENT_FLAG_DATA) {
+ ret = btrfs_lookup_csums_range(csum_root, cur_logical,
+ cur_logical + scrub_len - 1,
+ &sctx->csum_list, 1);
+ if (ret)
+ break;
+ }
+ if ((extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
+ does_range_cross_boundary(extent_start, extent_len,
+ logical_start, logical_length)) {
+ btrfs_err(fs_info,
+"scrub: tree block %llu spanning boundaries, ignored. boundary=[%llu, %llu)",
+ extent_start, logical_start, logical_end);
+ spin_lock(&sctx->stat_lock);
+ sctx->stat.uncorrectable_errors++;
+ spin_unlock(&sctx->stat_lock);
+ cur_logical += scrub_len;
+ continue;
+ }
+ ret = scrub_extent(sctx, map, cur_logical, scrub_len, cur_physical,
+ target_dev, extent_flags, extent_gen,
+ cur_mirror, cur_logical - logical_start +
+ physical);
+ scrub_free_csums(sctx);
+ if (ret)
+ break;
+ if (sctx->is_dev_replace)
+ sync_replace_for_zoned(sctx);
+ cur_logical += scrub_len;
+ /* Don't hold CPU for too long time */
+ cond_resched();
+ }
+ btrfs_release_path(&path);
+ return ret;
+}
+
static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
struct btrfs_block_group *bg,
struct map_lookup *map,
@@ -3285,6 +3451,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
struct btrfs_root *csum_root;
struct btrfs_extent_item *extent;
struct blk_plug plug;
+ const u64 profile = map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK;
const u64 chunk_logical = bg->start;
u64 flags;
int ret;
@@ -3377,6 +3544,29 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
sctx->flush_all_writes = true;
}

+ /*
+ * There used to be a big double loop to handle all profiles using the
+ * same routine, which grows larger and more gross over time.
+ *
+ * So here we handle each profile differently, so simpler profiles
+ * have simpler scrubing function.
+ */
+ if (!(profile & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10 |
+ BTRFS_BLOCK_GROUP_RAID56_MASK))) {
+ /*
+ * Above check rules out all complex profile, the remaining
+ * profiles are SINGLE|DUP|RAID1|RAID1C*, which is simple
+ * mirrored duplication without stripe.
+ *
+ * Only @phsyical and @mirror_num needs to calculated using
+ * @stripe_index.
+ */
+ ret = scrub_simple_mirror(sctx, root, csum_root, bg, map,
+ bg->start, bg->length, scrub_dev,
+ map->stripes[stripe_index].physical,
+ stripe_index + 1);
+ goto out;
+ }
/*
* now find all extents for each stripe and scrub them
*/
--
2.35.1