[PATCH v4 7/9] btrfs: refactor scrub_raid56_parity()

Qu Wenruo
2022-03-11T07:39:19Z

Currently scrub_raid56_parity() has a large double loop, handling the
following things at the same time:

- Iterate each data stripe
- Iterate each extent item in one data stripe

Refactor this mess by:

- Introduce a new helper to handle data stripe iteration
The new helper is scrub_raid56_data_stripe_for_parity(), which
only has one while() loop handling the extent items inside the
data stripe.

The code is still mostly the same as the old code.

- Call cond_resched() for each extent
Previously we only call cond_resched() under a complex if () check.
I see no special reason to do that, and for other scrub functions,
like scrub_simple_mirror() we're already doing the same cond_resched()
after scrubbing one extent.

- Add extra comments
To improve the readability

Please note that, this patch is only to address the double loop, there
are incoming patches to do extra cleanup.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/scrub.c | 345 ++++++++++++++++++++++-------------------------
1 file changed, 164 insertions(+), 181 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index cd34db07e387..5c538bc7414e 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3019,6 +3019,164 @@ static bool does_range_cross_boundary(u64 extent_start, u64 extent_len,
extent_start + extent_len > boundary_start + boudary_len);
}

+static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
+ struct scrub_parity *sparity,
+ struct map_lookup *map,
+ struct btrfs_device *sdev,
+ struct btrfs_path *path,
+ u64 logical)
+{
+ struct btrfs_fs_info *fs_info = sctx->fs_info;
+ struct btrfs_root *extent_root = btrfs_extent_root(fs_info, logical);
+ struct btrfs_root *csum_root = btrfs_csum_root(fs_info, logical);
+ struct btrfs_key key;
+ int ret;
+
+ ASSERT(map->type & BTRFS_BLOCK_GROUP_RAID56_MASK);
+
+ /* Path should not be populated */
+ ASSERT(!path->nodes[0]);
+
+ if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
+ key.type = BTRFS_METADATA_ITEM_KEY;
+ else
+ key.type = BTRFS_EXTENT_ITEM_KEY;
+ key.objectid = logical;
+ key.offset = (u64)-1;
+
+ ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
+ if (ret < 0)
+ return ret;
+
+ if (ret > 0) {
+ ret = btrfs_previous_extent_item(extent_root, path, 0);
+ if (ret < 0)
+ return ret;
+ if (ret > 0) {
+ btrfs_release_path(path);
+ ret = btrfs_search_slot(NULL, extent_root, &key, path,
+ 0, 0);
+ if (ret < 0)
+ return ret;
+ }
+ }
+
+ while (1) {
+ struct btrfs_io_context *bioc = NULL;
+ struct btrfs_device *extent_dev;
+ struct btrfs_extent_item *ei;
+ struct extent_buffer *l;
+ int slot;
+ u64 extent_start;
+ u64 extent_size;
+ u64 mapped_length;
+ u64 extent_flags;
+ u64 extent_gen;
+ u64 extent_physical;
+ u64 extent_mirror_num;
+
+ l = path->nodes[0];
+ slot = path->slots[0];
+ if (slot >= btrfs_header_nritems(l)) {
+ ret = btrfs_next_leaf(extent_root, path);
+ if (ret == 0)
+ continue;
+
+ /* No more extent items or error, exit */
+ break;
+ }
+ btrfs_item_key_to_cpu(l, &key, slot);
+
+ if (key.type != BTRFS_EXTENT_ITEM_KEY &&
+ key.type != BTRFS_METADATA_ITEM_KEY)
+ goto next;
+
+ if (key.type == BTRFS_METADATA_ITEM_KEY)
+ extent_size = fs_info->nodesize;
+ else
+ extent_size = key.offset;
+
+ if (key.objectid + extent_size <= logical)
+ goto next;
+
+ /* Beyond this data stripe */
+ if (key.objectid >= logical + map->stripe_len)
+ break;
+
+ ei = btrfs_item_ptr(l, slot, struct btrfs_extent_item);
+ extent_flags = btrfs_extent_flags(l, ei);
+ extent_gen = btrfs_extent_generation(l, ei);
+
+ if ((extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
+ (key.objectid < logical || key.objectid + extent_size >
+ logical + map->stripe_len)) {
+ btrfs_err(fs_info,
+ "scrub: tree block %llu spanning stripes, ignored. logical=%llu",
+ key.objectid, logical);
+ spin_lock(&sctx->stat_lock);
+ sctx->stat.uncorrectable_errors++;
+ spin_unlock(&sctx->stat_lock);
+ goto next;
+ }
+
+ extent_start = key.objectid;
+ ASSERT(extent_size <= U32_MAX);
+
+ /* Truncate the range inside the data stripe */
+ if (extent_start < logical) {
+ extent_size -= logical - extent_start;
+ extent_start = logical;
+ }
+ if (extent_start + extent_size > logical + map->stripe_len)
+ extent_size = logical + map->stripe_len - extent_start;
+
+ scrub_parity_mark_sectors_data(sparity, extent_start, extent_size);
+
+ mapped_length = extent_size;
+ ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, extent_start,
+ &mapped_length, &bioc, 0);
+ if (!ret && (!bioc || mapped_length < extent_size))
+ ret = -EIO;
+ if (ret) {
+ btrfs_put_bioc(bioc);
+ scrub_parity_mark_sectors_error(sparity, extent_start,
+ extent_size);
+ break;
+ }
+ extent_physical = bioc->stripes[0].physical;
+ extent_mirror_num = bioc->mirror_num;
+ extent_dev = bioc->stripes[0].dev;
+ btrfs_put_bioc(bioc);
+
+ ret = btrfs_lookup_csums_range(csum_root, extent_start,
+ extent_start + extent_size - 1,
+ &sctx->csum_list, 1);
+ if (ret) {
+ scrub_parity_mark_sectors_error(sparity, extent_start,
+ extent_size);
+ break;
+ }
+
+ ret = scrub_extent_for_parity(sparity, extent_start,
+ extent_size, extent_physical,
+ extent_dev, extent_flags,
+ extent_gen, extent_mirror_num);
+ scrub_free_csums(sctx);
+
+ if (ret) {
+ scrub_parity_mark_sectors_error(sparity, extent_start,
+ extent_size);
+ break;
+ }
+
+ cond_resched();
+next:
+ path->slots[0]++;
+ }
+ btrfs_release_path(path);
+ return ret;
+}
+
static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
struct map_lookup *map,
struct btrfs_device *sdev,
@@ -3026,28 +3184,12 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
u64 logic_end)
{
struct btrfs_fs_info *fs_info = sctx->fs_info;
- struct btrfs_root *root = btrfs_extent_root(fs_info, logic_start);
- struct btrfs_root *csum_root;
- struct btrfs_extent_item *extent;
- struct btrfs_io_context *bioc = NULL;
struct btrfs_path *path;
- u64 flags;
+ u64 cur_logical;
int ret;
- int slot;
- struct extent_buffer *l;
- struct btrfs_key key;
- u64 generation;
- u64 extent_logical;
- u64 extent_physical;
- /* Check the comment in scrub_stripe() for why u32 is enough here */
- u32 extent_len;
- u64 mapped_length;
- struct btrfs_device *extent_dev;
struct scrub_parity *sparity;
int nsectors;
int bitmap_len;
- int extent_mirror_num;
- int stop_loop = 0;

path = btrfs_alloc_path();
if (!path) {
@@ -3085,173 +3227,14 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
sparity->ebitmap = (void *)sparity->bitmap + bitmap_len;

ret = 0;
- while (logic_start < logic_end) {
- if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
- key.type = BTRFS_METADATA_ITEM_KEY;
- else
- key.type = BTRFS_EXTENT_ITEM_KEY;
- key.objectid = logic_start;
- key.offset = (u64)-1;
-
- ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+ for (cur_logical = logic_start; cur_logical < logic_end;
+ cur_logical += map->stripe_len) {
+ ret = scrub_raid56_data_stripe_for_parity(sctx, sparity, map,
+ sdev, path, cur_logical);
if (ret < 0)
- goto out;
-
- if (ret > 0) {
- ret = btrfs_previous_extent_item(root, path, 0);
- if (ret < 0)
- goto out;
- if (ret > 0) {
- btrfs_release_path(path);
- ret = btrfs_search_slot(NULL, root, &key,
- path, 0, 0);
- if (ret < 0)
- goto out;
- }
- }
-
- stop_loop = 0;
- while (1) {
- u64 bytes;
-
- l = path->nodes[0];
- slot = path->slots[0];
- if (slot >= btrfs_header_nritems(l)) {
- ret = btrfs_next_leaf(root, path);
- if (ret == 0)
- continue;
- if (ret < 0)
- goto out;
-
- stop_loop = 1;
- break;
- }
- btrfs_item_key_to_cpu(l, &key, slot);
-
- if (key.type != BTRFS_EXTENT_ITEM_KEY &&
- key.type != BTRFS_METADATA_ITEM_KEY)
- goto next;
-
- if (key.type == BTRFS_METADATA_ITEM_KEY)
- bytes = fs_info->nodesize;
- else
- bytes = key.offset;
-
- if (key.objectid + bytes <= logic_start)
- goto next;
-
- if (key.objectid >= logic_end) {
- stop_loop = 1;
- break;
- }
-
- while (key.objectid >= logic_start + map->stripe_len)
- logic_start += map->stripe_len;
-
- extent = btrfs_item_ptr(l, slot,
- struct btrfs_extent_item);
- flags = btrfs_extent_flags(l, extent);
- generation = btrfs_extent_generation(l, extent);
-
- if ((flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
- (key.objectid < logic_start ||
- key.objectid + bytes >
- logic_start + map->stripe_len)) {
- btrfs_err(fs_info,
- "scrub: tree block %llu spanning stripes, ignored. logical=%llu",
- key.objectid, logic_start);
- spin_lock(&sctx->stat_lock);
- sctx->stat.uncorrectable_errors++;
- spin_unlock(&sctx->stat_lock);
- goto next;
- }
-again:
- extent_logical = key.objectid;
- ASSERT(bytes <= U32_MAX);
- extent_len = bytes;
-
- if (extent_logical < logic_start) {
- extent_len -= logic_start - extent_logical;
- extent_logical = logic_start;
- }
-
- if (extent_logical + extent_len >
- logic_start + map->stripe_len)
- extent_len = logic_start + map->stripe_len -
- extent_logical;
-
- scrub_parity_mark_sectors_data(sparity, extent_logical,
- extent_len);
-
- mapped_length = extent_len;
- bioc = NULL;
- ret = btrfs_map_block(fs_info, BTRFS_MAP_READ,
- extent_logical, &mapped_length, &bioc,
- 0);
- if (!ret) {
- if (!bioc || mapped_length < extent_len)
- ret = -EIO;
- }
- if (ret) {
- btrfs_put_bioc(bioc);
- goto out;
- }
- extent_physical = bioc->stripes[0].physical;
- extent_mirror_num = bioc->mirror_num;
- extent_dev = bioc->stripes[0].dev;
- btrfs_put_bioc(bioc);
-
- csum_root = btrfs_csum_root(fs_info, extent_logical);
- ret = btrfs_lookup_csums_range(csum_root,
- extent_logical,
- extent_logical + extent_len - 1,
- &sctx->csum_list, 1);
- if (ret)
- goto out;
-
- ret = scrub_extent_for_parity(sparity, extent_logical,
- extent_len,
- extent_physical,
- extent_dev, flags,
- generation,
- extent_mirror_num);
-
- scrub_free_csums(sctx);
-
- if (ret)
- goto out;
-
- if (extent_logical + extent_len <
- key.objectid + bytes) {
- logic_start += map->stripe_len;
-
- if (logic_start >= logic_end) {
- stop_loop = 1;
- break;
- }
-
- if (logic_start < key.objectid + bytes) {
- cond_resched();
- goto again;
- }
- }
-next:
- path->slots[0]++;
- }
-
- btrfs_release_path(path);
-
- if (stop_loop)
break;
-
- logic_start += map->stripe_len;
- }
-out:
- if (ret < 0) {
- ASSERT(logic_end - logic_start <= U32_MAX);
- scrub_parity_mark_sectors_error(sparity, logic_start,
- logic_end - logic_start);
}
+
scrub_parity_put(sparity);
scrub_submit(sctx);
mutex_lock(&sctx->wr_lock);
--
2.35.1