[PATCH v8 06/11] btrfs: implement RST version of scrub

[Johannes Thumshirn <johannes.thumshirn@wdc.com>]

A filesystem that uses the RAID stripe tree for logical to physical
address translation can't use the regular scrub path, that reads all
stripes and then checks if a sector is unused afterwards.

When using the RAID stripe tree, this will result in lookup errors, as the
stripe tree doesn't know the requested logical addresses.

Instead, look up stripes that are backed by the extent bitmap.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/scrub.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index f16220ce5fba..5101e0a3f83e 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -23,6 +23,7 @@
 #include "accessors.h"
 #include "file-item.h"
 #include "scrub.h"
+#include "raid-stripe-tree.h"
 
 /*
  * This is only the first step towards a full-features scrub. It reads all
@@ -1634,6 +1635,56 @@ static void scrub_reset_stripe(struct scrub_stripe *stripe)
 	}
 }
 
+static void scrub_submit_extent_sector_read(struct scrub_ctx *sctx,
+					    struct scrub_stripe *stripe)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	struct btrfs_bio *bbio = NULL;
+	int mirror = stripe->mirror_num;
+	int i;
+
+	atomic_inc(&stripe->pending_io);
+
+	for_each_set_bit(i, &stripe->extent_sector_bitmap, stripe->nr_sectors) {
+		struct page *page;
+		int pgoff;
+
+		page = scrub_stripe_get_page(stripe, i);
+		pgoff = scrub_stripe_get_page_offset(stripe, i);
+
+		/* The current sector cannot be merged, submit the bio. */
+		if (bbio &&
+		    ((i > 0 && !test_bit(i - 1, &stripe->extent_sector_bitmap)) ||
+		     bbio->bio.bi_iter.bi_size >= BTRFS_STRIPE_LEN)) {
+			ASSERT(bbio->bio.bi_iter.bi_size);
+			atomic_inc(&stripe->pending_io);
+			btrfs_submit_bio(bbio, mirror);
+			bbio = NULL;
+		}
+
+		if (!bbio) {
+			bbio = btrfs_bio_alloc(stripe->nr_sectors, REQ_OP_READ,
+				fs_info, scrub_read_endio, stripe);
+			bbio->bio.bi_iter.bi_sector = (stripe->logical +
+				(i << fs_info->sectorsize_bits)) >> SECTOR_SHIFT;
+		}
+
+		__bio_add_page(&bbio->bio, page, fs_info->sectorsize, pgoff);
+	}
+
+	if (bbio) {
+		ASSERT(bbio->bio.bi_iter.bi_size);
+		atomic_inc(&stripe->pending_io);
+		btrfs_submit_bio(bbio, mirror);
+	}
+
+	if (atomic_dec_and_test(&stripe->pending_io)) {
+		wake_up(&stripe->io_wait);
+		INIT_WORK(&stripe->work, scrub_stripe_read_repair_worker);
+		queue_work(stripe->bg->fs_info->scrub_workers, &stripe->work);
+	}
+}
+
 static void scrub_submit_initial_read(struct scrub_ctx *sctx,
 				      struct scrub_stripe *stripe)
 {
@@ -1645,6 +1696,11 @@ static void scrub_submit_initial_read(struct scrub_ctx *sctx,
 	ASSERT(stripe->mirror_num > 0);
 	ASSERT(test_bit(SCRUB_STRIPE_FLAG_INITIALIZED, &stripe->state));
 
+	if (btrfs_need_stripe_tree_update(fs_info, stripe->bg->flags)) {
+		scrub_submit_extent_sector_read(sctx, stripe);
+		return;
+	}
+
 	bbio = btrfs_bio_alloc(SCRUB_STRIPE_PAGES, REQ_OP_READ, fs_info,
 			       scrub_read_endio, stripe);
 

-- 
2.41.0