From: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Date: Sun, 6 Sep 2026 13:02:29 +0000 (-0400)
Subject: btrfs: stripe_alloc: DEBUG: on a live metadata write-hole hit, print the written... 
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=580309ebd9563b652bd1694a549b64d3b141f00a;p=linux

btrfs: stripe_alloc: DEBUG: on a live metadata write-hole hit, print the written blocks and the runs covering the stripe

Candidate-only diagnostic for the 90 live old-generation hits outside the
system chunk (dhive cand16): which owner wrote the new-generation blocks
into a stripe that still holds committed blocks, and what open runs the
allocator had over that stripe.

Assisted-by: Claude:claude-fable-5
---

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 8ee3a64dddb90..daa2404cb75ae 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -511,6 +511,42 @@ static void btrfs_dump_open_meta_runs(struct btrfs_block_group *bg)
 	spin_unlock_irqrestore(&bg->stripe_run_lock, flags);
 }
 
+/* DEBUG: every open run overlapping [logical, logical + len), any class. */
+void btrfs_stripe_dump_runs_at(struct btrfs_fs_info *fs_info, u64 logical,
+			       u64 len)
+{
+	struct btrfs_block_group *bg = btrfs_lookup_block_group(fs_info, logical);
+	struct btrfs_open_stripe_run *run;
+	unsigned long flags;
+	int n = 0;
+
+	if (!bg) {
+		btrfs_warn(fs_info, "  no block group for %llu", logical);
+		return;
+	}
+	btrfs_warn(fs_info,
+"  bg %llu len %llu ro %d armed %d claimable %llu trapped %llu fsl %llu",
+		   bg->start, bg->length, bg->ro,
+		   READ_ONCE(bg->stripe_unusable_ready),
+		   (u64)bg->stripe_claimable, (u64)bg->stripe_unusable,
+		   (u64)bg->full_stripe_len);
+	spin_lock_irqsave(&bg->stripe_run_lock, flags);
+	list_for_each_entry(run, &bg->open_stripe_runs, list) {
+		if (run->end <= logical || run->start >= logical + len)
+			continue;
+		n++;
+		btrfs_warn(fs_info,
+"  run %llu..%llu frontier %llu open %d inflight %llu transid %llu class %d open_seq %llu",
+			   run->start, run->end, run->offset, run->open,
+			   run->inflight_bytes, run->transid, run->class,
+			   run->open_seq);
+	}
+	spin_unlock_irqrestore(&bg->stripe_run_lock, flags);
+	if (!n)
+		btrfs_warn(fs_info, "  no open run covers %llu", logical);
+	btrfs_put_block_group(bg);
+}
+
 static bool bg_has_undrained_meta_runs(struct btrfs_block_group *bg,
 				       u64 transid)
 {
diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index 44eee7e5e740d..25f9cca2fbf82 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -508,6 +508,8 @@ void btrfs_log_settle_stripes(struct btrfs_inode *inode, u64 file_start,
 int btrfs_stripe_alloc_check_support(struct btrfs_fs_info *fs_info);
 int btrfs_enable_stripe_alloc(struct btrfs_fs_info *fs_info);
 void btrfs_disable_stripe_alloc(struct btrfs_fs_info *fs_info);
+void btrfs_stripe_dump_runs_at(struct btrfs_fs_info *fs_info, u64 logical,
+			       u64 len);
 void btrfs_retire_open_stripes(struct btrfs_fs_info *fs_info,
 			       struct btrfs_transaction *trans);
 void btrfs_clear_data_reloc_bg(struct btrfs_block_group *bg);
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 7ebeb08f77615..ef7ac9aefa922 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -2987,6 +2987,8 @@ static void audit_uncovered_rmw(struct btrfs_raid_bio *rbio)
 	 */
 	index_rbio_pages(rbio);
 
+	bool dumped = false;
+
 	/* The generation this write is putting into the stripe. */
 	for (u32 i = 0; i < nsectors; i += sectors_per_tree) {
 		u64 gen;
@@ -3040,6 +3042,29 @@ static void audit_uncovered_rmw(struct btrfs_raid_bio *rbio)
 "read-modify-write of stripe %llu rewrites parity over committed tree block %llu at generation %llu (refs %llu, extent generation %llu) while writing generation %llu: write hole",
 				      rbio->bioc->full_stripe_logical, logical,
 				      gen, refs, egen, write_gen);
+			/* DEBUG: who wrote here, and which run handed it out */
+			if (!dumped) {
+				dumped = true;
+				for (u32 j = 0; j < nsectors; j += sectors_per_tree) {
+					struct btrfs_header *h;
+					void *ka;
+
+					if (!rbio->bio_sectors[j].has_paddr)
+						continue;
+					ka = kmap_local_sector(&rbio->bio_sectors[j]);
+					h = ka;
+					btrfs_warn(fs_info,
+"  covered block %llu owner %llu generation %llu level %u (sector %u)",
+						   btrfs_stack_header_bytenr(h),
+						   btrfs_stack_header_owner(h),
+						   btrfs_stack_header_generation(h),
+						   (unsigned int)h->level, j);
+					kunmap_local(ka);
+				}
+				btrfs_stripe_dump_runs_at(fs_info,
+					rbio->bioc->full_stripe_logical,
+					(u64)rbio->nr_data * BTRFS_STRIPE_LEN);
+			}
 		}
 	}
 }