[PATCH 08/18] bcachefs: bcachefs_metadata_version_cached_backpointers

[Kent Overstreet <kent.overstreet@linux.dev>]

Cached pointers now have backpointers.

This means that we'll be able to kill cached pointers in the
bucket_invalidate path, when invalidating/reusing buckets containing
cached data, instead of leaving them around to be cleaned up by gc_gens
garbago collection - which requires a full metadata scan.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 fs/bcachefs/backpointers.c    | 14 +++++++-------
 fs/bcachefs/bcachefs_format.h |  3 ++-
 fs/bcachefs/buckets.c         |  8 +++-----
 fs/bcachefs/sb-downgrade.c    |  3 +++
 4 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/fs/bcachefs/backpointers.c b/fs/bcachefs/backpointers.c
index bb799b86aa69..c9dfc3657696 100644
--- a/fs/bcachefs/backpointers.c
+++ b/fs/bcachefs/backpointers.c
@@ -611,9 +611,6 @@ static int check_extent_to_backpointers(struct btree_trans *trans,
 	struct extent_ptr_decoded p;
 
 	bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
-		if (p.ptr.cached)
-			continue;
-
 		if (p.ptr.dev == BCH_SB_MEMBER_INVALID)
 			continue;
 
@@ -621,9 +618,11 @@ static int check_extent_to_backpointers(struct btree_trans *trans,
 		struct bch_dev *ca = bch2_dev_rcu_noerror(c, p.ptr.dev);
 		bool check = ca && test_bit(PTR_BUCKET_NR(ca, &p.ptr), ca->bucket_backpointer_mismatches);
 		bool empty = ca && test_bit(PTR_BUCKET_NR(ca, &p.ptr), ca->bucket_backpointer_empty);
+
+		bool stale = p.ptr.cached && (!ca || dev_ptr_stale_rcu(ca, &p.ptr));
 		rcu_read_unlock();
 
-		if (check || empty) {
+		if ((check || empty) && !stale) {
 			struct bkey_i_backpointer bp;
 			bch2_extent_ptr_to_bp(c, btree, level, k, p, entry, &bp);
 
@@ -857,9 +856,8 @@ static int check_bucket_backpointer_mismatch(struct btree_trans *trans, struct b
 			goto err;
 	}
 
-	/* Cached pointers don't have backpointers: */
-
 	if (sectors[ALLOC_dirty]  != a->dirty_sectors ||
+	    sectors[ALLOC_cached] != a->cached_sectors ||
 	    sectors[ALLOC_stripe] != a->stripe_sectors) {
 		if (c->sb.version_upgrade_complete >= bcachefs_metadata_version_backpointer_bucket_gen) {
 			ret = bch2_backpointers_maybe_flush(trans, alloc_k, last_flushed);
@@ -868,6 +866,7 @@ static int check_bucket_backpointer_mismatch(struct btree_trans *trans, struct b
 		}
 
 		if (sectors[ALLOC_dirty]  > a->dirty_sectors ||
+		    sectors[ALLOC_cached] > a->cached_sectors ||
 		    sectors[ALLOC_stripe] > a->stripe_sectors) {
 			ret = check_bucket_backpointers_to_extents(trans, ca, alloc_k.k->p) ?:
 				-BCH_ERR_transaction_restart_nested;
@@ -875,7 +874,8 @@ static int check_bucket_backpointer_mismatch(struct btree_trans *trans, struct b
 		}
 
 		if (!sectors[ALLOC_dirty] &&
-		    !sectors[ALLOC_stripe])
+		    !sectors[ALLOC_stripe] &&
+		    !sectors[ALLOC_cached])
 			__set_bit(alloc_k.k->p.offset, ca->bucket_backpointer_empty);
 		else
 			__set_bit(alloc_k.k->p.offset, ca->bucket_backpointer_mismatches);
diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index f70f0108401f..ef5009b18dd5 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -686,7 +686,8 @@ struct bch_sb_field_ext {
 	x(inode_depth,			BCH_VERSION(1, 17))		\
 	x(persistent_inode_cursors,	BCH_VERSION(1, 18))		\
 	x(autofix_errors,		BCH_VERSION(1, 19))		\
-	x(directory_size,		BCH_VERSION(1, 20))
+	x(directory_size,		BCH_VERSION(1, 20))		\
+	x(cached_backpointers,		BCH_VERSION(1, 21))
 
 enum bcachefs_metadata_version {
 	bcachefs_metadata_version_min = 9,
diff --git a/fs/bcachefs/buckets.c b/fs/bcachefs/buckets.c
index 88af61bc799d..bb7742cf0014 100644
--- a/fs/bcachefs/buckets.c
+++ b/fs/bcachefs/buckets.c
@@ -590,11 +590,9 @@ static int bch2_trigger_pointer(struct btree_trans *trans,
 		if (ret)
 			goto err;
 
-		if (!p.ptr.cached) {
-			ret = bch2_bucket_backpointer_mod(trans, k, &bp, insert);
-			if (ret)
-				goto err;
-		}
+		ret = bch2_bucket_backpointer_mod(trans, k, &bp, insert);
+		if (ret)
+			goto err;
 	}
 
 	if (flags & BTREE_TRIGGER_gc) {
diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c
index 14f6b6a5fb38..34fd897680b3 100644
--- a/fs/bcachefs/sb-downgrade.c
+++ b/fs/bcachefs/sb-downgrade.c
@@ -94,6 +94,9 @@
 	x(directory_size,					\
 	  BIT_ULL(BCH_RECOVERY_PASS_check_inodes),		\
 	  BCH_FSCK_ERR_directory_size_mismatch)			\
+	x(cached_backpointers,					\
+	  BIT_ULL(BCH_RECOVERY_PASS_check_extents_to_backpointers),\
+	  BCH_FSCK_ERR_ptr_to_missing_backpointer)
 
 #define DOWNGRADE_TABLE()					\
 	x(bucket_stripe_sectors,				\
-- 
2.45.2