bcachefs: Redo data_update interface

This patch significantly cleans up and simplifies the data_update
interface. Instead of only being able to specify a single pointer by
device to rewrite, we're now able to specify any or all of the pointers
in the original extent to be rewrited, as a bitmask.

data_cmd is no more: the various pred functions now just return true if
the extent should be moved/updated. All the data_update path does is
rewrite existing replicas, or add new ones.

This fixes a bug where with background compression on replicated
filesystems, where rebalance -> data_update would incorrectly drop the
wrong old replica, and keep trying to recompress an extent pointer and
each time failing to drop the right replica. Oops.

Now, the data update path doesn't look at the io options to decide which
pointers to keep and which to drop - it only goes off of the
data_update_options passed to it.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 31 insertions, 32 deletions

diff --git a/fs/bcachefs/movinggc.c b/fs/bcachefs/movinggc.c
index 1e2de1e818c1..d63b9fea4f05 100644
--- a/fs/bcachefs/movinggc.c
+++ b/fs/bcachefs/movinggc.c
@@ -39,15 +39,32 @@ static int bucket_offset_cmp(const void *_l, const void *_r, size_t size)
 		cmp_int(l->offset, r->offset);
 }
 
-static enum data_cmd copygc_pred(struct bch_fs *c, void *arg,
-				 struct bkey_s_c k,
-				 struct bch_io_opts *io_opts,
-				 struct data_opts *data_opts)
+static bool copygc_pred(struct bch_fs *c, void *arg,
+			struct bkey_s_c k,
+			struct bch_io_opts *io_opts,
+			struct data_update_opts *data_opts)
 {
 	copygc_heap *h = &c->copygc_heap;
 	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
 	const union bch_extent_entry *entry;
 	struct extent_ptr_decoded p = { 0 };
+	unsigned i = 0;
+
+	/*
+	 * We need to use the journal reserve here, because
+	 *  - journal reclaim depends on btree key cache
+	 *    flushing to make forward progress,
+	 *  - which has to make forward progress when the
+	 *    journal is pre-reservation full,
+	 *  - and depends on allocation - meaning allocator and
+	 *    copygc
+	 */
+
+	data_opts->rewrite_ptrs		= 0;
+	data_opts->target		= io_opts->background_target;
+	data_opts->extra_replicas	= 0;
+	data_opts->btree_insert_flags	= BTREE_INSERT_USE_RESERVE|
+		JOURNAL_WATERMARK_copygc;
 
 	bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
 		struct bch_dev *ca = bch_dev_bkey_exists(c, p.ptr.dev);
@@ -55,12 +72,12 @@ static enum data_cmd copygc_pred(struct bch_fs *c, void *arg,
 			.dev	= p.ptr.dev,
 			.offset	= p.ptr.offset,
 		};
-		ssize_t i;
+		ssize_t eytz;
 
 		if (p.ptr.cached)
 			continue;
 
-		i = eytzinger0_find_le(h->data, h->used,
+		eytz = eytzinger0_find_le(h->data, h->used,
 				       sizeof(h->data[0]),
 				       bucket_offset_cmp, &search);
 #if 0
@@ -74,34 +91,16 @@ static enum data_cmd copygc_pred(struct bch_fs *c, void *arg,
 
 		BUG_ON(i != j);
 #endif
-		if (i >= 0 &&
-		    p.ptr.dev == h->data[i].dev &&
-		    p.ptr.offset < h->data[i].offset + ca->mi.bucket_size &&
-		    p.ptr.gen == h->data[i].gen) {
-			/*
-			 * We need to use the journal reserve here, because
-			 *  - journal reclaim depends on btree key cache
-			 *    flushing to make forward progress,
-			 *  - which has to make forward progress when the
-			 *    journal is pre-reservation full,
-			 *  - and depends on allocation - meaning allocator and
-			 *    copygc
-			 */
-
-			data_opts->target		= io_opts->background_target;
-			data_opts->nr_replicas		= 1;
-			data_opts->btree_insert_flags	= BTREE_INSERT_USE_RESERVE|
-				JOURNAL_WATERMARK_copygc;
-			data_opts->rewrite_dev		= p.ptr.dev;
-
-			if (p.has_ec)
-				data_opts->nr_replicas += p.ec.redundancy;
-
-			return DATA_REWRITE;
-		}
+		if (eytz >= 0 &&
+		    p.ptr.dev == h->data[eytz].dev &&
+		    p.ptr.offset < h->data[eytz].offset + ca->mi.bucket_size &&
+		    p.ptr.gen == h->data[eytz].gen)
+			data_opts->rewrite_ptrs |= 1U << i;
+
+		i++;
 	}
 
-	return DATA_SKIP;
+	return data_opts->rewrite_ptrs != 0;
 }
 
 static inline int fragmentation_cmp(copygc_heap *heap,