X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libbcachefs%2Fdata_update.c;h=6b0a5fbe377ca59607fcdac49dd4c4984332fac0;hb=9690f783569ebeb166dfc1745c0ba0f48db523d0;hp=3102166d38c22ab297ed1f085f8f2ed617a9e774;hpb=8d6138baac3b4fcd715c34cf325ae11b01a4ca67;p=bcachefs-tools-debian

diff --git a/libbcachefs/data_update.c b/libbcachefs/data_update.c
index 3102166..6b0a5fb 100644
--- a/libbcachefs/data_update.c
+++ b/libbcachefs/data_update.c
@@ -7,10 +7,12 @@
 #include "buckets.h"
 #include "data_update.h"
 #include "ec.h"
+#include "error.h"
 #include "extents.h"
 #include "io.h"
 #include "keylist.h"
 #include "move.h"
+#include "nocow_locking.h"
 #include "subvolume.h"
 
 #include <trace/events/bcachefs.h>
@@ -21,9 +23,10 @@ static int insert_snapshot_whiteouts(struct btree_trans *trans,
 				     struct bpos new_pos)
 {
 	struct bch_fs *c = trans->c;
-	struct btree_iter iter, update_iter;
-	struct bkey_s_c k;
+	struct btree_iter iter, iter2;
+	struct bkey_s_c k, k2;
 	snapshot_id_list s;
+	struct bkey_i *update;
 	int ret;
 
 	if (!btree_type_has_snapshots(id))
@@ -31,10 +34,7 @@ static int insert_snapshot_whiteouts(struct btree_trans *trans,
 
 	darray_init(&s);
 
-	if (!bkey_cmp(old_pos, new_pos))
-		return 0;
-
-	if (!snapshot_t(c, old_pos.snapshot)->children[0])
+	if (!bch2_snapshot_has_children(c, old_pos.snapshot))
 		return 0;
 
 	bch2_trans_iter_init(trans, &iter, id, old_pos,
@@ -46,33 +46,39 @@ static int insert_snapshot_whiteouts(struct btree_trans *trans,
 		if (ret)
 			break;
 
-		if (bkey_cmp(old_pos, k.k->p))
+		if (!k.k)
 			break;
 
-		if (bch2_snapshot_is_ancestor(c, k.k->p.snapshot, old_pos.snapshot)) {
-			struct bkey_i *update;
-
-			if (snapshot_list_has_ancestor(c, &s, k.k->p.snapshot))
-				continue;
-
-			update = bch2_trans_kmalloc(trans, sizeof(struct bkey_i));
+		if (!bkey_eq(old_pos, k.k->p))
+			break;
 
-			ret = PTR_ERR_OR_ZERO(update);
-			if (ret)
-				break;
+		if (bch2_snapshot_is_ancestor(c, k.k->p.snapshot, old_pos.snapshot) &&
+		    !snapshot_list_has_ancestor(c, &s, k.k->p.snapshot)) {
+			struct bpos whiteout_pos = new_pos;
 
-			bkey_init(&update->k);
-			update->k.p = new_pos;
-			update->k.p.snapshot = k.k->p.snapshot;
+			whiteout_pos.snapshot = k.k->p.snapshot;
 
-			bch2_trans_iter_init(trans, &update_iter, id, update->k.p,
+			bch2_trans_iter_init(trans, &iter2, id, whiteout_pos,
 					     BTREE_ITER_NOT_EXTENTS|
-					     BTREE_ITER_ALL_SNAPSHOTS|
 					     BTREE_ITER_INTENT);
-			ret   = bch2_btree_iter_traverse(&update_iter) ?:
-				bch2_trans_update(trans, &update_iter, update,
-					  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-			bch2_trans_iter_exit(trans, &update_iter);
+			k2 = bch2_btree_iter_peek_slot(&iter2);
+			ret = bkey_err(k2);
+
+			if (!ret && k2.k->type == KEY_TYPE_deleted) {
+				update = bch2_trans_kmalloc(trans, sizeof(struct bkey_i));
+				ret = PTR_ERR_OR_ZERO(update);
+				if (ret)
+					break;
+
+				bkey_init(&update->k);
+				update->k.p		= whiteout_pos;
+				update->k.type		= KEY_TYPE_whiteout;
+
+				ret = bch2_trans_update(trans, &iter2, update,
+							BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+			}
+			bch2_trans_iter_exit(trans, &iter2);
+
 			if (ret)
 				break;
 
@@ -87,20 +93,74 @@ static int insert_snapshot_whiteouts(struct btree_trans *trans,
 	return ret;
 }
 
-static void bch2_bkey_mark_dev_cached(struct bkey_s k, unsigned dev)
+static void trace_move_extent_fail2(struct data_update *m,
+			 struct bkey_s_c new,
+			 struct bkey_s_c wrote,
+			 struct bkey_i *insert,
+			 const char *msg)
 {
-	struct bkey_ptrs ptrs = bch2_bkey_ptrs(k);
+	struct bch_fs *c = m->op.c;
+	struct bkey_s_c old = bkey_i_to_s_c(m->k.k);
+	const union bch_extent_entry *entry;
 	struct bch_extent_ptr *ptr;
+	struct extent_ptr_decoded p;
+	struct printbuf buf = PRINTBUF;
+	unsigned i, rewrites_found = 0;
 
-	bkey_for_each_ptr(ptrs, ptr)
-		if (ptr->dev == dev)
-			ptr->cached = true;
+	if (!trace_move_extent_fail_enabled())
+		return;
+
+	prt_str(&buf, msg);
+
+	if (insert) {
+		i = 0;
+		bkey_for_each_ptr_decode(old.k, bch2_bkey_ptrs_c(old), p, entry) {
+			struct bkey_s new_s;
+			new_s.k = (void *) new.k;
+			new_s.v = (void *) new.v;
+
+			if (((1U << i) & m->data_opts.rewrite_ptrs) &&
+			    (ptr = bch2_extent_has_ptr(old, p, bkey_i_to_s(insert))) &&
+			    !ptr->cached)
+				rewrites_found |= 1U << i;
+			i++;
+		}
+	}
+
+	prt_printf(&buf, "\nrewrite ptrs:   %u%u%u%u",
+		   (m->data_opts.rewrite_ptrs & (1 << 0)) != 0,
+		   (m->data_opts.rewrite_ptrs & (1 << 1)) != 0,
+		   (m->data_opts.rewrite_ptrs & (1 << 2)) != 0,
+		   (m->data_opts.rewrite_ptrs & (1 << 3)) != 0);
+
+	prt_printf(&buf, "\nrewrites found: %u%u%u%u",
+		   (rewrites_found & (1 << 0)) != 0,
+		   (rewrites_found & (1 << 1)) != 0,
+		   (rewrites_found & (1 << 2)) != 0,
+		   (rewrites_found & (1 << 3)) != 0);
+
+	prt_str(&buf, "\nold:    ");
+	bch2_bkey_val_to_text(&buf, c, old);
+
+	prt_str(&buf, "\nnew:    ");
+	bch2_bkey_val_to_text(&buf, c, new);
+
+	prt_str(&buf, "\nwrote:  ");
+	bch2_bkey_val_to_text(&buf, c, wrote);
+
+	if (insert) {
+		prt_str(&buf, "\ninsert: ");
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(insert));
+	}
+
+	trace_move_extent_fail(c, buf.buf);
+	printbuf_exit(&buf);
 }
 
-static int bch2_data_update_index_update(struct bch_write_op *op)
+static int __bch2_data_update_index_update(struct btree_trans *trans,
+					   struct bch_write_op *op)
 {
 	struct bch_fs *c = op->c;
-	struct btree_trans trans;
 	struct btree_iter iter;
 	struct data_update *m =
 		container_of(op, struct data_update, op);
@@ -112,26 +172,26 @@ static int bch2_data_update_index_update(struct bch_write_op *op)
 	bch2_bkey_buf_init(&_insert);
 	bch2_bkey_buf_realloc(&_insert, c, U8_MAX);
 
-	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
-
-	bch2_trans_iter_init(&trans, &iter, m->btree_id,
+	bch2_trans_iter_init(trans, &iter, m->btree_id,
 			     bkey_start_pos(&bch2_keylist_front(keys)->k),
 			     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 
 	while (1) {
 		struct bkey_s_c k;
 		struct bkey_s_c old = bkey_i_to_s_c(m->k.k);
-		struct bkey_i *insert;
+		struct bkey_i *insert = NULL;
 		struct bkey_i_extent *new;
-		const union bch_extent_entry *entry;
+		const union bch_extent_entry *entry_c;
+		union bch_extent_entry *entry;
 		struct extent_ptr_decoded p;
+		struct bch_extent_ptr *ptr;
+		const struct bch_extent_ptr *ptr_c;
 		struct bpos next_pos;
-		bool did_work = false;
 		bool should_check_enospc;
 		s64 i_sectors_delta = 0, disk_sectors_delta = 0;
-		unsigned i;
+		unsigned rewrites_found = 0, durability, i;
 
-		bch2_trans_begin(&trans);
+		bch2_trans_begin(trans);
 
 		k = bch2_btree_iter_peek_slot(&iter);
 		ret = bkey_err(k);
@@ -140,8 +200,11 @@ static int bch2_data_update_index_update(struct bch_write_op *op)
 
 		new = bkey_i_to_extent(bch2_keylist_front(keys));
 
-		if (!bch2_extents_match(k, old))
-			goto nomatch;
+		if (!bch2_extents_match(k, old)) {
+			trace_move_extent_fail2(m, k, bkey_i_to_s_c(&new->k_i),
+						NULL, "no match:");
+			goto nowork;
+		}
 
 		bkey_reassemble(_insert.k, k);
 		insert = _insert.k;
@@ -164,45 +227,80 @@ static int bch2_data_update_index_update(struct bch_write_op *op)
 		 * Fist, drop rewrite_ptrs from @new:
 		 */
 		i = 0;
-		bkey_for_each_ptr_decode(old.k, bch2_bkey_ptrs_c(old), p, entry) {
+		bkey_for_each_ptr_decode(old.k, bch2_bkey_ptrs_c(old), p, entry_c) {
 			if (((1U << i) & m->data_opts.rewrite_ptrs) &&
-			    bch2_extent_has_ptr(old, p, bkey_i_to_s_c(insert))) {
+			    (ptr = bch2_extent_has_ptr(old, p, bkey_i_to_s(insert))) &&
+			    !ptr->cached) {
+				bch2_bkey_drop_ptr_noerror(bkey_i_to_s(insert), ptr);
 				/*
-				 * If we're going to be adding a pointer to the
-				 * same device, we have to drop the old one -
-				 * otherwise, we can just mark it cached:
-				 */
-				if (bch2_bkey_has_device(bkey_i_to_s_c(&new->k_i), p.ptr.dev))
-					bch2_bkey_drop_device_noerror(bkey_i_to_s(insert), p.ptr.dev);
-				else
-					bch2_bkey_mark_dev_cached(bkey_i_to_s(insert), p.ptr.dev);
+				 * See comment below:
+				bch2_extent_ptr_set_cached(bkey_i_to_s(insert), ptr);
+				*/
+				rewrites_found |= 1U << i;
 			}
 			i++;
 		}
 
+		if (m->data_opts.rewrite_ptrs &&
+		    !rewrites_found &&
+		    bch2_bkey_durability(c, k) >= m->op.opts.data_replicas) {
+			trace_move_extent_fail2(m, k, bkey_i_to_s_c(&new->k_i), insert, "no rewrites found:");
+			goto nowork;
+		}
 
-		/* Add new ptrs: */
-		extent_for_each_ptr_decode(extent_i_to_s(new), p, entry) {
-			if (bch2_bkey_has_device(bkey_i_to_s_c(insert), p.ptr.dev)) {
-				/*
-				 * raced with another move op? extent already
-				 * has a pointer to the device we just wrote
-				 * data to
-				 */
-				continue;
+		/*
+		 * A replica that we just wrote might conflict with a replica
+		 * that we want to keep, due to racing with another move:
+		 */
+restart_drop_conflicting_replicas:
+		extent_for_each_ptr(extent_i_to_s(new), ptr)
+			if ((ptr_c = bch2_bkey_has_device_c(bkey_i_to_s_c(insert), ptr->dev)) &&
+			    !ptr_c->cached) {
+				bch2_bkey_drop_ptr_noerror(bkey_i_to_s(&new->k_i), ptr);
+				goto restart_drop_conflicting_replicas;
 			}
 
-			bch2_extent_ptr_decoded_append(insert, &p);
-			did_work = true;
+		if (!bkey_val_u64s(&new->k)) {
+			trace_move_extent_fail2(m, k, bkey_i_to_s_c(&new->k_i), insert, "new replicas conflicted:");
+			goto nowork;
+		}
+
+		/* Now, drop pointers that conflict with what we just wrote: */
+		extent_for_each_ptr_decode(extent_i_to_s(new), p, entry)
+			if ((ptr = bch2_bkey_has_device(bkey_i_to_s(insert), p.ptr.dev)))
+				bch2_bkey_drop_ptr_noerror(bkey_i_to_s(insert), ptr);
+
+		durability = bch2_bkey_durability(c, bkey_i_to_s_c(insert)) +
+			bch2_bkey_durability(c, bkey_i_to_s_c(&new->k_i));
+
+		/* Now, drop excess replicas: */
+restart_drop_extra_replicas:
+		bkey_for_each_ptr_decode(old.k, bch2_bkey_ptrs(bkey_i_to_s(insert)), p, entry) {
+			unsigned ptr_durability = bch2_extent_ptr_durability(c, &p);
+
+			if (!p.ptr.cached &&
+			    durability - ptr_durability >= m->op.opts.data_replicas) {
+				durability -= ptr_durability;
+				bch2_bkey_drop_ptr_noerror(bkey_i_to_s(insert), &entry->ptr);
+				/*
+				 * Currently, we're dropping unneeded replicas
+				 * instead of marking them as cached, since
+				 * cached data in stripe buckets prevents them
+				 * from being reused:
+				bch2_extent_ptr_set_cached(bkey_i_to_s(insert), &entry->ptr);
+				*/
+				goto restart_drop_extra_replicas;
+			}
 		}
 
-		if (!did_work)
-			goto nomatch;
+		/* Finally, add the pointers we just wrote: */
+		extent_for_each_ptr_decode(extent_i_to_s(new), p, entry)
+			bch2_extent_ptr_decoded_append(insert, &p);
 
 		bch2_bkey_narrow_crcs(insert, (struct bch_extent_crc_unpacked) { 0 });
 		bch2_extent_normalize(c, bkey_i_to_s(insert));
 
-		ret = bch2_sum_sector_overwrites(&trans, &iter, insert,
+		ret = bch2_sum_sector_overwrites(trans, &iter, insert,
 						 &should_check_enospc,
 						 &i_sectors_delta,
 						 &disk_sectors_delta);
@@ -220,12 +318,25 @@ static int bch2_data_update_index_update(struct bch_write_op *op)
 
 		next_pos = insert->k.p;
 
-		ret   = insert_snapshot_whiteouts(&trans, m->btree_id,
-						  k.k->p, insert->k.p) ?:
-			bch2_trans_update(&trans, &iter, insert,
+		if (!bkey_eq(bkey_start_pos(&insert->k), bkey_start_pos(k.k))) {
+			ret = insert_snapshot_whiteouts(trans, m->btree_id, k.k->p,
+							bkey_start_pos(&insert->k));
+			if (ret)
+				goto err;
+		}
+
+		if (!bkey_eq(insert->k.p, k.k->p)) {
+			ret = insert_snapshot_whiteouts(trans, m->btree_id,
+							k.k->p, insert->k.p);
+			if (ret)
+				goto err;
+		}
+
+		ret   = bch2_trans_update(trans, &iter, insert,
 				BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE) ?:
-			bch2_trans_commit(&trans, &op->res,
-				op_journal_seq(op),
+			bch2_trans_commit(trans, &op->res,
+				NULL,
+				BTREE_INSERT_NOCHECK_RW|
 				BTREE_INSERT_NOFAIL|
 				m->data_opts.btree_insert_flags);
 		if (!ret) {
@@ -240,38 +351,40 @@ err:
 		if (ret)
 			break;
 next:
-		while (bkey_cmp(iter.pos, bch2_keylist_front(keys)->k.p) >= 0) {
+		while (bkey_ge(iter.pos, bch2_keylist_front(keys)->k.p)) {
 			bch2_keylist_pop_front(keys);
 			if (bch2_keylist_empty(keys))
 				goto out;
 		}
 		continue;
-nomatch:
-		if (m->ctxt) {
+nowork:
+		if (m->ctxt && m->ctxt->stats) {
 			BUG_ON(k.k->p.offset <= iter.pos.offset);
 			atomic64_inc(&m->ctxt->stats->keys_raced);
 			atomic64_add(k.k->p.offset - iter.pos.offset,
 				     &m->ctxt->stats->sectors_raced);
 		}
 
-		this_cpu_add(c->counters[BCH_COUNTER_move_extent_race], new->k.size);
-		trace_move_extent_race(&new->k);
+		this_cpu_add(c->counters[BCH_COUNTER_move_extent_fail], new->k.size);
 
 		bch2_btree_iter_advance(&iter);
 		goto next;
 	}
 out:
-	bch2_trans_iter_exit(&trans, &iter);
-	bch2_trans_exit(&trans);
+	bch2_trans_iter_exit(trans, &iter);
 	bch2_bkey_buf_exit(&_insert, c);
 	bch2_bkey_buf_exit(&_new, c);
 	BUG_ON(bch2_err_matches(ret, BCH_ERR_transaction_restart));
 	return ret;
 }
 
+int bch2_data_update_index_update(struct bch_write_op *op)
+{
+	return bch2_trans_run(op->c, __bch2_data_update_index_update(&trans, op));
+}
+
 void bch2_data_update_read_done(struct data_update *m,
-				struct bch_extent_crc_unpacked crc,
-				struct closure *cl)
+				struct bch_extent_crc_unpacked crc)
 {
 	/* write bio must own pages: */
 	BUG_ON(!m->op.wbio.bio.bi_vcnt);
@@ -279,29 +392,124 @@ void bch2_data_update_read_done(struct data_update *m,
 	m->op.crc = crc;
 	m->op.wbio.bio.bi_iter.bi_size = crc.compressed_size << 9;
 
-	closure_call(&m->op.cl, bch2_write, NULL, cl);
+	closure_call(&m->op.cl, bch2_write, NULL, NULL);
 }
 
 void bch2_data_update_exit(struct data_update *update)
 {
 	struct bch_fs *c = update->op.c;
+	struct bkey_ptrs_c ptrs =
+		bch2_bkey_ptrs_c(bkey_i_to_s_c(update->k.k));
+	const struct bch_extent_ptr *ptr;
+
+	bkey_for_each_ptr(ptrs, ptr) {
+		if (c->opts.nocow_enabled)
+			bch2_bucket_nocow_unlock(&c->nocow_locks,
+						 PTR_BUCKET_POS(c, ptr), 0);
+		percpu_ref_put(&bch_dev_bkey_exists(c, ptr->dev)->ref);
+	}
 
 	bch2_bkey_buf_exit(&update->k, c);
 	bch2_disk_reservation_put(c, &update->op.res);
 	bch2_bio_free_pages_pool(c, &update->op.wbio.bio);
 }
 
-int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
+void bch2_update_unwritten_extent(struct btree_trans *trans,
+				  struct data_update *update)
+{
+	struct bch_fs *c = update->op.c;
+	struct bio *bio = &update->op.wbio.bio;
+	struct bkey_i_extent *e;
+	struct write_point *wp;
+	struct bch_extent_ptr *ptr;
+	struct closure cl;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	int ret;
+
+	closure_init_stack(&cl);
+	bch2_keylist_init(&update->op.insert_keys, update->op.inline_keys);
+
+	while (bio_sectors(bio)) {
+		unsigned sectors = bio_sectors(bio);
+
+		bch2_trans_iter_init(trans, &iter, update->btree_id, update->op.pos,
+				     BTREE_ITER_SLOTS);
+		ret = lockrestart_do(trans, ({
+			k = bch2_btree_iter_peek_slot(&iter);
+			bkey_err(k);
+		}));
+		bch2_trans_iter_exit(trans, &iter);
+
+		if (ret || !bch2_extents_match(k, bkey_i_to_s_c(update->k.k)))
+			break;
+
+		e = bkey_extent_init(update->op.insert_keys.top);
+		e->k.p = update->op.pos;
+
+		ret = bch2_alloc_sectors_start_trans(trans,
+				update->op.target,
+				false,
+				update->op.write_point,
+				&update->op.devs_have,
+				update->op.nr_replicas,
+				update->op.nr_replicas,
+				update->op.alloc_reserve,
+				0, &cl, &wp);
+		if (bch2_err_matches(ret, BCH_ERR_operation_blocked)) {
+			bch2_trans_unlock(trans);
+			closure_sync(&cl);
+			continue;
+		}
+
+		if (ret)
+			return;
+
+		sectors = min(sectors, wp->sectors_free);
+
+		bch2_key_resize(&e->k, sectors);
+
+		bch2_open_bucket_get(c, wp, &update->op.open_buckets);
+		bch2_alloc_sectors_append_ptrs(c, wp, &e->k_i, sectors, false);
+		bch2_alloc_sectors_done(c, wp);
+
+		bio_advance(bio, sectors << 9);
+		update->op.pos.offset += sectors;
+
+		extent_for_each_ptr(extent_i_to_s(e), ptr)
+			ptr->unwritten = true;
+		bch2_keylist_push(&update->op.insert_keys);
+
+		ret = __bch2_data_update_index_update(trans, &update->op);
+
+		bch2_open_buckets_put(c, &update->op.open_buckets);
+
+		if (ret)
+			break;
+	}
+
+	if ((atomic_read(&cl.remaining) & CLOSURE_REMAINING_MASK) != 1) {
+		bch2_trans_unlock(trans);
+		closure_sync(&cl);
+	}
+}
+
+int bch2_data_update_init(struct btree_trans *trans,
+			  struct moving_context *ctxt,
+			  struct data_update *m,
 			  struct write_point_specifier wp,
 			  struct bch_io_opts io_opts,
 			  struct data_update_opts data_opts,
 			  enum btree_id btree_id,
 			  struct bkey_s_c k)
 {
+	struct bch_fs *c = trans->c;
 	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
 	const union bch_extent_entry *entry;
 	struct extent_ptr_decoded p;
+	const struct bch_extent_ptr *ptr;
 	unsigned i, reserve_sectors = k.k->size * data_opts.extra_replicas;
+	unsigned ptrs_locked = 0;
 	int ret;
 
 	bch2_bkey_buf_init(&m->k);
@@ -312,31 +520,37 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
 	bch2_write_op_init(&m->op, c, io_opts);
 	m->op.pos	= bkey_start_pos(k.k);
 	m->op.version	= k.k->version;
-	m->op.target	= data_opts.target,
+	m->op.target	= data_opts.target;
 	m->op.write_point = wp;
+	m->op.nr_replicas = 0;
 	m->op.flags	|= BCH_WRITE_PAGES_STABLE|
 		BCH_WRITE_PAGES_OWNED|
 		BCH_WRITE_DATA_ENCODED|
-		BCH_WRITE_FROM_INTERNAL|
+		BCH_WRITE_MOVE|
 		m->data_opts.write_flags;
 	m->op.compression_type =
 		bch2_compression_opt_to_type[io_opts.background_compression ?:
 					     io_opts.compression];
 	if (m->data_opts.btree_insert_flags & BTREE_INSERT_USE_RESERVE)
 		m->op.alloc_reserve = RESERVE_movinggc;
-	m->op.index_update_fn	= bch2_data_update_index_update;
+
+	bkey_for_each_ptr(ptrs, ptr)
+		percpu_ref_get(&bch_dev_bkey_exists(c, ptr->dev)->ref);
 
 	i = 0;
 	bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
-		if (p.ptr.cached)
-			m->data_opts.rewrite_ptrs &= ~(1U << i);
+		bool locked;
 
-		if (!((1U << i) & m->data_opts.rewrite_ptrs))
-			bch2_dev_list_add_dev(&m->op.devs_have, p.ptr.dev);
+		if (((1U << i) & m->data_opts.rewrite_ptrs)) {
+			BUG_ON(p.ptr.cached);
 
-		if (((1U << i) & m->data_opts.rewrite_ptrs) &&
-		    crc_is_compressed(p.crc))
-			reserve_sectors += k.k->size;
+			if (crc_is_compressed(p.crc))
+				reserve_sectors += k.k->size;
+
+			m->op.nr_replicas += bch2_extent_ptr_durability(c, &p);
+		} else if (!p.ptr.cached) {
+			bch2_dev_list_add_dev(&m->op.devs_have, p.ptr.dev);
+		}
 
 		/*
 		 * op->csum_type is normally initialized from the fs/file's
@@ -351,6 +565,26 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
 		if (p.crc.compression_type == BCH_COMPRESSION_TYPE_incompressible)
 			m->op.incompressible = true;
 
+		if (c->opts.nocow_enabled) {
+			if (ctxt) {
+				move_ctxt_wait_event(ctxt, trans,
+						(locked = bch2_bucket_nocow_trylock(&c->nocow_locks,
+									  PTR_BUCKET_POS(c, &p.ptr), 0)) ||
+						!atomic_read(&ctxt->read_sectors));
+
+				if (!locked)
+					bch2_bucket_nocow_lock(&c->nocow_locks,
+							       PTR_BUCKET_POS(c, &p.ptr), 0);
+			} else {
+				if (!bch2_bucket_nocow_trylock(&c->nocow_locks,
+							       PTR_BUCKET_POS(c, &p.ptr), 0)) {
+					ret = -BCH_ERR_nocow_lock_blocked;
+					goto err;
+				}
+			}
+			ptrs_locked |= (1U << i);
+		}
+
 		i++;
 	}
 
@@ -360,10 +594,45 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
 				? 0
 				: BCH_DISK_RESERVATION_NOFAIL);
 		if (ret)
-			return ret;
+			goto err;
 	}
 
-	m->op.nr_replicas = m->op.nr_replicas_required =
-		hweight32(m->data_opts.rewrite_ptrs) + m->data_opts.extra_replicas;
+	m->op.nr_replicas += m->data_opts.extra_replicas;
+	m->op.nr_replicas_required = m->op.nr_replicas;
+
+	BUG_ON(!m->op.nr_replicas);
+
+	/* Special handling required: */
+	if (bkey_extent_is_unwritten(k))
+		return -BCH_ERR_unwritten_extent_update;
 	return 0;
+err:
+	i = 0;
+	bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
+		if ((1U << i) & ptrs_locked)
+			bch2_bucket_nocow_unlock(&c->nocow_locks,
+						 PTR_BUCKET_POS(c, &p.ptr), 0);
+		percpu_ref_put(&bch_dev_bkey_exists(c, p.ptr.dev)->ref);
+		i++;
+	}
+
+	bch2_bkey_buf_exit(&m->k, c);
+	bch2_bio_free_pages_pool(c, &m->op.wbio.bio);
+	return ret;
+}
+
+void bch2_data_update_opts_normalize(struct bkey_s_c k, struct data_update_opts *opts)
+{
+	struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
+	const struct bch_extent_ptr *ptr;
+	unsigned i = 0;
+
+	bkey_for_each_ptr(ptrs, ptr) {
+		if ((opts->rewrite_ptrs & (1U << i)) && ptr->cached) {
+			opts->kill_ptrs |= 1U << i;
+			opts->rewrite_ptrs ^= 1U << i;
+		}
+
+		i++;
+	}
 }