bcachefs: Rework __bch2_data_update_index_update()

This makes some improvements to the logic for adding/removing replicas,
as part of the larger erasure coding improvements. We now directly
consider number of replicas desired for the given inode, and
extent/pointer durability: this ensures that the extent ends up with the
desired number of replicas when we're replacing multiple pointers with
one that has higher durability (e.g. erasure coded).

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c
index 8332e8a0b05af0f7f32fa898514c5140fa26fb40..447863825a8923580e195c50db9af0e062df5be9 100644 (file)
--- a/fs/bcachefs/data_update.c
+++ b/fs/bcachefs/data_update.c
@@ -91,18 +91,6 @@ static int insert_snapshot_whiteouts(struct btree_trans *trans,
        return ret;
 }
 
-static void bch2_bkey_mark_dev_cached(struct bkey_s k, unsigned dev)
-{
-       struct bkey_ptrs ptrs = bch2_bkey_ptrs(k);
-       struct bch_extent_ptr *ptr;
-
-       bkey_for_each_ptr(ptrs, ptr)
-               if (ptr->dev == dev) {
-                       bch2_extent_ptr_set_cached(k, ptr);
-                       return;
-               }
-}
-
 static int __bch2_data_update_index_update(struct btree_trans *trans,
                                           struct bch_write_op *op)
 {
@@ -125,15 +113,17 @@ static int __bch2_data_update_index_update(struct btree_trans *trans,
        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);
 
@@ -145,7 +135,7 @@ static int __bch2_data_update_index_update(struct btree_trans *trans,
                new = bkey_i_to_extent(bch2_keylist_front(keys));
 
                if (!bch2_extents_match(k, old))
-                       goto nomatch;
+                       goto nowork;
 
                bkey_reassemble(_insert.k, k);
                insert = _insert.k;
@@ -168,50 +158,60 @@ static int __bch2_data_update_index_update(struct btree_trans *trans,
                 * 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(insert))) {
-                               /*
-                                * 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_c(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);
+                           (ptr = bch2_extent_has_ptr(old, p, bkey_i_to_s(insert))) &&
+                           !ptr->cached) {
+                               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)
+                       goto nowork;
 
-               /* Add new ptrs: */
-               extent_for_each_ptr_decode(extent_i_to_s(new), p, entry) {
-                       const struct bch_extent_ptr *existing_ptr =
-                               bch2_bkey_has_device_c(bkey_i_to_s_c(insert), p.ptr.dev);
-
-                       if (existing_ptr && existing_ptr->cached) {
-                               /*
-                                * We're replacing a cached pointer with a non
-                                * cached pointer:
-                                */
-                               bch2_bkey_drop_device_noerror(bkey_i_to_s(insert),
-                                                             existing_ptr->dev);
-                       } else if (existing_ptr) {
-                               /*
-                                * 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))
+                       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_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));
@@ -272,7 +272,7 @@ next:
                                goto out;
                }
                continue;
-nomatch:
+nowork:
                if (m->ctxt && m->ctxt->stats) {
                        BUG_ON(k.k->p.offset <= iter.pos.offset);
                        atomic64_inc(&m->ctxt->stats->keys_raced);