bcachefs: Fix rereplicate when we already have a cached pointer

When we need to add more replicas to an extent, it might be the case
that we already have a replica on every device, but some of them are
cached.

This patch fixes a bug where we'd spin on that extent because the write
path fails to find a device we can allocate from: we allow allocating
from devices that already have cached replicas on them, and change
bch2_data_update_index_update() to drop the cached replica if needed.

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

diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c
index b4480852e935f6a9fd7aeda934f52297a6706849..acb634b3480ba757bcadf1708dbdab86d521138f 100644 (file)
--- a/fs/bcachefs/data_update.c
+++ b/fs/bcachefs/data_update.c
@@ -183,7 +183,17 @@ int bch2_data_update_index_update(struct bch_write_op *op)
 
                /* 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)) {
+                       const struct bch_extent_ptr *existing_ptr =
+                               bch2_bkey_has_device(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
@@ -334,7 +344,8 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
                    p.ptr.cached)
                        BUG();
 
-               if (!((1U << i) & m->data_opts.rewrite_ptrs))
+               if (!((1U << i) & m->data_opts.rewrite_ptrs) &&
+                   !p.ptr.cached)
                        bch2_dev_list_add_dev(&m->op.devs_have, p.ptr.dev);
 
                if (((1U << i) & m->data_opts.rewrite_ptrs) &&