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bcachefs: Handle dropping pointers in data_update path

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Cached pointers are generally dropped, not moved: this led to an
assertion firing in the data update path when there were no new replicas
being written.

This path adds a data_options field for pointers to be dropped, and
tweaks move_extent() to check if we're only dropping pointers, not
writing new ones, before kicking off a data update operation.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2022-10-09 03:32:17 -04:00
parent 160dff6dad
commit 1be887979b
3 changed files with 78 additions and 3 deletions
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23
fs/bcachefs/data_update.c
View file

@ -331,8 +331,9 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
i = 0;
bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
if (p.ptr.cached)
m->data_opts.rewrite_ptrs &= ~(1U << i);
if (((1U << i) & m->data_opts.rewrite_ptrs) &&
p.ptr.cached)
BUG();
if (!((1U << i) & m->data_opts.rewrite_ptrs))
bch2_dev_list_add_dev(&m->op.devs_have, p.ptr.dev);
@ -368,5 +369,23 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m,
m->op.nr_replicas = m->op.nr_replicas_required =
hweight32(m->data_opts.rewrite_ptrs) + m->data_opts.extra_replicas;
BUG_ON(!m->op.nr_replicas);
return 0;
}
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++;
}
}

2
fs/bcachefs/data_update.h
View file

@ -10,6 +10,7 @@ struct moving_context;
struct data_update_opts {
unsigned rewrite_ptrs;
unsigned kill_ptrs;
u16 target;
u8 extra_replicas;
unsigned btree_insert_flags;
@ -35,5 +36,6 @@ int bch2_data_update_init(struct bch_fs *, struct data_update *,
struct write_point_specifier,
struct bch_io_opts, struct data_update_opts,
enum btree_id, struct bkey_s_c);
void bch2_data_update_opts_normalize(struct bkey_s_c, struct data_update_opts *);
#endif /* _BCACHEFS_DATA_UPDATE_H */

56
fs/bcachefs/move.c
View file

@ -183,7 +183,52 @@ void bch_move_stats_init(struct bch_move_stats *stats, char *name)
scnprintf(stats->name, sizeof(stats->name), "%s", name);
}
static int bch2_extent_drop_ptrs(struct btree_trans *trans,
struct btree_iter *iter,
struct bkey_s_c k,
struct data_update_opts data_opts)
{
struct bch_fs *c = trans->c;
struct bkey_i *n;
int ret;
n = bch2_trans_kmalloc(trans, bkey_bytes(k.k));
ret = PTR_ERR_OR_ZERO(n);
if (ret)
return ret;
bkey_reassemble(n, k);
while (data_opts.kill_ptrs) {
unsigned i = 0, drop = __fls(data_opts.kill_ptrs);
struct bch_extent_ptr *ptr;
bch2_bkey_drop_ptrs(bkey_i_to_s(n), ptr, i++ == drop);
data_opts.kill_ptrs ^= 1U << drop;
}
/*
* If the new extent no longer has any pointers, bch2_extent_normalize()
* will do the appropriate thing with it (turning it into a
* KEY_TYPE_error key, or just a discard if it was a cached extent)
*/
bch2_extent_normalize(c, bkey_i_to_s(n));
/*
* Since we're not inserting through an extent iterator
* (BTREE_ITER_ALL_SNAPSHOTS iterators aren't extent iterators),
* we aren't using the extent overwrite path to delete, we're
* just using the normal key deletion path:
*/
if (bkey_deleted(&n->k))
n->k.size = 0;
return bch2_trans_update(trans, iter, n, BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE) ?:
bch2_trans_commit(trans, NULL, NULL, BTREE_INSERT_NOFAIL);
}
static int bch2_move_extent(struct btree_trans *trans,
struct btree_iter *iter,
struct moving_context *ctxt,
struct bch_io_opts io_opts,
enum btree_id btree_id,
@ -198,6 +243,15 @@ static int bch2_move_extent(struct btree_trans *trans,
unsigned sectors = k.k->size, pages;
int ret = -ENOMEM;
bch2_data_update_opts_normalize(k, &data_opts);
if (!data_opts.rewrite_ptrs &&
!data_opts.extra_replicas) {
if (data_opts.kill_ptrs)
return bch2_extent_drop_ptrs(trans, iter, k, data_opts);
return 0;
}
if (!percpu_ref_tryget_live(&c->writes))
return -EROFS;
@ -429,7 +483,7 @@ static int __bch2_move_data(struct moving_context *ctxt,
bch2_bkey_buf_reassemble(&sk, c, k);
k = bkey_i_to_s_c(sk.k);
ret2 = bch2_move_extent(&trans, ctxt, io_opts,
ret2 = bch2_move_extent(&trans, &iter, ctxt, io_opts,
btree_id, k, data_opts);
if (ret2) {
if (bch2_err_matches(ret2, BCH_ERR_transaction_restart))