From ad520141b155786800261cc7e02ec02f0afe2643 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Sat, 27 May 2023 23:19:13 -0400
Subject: [PATCH] bcachefs: Fix corruption with writeable snapshots
When partially overwriting an extent in an older snapshot, the existing
extent has to be split.
If the existing extent was overwritten in a different (sibling)
snapshot, we have to ensure that the split won't be visible in the
sibling snapshot.
data_update.c already has code for this,
bch2_insert_snapshot_writeouts() - we just need to move it into
btree_update_leaf.c and change bch2_trans_update_extent() to use it as
well.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/bcachefs/btree_update.h | 23 ++++++++
fs/bcachefs/btree_update_leaf.c | 73 +++++++++++++++++++++++--
fs/bcachefs/data_update.c | 94 +++------------------------------
3 files changed, 99 insertions(+), 91 deletions(-)
diff --git a/fs/bcachefs/btree_update.h b/fs/bcachefs/btree_update.h
index 1ac3a81e0af6f..e90cf292f80bf 100644
--- a/fs/bcachefs/btree_update.h
+++ b/fs/bcachefs/btree_update.h
@@ -4,6 +4,7 @@
#include "btree_iter.h"
#include "journal.h"
+#include "journal.h"
struct bch_fs;
struct btree;
@@ -83,6 +84,28 @@ int bch2_btree_node_update_key(struct btree_trans *, struct btree_iter *,
int bch2_btree_node_update_key_get_iter(struct btree_trans *,
struct btree *, struct bkey_i *, bool);
+int __bch2_insert_snapshot_whiteouts(struct btree_trans *, enum btree_id,
+ struct bpos, struct bpos);
+
+/*
+ * For use when splitting extents in existing snapshots:
+ *
+ * If @old_pos is an interior snapshot node, iterate over descendent snapshot
+ * nodes: for every descendent snapshot in whiche @old_pos is overwritten and
+ * not visible, emit a whiteout at @new_pos.
+ */
+static inline int bch2_insert_snapshot_whiteouts(struct btree_trans *trans,
+ enum btree_id btree,
+ struct bpos old_pos,
+ struct bpos new_pos)
+{
+ if (!btree_type_has_snapshots(btree) ||
+ bkey_eq(old_pos, new_pos))
+ return 0;
+
+ return __bch2_insert_snapshot_whiteouts(trans, btree, old_pos, new_pos);
+}
+
int bch2_trans_update_extent(struct btree_trans *, struct btree_iter *,
struct bkey_i *, enum btree_update_flags);
diff --git a/fs/bcachefs/btree_update_leaf.c b/fs/bcachefs/btree_update_leaf.c
index 33693467810b2..25d73db9adc69 100644
--- a/fs/bcachefs/btree_update_leaf.c
+++ b/fs/bcachefs/btree_update_leaf.c
@@ -1343,6 +1343,69 @@ static int need_whiteout_for_snapshot(struct btree_trans *trans,
return ret;
}
+
+int __bch2_insert_snapshot_whiteouts(struct btree_trans *trans,
+ enum btree_id id,
+ struct bpos old_pos,
+ struct bpos new_pos)
+{
+ struct bch_fs *c = trans->c;
+ struct btree_iter old_iter, new_iter;
+ struct bkey_s_c old_k, new_k;
+ snapshot_id_list s;
+ struct bkey_i *update;
+ int ret;
+
+ if (!bch2_snapshot_has_children(c, old_pos.snapshot))
+ return 0;
+
+ darray_init(&s);
+
+ bch2_trans_iter_init(trans, &old_iter, id, old_pos,
+ BTREE_ITER_NOT_EXTENTS|
+ BTREE_ITER_ALL_SNAPSHOTS);
+ while ((old_k = bch2_btree_iter_prev(&old_iter)).k &&
+ !(ret = bkey_err(old_k)) &&
+ bkey_eq(old_pos, old_k.k->p)) {
+ struct bpos whiteout_pos =
+ SPOS(new_pos.inode, new_pos.offset, old_k.k->p.snapshot);;
+
+ if (!bch2_snapshot_is_ancestor(c, old_k.k->p.snapshot, old_pos.snapshot) ||
+ snapshot_list_has_ancestor(c, &s, old_k.k->p.snapshot))
+ continue;
+
+ new_k = bch2_bkey_get_iter(trans, &new_iter, id, whiteout_pos,
+ BTREE_ITER_NOT_EXTENTS|
+ BTREE_ITER_INTENT);
+ ret = bkey_err(new_k);
+ if (ret)
+ break;
+
+ if (new_k.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, &new_iter, update,
+ BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+ }
+ bch2_trans_iter_exit(trans, &new_iter);
+
+ ret = snapshot_list_add(c, &s, old_k.k->p.snapshot);
+ if (ret)
+ break;
+ }
+ bch2_trans_iter_exit(trans, &old_iter);
+ darray_exit(&s);
+
+ return ret;
+}
+
int bch2_trans_update_extent(struct btree_trans *trans,
struct btree_iter *orig_iter,
struct bkey_i *insert,
@@ -1396,8 +1459,10 @@ int bch2_trans_update_extent(struct btree_trans *trans,
bch2_cut_back(start, update);
- ret = bch2_btree_insert_nonextent(trans, btree_id, update,
- BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|flags);
+ ret = bch2_insert_snapshot_whiteouts(trans, btree_id,
+ k.k->p, update->k.p) ?:
+ bch2_btree_insert_nonextent(trans, btree_id, update,
+ BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|flags);
if (ret)
goto err;
}
@@ -1411,7 +1476,9 @@ int bch2_trans_update_extent(struct btree_trans *trans,
bch2_cut_front(start, update);
bch2_cut_back(insert->k.p, update);
- ret = bch2_btree_insert_nonextent(trans, btree_id, update,
+ ret = bch2_insert_snapshot_whiteouts(trans, btree_id,
+ k.k->p, update->k.p) ?:
+ bch2_btree_insert_nonextent(trans, btree_id, update,
BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|flags);
if (ret)
goto err;
diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c
index ae7e60d6e5836..c89ee14f8b6b8 100644
--- a/fs/bcachefs/data_update.c
+++ b/fs/bcachefs/data_update.c
@@ -16,81 +16,6 @@
#include "subvolume.h"
#include "trace.h"
-static int insert_snapshot_whiteouts(struct btree_trans *trans,
- enum btree_id id,
- struct bpos old_pos,
- struct bpos new_pos)
-{
- struct bch_fs *c = trans->c;
- 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))
- return 0;
-
- darray_init(&s);
-
- if (!bch2_snapshot_has_children(c, old_pos.snapshot))
- return 0;
-
- bch2_trans_iter_init(trans, &iter, id, old_pos,
- BTREE_ITER_NOT_EXTENTS|
- BTREE_ITER_ALL_SNAPSHOTS);
- while (1) {
- k = bch2_btree_iter_prev(&iter);
- ret = bkey_err(k);
- if (ret)
- break;
-
- if (!k.k)
- break;
-
- if (!bkey_eq(old_pos, k.k->p))
- 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;
-
- whiteout_pos.snapshot = k.k->p.snapshot;
-
- k2 = bch2_bkey_get_iter(trans, &iter2, id, whiteout_pos,
- BTREE_ITER_NOT_EXTENTS|
- BTREE_ITER_INTENT);
- 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;
-
- ret = snapshot_list_add(c, &s, k.k->p.snapshot);
- if (ret)
- break;
- }
- }
- bch2_trans_iter_exit(trans, &iter);
- darray_exit(&s);
-
- return ret;
-}
-
static void trace_move_extent_finish2(struct bch_fs *c, struct bkey_s_c k)
{
if (trace_move_extent_finish_enabled()) {
@@ -327,19 +252,12 @@ restart_drop_extra_replicas:
next_pos = insert->k.p;
- 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_insert_snapshot_whiteouts(trans, m->btree_id,
+ k.k->p, bkey_start_pos(&insert->k)) ?:
+ bch2_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) ?:
--
2.30.2