Current btrfs qgroup design implies a requirement that after calling
btrfs_qgroup_account_extents() there must be a commit root switch.
Normally this is OK, as btrfs_qgroup_accounting_extents() is only called
inside btrfs_commit_transaction() just be commit_cowonly_roots().
However there is a exception at create_pending_snapshot(), which will
call btrfs_qgroup_account_extents() but no any commit root switch.
In case of creating a snapshot whose parent root is itself (create a
snapshot of fs tree), it will corrupt qgroup by the following trace:
(skipped unrelated data)
======
btrfs_qgroup_account_extent: bytenr = 29786112, num_bytes = 16384, nr_old_roots
= 0, nr_new_roots = 1
qgroup_update_counters: qgid = 5, cur_old_count = 0, cur_new_count = 1, rfer =
0, excl = 0
qgroup_update_counters: qgid = 5, cur_old_count = 0, cur_new_count = 1, rfer =
16384, excl = 16384
btrfs_qgroup_account_extent: bytenr = 29786112, num_bytes = 16384, nr_old_roots
= 0, nr_new_roots = 0
======
The problem here is in first qgroup_account_extent(), the
nr_new_roots of the extent is 1, which means its reference got
increased, and qgroup increased its rfer and excl.
But at second qgroup_account_extent(), its reference got decreased, but
between these two qgroup_account_extent(), there is no switch roots.
This leads to the same nr_old_roots, and this extent just got ignored by
qgroup, which means this extent is wrongly accounted.
Fix it by call commit_cowonly_roots() after qgroup_account_extent() in
create_pending_snapshot(), with needed preparation.
Reported-by: Mark Fasheh <mfas...@suse.de>
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
v2:
Fix a soft lockup caused by missing switch_commit_root() call.
Fix a warning caused by dirty-but-not-committed root.
v3:
Fix a difference behavior that btrfs qgroup will start accounting
dropped roots if we are creating snapshots.
Other than always account them in next transaction.
---
fs/btrfs/transaction.c | 122 +++++++++++++++++++++++++++++++++++--------------
1 file changed, 87 insertions(+), 35 deletions(-)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 43885e5..5ba0d9a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -126,7 +126,8 @@ static void clear_btree_io_tree(struct extent_io_tree *tree)
}
static noinline void switch_commit_roots(struct btrfs_transaction *trans,
- struct btrfs_fs_info *fs_info)
+ struct btrfs_fs_info *fs_info,
+ int free_dropped_roots)
{
struct btrfs_root *root, *tmp;
@@ -142,16 +143,18 @@ static noinline void switch_commit_roots(struct
btrfs_transaction *trans,
}
/* We can free old roots now. */
- spin_lock(&trans->dropped_roots_lock);
- while (!list_empty(&trans->dropped_roots)) {
- root = list_first_entry(&trans->dropped_roots,
- struct btrfs_root, root_list);
- list_del_init(&root->root_list);
- spin_unlock(&trans->dropped_roots_lock);
- btrfs_drop_and_free_fs_root(fs_info, root);
+ if (free_dropped_roots) {
spin_lock(&trans->dropped_roots_lock);
+ while (!list_empty(&trans->dropped_roots)) {
+ root = list_first_entry(&trans->dropped_roots,
+ struct btrfs_root, root_list);
+ list_del_init(&root->root_list);
+ spin_unlock(&trans->dropped_roots_lock);
+ btrfs_drop_and_free_fs_root(fs_info, root);
+ spin_lock(&trans->dropped_roots_lock);
+ }
+ spin_unlock(&trans->dropped_roots_lock);
}
- spin_unlock(&trans->dropped_roots_lock);
up_write(&fs_info->commit_root_sem);
}
@@ -311,12 +314,13 @@ loop:
* when the transaction commits
*/
static int record_root_in_trans(struct btrfs_trans_handle *trans,
- struct btrfs_root *root)
+ struct btrfs_root *root,
+ int force)
{
- if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
- root->last_trans < trans->transid) {
+ if ((test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
+ root->last_trans < trans->transid) || force) {
WARN_ON(root == root->fs_info->extent_root);
- WARN_ON(root->commit_root != root->node);
+ WARN_ON(root->commit_root != root->node && !force);
/*
* see below for IN_TRANS_SETUP usage rules
@@ -331,7 +335,7 @@ static int record_root_in_trans(struct btrfs_trans_handle
*trans,
smp_wmb();
spin_lock(&root->fs_info->fs_roots_radix_lock);
- if (root->last_trans == trans->transid) {
+ if (root->last_trans == trans->transid && !force) {
spin_unlock(&root->fs_info->fs_roots_radix_lock);
return 0;
}
@@ -402,7 +406,7 @@ int btrfs_record_root_in_trans(struct btrfs_trans_handle
*trans,
return 0;
mutex_lock(&root->fs_info->reloc_mutex);
- record_root_in_trans(trans, root);
+ record_root_in_trans(trans, root, 0);
mutex_unlock(&root->fs_info->reloc_mutex);
return 0;
@@ -1383,7 +1387,7 @@ static noinline int create_pending_snapshot(struct
btrfs_trans_handle *trans,
dentry = pending->dentry;
parent_inode = pending->dir;
parent_root = BTRFS_I(parent_inode)->root;
- record_root_in_trans(trans, parent_root);
+ record_root_in_trans(trans, parent_root, 0);
cur_time = current_fs_time(parent_inode->i_sb);
@@ -1420,7 +1424,7 @@ static noinline int create_pending_snapshot(struct
btrfs_trans_handle *trans,
goto fail;
}
- record_root_in_trans(trans, root);
+ record_root_in_trans(trans, root, 0);
btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
btrfs_check_and_init_root_item(new_root_item);
@@ -1516,6 +1520,65 @@ static noinline int create_pending_snapshot(struct
btrfs_trans_handle *trans,
goto fail;
}
+ /*
+ * Account qgroups before insert the dir item
+ * As such dir item insert will modify parent_root, which could be
+ * src root. If we don't do it now, wrong accounting may be inherited
+ * to snapshot qgroup.
+ *
+ * For reason locking tree_log_mutex, see btrfs_commit_transaction()
+ * comment
+ */
+ mutex_lock(&root->fs_info->tree_log_mutex);
+
+ ret = commit_fs_roots(trans, root);
+ if (ret) {
+ mutex_unlock(&root->fs_info->tree_log_mutex);
+ goto fail;
+ }
+
+ ret = btrfs_qgroup_prepare_account_extents(trans, root->fs_info);
+ if (ret < 0) {
+ mutex_unlock(&root->fs_info->tree_log_mutex);
+ goto fail;
+ }
+ ret = btrfs_qgroup_account_extents(trans, root->fs_info);
+ if (ret < 0) {
+ mutex_unlock(&root->fs_info->tree_log_mutex);
+ goto fail;
+ }
+ /*
+ * Now qgroup are all updated, we can inherit it to new qgroups
+ */
+ ret = btrfs_qgroup_inherit(trans, fs_info,
+ root->root_key.objectid,
+ objectid, pending->inherit);
+ if (ret < 0) {
+ mutex_unlock(&root->fs_info->tree_log_mutex);
+ goto fail;
+ }
+ /*
+ * qgroup_account_extents() must be followed by a
+ * switch_commit_roots(), or next qgroup_account_extents() will
+ * be corrupted
+ */
+ ret = commit_cowonly_roots(trans, root);
+ if (ret) {
+ mutex_unlock(&root->fs_info->tree_log_mutex);
+ goto fail;
+ }
+ /*
+ * Just like in btrfs_commit_transaction(), we need to
+ * switch_commit_roots().
+ * However this time we don't need to do a full one,
+ * excluding tree root and chunk root should be OK.
+ *
+ * Also we don't want to free dropped roots here.
+ * Only the final switch_commit_roots() will free them
+ */
+ switch_commit_roots(trans->transaction, root->fs_info, 0);
+ mutex_unlock(&root->fs_info->tree_log_mutex);
+
ret = btrfs_insert_dir_item(trans, parent_root,
dentry->d_name.name, dentry->d_name.len,
parent_inode, &key,
@@ -1527,6 +1590,12 @@ static noinline int create_pending_snapshot(struct
btrfs_trans_handle *trans,
goto fail;
}
+ /*
+ * Force parent root to be updated, as we recorded it before its
+ * last_trans == cur_transid
+ */
+ record_root_in_trans(trans, parent_root, 1);
+
btrfs_i_size_write(parent_inode, parent_inode->i_size +
dentry->d_name.len * 2);
parent_inode->i_mtime = parent_inode->i_ctime =
@@ -1559,23 +1628,6 @@ static noinline int create_pending_snapshot(struct
btrfs_trans_handle *trans,
goto fail;
}
- /*
- * account qgroup counters before qgroup_inherit()
- */
- ret = btrfs_qgroup_prepare_account_extents(trans, fs_info);
- if (ret)
- goto fail;
- ret = btrfs_qgroup_account_extents(trans, fs_info);
- if (ret)
- goto fail;
- ret = btrfs_qgroup_inherit(trans, fs_info,
- root->root_key.objectid,
- objectid, pending->inherit);
- if (ret) {
- btrfs_abort_transaction(trans, root, ret);
- goto fail;
- }
-
fail:
pending->error = ret;
dir_item_existed:
@@ -2115,7 +2167,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle
*trans,
list_add_tail(&root->fs_info->chunk_root->dirty_list,
&cur_trans->switch_commits);
- switch_commit_roots(cur_trans, root->fs_info);
+ switch_commit_roots(cur_trans, root->fs_info, 1);
assert_qgroups_uptodate(trans);
ASSERT(list_empty(&cur_trans->dirty_bgs));
--
2.8.0
--
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