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Protect get_log_trees corruption with assertion

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Like a lot of places in the server, get_log_trees() doesn't have the
tools in needs to safely unwind partial changes in the face of an error.

In the worst case, it can have moved extents from the mount's log_trees
item into the server's main data allocator.  The dirty data allocator
reference is in the super block so it can be written later.   The dirty
log_trees reference is on stack, though, so it will be thrown away on
error.  This ends up duplicating extents in the persistent structures
because they're written in the new dirty allocator but still remain in
the unwritten source log_trees allocator.

This change makes it harder for that to happen.   It dirties the
log_trees item and always tries to update so that the dirty blocks are
consistent if they're later written out.  If we do get an error updating
the item we throw an assertion.   It's not great, but it matches other
similar circumstances in other parts of the server.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2022-06-17 11:23:39 -07:00
parent dcf8202d7c
commit 31e474c5fa
1 changed files with 29 additions and 12 deletions
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41
kmod/src/server.c
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@@ -1267,6 +1267,7 @@ static int server_get_log_trees(struct super_block *sb,
char *err_str = NULL;
u64 nr;
int ret;
int err;
if (arg_len != 0) {
ret = -EINVAL;
@@ -1310,16 +1311,27 @@ static int server_get_log_trees(struct super_block *sb,
goto unlock;
}
if (ret != -ENOENT) {
/* need to sync lt with respect to changes in other structures */
scoutfs_key_init_log_trees(&key, le64_to_cpu(lt.rid), le64_to_cpu(lt.nr));
ret = scoutfs_btree_dirty(sb, &server->alloc, &server->wri,
&super->logs_root, &key);
if (ret < 0) {
err_str = "dirtying lt btree key";
goto unlock;
}
}
/* drops and re-acquires the mutex and commit if it has to wait */
ret = finalize_and_start_log_merge(sb, &lt, rid, &hold);
if (ret < 0)
goto unlock;
goto update;
if (get_volopt_val(server, SCOUTFS_VOLOPT_DATA_ALLOC_ZONE_BLOCKS_NR, &data_zone_blocks)) {
ret = get_data_alloc_zone_bits(sb, rid, exclusive, vacant, data_zone_blocks);
if (ret < 0) {
err_str = "getting alloc zone bits";
goto unlock;
goto update;
}
} else {
data_zone_blocks = 0;
@@ -1336,13 +1348,13 @@ static int server_get_log_trees(struct super_block *sb,
&lt.meta_freed);
if (ret < 0) {
err_str = "splicing committed meta_freed";
goto unlock;
goto update;
}
ret = alloc_move_empty(sb, &super->data_alloc, &lt.data_freed, 0);
if (ret < 0) {
err_str = "emptying committed data_freed";
goto unlock;
goto update;
}
ret = scoutfs_alloc_fill_list(sb, &server->alloc, &server->wri,
@@ -1351,7 +1363,7 @@ static int server_get_log_trees(struct super_block *sb,
SCOUTFS_SERVER_META_FILL_TARGET);
if (ret < 0) {
err_str = "filling meta_avail";
goto unlock;
goto update;
}
if (le64_to_cpu(server->meta_avail->total_len) <= scoutfs_server_reserved_meta_blocks(sb))
@@ -1364,7 +1376,7 @@ static int server_get_log_trees(struct super_block *sb,
exclusive, vacant, data_zone_blocks);
if (ret < 0) {
err_str = "refilling data_avail";
goto unlock;
goto update;
}
if (le64_to_cpu(lt.data_avail.total_len) < SCOUTFS_SERVER_DATA_FILL_LO)
@@ -1384,7 +1396,7 @@ static int server_get_log_trees(struct super_block *sb,
if (ret < 0) {
zero_data_alloc_zone_bits(&lt);
err_str = "setting data_avail zone bits";
goto unlock;
goto update;
}
lt.data_alloc_zone_blocks = cpu_to_le64(data_zone_blocks);
@@ -1393,13 +1405,18 @@ static int server_get_log_trees(struct super_block *sb,
/* give the transaction a new seq (must have been ==) */
lt.get_trans_seq = cpu_to_le64(scoutfs_server_next_seq(sb));
update:
/* update client's log tree's item */
scoutfs_key_init_log_trees(&key, le64_to_cpu(lt.rid),
le64_to_cpu(lt.nr));
ret = scoutfs_btree_force(sb, &server->alloc, &server->wri,
scoutfs_key_init_log_trees(&key, le64_to_cpu(lt.rid), le64_to_cpu(lt.nr));
err = scoutfs_btree_force(sb, &server->alloc, &server->wri,
&super->logs_root, &key, &lt, sizeof(lt));
if (ret < 0)
err_str = "updating log trees";
BUG_ON(err < 0); /* can duplicate extents.. move dst in super, still in in lt src */
if (err < 0) {
if (ret == 0) {
ret = err;
err_str = "updating log trees";
}
}
unlock:
if (unlock_alloc)