reftable/stack: use lock_file when adding table to "tables.list"

When modifying "tables.list", we need to lock the list before updating
it to ensure that no concurrent writers modify the list at the same
point in time. While we do this via the `lock_file` subsystem when
compacting the stack, we manually handle the lock when adding a new
table to it. While not wrong, it is at least inconsistent.

Refactor the code to consistently lock "tables.list" via the `lock_file`
subsytem.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/reftable/stack.c b/reftable/stack.c
index 9ca549294f0f7dddaddd47acf767d1fd806b3dd1..54982e0f7d9d6aed50eca1ceace4a769fbb4994f 100644 (file)
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -567,7 +567,7 @@ static void format_name(struct strbuf *dest, uint64_t min, uint64_t max)
 }
 
 struct reftable_addition {
-       struct tempfile *lock_file;
+       struct lock_file tables_list_lock;
        struct reftable_stack *stack;
 
        char **new_tables;
@@ -581,13 +581,13 @@ static int reftable_stack_init_addition(struct reftable_addition *add,
                                        struct reftable_stack *st)
 {
        struct strbuf lock_file_name = STRBUF_INIT;
-       int err = 0;
-       add->stack = st;
+       int err;
 
-       strbuf_addf(&lock_file_name, "%s.lock", st->list_file);
+       add->stack = st;
 
-       add->lock_file = create_tempfile(lock_file_name.buf);
-       if (!add->lock_file) {
+       err = hold_lock_file_for_update(&add->tables_list_lock, st->list_file,
+                                       LOCK_NO_DEREF);
+       if (err < 0) {
                if (errno == EEXIST) {
                        err = REFTABLE_LOCK_ERROR;
                } else {
@@ -596,7 +596,8 @@ static int reftable_stack_init_addition(struct reftable_addition *add,
                goto done;
        }
        if (st->opts.default_permissions) {
-               if (chmod(add->lock_file->filename.buf, st->opts.default_permissions) < 0) {
+               if (chmod(get_lock_file_path(&add->tables_list_lock),
+                         st->opts.default_permissions) < 0) {
                        err = REFTABLE_IO_ERROR;
                        goto done;
                }
@@ -635,7 +636,7 @@ static void reftable_addition_close(struct reftable_addition *add)
        add->new_tables_len = 0;
        add->new_tables_cap = 0;
 
-       delete_tempfile(&add->lock_file);
+       rollback_lock_file(&add->tables_list_lock);
        strbuf_release(&nm);
 }
 
@@ -651,7 +652,7 @@ void reftable_addition_destroy(struct reftable_addition *add)
 int reftable_addition_commit(struct reftable_addition *add)
 {
        struct strbuf table_list = STRBUF_INIT;
-       int lock_file_fd = get_tempfile_fd(add->lock_file);
+       int lock_file_fd = get_lock_file_fd(&add->tables_list_lock);
        int err = 0;
        size_t i;
 
@@ -680,7 +681,7 @@ int reftable_addition_commit(struct reftable_addition *add)
                goto done;
        }
 
-       err = rename_tempfile(&add->lock_file, add->stack->list_file);
+       err = commit_lock_file(&add->tables_list_lock);
        if (err < 0) {
                err = REFTABLE_IO_ERROR;
                goto done;