From: Ronnie Sahlberg <sahlb...@google.com>
Update receive-pack to use an atomic transaction iff the client negotiated
that it wanted atomic-push. This leaves the default behavior to be the old
non-atomic one ref at a time update. This is to cause as little disruption
as possible to existing clients. It is unknown if there are client scripts
that depend on the old non-atomic behavior so we make it opt-in for now.
If it turns out over time that there are no client scripts that depend on the
old behavior we can change git to default to use atomic pushes and instead
offer an opt-out argument for people that do not want atomic pushes.
Signed-off-by: Ronnie Sahlberg <sahlb...@google.com>
Signed-off-by: Stefan Beller <sbel...@google.com>
---
Notes:
Changes v1 -> v2:
* update(...) assumes to be always in a transaction
* Caring about when to begin/commit transactions is put
into execute_commands
v2->v3:
* meditated about the error flow. Now we always construct a local
strbuf err if required. Then the flow is easier to follow and
destruction of it is performed nearby.
* early return in execute_commands if transaction_begin fails.
builtin/receive-pack.c | 83 +++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 68 insertions(+), 15 deletions(-)
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e76e5d5..c942a3b 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -67,6 +67,7 @@ static const char *NONCE_SLOP = "SLOP";
static const char *nonce_status;
static long nonce_stamp_slop;
static unsigned long nonce_stamp_slop_limit;
+static struct ref_transaction *transaction;
static enum deny_action parse_deny_action(const char *var, const char *value)
{
@@ -823,6 +824,7 @@ static const char *update(struct command *cmd, struct
shallow_info *si)
}
if (is_null_sha1(new_sha1)) {
+ struct strbuf err = STRBUF_INIT;
if (!parse_object(old_sha1)) {
old_sha1 = NULL;
if (ref_exists(name)) {
@@ -832,35 +834,36 @@ static const char *update(struct command *cmd, struct
shallow_info *si)
cmd->did_not_exist = 1;
}
}
- if (delete_ref(namespaced_name, old_sha1, 0)) {
- rp_error("failed to delete %s", name);
+ if (ref_transaction_delete(transaction,
+ namespaced_name,
+ old_sha1,
+ 0, old_sha1 != NULL,
+ "push", &err)) {
+ rp_error("%s", err.buf);
+ strbuf_release(&err);
return "failed to delete";
}
+ strbuf_release(&err);
return NULL; /* good */
}
else {
struct strbuf err = STRBUF_INIT;
- struct ref_transaction *transaction;
-
if (shallow_update && si->shallow_ref[cmd->index] &&
update_shallow_ref(cmd, si))
return "shallow error";
- transaction = ref_transaction_begin(&err);
- if (!transaction ||
- ref_transaction_update(transaction, namespaced_name,
- new_sha1, old_sha1, 0, 1, "push",
- &err) ||
- ref_transaction_commit(transaction, &err)) {
- ref_transaction_free(transaction);
-
+ if (ref_transaction_update(transaction,
+ namespaced_name,
+ new_sha1, old_sha1,
+ 0, 1, "push",
+ &err)) {
rp_error("%s", err.buf);
strbuf_release(&err);
+
return "failed to update ref";
}
-
- ref_transaction_free(transaction);
strbuf_release(&err);
+
return NULL; /* good */
}
}
@@ -1052,6 +1055,7 @@ static void execute_commands(struct command *commands,
struct command *cmd;
unsigned char sha1[20];
struct iterate_data data;
+ struct strbuf err = STRBUF_INIT;
if (unpacker_error) {
for (cmd = commands; cmd; cmd = cmd->next)
@@ -1059,6 +1063,16 @@ static void execute_commands(struct command *commands,
return;
}
+ if (use_atomic) {
+ transaction = ref_transaction_begin(&err);
+ if (!transaction) {
+ error("%s", err.buf);
+ strbuf_release(&err);
+ for (cmd = commands; cmd; cmd = cmd->next)
+ cmd->error_string = "transaction error";
+ return;
+ }
+ }
data.cmds = commands;
data.si = si;
if (check_everything_connected(iterate_receive_command_list, 0, &data))
@@ -1086,8 +1100,25 @@ static void execute_commands(struct command *commands,
if (cmd->skip_update)
continue;
-
+ if (!use_atomic) {
+ transaction = ref_transaction_begin(&err);
+ if (!transaction) {
+ rp_error("%s", err.buf);
+ strbuf_release(&err);
+ cmd->error_string = "failed to start
transaction";
+ return;
+ }
+ }
cmd->error_string = update(cmd, si);
+ if (!use_atomic)
+ if (ref_transaction_commit(transaction, &err)) {
+ ref_transaction_free(transaction);
+ rp_error("%s", err.buf);
+ strbuf_release(&err);
+ cmd->error_string = "failed to update ref";
+ return;
+ }
+
if (shallow_update && !cmd->error_string &&
si->shallow_ref[cmd->index]) {
error("BUG: connectivity check has not been run on ref
%s",
@@ -1096,10 +1127,32 @@ static void execute_commands(struct command *commands,
}
}
+ if (use_atomic) {
+ /*
+ * update(...) may abort early (i.e. because the hook refused to
+ * update that ref) which then doesn't even record a transaction
+ * regarding that ref. Make sure all commands are without error
+ * and then commit atomically.
+ */
+ for (cmd = commands; cmd; cmd = cmd->next)
+ if (cmd->error_string)
+ break;
+ if (cmd) {
+ for (cmd = commands; cmd; cmd = cmd->next)
+ if (!cmd->error_string)
+ cmd->error_string = "atomic push
failure";
+ } else if (ref_transaction_commit(transaction, &err)) {
+ rp_error("%s", err.buf);
+ for (cmd = commands; cmd; cmd = cmd->next)
+ cmd->error_string = err.buf;
+ }
+ ref_transaction_free(transaction);
+ }
if (shallow_update && !checked_connectivity)
error("BUG: run 'git fsck' for safety.\n"
"If there are errors, try to remove "
"the reported refs above");
+ strbuf_release(&err);
}
static struct command **queue_command(struct command **tail,
--
2.2.0.31.gad78000.dirty
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