Implement the methods needed to support reference transactions for
the packed-refs backend. The new methods are not yet used.
Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
---
refs/packed-backend.c | 313 +++++++++++++++++++++++++++++++++++++++++++++++++-
refs/packed-backend.h | 9 ++
2 files changed, 319 insertions(+), 3 deletions(-)
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 7e348feac3..d19b3bfba5 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -744,25 +744,332 @@ static int packed_init_db(struct ref_store *ref_store, struct strbuf *err)
return 0;
}
+/*
+ * Write the packed-refs from the cache to the packed-refs tempfile,
+ * incorporating any changes from `updates`. `updates` must be a
+ * sorted string list whose keys are the refnames and whose util
+ * values are `struct ref_update *`. On error, rollback the tempfile,
+ * write an error message to `err`, and return a nonzero value.
+ *
+ * The packfile must be locked before calling this function and will
+ * remain locked when it is done.
+ */
+static int write_with_updates(struct packed_ref_store *refs,
+ struct string_list *updates,
+ struct strbuf *err)
+{
+ struct ref_iterator *iter = NULL;
+ size_t i;
+ int ok;
+ FILE *out;
+ struct strbuf sb = STRBUF_INIT;
+ char *packed_refs_path;
+
+ if (!is_lock_file_locked(&refs->lock))
+ die("BUG: write_with_updates() called while unlocked");
+
+ /*
+ * If packed-refs is a symlink, we want to overwrite the
+ * symlinked-to file, not the symlink itself. Also, put the
+ * staging file next to it:
+ */
+ packed_refs_path = get_locked_file_path(&refs->lock);
+ strbuf_addf(&sb, "%s.new", packed_refs_path);
+ free(packed_refs_path);
+ if (create_tempfile(&refs->tempfile, sb.buf) < 0) {
+ strbuf_addf(err, "unable to create file %s: %s",
+ sb.buf, strerror(errno));
+ strbuf_release(&sb);
+ return -1;
+ }
+ strbuf_release(&sb);
+
+ out = fdopen_tempfile(&refs->tempfile, "w");
+ if (!out) {
+ strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s",
+ strerror(errno));
+ goto error;
+ }
+
+ if (fprintf(out, "%s", PACKED_REFS_HEADER) < 0)
+ goto write_error;
+
+ /*
+ * We iterate in parallel through the current list of refs and
+ * the list of updates, processing an entry from at least one
+ * of the lists each time through the loop. When the current
+ * list of refs is exhausted, set iter to NULL. When the list
+ * of updates is exhausted, leave i set to updates->nr.
+ */
+ iter = packed_ref_iterator_begin(&refs->base, "",
+ DO_FOR_EACH_INCLUDE_BROKEN);
+ if ((ok = ref_iterator_advance(iter)) != ITER_OK)
+ iter = NULL;
+
+ i = 0;
+
+ while (iter || i < updates->nr) {
+ struct ref_update *update = NULL;
+ int cmp;
+
+ if (i >= updates->nr) {
+ cmp = -1;
+ } else {
+ update = updates->items[i].util;
+
+ if (!iter)
+ cmp = +1;
+ else
+ cmp = strcmp(iter->refname, update->refname);
+ }
+
+ if (!cmp) {
+ /*
+ * There is both an old value and an update
+ * for this reference. Check the old value if
+ * necessary:
+ */
+ if ((update->flags & REF_HAVE_OLD)) {
+ if (is_null_oid(&update->old_oid)) {
+ strbuf_addf(err, "cannot update ref '%s': "
+ "reference already exists",
+ update->refname);
+ goto error;
+ } else if (oidcmp(&update->old_oid, iter->oid)) {
+ strbuf_addf(err, "cannot update ref '%s': "
+ "is at %s but expected %s",
+ update->refname,
+ oid_to_hex(iter->oid),
+ oid_to_hex(&update->old_oid));
+ goto error;
+ }
+ }
+
+ /* Now figure out what to use for the new value: */
+ if ((update->flags & REF_HAVE_NEW)) {
+ /*
+ * The update takes precedence. Skip
+ * the iterator over the unneeded
+ * value.
+ */
+ if ((ok = ref_iterator_advance(iter)) != ITER_OK)
+ iter = NULL;
+ cmp = +1;
+ } else {
+ /*
+ * The update doesn't actually want to
+ * change anything. We're done with it.
+ */
+ i++;
+ cmp = -1;
+ }
+ } else if (cmp > 0) {
+ /*
+ * There is no old value but there is an
+ * update for this reference. Make sure that
+ * the update didn't expect an existing value:
+ */
+ if ((update->flags & REF_HAVE_OLD) &&
+ !is_null_oid(&update->old_oid)) {
+ strbuf_addf(err, "cannot update ref '%s': "
+ "reference is missing but expected %s",
+ update->refname,
+ oid_to_hex(&update->old_oid));
+ goto error;
+ }
+ }
+
+ if (cmp < 0) {
+ /* Pass the old reference through. */
+
+ struct object_id peeled;
+ int peel_error = ref_iterator_peel(iter, &peeled);
+
+ if (write_packed_entry(out, iter->refname,
+ iter->oid->hash,
+ peel_error ? NULL : peeled.hash))
+ goto write_error;
+
+ if ((ok = ref_iterator_advance(iter)) != ITER_OK)
+ iter = NULL;
+ } else if (is_null_oid(&update->new_oid)) {
+ /*
+ * The update wants to delete the reference,
+ * and the reference either didn't exist or we
+ * have already skipped it. So we're done with
+ * the update (and don't have to write
+ * anything).
+ */
+ i++;
+ } else {
+ struct object_id peeled;
+ int peel_error = peel_object(update->new_oid.hash,
+ peeled.hash);
+
+ if (write_packed_entry(out, update->refname,
+ update->new_oid.hash,
+ peel_error ? NULL : peeled.hash))
+ goto write_error;
+
+ i++;
+ }
+ }
+
+ if (ok != ITER_DONE) {
+ strbuf_addf(err, "unable to write packed-refs file: "
+ "error iterating over old contents");
+ goto error;
+ }
+
+ if (close_tempfile(&refs->tempfile)) {
+ strbuf_addf(err, "error closing file %s: %s",
+ get_tempfile_path(&refs->tempfile),
+ strerror(errno));
+ strbuf_release(&sb);
+ return -1;
+ }
+
+ return 0;
+
+write_error:
+ strbuf_addf(err, "error writing to %s: %s",
+ get_tempfile_path(&refs->tempfile), strerror(errno));
+
+error:
+ if (iter)
+ ref_iterator_abort(iter);
+
+ delete_tempfile(&refs->tempfile);
+ return -1;
+}
+
+struct packed_transaction_backend_data {
+ /* True iff the transaction owns the packed-refs lock. */
+ int own_lock;
+
+ struct string_list updates;
+};
+
+static void packed_transaction_cleanup(struct packed_ref_store *refs,
+ struct ref_transaction *transaction)
+{
+ struct packed_transaction_backend_data *data = transaction->backend_data;
+
+ if (data) {
+ string_list_clear(&data->updates, 0);
+
+ if (is_tempfile_active(&refs->tempfile))
+ delete_tempfile(&refs->tempfile);
+
+ if (data->own_lock && is_lock_file_locked(&refs->lock)) {
+ packed_refs_unlock(&refs->base);
+ data->own_lock = 0;
+ }
+
+ free(data);
+ transaction->backend_data = NULL;
+ }
+
+ transaction->state = REF_TRANSACTION_CLOSED;
+}
+
static int packed_transaction_prepare(struct ref_store *ref_store,
struct ref_transaction *transaction,
struct strbuf *err)
{
- die("BUG: not implemented yet");
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
+ "ref_transaction_prepare");
+ struct packed_transaction_backend_data *data;
+ size_t i;
+ int ret = TRANSACTION_GENERIC_ERROR;
+
+ /*
+ * Note that we *don't* skip transactions with zero updates,
+ * because such a transaction might be executed for the side
+ * effect of ensuring that all of the references are peeled.
+ * If the caller wants to optimize away empty transactions, it
+ * should do so itself.
+ */
+
+ data = xcalloc(1, sizeof(*data));
+ string_list_init(&data->updates, 0);
+
+ transaction->backend_data = data;
+
+ /*
+ * Stick the updates in a string list by refname so that we
+ * can sort them:
+ */
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+ struct string_list_item *item =
+ string_list_append(&data->updates, update->refname);
+
+ /* Store a pointer to update in item->util: */
+ item->util = update;
+ }
+ string_list_sort(&data->updates);
+
+ if (ref_update_reject_duplicates(&data->updates, err))
+ goto failure;
+
+ if (!is_lock_file_locked(&refs->lock)) {
+ if (packed_refs_lock(ref_store, 0, err))
+ goto failure;
+ data->own_lock = 1;
+ }
+
+ if (write_with_updates(refs, &data->updates, err))
+ goto failure;
+
+ transaction->state = REF_TRANSACTION_PREPARED;
+ return 0;
+
+failure:
+ packed_transaction_cleanup(refs, transaction);
+ return ret;
}
static int packed_transaction_abort(struct ref_store *ref_store,
struct ref_transaction *transaction,
struct strbuf *err)
{
- die("BUG: not implemented yet");
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
+ "ref_transaction_abort");
+
+ packed_transaction_cleanup(refs, transaction);
+ return 0;
}
static int packed_transaction_finish(struct ref_store *ref_store,
struct ref_transaction *transaction,
struct strbuf *err)
{
- die("BUG: not implemented yet");
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
+ "ref_transaction_finish");
+ int ret = TRANSACTION_GENERIC_ERROR;
+ char *packed_refs_path;
+
+ packed_refs_path = get_locked_file_path(&refs->lock);
+ if (rename_tempfile(&refs->tempfile, packed_refs_path)) {
+ strbuf_addf(err, "error replacing %s: %s",
+ refs->path, strerror(errno));
+ goto cleanup;
+ }
+
+ clear_packed_ref_cache(refs);
+ ret = 0;
+
+cleanup:
+ free(packed_refs_path);
+ packed_transaction_cleanup(refs, transaction);
+ return ret;
}
static int packed_initial_transaction_commit(struct ref_store *ref_store,
diff --git a/refs/packed-backend.h b/refs/packed-backend.h
index 03b7c1de95..7af2897757 100644
--- a/refs/packed-backend.h
+++ b/refs/packed-backend.h
@@ -1,6 +1,15 @@
#ifndef REFS_PACKED_BACKEND_H
#define REFS_PACKED_BACKEND_H
+/*
+ * Support for storing references in a `packed-refs` file.
+ *
+ * Note that this backend doesn't check for D/F conflicts, because it
+ * doesn't care about them. But usually it should be wrapped in a
+ * `files_ref_store` that prevents D/F conflicts from being created,
+ * even among packed refs.
+ */
+
struct ref_store *packed_ref_store_create(const char *path,
unsigned int store_flags);
--
2.14.1
