git/refs/debug.c
Patrick Steinhardt cd475b3b03 refs: add ability for backends to special-case reading of symbolic refs
Reading of symbolic and non-symbolic references is currently treated the
same in reference backends: we always call `refs_read_raw_ref()` and
then decide based on the returned flags what type it is. This has one
downside though: symbolic references may be treated different from
normal references in a backend from normal references. The packed-refs
backend for example doesn't even know about symbolic references, and as
a result it is pointless to even ask it for one.

There are cases where we really only care about whether a reference is
symbolic or not, but don't care about whether it exists at all or may be
a non-symbolic reference. But it is not possible to optimize for this
case right now, and as a consequence we will always first check for a
loose reference to exist, and if it doesn't, we'll query the packed-refs
backend for a known-to-not-be-symbolic reference. This is inefficient
and requires us to search all packed references even though we know to
not care for the result at all.

Introduce a new function `refs_read_symbolic_ref()` which allows us to
fix this case. This function will only ever return symbolic references
and can thus optimize for the scenario layed out above. By default, if
the backend doesn't provide an implementation for it, we just use the
old code path and fall back to `read_raw_ref()`. But in case the backend
provides its own, more efficient implementation, we will use that one
instead.

Note that this function is explicitly designed to not distinguish
between missing references and non-symbolic references. If it did, we'd
be forced to always search the packed-refs backend to see whether the
symbolic reference the user asked for really doesn't exist, or if it
exists as a non-symbolic reference.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-03-01 10:13:46 -08:00

448 lines
14 KiB
C

#include "refs-internal.h"
#include "trace.h"
static struct trace_key trace_refs = TRACE_KEY_INIT(REFS);
struct debug_ref_store {
struct ref_store base;
struct ref_store *refs;
};
extern struct ref_storage_be refs_be_debug;
struct ref_store *maybe_debug_wrap_ref_store(const char *gitdir, struct ref_store *store)
{
struct debug_ref_store *res;
struct ref_storage_be *be_copy;
if (!trace_want(&trace_refs)) {
return store;
}
res = xmalloc(sizeof(struct debug_ref_store));
be_copy = xmalloc(sizeof(*be_copy));
*be_copy = refs_be_debug;
/* we never deallocate backends, so safe to copy the pointer. */
be_copy->name = store->be->name;
trace_printf_key(&trace_refs, "ref_store for %s\n", gitdir);
res->refs = store;
base_ref_store_init((struct ref_store *)res, store->repo, gitdir,
be_copy);
return (struct ref_store *)res;
}
static int debug_init_db(struct ref_store *refs, struct strbuf *err)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
int res = drefs->refs->be->init_db(drefs->refs, err);
trace_printf_key(&trace_refs, "init_db: %d\n", res);
return res;
}
static int debug_transaction_prepare(struct ref_store *refs,
struct ref_transaction *transaction,
struct strbuf *err)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
int res;
transaction->ref_store = drefs->refs;
res = drefs->refs->be->transaction_prepare(drefs->refs, transaction,
err);
trace_printf_key(&trace_refs, "transaction_prepare: %d \"%s\"\n", res,
err->buf);
return res;
}
static void print_update(int i, const char *refname,
const struct object_id *old_oid,
const struct object_id *new_oid, unsigned int flags,
unsigned int type, const char *msg)
{
char o[GIT_MAX_HEXSZ + 1] = "null";
char n[GIT_MAX_HEXSZ + 1] = "null";
if (old_oid)
oid_to_hex_r(o, old_oid);
if (new_oid)
oid_to_hex_r(n, new_oid);
type &= 0xf; /* see refs.h REF_* */
flags &= REF_HAVE_NEW | REF_HAVE_OLD | REF_NO_DEREF |
REF_FORCE_CREATE_REFLOG;
trace_printf_key(&trace_refs, "%d: %s %s -> %s (F=0x%x, T=0x%x) \"%s\"\n", i, refname,
o, n, flags, type, msg);
}
static void print_transaction(struct ref_transaction *transaction)
{
int i;
trace_printf_key(&trace_refs, "transaction {\n");
for (i = 0; i < transaction->nr; i++) {
struct ref_update *u = transaction->updates[i];
print_update(i, u->refname, &u->old_oid, &u->new_oid, u->flags,
u->type, u->msg);
}
trace_printf_key(&trace_refs, "}\n");
}
static int debug_transaction_finish(struct ref_store *refs,
struct ref_transaction *transaction,
struct strbuf *err)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
int res;
transaction->ref_store = drefs->refs;
res = drefs->refs->be->transaction_finish(drefs->refs, transaction,
err);
print_transaction(transaction);
trace_printf_key(&trace_refs, "finish: %d\n", res);
return res;
}
static int debug_transaction_abort(struct ref_store *refs,
struct ref_transaction *transaction,
struct strbuf *err)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
int res;
transaction->ref_store = drefs->refs;
res = drefs->refs->be->transaction_abort(drefs->refs, transaction, err);
return res;
}
static int debug_initial_transaction_commit(struct ref_store *refs,
struct ref_transaction *transaction,
struct strbuf *err)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
int res;
transaction->ref_store = drefs->refs;
res = drefs->refs->be->initial_transaction_commit(drefs->refs,
transaction, err);
return res;
}
static int debug_pack_refs(struct ref_store *ref_store, unsigned int flags)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = drefs->refs->be->pack_refs(drefs->refs, flags);
trace_printf_key(&trace_refs, "pack_refs: %d\n", res);
return res;
}
static int debug_create_symref(struct ref_store *ref_store,
const char *ref_name, const char *target,
const char *logmsg)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = drefs->refs->be->create_symref(drefs->refs, ref_name, target,
logmsg);
trace_printf_key(&trace_refs, "create_symref: %s -> %s \"%s\": %d\n", ref_name,
target, logmsg, res);
return res;
}
static int debug_delete_refs(struct ref_store *ref_store, const char *msg,
struct string_list *refnames, unsigned int flags)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res =
drefs->refs->be->delete_refs(drefs->refs, msg, refnames, flags);
int i;
trace_printf_key(&trace_refs, "delete_refs {\n");
for (i = 0; i < refnames->nr; i++)
trace_printf_key(&trace_refs, "%s\n", refnames->items[i].string);
trace_printf_key(&trace_refs, "}: %d\n", res);
return res;
}
static int debug_rename_ref(struct ref_store *ref_store, const char *oldref,
const char *newref, const char *logmsg)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = drefs->refs->be->rename_ref(drefs->refs, oldref, newref,
logmsg);
trace_printf_key(&trace_refs, "rename_ref: %s -> %s \"%s\": %d\n", oldref, newref,
logmsg, res);
return res;
}
static int debug_copy_ref(struct ref_store *ref_store, const char *oldref,
const char *newref, const char *logmsg)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res =
drefs->refs->be->copy_ref(drefs->refs, oldref, newref, logmsg);
trace_printf_key(&trace_refs, "copy_ref: %s -> %s \"%s\": %d\n", oldref, newref,
logmsg, res);
return res;
}
struct debug_ref_iterator {
struct ref_iterator base;
struct ref_iterator *iter;
};
static int debug_ref_iterator_advance(struct ref_iterator *ref_iterator)
{
struct debug_ref_iterator *diter =
(struct debug_ref_iterator *)ref_iterator;
int res = diter->iter->vtable->advance(diter->iter);
if (res)
trace_printf_key(&trace_refs, "iterator_advance: (%d)\n", res);
else
trace_printf_key(&trace_refs, "iterator_advance: %s (0)\n",
diter->iter->refname);
diter->base.ordered = diter->iter->ordered;
diter->base.refname = diter->iter->refname;
diter->base.oid = diter->iter->oid;
diter->base.flags = diter->iter->flags;
return res;
}
static int debug_ref_iterator_peel(struct ref_iterator *ref_iterator,
struct object_id *peeled)
{
struct debug_ref_iterator *diter =
(struct debug_ref_iterator *)ref_iterator;
int res = diter->iter->vtable->peel(diter->iter, peeled);
trace_printf_key(&trace_refs, "iterator_peel: %s: %d\n", diter->iter->refname, res);
return res;
}
static int debug_ref_iterator_abort(struct ref_iterator *ref_iterator)
{
struct debug_ref_iterator *diter =
(struct debug_ref_iterator *)ref_iterator;
int res = diter->iter->vtable->abort(diter->iter);
trace_printf_key(&trace_refs, "iterator_abort: %d\n", res);
return res;
}
static struct ref_iterator_vtable debug_ref_iterator_vtable = {
debug_ref_iterator_advance, debug_ref_iterator_peel,
debug_ref_iterator_abort
};
static struct ref_iterator *
debug_ref_iterator_begin(struct ref_store *ref_store, const char *prefix,
unsigned int flags)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
struct ref_iterator *res =
drefs->refs->be->iterator_begin(drefs->refs, prefix, flags);
struct debug_ref_iterator *diter = xcalloc(1, sizeof(*diter));
base_ref_iterator_init(&diter->base, &debug_ref_iterator_vtable, 1);
diter->iter = res;
trace_printf_key(&trace_refs, "ref_iterator_begin: \"%s\" (0x%x)\n",
prefix, flags);
return &diter->base;
}
static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
struct object_id *oid, struct strbuf *referent,
unsigned int *type, int *failure_errno)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = 0;
oidcpy(oid, null_oid());
res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
type, failure_errno);
if (res == 0) {
trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
refname, oid_to_hex(oid), referent->buf, *type, res);
} else {
trace_printf_key(&trace_refs,
"read_raw_ref: %s: %d (errno %d)\n", refname,
res, *failure_errno);
}
return res;
}
static struct ref_iterator *
debug_reflog_iterator_begin(struct ref_store *ref_store)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
struct ref_iterator *res =
drefs->refs->be->reflog_iterator_begin(drefs->refs);
trace_printf_key(&trace_refs, "for_each_reflog_iterator_begin\n");
return res;
}
struct debug_reflog {
const char *refname;
each_reflog_ent_fn *fn;
void *cb_data;
};
static int debug_print_reflog_ent(struct object_id *old_oid,
struct object_id *new_oid,
const char *committer, timestamp_t timestamp,
int tz, const char *msg, void *cb_data)
{
struct debug_reflog *dbg = (struct debug_reflog *)cb_data;
int ret;
char o[GIT_MAX_HEXSZ + 1] = "null";
char n[GIT_MAX_HEXSZ + 1] = "null";
char *msgend = strchrnul(msg, '\n');
if (old_oid)
oid_to_hex_r(o, old_oid);
if (new_oid)
oid_to_hex_r(n, new_oid);
ret = dbg->fn(old_oid, new_oid, committer, timestamp, tz, msg,
dbg->cb_data);
trace_printf_key(&trace_refs,
"reflog_ent %s (ret %d): %s -> %s, %s %ld \"%.*s\"\n",
dbg->refname, ret, o, n, committer,
(long int)timestamp, (int)(msgend - msg), msg);
return ret;
}
static int debug_for_each_reflog_ent(struct ref_store *ref_store,
const char *refname, each_reflog_ent_fn fn,
void *cb_data)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
struct debug_reflog dbg = {
.refname = refname,
.fn = fn,
.cb_data = cb_data,
};
int res = drefs->refs->be->for_each_reflog_ent(
drefs->refs, refname, &debug_print_reflog_ent, &dbg);
trace_printf_key(&trace_refs, "for_each_reflog: %s: %d\n", refname, res);
return res;
}
static int debug_for_each_reflog_ent_reverse(struct ref_store *ref_store,
const char *refname,
each_reflog_ent_fn fn,
void *cb_data)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
struct debug_reflog dbg = {
.refname = refname,
.fn = fn,
.cb_data = cb_data,
};
int res = drefs->refs->be->for_each_reflog_ent_reverse(
drefs->refs, refname, &debug_print_reflog_ent, &dbg);
trace_printf_key(&trace_refs, "for_each_reflog_reverse: %s: %d\n", refname, res);
return res;
}
static int debug_reflog_exists(struct ref_store *ref_store, const char *refname)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = drefs->refs->be->reflog_exists(drefs->refs, refname);
trace_printf_key(&trace_refs, "reflog_exists: %s: %d\n", refname, res);
return res;
}
static int debug_create_reflog(struct ref_store *ref_store, const char *refname,
struct strbuf *err)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = drefs->refs->be->create_reflog(drefs->refs, refname, err);
trace_printf_key(&trace_refs, "create_reflog: %s: %d\n", refname, res);
return res;
}
static int debug_delete_reflog(struct ref_store *ref_store, const char *refname)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = drefs->refs->be->delete_reflog(drefs->refs, refname);
trace_printf_key(&trace_refs, "delete_reflog: %s: %d\n", refname, res);
return res;
}
struct debug_reflog_expiry_should_prune {
reflog_expiry_prepare_fn *prepare;
reflog_expiry_should_prune_fn *should_prune;
reflog_expiry_cleanup_fn *cleanup;
void *cb_data;
};
static void debug_reflog_expiry_prepare(const char *refname,
const struct object_id *oid,
void *cb_data)
{
struct debug_reflog_expiry_should_prune *prune = cb_data;
trace_printf_key(&trace_refs, "reflog_expire_prepare: %s\n", refname);
prune->prepare(refname, oid, prune->cb_data);
}
static int debug_reflog_expiry_should_prune_fn(struct object_id *ooid,
struct object_id *noid,
const char *email,
timestamp_t timestamp, int tz,
const char *message, void *cb_data) {
struct debug_reflog_expiry_should_prune *prune = cb_data;
int result = prune->should_prune(ooid, noid, email, timestamp, tz, message, prune->cb_data);
trace_printf_key(&trace_refs, "reflog_expire_should_prune: %s %ld: %d\n", message, (long int) timestamp, result);
return result;
}
static void debug_reflog_expiry_cleanup(void *cb_data)
{
struct debug_reflog_expiry_should_prune *prune = cb_data;
prune->cleanup(prune->cb_data);
}
static int debug_reflog_expire(struct ref_store *ref_store, const char *refname,
unsigned int flags,
reflog_expiry_prepare_fn prepare_fn,
reflog_expiry_should_prune_fn should_prune_fn,
reflog_expiry_cleanup_fn cleanup_fn,
void *policy_cb_data)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
struct debug_reflog_expiry_should_prune prune = {
.prepare = prepare_fn,
.cleanup = cleanup_fn,
.should_prune = should_prune_fn,
.cb_data = policy_cb_data,
};
int res = drefs->refs->be->reflog_expire(drefs->refs, refname,
flags, &debug_reflog_expiry_prepare,
&debug_reflog_expiry_should_prune_fn,
&debug_reflog_expiry_cleanup,
&prune);
trace_printf_key(&trace_refs, "reflog_expire: %s: %d\n", refname, res);
return res;
}
struct ref_storage_be refs_be_debug = {
NULL,
"debug",
NULL,
debug_init_db,
debug_transaction_prepare,
debug_transaction_finish,
debug_transaction_abort,
debug_initial_transaction_commit,
debug_pack_refs,
debug_create_symref,
debug_delete_refs,
debug_rename_ref,
debug_copy_ref,
debug_ref_iterator_begin,
debug_read_raw_ref,
NULL,
debug_reflog_iterator_begin,
debug_for_each_reflog_ent,
debug_for_each_reflog_ent_reverse,
debug_reflog_exists,
debug_create_reflog,
debug_delete_reflog,
debug_reflog_expire,
};