refs: make errno output explicit for read_raw_ref_fn
This makes it explicit how alternative ref backends should report errors in read_raw_ref_fn. read_raw_ref_fn needs to supply a credible errno for a number of cases. These are primarily: 1) The files backend calls read_raw_ref from lock_raw_ref, and uses the resulting error codes to create/remove directories as needed. 2) ENOENT should be translated in a zero OID, optionally with REF_ISBROKEN set, returning the last successfully resolved symref. This is necessary so read_raw_ref("HEAD") on an empty repo returns refs/heads/main (or the default branch du-jour), and we know on which branch to create the first commit. Make this information flow explicit by adding a failure_errno to the signature of read_raw_ref. All errnos from the files backend are still propagated unchanged, even though inspection suggests only ENOTDIR, EISDIR and ENOENT are relevant. Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Han-Wen Nienhuys committed
Aug 23, 2021 at 13:52 UTC
5b12e16bb134969747eaa983ab8d83d57f41e960
5 files changed
+35
-31
refs.c
+1
-1
@@ -1682,7 +1682,7 @@ int refs_read_raw_ref(struct ref_store *ref_store,
1682
}
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return ref_store->be->read_raw_ref(ref_store, refname, oid, referent,
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- type);
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+ type, &errno);
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}
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/* This function needs to return a meaningful errno on failure */
refs/debug.c
+3
-4
@@ -238,15 +238,14 @@ debug_ref_iterator_begin(struct ref_store *ref_store, const char *prefix,
238
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static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
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struct object_id *oid, struct strbuf *referent,
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- unsigned int *type)
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+ unsigned int *type, int *failure_errno)
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{
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struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
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int res = 0;
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oidcpy(oid, null_oid());
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- errno = 0;
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res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
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- type);
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+ type, failure_errno);
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if (res == 0) {
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trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
@@ -254,7 +253,7 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
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} else {
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trace_printf_key(&trace_refs,
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"read_raw_ref: %s: %d (errno %d)\n", refname,
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- res, errno);
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+ res, *failure_errno);
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}
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return res;
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}
refs/files-backend.c
+15
-14
@@ -341,9 +341,9 @@ static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
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return refs->loose;
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}
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-static int files_read_raw_ref(struct ref_store *ref_store,
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- const char *refname, struct object_id *oid,
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- struct strbuf *referent, unsigned int *type)
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+static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
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+ struct object_id *oid, struct strbuf *referent,
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+ unsigned int *type, int *failure_errno)
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{
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struct files_ref_store *refs =
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files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
@@ -354,7 +354,6 @@ static int files_read_raw_ref(struct ref_store *ref_store,
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struct stat st;
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int fd;
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int ret = -1;
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- int save_errno;
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int remaining_retries = 3;
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*type = 0;
@@ -459,10 +458,9 @@ stat_ref:
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ret = parse_loose_ref_contents(buf, oid, referent, type);
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out:
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- save_errno = errno;
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+ *failure_errno = errno;
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strbuf_release(&sb_path);
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strbuf_release(&sb_contents);
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- errno = save_errno;
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return ret;
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}
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@@ -540,6 +538,7 @@ static int lock_raw_ref(struct files_ref_store *refs,
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struct strbuf ref_file = STRBUF_INIT;
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int attempts_remaining = 3;
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int ret = TRANSACTION_GENERIC_ERROR;
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+ int failure_errno;
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assert(err);
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files_assert_main_repository(refs, "lock_raw_ref");
@@ -610,7 +609,9 @@ retry:
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if (hold_lock_file_for_update_timeout(
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&lock->lk, ref_file.buf, LOCK_NO_DEREF,
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get_files_ref_lock_timeout_ms()) < 0) {
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- if (errno == ENOENT && --attempts_remaining > 0) {
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+ int myerr = errno;
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+ errno = 0;
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+ if (myerr == ENOENT && --attempts_remaining > 0) {
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/*
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* Maybe somebody just deleted one of the
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* directories leading to ref_file. Try
@@ -618,7 +619,7 @@ retry:
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*/
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goto retry;
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} else {
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- unable_to_lock_message(ref_file.buf, errno, err);
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+ unable_to_lock_message(ref_file.buf, myerr, err);
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goto error_return;
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}
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}
@@ -628,9 +629,9 @@ retry:
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* fear that its value will change.
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*/
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- if (files_read_raw_ref(&refs->base, refname,
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- &lock->old_oid, referent, type)) {
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- if (errno == ENOENT) {
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+ if (files_read_raw_ref(&refs->base, refname, &lock->old_oid, referent,
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+ type, &failure_errno)) {
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+ if (failure_errno == ENOENT) {
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if (mustexist) {
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/* Garden variety missing reference. */
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strbuf_addf(err, "unable to resolve reference '%s'",
@@ -654,7 +655,7 @@ retry:
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* reference named "refs/foo/bar/baz".
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*/
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}
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- } else if (errno == EISDIR) {
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+ } else if (failure_errno == EISDIR) {
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/*
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* There is a directory in the way. It might have
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* contained references that have been deleted. If
@@ -692,13 +693,13 @@ retry:
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goto error_return;
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}
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}
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- } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
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+ } else if (failure_errno == EINVAL && (*type & REF_ISBROKEN)) {
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strbuf_addf(err, "unable to resolve reference '%s': "
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"reference broken", refname);
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goto error_return;
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} else {
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strbuf_addf(err, "unable to resolve reference '%s': %s",
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- refname, strerror(errno));
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+ refname, strerror(failure_errno));
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goto error_return;
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}
705
refs/packed-backend.c
+4
-4
@@ -724,9 +724,9 @@ static struct snapshot *get_snapshot(struct packed_ref_store *refs)
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return refs->snapshot;
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}
726
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-static int packed_read_raw_ref(struct ref_store *ref_store,
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- const char *refname, struct object_id *oid,
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- struct strbuf *referent, unsigned int *type)
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+static int packed_read_raw_ref(struct ref_store *ref_store, const char *refname,
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+ struct object_id *oid, struct strbuf *referent,
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+ unsigned int *type, int *failure_errno)
730
{
731
struct packed_ref_store *refs =
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packed_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
@@ -739,7 +739,7 @@ static int packed_read_raw_ref(struct ref_store *ref_store,
739
740
if (!rec) {
741
/* refname is not a packed reference. */
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- errno = ENOENT;
742
+ *failure_errno = ENOENT;
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return -1;
744
}
745
refs/refs-internal.h
+12
-8
@@ -620,11 +620,15 @@ typedef int reflog_expire_fn(struct ref_store *ref_store,
620
* properly-formatted or even safe reference name. NEITHER INPUT NOR
621
* OUTPUT REFERENCE NAMES ARE VALIDATED WITHIN THIS FUNCTION.
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*
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- * Return 0 on success. If the ref doesn't exist, set errno to ENOENT
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- * and return -1. If the ref exists but is neither a symbolic ref nor
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- * an object ID, it is broken; set REF_ISBROKEN in type, and return -1
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- * (errno should not be ENOENT) If there is another error reading the
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- * ref, set errno appropriately and return -1.
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+ * Return 0 on success, or -1 on failure. If the ref exists but is neither a
624
+ * symbolic ref nor an object ID, it is broken. In this case set REF_ISBROKEN in
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+ * type, and return -1 (failure_errno should not be ENOENT)
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+ *
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+ * failure_errno provides errno codes that are interpreted beyond error
628
+ * reporting. The following error codes have special meaning:
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+ * * ENOENT: the ref doesn't exist
630
+ * * EISDIR: ref name is a directory
631
+ * * ENOTDIR: ref prefix is not a directory
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*
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* Backend-specific flags might be set in type as well, regardless of
634
* outcome.
@@ -638,9 +642,9 @@ typedef int reflog_expire_fn(struct ref_store *ref_store,
642
* - in all other cases, referent will be untouched, and therefore
643
* refname will still be valid and unchanged.
644
*/
641
-typedef int read_raw_ref_fn(struct ref_store *ref_store,
642
- const char *refname, struct object_id *oid,
643
- struct strbuf *referent, unsigned int *type);
645
+typedef int read_raw_ref_fn(struct ref_store *ref_store, const char *refname,
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+ struct object_id *oid, struct strbuf *referent,
647
+ unsigned int *type, int *failure_errno);
648
649
struct ref_storage_be {
650
struct ref_storage_be *next;