| Message ID | patch-11.11-96c3e5e9f79-20210716T140631Z-avarab@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | fix "git reflog expire" race & get rid of EISDIR in refs API | expand |
On Fri, Jul 16, 2021 at 04:13:07PM +0200, Ævar Arnfjörð Bjarmason wrote: > Further historical commentary: > > Before the two preceding commits the caller in files_reflog_expire() > was the only one out of our 4 callers that would pass non-NULL as an > oid. We would then set a (now gone) "resolve_flags" to > "RESOLVE_REF_READING" and just before that "errno != EISDIR" check do: > [...] Right, thanks for digging into this situation in the commit message. > @@ -891,30 +890,9 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, > CALLOC_ARRAY(lock, 1); > > files_ref_path(refs, &ref_file, refname); > - resolved = !!refs_resolve_ref_unsafe(&refs->base, refname, > - RESOLVE_REF_NO_RECURSE, > - &lock->old_oid, type); > - if (!resolved && errno == EISDIR) { > - /* > - * we are trying to lock foo but we used to > - * have foo/bar which now does not exist; > - * it is normal for the empty directory 'foo' > - * to remain. > - */ > - if (remove_empty_directories(&ref_file)) { > - last_errno = errno; > - if (!refs_verify_refname_available( > - &refs->base, > - refname, NULL, NULL, err)) > - strbuf_addf(err, "there are still refs under '%s'", > - refname); > - goto error_return; > - } > - resolved = !!refs_resolve_ref_unsafe(&refs->base, refname, > - RESOLVE_REF_NO_RECURSE, > - &lock->old_oid, type); > - } > - if (!resolved) { > + if (!refs_resolve_ref_unsafe(&refs->base, refname, > + RESOLVE_REF_NO_RECURSE, > + &lock->old_oid, type)) { I agree that this is all trivially dead code now, and can be removed. > last_errno = errno; > if (last_errno != ENOTDIR || > !refs_verify_refname_available(&refs->base, refname, Not necessary, but I think "last_errno != ENOTDIR" will always be true now, too. We treat it the same as EISDIR in refs_resolve_ref_unsafe(). It's not that big a cleanup, but it could easily go on top. -Peff
diff --git a/refs/files-backend.c b/refs/files-backend.c index 3e7598cc86c..bd99bc570de 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c @@ -883,7 +883,6 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, struct strbuf ref_file = STRBUF_INIT; struct ref_lock *lock; int last_errno = 0; - int resolved; files_assert_main_repository(refs, "lock_ref_oid_basic"); assert(err); @@ -891,30 +890,9 @@ static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs, CALLOC_ARRAY(lock, 1); files_ref_path(refs, &ref_file, refname); - resolved = !!refs_resolve_ref_unsafe(&refs->base, refname, - RESOLVE_REF_NO_RECURSE, - &lock->old_oid, type); - if (!resolved && errno == EISDIR) { - /* - * we are trying to lock foo but we used to - * have foo/bar which now does not exist; - * it is normal for the empty directory 'foo' - * to remain. - */ - if (remove_empty_directories(&ref_file)) { - last_errno = errno; - if (!refs_verify_refname_available( - &refs->base, - refname, NULL, NULL, err)) - strbuf_addf(err, "there are still refs under '%s'", - refname); - goto error_return; - } - resolved = !!refs_resolve_ref_unsafe(&refs->base, refname, - RESOLVE_REF_NO_RECURSE, - &lock->old_oid, type); - } - if (!resolved) { + if (!refs_resolve_ref_unsafe(&refs->base, refname, + RESOLVE_REF_NO_RECURSE, + &lock->old_oid, type)) { last_errno = errno; if (last_errno != ENOTDIR || !refs_verify_refname_available(&refs->base, refname,
When we lock a reference like "foo" we need to handle the case where "foo" exists, but is an empty directory. That's what this code added in bc7127ef0f (ref locking: allow 'foo' when 'foo/bar' used to exist but not anymore., 2006-09-30) seems like it should be dealing with. Except it doesn't, and we never take this branch. The reason is that when bc7127ef0f was written this looked like: ref = resolve_ref([...]); if (!ref && errno == EISDIR) { [...] And in resolve_ref() we had this code: fd = open(path, O_RDONLY); if (fd < 0) return NULL; I.e. we would attempt to read "foo" with open(), which would fail with EISDIR and we'd return NULL. We'd then take this branch, call remove_empty_directories() and continue. Since a1c1d8170d (refs_resolve_ref_unsafe: handle d/f conflicts for writes, 2017-10-06) we don't. E.g. in the case of files_copy_or_rename_ref() our callstack will look something like: [...] -> files_copy_or_rename_ref() -> lock_ref_oid_basic() -> refs_resolve_ref_unsafe() At that point the first (now only) refs_resolve_ref_unsafe() call in lock_ref_oid_basic() would do the equivalent of this in the resulting call to refs_read_raw_ref() in refs_resolve_ref_unsafe(): /* Via refs_read_raw_ref() */ fd = open(path, O_RDONLY); if (fd < 0) /* get errno == EISDIR */ /* later, in refs_resolve_ref_unsafe() */ if ([...] && errno != EISDIR) return NULL; [...] /* returns the refs/heads/foo to the caller, even though it's a directory */ return refname; I.e. even though we got an "errno == EISDIR" we won't take this branch, since in cases of EISDIR "resolved" is always non-NULL. I.e. we pretend at this point as though everything's OK and there is no "foo" directory. We then proceed with the entire ref update and don't call remove_empty_directories() until we call commit_ref_update(). See 5387c0d883 (commit_ref(): if there is an empty dir in the way, delete it, 2016-05-05) for the addition of that code, and a1c1d8170db (refs_resolve_ref_unsafe: handle d/f conflicts for writes, 2017-10-06) for the commit that changed the original codepath added in bc7127ef0f to use this "EISDIR" handling. Further historical commentary: Before the two preceding commits the caller in files_reflog_expire() was the only one out of our 4 callers that would pass non-NULL as an oid. We would then set a (now gone) "resolve_flags" to "RESOLVE_REF_READING" and just before that "errno != EISDIR" check do: if (resolve_flags & RESOLVE_REF_READING) return NULL; There may have been some case where this ended up mattering and we couldn't safely make this change before we removed the "oid" parameter, but I don't think there was, see [1] for some discussion on that. In any case, now that we've removed the "oid" parameter in a preceding commit we can be sure that this code is redundant, so let's remove it. 1. http://lore.kernel.org/git/871r801yp6.fsf@evledraar.gmail.com Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> --- refs/files-backend.c | 28 +++------------------------- 1 file changed, 3 insertions(+), 25 deletions(-)