From: Phillip Wood Date: Sun, 13 Oct 2024 13:52:58 GMT Subject: Re: [PATCH v7 1/6] refs: atomically record overwritten ref in update_symref Message-ID: <3c848f10-ac14-4cd7-8fbe-868da9599244@gmail.com> In-Reply-To: <20241012230428.3259229-1-bence@ferdinandy.com> Hi Bence On 13/10/2024 00:03, Bence Ferdinandy wrote: > When updating a symref it's currently not possible to know for sure what > was the previous value that was overwritten. It is if you use a ref transaction rather than call refs_update_symref() and query the ref after calling ref_transaction_prepare() and before calling ref_transaction_commit() which is what the code below does. > Record the value after the > ref has been locked if the caller of refs_update_symref requests it via > a new variable in the function call. To me this patch and patch 5 feel quite disruptive to all the existing callers which don't need this specialized functionality. I think it would be less disruptive over all if you used a ref transaction rather than calling refs_update_symref() in the final patch. That would enable us to keep the simpler interface for refs_update_symref(). I'm also not sure about the proposed interface I would have thought it would be simpler to take a "char**" rather than an "struct strbuf*" if we do decide that it is useful for callers of refs_update_symref() to query the old value. Best Wishes Phillip > Signed-off-by: Bence Ferdinandy > --- > > Notes: > v4: new patch > > v5: - added before_target to reftables backend > - added an extra safety check for transaction's existence in refs.c > > v6: - no change > > v7: - remove the whole before_target concept from the backends and > handle checking it in refs.c instead (thanks Karthik) > - rename the before_target to referent which is how the same concept > is called in the backends > - change commit prefix to be more in line with project standards > > builtin/branch.c | 2 +- > builtin/checkout.c | 4 ++-- > builtin/clone.c | 6 +++--- > builtin/notes.c | 2 +- > builtin/remote.c | 6 +++--- > builtin/symbolic-ref.c | 2 +- > builtin/worktree.c | 2 +- > refs.c | 16 +++++++++++----- > refs.h | 3 ++- > reset.c | 2 +- > sequencer.c | 2 +- > setup.c | 2 +- > t/helper/test-ref-store.c | 2 +- > 13 files changed, 29 insertions(+), 22 deletions(-) > > diff --git a/builtin/branch.c b/builtin/branch.c > index fd1611ebf5..6c87690b58 100644 > --- a/builtin/branch.c > +++ b/builtin/branch.c > @@ -559,7 +559,7 @@ static int replace_each_worktree_head_symref(struct worktree **worktrees, > continue; > > refs = get_worktree_ref_store(worktrees[i]); > - if (refs_update_symref(refs, "HEAD", newref, logmsg)) > + if (refs_update_symref(refs, "HEAD", newref, logmsg, NULL)) > ret = error(_("HEAD of working tree %s is not updated"), > worktrees[i]->path); > } > diff --git a/builtin/checkout.c b/builtin/checkout.c > index 9c30000d3a..356ee9bcde 100644 > --- a/builtin/checkout.c > +++ b/builtin/checkout.c > @@ -1015,7 +1015,7 @@ static void update_refs_for_switch(const struct checkout_opts *opts, > describe_detached_head(_("HEAD is now at"), new_branch_info->commit); > } > } else if (new_branch_info->path) { /* Switch branches. */ > - if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", new_branch_info->path, msg.buf) < 0) > + if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", new_branch_info->path, msg.buf, NULL) < 0) > die(_("unable to update HEAD")); > if (!opts->quiet) { > if (old_branch_info->path && !strcmp(new_branch_info->path, old_branch_info->path)) { > @@ -1479,7 +1479,7 @@ static int switch_unborn_to_new_branch(const struct checkout_opts *opts) > die(_("You are on a branch yet to be born")); > strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch); > status = refs_update_symref(get_main_ref_store(the_repository), > - "HEAD", branch_ref.buf, "checkout -b"); > + "HEAD", branch_ref.buf, "checkout -b", NULL); > strbuf_release(&branch_ref); > if (!opts->quiet) > fprintf(stderr, _("Switched to a new branch '%s'\n"), > diff --git a/builtin/clone.c b/builtin/clone.c > index e77339c847..ead2af20ea 100644 > --- a/builtin/clone.c > +++ b/builtin/clone.c > @@ -661,7 +661,7 @@ static void update_remote_refs(const struct ref *refs, > strbuf_addstr(&head_ref, "HEAD"); > if (refs_update_symref(get_main_ref_store(the_repository), head_ref.buf, > remote_head_points_at->peer_ref->name, > - msg) < 0) > + msg, NULL) < 0) > die(_("unable to update %s"), head_ref.buf); > strbuf_release(&head_ref); > } > @@ -673,7 +673,7 @@ static void update_head(const struct ref *our, const struct ref *remote, > const char *head; > if (our && skip_prefix(our->name, "refs/heads/", &head)) { > /* Local default branch link */ > - if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", our->name, NULL) < 0) > + if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", our->name, NULL, NULL) < 0) > die(_("unable to update HEAD")); > if (!option_bare) { > refs_update_ref(get_main_ref_store(the_repository), > @@ -702,7 +702,7 @@ static void update_head(const struct ref *our, const struct ref *remote, > * Unborn head from remote; same as "our" case above except > * that we have no ref to update. > */ > - if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", unborn, NULL) < 0) > + if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", unborn, NULL, NULL) < 0) > die(_("unable to update HEAD")); > if (!option_bare) > install_branch_config(0, head, remote_name, unborn); > diff --git a/builtin/notes.c b/builtin/notes.c > index 8c26e45526..ba646f06ff 100644 > --- a/builtin/notes.c > +++ b/builtin/notes.c > @@ -980,7 +980,7 @@ static int merge(int argc, const char **argv, const char *prefix) > die(_("a notes merge into %s is already in-progress at %s"), > notes_ref, wt->path); > free_worktrees(worktrees); > - if (refs_update_symref(get_main_ref_store(the_repository), "NOTES_MERGE_REF", notes_ref, NULL)) > + if (refs_update_symref(get_main_ref_store(the_repository), "NOTES_MERGE_REF", notes_ref, NULL, NULL)) > die(_("failed to store link to current notes ref (%s)"), > notes_ref); > fprintf(stderr, _("Automatic notes merge failed. Fix conflicts in %s " > diff --git a/builtin/remote.c b/builtin/remote.c > index 76670ddd8b..d8ff440027 100644 > --- a/builtin/remote.c > +++ b/builtin/remote.c > @@ -244,7 +244,7 @@ static int add(int argc, const char **argv, const char *prefix) > strbuf_reset(&buf2); > strbuf_addf(&buf2, "refs/remotes/%s/%s", name, master); > > - if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote add")) > + if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote add", NULL)) > result = error(_("Could not setup master '%s'"), master); > } > > @@ -864,7 +864,7 @@ static int mv(int argc, const char **argv, const char *prefix) > strbuf_reset(&buf3); > strbuf_addf(&buf3, "remote: renamed %s to %s", > item->string, buf.buf); > - if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, buf3.buf)) > + if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, buf3.buf, NULL)) > die(_("creating '%s' failed"), buf.buf); > display_progress(progress, ++refs_renamed_nr); > } > @@ -1444,7 +1444,7 @@ static int set_head(int argc, const char **argv, const char *prefix) > /* make sure it's valid */ > if (!refs_ref_exists(get_main_ref_store(the_repository), buf2.buf)) > result |= error(_("Not a valid ref: %s"), buf2.buf); > - else if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote set-head")) > + else if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote set-head", NULL)) > result |= error(_("Could not setup %s"), buf.buf); > else if (opt_a) > printf("%s/HEAD set to %s\n", argv[0], head_name); > diff --git a/builtin/symbolic-ref.c b/builtin/symbolic-ref.c > index 299d23d76a..7728fbc3c1 100644 > --- a/builtin/symbolic-ref.c > +++ b/builtin/symbolic-ref.c > @@ -88,7 +88,7 @@ int cmd_symbolic_ref(int argc, > if (check_refname_format(argv[1], REFNAME_ALLOW_ONELEVEL) < 0) > die("Refusing to set '%s' to invalid ref '%s'", argv[0], argv[1]); > ret = !!refs_update_symref(get_main_ref_store(the_repository), > - argv[0], argv[1], msg); > + argv[0], argv[1], msg, NULL); > break; > default: > usage_with_options(git_symbolic_ref_usage, options); > diff --git a/builtin/worktree.c b/builtin/worktree.c > index fc31d072a6..a7ab4193c1 100644 > --- a/builtin/worktree.c > +++ b/builtin/worktree.c > @@ -517,7 +517,7 @@ static int add_worktree(const char *path, const char *refname, > ret = refs_update_ref(wt_refs, NULL, "HEAD", &commit->object.oid, > NULL, 0, UPDATE_REFS_MSG_ON_ERR); > else > - ret = refs_update_symref(wt_refs, "HEAD", symref.buf, NULL); > + ret = refs_update_symref(wt_refs, "HEAD", symref.buf, NULL, NULL); > if (ret) > goto done; > > diff --git a/refs.c b/refs.c > index 5f729ed412..b964ac44d0 100644 > --- a/refs.c > +++ b/refs.c > @@ -2114,7 +2114,8 @@ int peel_iterated_oid(struct repository *r, const struct object_id *base, struct > } > > int refs_update_symref(struct ref_store *refs, const char *ref, > - const char *target, const char *logmsg) > + const char *target, const char *logmsg, > + struct strbuf *referent) > { > struct ref_transaction *transaction; > struct strbuf err = STRBUF_INIT; > @@ -2122,17 +2123,23 @@ int refs_update_symref(struct ref_store *refs, const char *ref, > > transaction = ref_store_transaction_begin(refs, &err); > if (!transaction || > - ref_transaction_update(transaction, ref, NULL, NULL, > + ref_transaction_update(transaction, ref, NULL, NULL, > target, NULL, REF_NO_DEREF, > logmsg, &err) || > - ref_transaction_commit(transaction, &err)) { > + ref_transaction_prepare(transaction, &err)) { > ret = error("%s", err.buf); > + goto cleanup; > } > + if (referent) > + refs_read_symbolic_ref(refs, ref, referent); > + > + if (ref_transaction_commit(transaction, &err)) > + ret = error("%s", err.buf); > > +cleanup: > strbuf_release(&err); > if (transaction) > ref_transaction_free(transaction); > - > return ret; > } > > @@ -2948,4 +2955,3 @@ int ref_update_expects_existing_old_ref(struct ref_update *update) > return (update->flags & REF_HAVE_OLD) && > (!is_null_oid(&update->old_oid) || update->old_target); > } > - > diff --git a/refs.h b/refs.h > index 108dfc93b3..b09a3a4384 100644 > --- a/refs.h > +++ b/refs.h > @@ -571,7 +571,8 @@ int refs_copy_existing_ref(struct ref_store *refs, const char *oldref, > const char *newref, const char *logmsg); > > int refs_update_symref(struct ref_store *refs, const char *refname, > - const char *target, const char *logmsg); > + const char *target, const char *logmsg, > + struct strbuf *referent); > > enum action_on_err { > UPDATE_REFS_MSG_ON_ERR, > diff --git a/reset.c b/reset.c > index b22b1be792..cc36a9ed56 100644 > --- a/reset.c > +++ b/reset.c > @@ -76,7 +76,7 @@ static int update_refs(const struct reset_head_opts *opts, > if (!ret) > ret = refs_update_symref(get_main_ref_store(the_repository), > "HEAD", switch_to_branch, > - reflog_head); > + reflog_head, NULL); > } > if (!ret && run_hook) > run_hooks_l(the_repository, "post-checkout", > diff --git a/sequencer.c b/sequencer.c > index 8d01cd50ac..23b162924c 100644 > --- a/sequencer.c > +++ b/sequencer.c > @@ -5107,7 +5107,7 @@ static int pick_commits(struct repository *r, > } > msg = reflog_message(opts, "finish", "returning to %s", > head_ref.buf); > - if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", head_ref.buf, msg)) { > + if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", head_ref.buf, msg, NULL)) { > res = error(_("could not update HEAD to %s"), > head_ref.buf); > goto cleanup_head_ref; > diff --git a/setup.c b/setup.c > index 94e79b2e48..d95f051465 100644 > --- a/setup.c > +++ b/setup.c > @@ -2275,7 +2275,7 @@ void create_reference_database(enum ref_storage_format ref_storage_format, > die(_("invalid initial branch name: '%s'"), > initial_branch); > > - if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", ref, NULL) < 0) > + if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", ref, NULL, NULL) < 0) > exit(1); > free(ref); > } > diff --git a/t/helper/test-ref-store.c b/t/helper/test-ref-store.c > index 65346dee55..a911302bea 100644 > --- a/t/helper/test-ref-store.c > +++ b/t/helper/test-ref-store.c > @@ -120,7 +120,7 @@ static int cmd_create_symref(struct ref_store *refs, const char **argv) > const char *target = notnull(*argv++, "target"); > const char *logmsg = *argv++; > > - return refs_update_symref(refs, refname, target, logmsg); > + return refs_update_symref(refs, refname, target, logmsg, NULL); > } > > static struct flag_definition transaction_flags[] = {