On Fri, Dec 12, 2014 at 12:56 AM, Michael Haggerty <mhagger@xxxxxxxxxxxx> wrote:
> We don't actually need the locking functionality, because we already
> hold the lock on the reference itself, which is how the reflog file is
> locked. But the lock_file code can do some of the bookkeeping for us,
> and it is more careful than the old code here was. For example:
>
> * It correctly handles the case that the reflog lock file already
> exists for some reason or cannot be opened.
>
> * It correctly cleans up the lockfile if the program dies.
>
> Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
> ---
> builtin/reflog.c | 60 ++++++++++++++++++++++++++++++++++++++------------------
> 1 file changed, 41 insertions(+), 19 deletions(-)
>
> diff --git a/builtin/reflog.c b/builtin/reflog.c
> index 37b33c9..ba5b3d3 100644
> --- a/builtin/reflog.c
> +++ b/builtin/reflog.c
> @@ -352,9 +352,10 @@ static int push_tip_to_list(const char *refname, const unsigned char *sha1, int
> static int expire_reflog(const char *refname, const unsigned char *sha1,
> struct cmd_reflog_expire_cb *cmd)
> {
> + static struct lock_file reflog_lock;
> struct expire_reflog_cb cb;
> struct ref_lock *lock;
> - char *log_file, *newlog_path = NULL;
> + char *log_file;
> struct commit *tip_commit;
> struct commit_list *tips;
> int status = 0;
> @@ -362,8 +363,9 @@ static int expire_reflog(const char *refname, const unsigned char *sha1,
> memset(&cb, 0, sizeof(cb));
>
> /*
> - * we take the lock for the ref itself to prevent it from
> - * getting updated.
> + * The reflog file is locked by holding the lock on the
> + * reference itself, plus we might need to update the
> + * reference if --updateref was specified:
> */
> lock = lock_any_ref_for_update(refname, sha1, 0, NULL);
> if (!lock)
> @@ -372,10 +374,29 @@ static int expire_reflog(const char *refname, const unsigned char *sha1,
> unlock_ref(lock);
> return 0;
> }
> +
> log_file = git_pathdup("logs/%s", refname);
> if (!cmd->dry_run) {
> - newlog_path = git_pathdup("logs/%s.lock", refname);
> - cb.newlog = fopen(newlog_path, "w");
> + /*
> + * Even though holding $GIT_DIR/logs/$reflog.lock has
> + * no locking implications, we use the lock_file
> + * machinery here anyway because it does a lot of the
> + * work we need, including cleaning up if the program
> + * exits unexpectedly.
> + */
> + if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
> + struct strbuf err = STRBUF_INIT;
> + unable_to_lock_message(log_file, errno, &err);
> + error("%s", err.buf);
> + strbuf_release(&err);
> + goto failure;
> + }
> + cb.newlog = fdopen_lock_file(&reflog_lock, "w");
> + if (!cb.newlog) {
> + error("cannot fdopen %s (%s)",
> + reflog_lock.filename.buf, strerror(errno));
> + goto failure;
> + }
> }
>
> cb.cmd = cmd;
> @@ -423,32 +444,33 @@ static int expire_reflog(const char *refname, const unsigned char *sha1,
> }
>
> if (cb.newlog) {
> - if (fclose(cb.newlog)) {
> - status |= error("%s: %s", strerror(errno),
> - newlog_path);
> - unlink(newlog_path);
> + if (close_lock_file(&reflog_lock)) {
> + status |= error("couldn't write %s: %s", log_file,
> + strerror(errno));
> } else if (cmd->updateref &&
> (write_in_full(lock->lock_fd,
> sha1_to_hex(cb.last_kept_sha1), 40) != 40 ||
optional nit:
While being here, you may fix the indentation of the sha1_to_hex to align to the
opening parentheses of write_in_full the line before.
> write_str_in_full(lock->lock_fd, "\n") != 1 ||
> close_ref(lock) < 0)) {
> - status |= error("Couldn't write %s",
> + status |= error("couldn't write %s",
> lock->lk->filename.buf);
> - unlink(newlog_path);
> - } else if (rename(newlog_path, log_file)) {
> - status |= error("cannot rename %s to %s",
> - newlog_path, log_file);
> - unlink(newlog_path);
> + rollback_lock_file(&reflog_lock);
> + } else if (commit_lock_file(&reflog_lock)) {
> + status |= error("unable to commit reflog '%s' (%s)",
> + log_file, strerror(errno));
> } else if (cmd->updateref && commit_ref(lock)) {
> - status |= error("Couldn't set %s", lock->ref_name);
> - } else {
> - adjust_shared_perm(log_file);
So we don't need adjust_shared_perm anymore?
I have been looking at this excerpt for a while now and I am confused by the
first and third statement in the origin/master state as well as after
your changes.
So it's essentially:
* write out the reflog lock file
* update ref in the lock file
* rename the reflog lock into place
* rename the ref lock into place
* (in origin/master) if everything went fine, call adjust_shared_perm.
* In your patch we actually don't need it as on locking the lock
file there is a call
to adjust_shared_perm already.
So I think it's clear to me now and looks good. It took me sometime to
understand
it. Maybe that's because I just got up or it's in fact hard to
understand. Would comments
help in laying out the sequence of actions beforehand?
I think the most confusing thing was the close_lock_file as a first
statement in the if chain.
close_lock_file is primarily used here to have the file written out to
disk, but the function
name suggests that the primary functionality is the closing of the fd.
> + status |= error("couldn't set %s", lock->ref_name);
> }
> }
> - free(newlog_path);
> free(log_file);
> unlock_ref(lock);
> return status;
> +
> + failure:
> + rollback_lock_file(&reflog_lock);
> + free(log_file);
> + unlock_ref(lock);
> + return -1;
> }
>
> static int collect_reflog(const char *ref, const unsigned char *sha1, int unused, void *cb_data)
> --
> 2.1.3
>
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