Subject: Re: [GSoC][PATCH v2 5/7] files-backend: add unified interface for refs scanning

From: shejialuo <[email-masked]>
Date: Tue, 18 Jun 2024 17:09:17 +0800

On Sat, Jun 15, 2024 at 04:51:14PM -0400, Karthik Nayak wrote:
> shejialuo <[email-masked]> writes:
> 
> > For refs and reflogs, we need to scan its corresponding directories to
> > check every regular file or symbolic link which shares the same pattern.
> > Introduce a unified interface for scanning directories for
> > files-backend.
> >
> 
> Here we talk about reflogs, but we only add a iterator for
> "$GIT_DIR/refs". Should we add something for reflogs too?
> 

Here, we simply set up the basic structure. For both refs and reflogs,
we will traverse the file system. What we concern about is the regular
file and symlink file. The "refs_check_dir" parameter is used to
indicate what we will check. Actually, we do not add any actual check
operations for refs in this commit.

> > Mentored-by: Patrick Steinhardt <[email-masked]>
> > Mentored-by: Karthik Nayak <[email-masked]>
> > Signed-off-by: shejialuo <[email-masked]>
> > ---
> >  refs/files-backend.c | 75 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 75 insertions(+)
> >
> > diff --git a/refs/files-backend.c b/refs/files-backend.c
> > index e965345ad8..b26cfb8ba6 100644
> > --- a/refs/files-backend.c
> > +++ b/refs/files-backend.c
> > @@ -4,6 +4,7 @@
> >  #include "../gettext.h"
> >  #include "../hash.h"
> >  #include "../hex.h"
> > +#include "../fsck.h"
> >  #include "../refs.h"
> >  #include "refs-internal.h"
> >  #include "ref-cache.h"
> > @@ -3402,6 +3403,78 @@ static int files_ref_store_remove_on_disk(struct ref_store *ref_store,
> >  	return ret;
> >  }
> >
> > +/*
> > + * For refs and reflogs, they share a unified interface when scanning
> > + * the whole directory. This function is used as the callback for each
> > + * regular file or symlink in the directory.
> > + */
> > +typedef int (*files_fsck_refs_fn)(struct fsck_refs_options *o,
> > +				  const char *gitdir,
> > +				  const char *refs_check_dir,
> > +				  struct dir_iterator *iter);
> > +
> > +static int files_fsck_refs_dir(struct ref_store *ref_store,
> > +			       struct fsck_refs_options *o,
> > +			       const char *refs_check_dir,
> > +			       files_fsck_refs_fn *fsck_refs_fns)
> > +{
> > +	const char *gitdir = ref_store->gitdir;
> > +	struct strbuf sb = STRBUF_INIT;
> > +	struct dir_iterator *iter;
> > +	int iter_status;
> > +	int ret = 0;
> > +
> > +	strbuf_addf(&sb, "%s/%s", gitdir, refs_check_dir);
> > +
> > +	iter = dir_iterator_begin(sb.buf, 0);
> > +
> > +	if (!iter) {
> > +		ret = error_errno("cannot open directory %s", sb.buf);
> > +		goto out;
> > +	}
> > +
> > +	while ((iter_status = dir_iterator_advance(iter)) == ITER_OK) {
> > +		if (S_ISDIR(iter->st.st_mode)) {
> > +			continue;
> > +		} else if (S_ISREG(iter->st.st_mode) ||
> > +			   S_ISLNK(iter->st.st_mode)) {
> > +			if (o->verbose)
> > +				fprintf_ln(stderr, "Checking %s/%s",
> > +					   refs_check_dir, iter->relative_path);
> > +			for (size_t i = 0; fsck_refs_fns[i]; i++) {
> > +				if (fsck_refs_fns[i](o, gitdir, refs_check_dir, iter))
> > +					ret = -1;
> > +			}
> > +		} else {
> > +			ret = error(_("unexpected file type for '%s'"),
> > +				    iter->basename);
> > +		}
> > +	}
> > +
> > +	if (iter_status != ITER_DONE)
> > +		ret = error(_("failed to iterate over '%s'"), sb.buf);
> > +
> > +out:
> > +	strbuf_release(&sb);
> > +	return ret;
> > +}
> > +
> > +static int files_fsck_refs(struct ref_store *ref_store,
> > +			   struct fsck_refs_options *o)
> > +{
> > +	int ret;
> > +	files_fsck_refs_fn fsck_refs_fns[]= {
> > +		NULL
> > +	};
> > +
> > +	if (o->verbose)
> > +		fprintf_ln(stderr, "Checking references consistency");
> > +
> > +	ret = files_fsck_refs_dir(ref_store, o, "refs", fsck_refs_fns);
> > +
> > +	return ret;
> > +}
> 
> I'm not fully sure why this needs to be separate from `files_fsck`. Is
> that because we plan to also introduce `files_fsck_reflogs`?
> 

Yes, exactly. Later we need to introduce "files_fsck_reflogs" which
should define the different `files_fsck_refs_fn` here. So just introduce
a function here.

> > +
> >  static int files_fsck(struct ref_store *ref_store,
> >  		      struct fsck_refs_options *o)
> >  {
> > @@ -3410,6 +3483,8 @@ static int files_fsck(struct ref_store *ref_store,
> >  		files_downcast(ref_store, REF_STORE_READ, "fsck");
> >
> >  	ret = refs->packed_ref_store->be->fsck(refs->packed_ref_store, o);
> > +	ret = files_fsck_refs(ref_store, o);
> > +
> >  	return ret;
> >  }
> >
> > --
> > 2.45.2