[PATCH 0/3] Close commit-graph before calling 'gc'

[PATCH 0/3] Close commit-graph before calling 'gc'

[Derrick Stolee via GitGitGadget]

In Windows, the way we rename a lock file to replace the underlying file
does not work when a process holds a read handle. For this reason, we call 
close_all_packs() everywhere before starting a git gc --auto subprocess. We
also call close_commit_graph() before renaming the commit-graph lock file.
But we don't close the commit-graph handles before running gc, which can
cause an issue when gc.writeCommitGraph is enabled.

This series adds close_commit_graph() to close_all_packs() and then renames 
close_all_packs() to close_object_store(). This name is more descriptive of
its larger purpose.

This is based on ds/commit-graph-write-refactor to avoid conflicts.

Thanks, -Stolee

Derrick Stolee (3):
  commit-graph: use raw_object_store when closing
  packfile: close commit-graph in close_all_packs
  packfile: close_all_packs to close_object_store

 builtin/am.c           | 2 +-
 builtin/clone.c        | 2 +-
 builtin/fetch.c        | 2 +-
 builtin/gc.c           | 4 ++--
 builtin/merge.c        | 2 +-
 builtin/rebase.c       | 2 +-
 builtin/receive-pack.c | 2 +-
 builtin/repack.c       | 2 +-
 commit-graph.c         | 8 ++++----
 commit-graph.h         | 2 +-
 object.c               | 2 +-
 packfile.c             | 5 ++++-
 packfile.h             | 2 +-
 upload-pack.c          | 2 +-
 14 files changed, 21 insertions(+), 18 deletions(-)


base-commit: 8520d7fc7c6edd4d71582c69a873436029b6cb1b
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-208%2Fderrickstolee%2Fclose-graph-everywhere-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-208/derrickstolee/close-graph-everywhere-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/208
-- 
gitgitgadget

[PATCH 1/3] commit-graph: use raw_object_store when closing

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dstolee@microsoft.com>

The close_commit_graph() method took a repository struct, but then
only uses the raw_object_store within. Change the function prototype
to make the method more flexible.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c | 8 ++++----
 commit-graph.h | 2 +-
 upload-pack.c  | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 7723156964..e777e269aa 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -359,10 +359,10 @@ int generation_numbers_enabled(struct repository *r)
 	return !!first_generation;
 }
 
-void close_commit_graph(struct repository *r)
+void close_commit_graph(struct raw_object_store *o)
 {
-	free_commit_graph(r->objects->commit_graph);
-	r->objects->commit_graph = NULL;
+	free_commit_graph(o->commit_graph);
+	o->commit_graph = NULL;
 }
 
 static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
@@ -1086,7 +1086,7 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
 	stop_progress(&ctx->progress);
 	strbuf_release(&progress_title);
 
-	close_commit_graph(ctx->r);
+	close_commit_graph(ctx->r->objects);
 	finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 	commit_lock_file(&lk);
 
diff --git a/commit-graph.h b/commit-graph.h
index 70f4caf0c7..afa3633592 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -76,7 +76,7 @@ int write_commit_graph(const char *obj_dir,
 
 int verify_commit_graph(struct repository *r, struct commit_graph *g);
 
-void close_commit_graph(struct repository *);
+void close_commit_graph(struct raw_object_store *);
 void free_commit_graph(struct commit_graph *);
 
 #endif
diff --git a/upload-pack.c b/upload-pack.c
index d098ef5982..b51bed21e4 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -717,7 +717,7 @@ static void deepen_by_rev_list(struct packet_writer *writer, int ac,
 {
 	struct commit_list *result;
 
-	close_commit_graph(the_repository);
+	close_commit_graph(the_repository->objects);
 	result = get_shallow_commits_by_rev_list(ac, av, SHALLOW, NOT_SHALLOW);
 	send_shallow(writer, result);
 	free_commit_list(result);
-- 
gitgitgadget

[PATCH 2/3] packfile: close commit-graph in close_all_packs

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dstolee@microsoft.com>

The close_all_packs() method is used to close all read handles to
pack-files and the multi-pack-index before running 'git gc --auto'.
This is particularly important on the Windows platform, where read
handles block any writes to those files. Replacing one of these
files with a rename() will fail in this situation.

The commit-graph also performs a rename, so is susceptable to this
problem. We are careful to close the commit-graph before writing,
but that doesn't work when a 'git fetch' (or similar) process runs
'git gc --auto' which may write a commit-graph.

Here, close the commit-graph as part of close_all_packs().

Reported-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 packfile.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/packfile.c b/packfile.c
index 16bcb75262..ce12bffe3e 100644
--- a/packfile.c
+++ b/packfile.c
@@ -16,6 +16,7 @@
 #include "tree.h"
 #include "object-store.h"
 #include "midx.h"
+#include "commit-graph.h"
 
 char *odb_pack_name(struct strbuf *buf,
 		    const unsigned char *sha1,
@@ -350,6 +351,8 @@ void close_all_packs(struct raw_object_store *o)
 		close_midx(o->multi_pack_index);
 		o->multi_pack_index = NULL;
 	}
+
+	close_commit_graph(o);
 }
 
 /*
-- 
gitgitgadget

[PATCH 3/3] packfile: close_all_packs to close_object_store

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <dstolee@microsoft.com>

The close_all_packs() method is now responsible for more than just pack-files.
It also closes the commit-graph and the multi-pack-index. Rename the function
to be more descriptive of its larger role. The name also fits because the
input parameter is a raw_object_store.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 builtin/am.c           | 2 +-
 builtin/clone.c        | 2 +-
 builtin/fetch.c        | 2 +-
 builtin/gc.c           | 4 ++--
 builtin/merge.c        | 2 +-
 builtin/rebase.c       | 2 +-
 builtin/receive-pack.c | 2 +-
 builtin/repack.c       | 2 +-
 object.c               | 2 +-
 packfile.c             | 2 +-
 packfile.h             | 2 +-
 11 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/builtin/am.c b/builtin/am.c
index 58a2aef28b..9315d32d2a 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1800,7 +1800,7 @@ static void am_run(struct am_state *state, int resume)
 	 */
 	if (!state->rebasing) {
 		am_destroy(state);
-		close_all_packs(the_repository->objects);
+		close_object_store(the_repository->objects);
 		run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 	}
 }
diff --git a/builtin/clone.c b/builtin/clone.c
index 50bde99618..82ce682c80 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -1240,7 +1240,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	transport_disconnect(transport);
 
 	if (option_dissociate) {
-		close_all_packs(the_repository->objects);
+		close_object_store(the_repository->objects);
 		dissociate_from_references();
 	}
 
diff --git a/builtin/fetch.c b/builtin/fetch.c
index b620fd54b4..3aec95608f 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1670,7 +1670,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 
 	string_list_clear(&list, 0);
 
-	close_all_packs(the_repository->objects);
+	close_object_store(the_repository->objects);
 
 	argv_array_pushl(&argv_gc_auto, "gc", "--auto", NULL);
 	if (verbosity < 0)
diff --git a/builtin/gc.c b/builtin/gc.c
index df2573f124..20c8f1bfe8 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -632,7 +632,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	gc_before_repack();
 
 	if (!repository_format_precious_objects) {
-		close_all_packs(the_repository->objects);
+		close_object_store(the_repository->objects);
 		if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
 			die(FAILED_RUN, repack.argv[0]);
 
@@ -660,7 +660,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	report_garbage = report_pack_garbage;
 	reprepare_packed_git(the_repository);
 	if (pack_garbage.nr > 0) {
-		close_all_packs(the_repository->objects);
+		close_object_store(the_repository->objects);
 		clean_pack_garbage();
 	}
 
diff --git a/builtin/merge.c b/builtin/merge.c
index e47d77baee..72d7a7c909 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -449,7 +449,7 @@ static void finish(struct commit *head_commit,
 			 * We ignore errors in 'gc --auto', since the
 			 * user should see them.
 			 */
-			close_all_packs(the_repository->objects);
+			close_object_store(the_repository->objects);
 			run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 		}
 	}
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 7c7bc13e91..ed30fcd633 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -328,7 +328,7 @@ static int finish_rebase(struct rebase_options *opts)
 
 	delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
 	apply_autostash(opts);
-	close_all_packs(the_repository->objects);
+	close_object_store(the_repository->objects);
 	/*
 	 * We ignore errors in 'gc --auto', since the
 	 * user should see them.
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index d58b7750b6..92cd1f508c 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -2032,7 +2032,7 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 			proc.git_cmd = 1;
 			proc.argv = argv_gc_auto;
 
-			close_all_packs(the_repository->objects);
+			close_object_store(the_repository->objects);
 			if (!start_command(&proc)) {
 				if (use_sideband)
 					copy_to_sideband(proc.err, -1, NULL);
diff --git a/builtin/repack.c b/builtin/repack.c
index 67f8978043..4de8b6600c 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -419,7 +419,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	if (!names.nr && !po_args.quiet)
 		printf_ln(_("Nothing new to pack."));
 
-	close_all_packs(the_repository->objects);
+	close_object_store(the_repository->objects);
 
 	/*
 	 * Ok we have prepared all new packfiles.
diff --git a/object.c b/object.c
index e81d47a79c..cf1a2b7086 100644
--- a/object.c
+++ b/object.c
@@ -517,7 +517,7 @@ void raw_object_store_clear(struct raw_object_store *o)
 	o->loaded_alternates = 0;
 
 	INIT_LIST_HEAD(&o->packed_git_mru);
-	close_all_packs(o);
+	close_object_store(o);
 	o->packed_git = NULL;
 }
 
diff --git a/packfile.c b/packfile.c
index ce12bffe3e..017046fcf9 100644
--- a/packfile.c
+++ b/packfile.c
@@ -337,7 +337,7 @@ void close_pack(struct packed_git *p)
 	close_pack_index(p);
 }
 
-void close_all_packs(struct raw_object_store *o)
+void close_object_store(struct raw_object_store *o)
 {
 	struct packed_git *p;
 
diff --git a/packfile.h b/packfile.h
index d70c6d9afb..e95e389eb8 100644
--- a/packfile.h
+++ b/packfile.h
@@ -81,7 +81,7 @@ extern uint32_t get_pack_fanout(struct packed_git *p, uint32_t value);
 extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned long *);
 extern void close_pack_windows(struct packed_git *);
 extern void close_pack(struct packed_git *);
-extern void close_all_packs(struct raw_object_store *o);
+extern void close_object_store(struct raw_object_store *o);
 extern void unuse_pack(struct pack_window **);
 extern void clear_delta_base_cache(void);
 extern struct packed_git *add_packed_git(const char *path, size_t path_len, int local);
-- 
gitgitgadget

Re: [PATCH 3/3] packfile: close_all_packs to close_object_store

[Johannes Schindelin]

Hi Stolee,

*really* minor nit: the commit subject probably wants to have a "rename"
after the colon ;-)

The patch looks sensible to me. Since Junio asked for a sanity check
whether all of the call sites of `close_all_packs()` actually want to
close the MIDX and the commit graph, too, I'll do the "speak out loud"
type of patch review here (spoiler: all of them check out):

On Fri, 17 May 2019, Derrick Stolee via GitGitGadget wrote:

> diff --git a/builtin/am.c b/builtin/am.c
> index 58a2aef28b..9315d32d2a 100644
> --- a/builtin/am.c
> +++ b/builtin/am.c
> @@ -1800,7 +1800,7 @@ static void am_run(struct am_state *state, int resume)
>  	 */
>  	if (!state->rebasing) {
>  		am_destroy(state);
> -		close_all_packs(the_repository->objects);
> +		close_object_store(the_repository->objects);
>  		run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);

Here, we run `git gc --auto`, so we obviously really want to close all
read handles.

Check.

>  	}
>  }
> diff --git a/builtin/clone.c b/builtin/clone.c
> index 50bde99618..82ce682c80 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -1240,7 +1240,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
>  	transport_disconnect(transport);
>
>  	if (option_dissociate) {
> -		close_all_packs(the_repository->objects);
> +		close_object_store(the_repository->objects);
>  		dissociate_from_references();

Here, we prepare for disassociating the reference repository specified via
`git clone --reference <directory>`. Obviously, we need to let go of all
the handles we might have open there.

Check.

>  	}
>
> diff --git a/builtin/fetch.c b/builtin/fetch.c
> index b620fd54b4..3aec95608f 100644
> --- a/builtin/fetch.c
> +++ b/builtin/fetch.c
> @@ -1670,7 +1670,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
>
>  	string_list_clear(&list, 0);
>
> -	close_all_packs(the_repository->objects);
> +	close_object_store(the_repository->objects);
>
>  	argv_array_pushl(&argv_gc_auto, "gc", "--auto", NULL);

Again, a `git gc --auto` that needs closing of all read handles to the
files that might be overwritten by the garbage collection.

Check.

>  	if (verbosity < 0)
> diff --git a/builtin/gc.c b/builtin/gc.c
> index df2573f124..20c8f1bfe8 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -632,7 +632,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>  	gc_before_repack();
>
>  	if (!repository_format_precious_objects) {
> -		close_all_packs(the_repository->objects);
> +		close_object_store(the_repository->objects);
>  		if (run_command_v_opt(repack.argv, RUN_GIT_CMD))

Here, we want to repack. AFAICT it is the only sane thing we can do to
invalidate whatever we read from the object store into memory.

Check.

>  			die(FAILED_RUN, repack.argv[0]);
>
> @@ -660,7 +660,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>  	report_garbage = report_pack_garbage;
>  	reprepare_packed_git(the_repository);
>  	if (pack_garbage.nr > 0) {
> -		close_all_packs(the_repository->objects);
> +		close_object_store(the_repository->objects);
>  		clean_pack_garbage();

This wants to delete a number of files that are now obsolete, and it makes
sense to make sure that there are no open read handles to those anymore.
It is a bit unclear from just reading the code what types of files are
accumulated into the `pack_garbage` string list, but then, we're in the
last throngs of a garbage collection, and *just* about to write a new
commit graph (if `gc.writeCommitGraph=true`), so I think it is quite okay
to close not only the packs here, but everything we opened from the object
store.

So I'd give this a check mark, too.

>  	}
>
> diff --git a/builtin/merge.c b/builtin/merge.c
> index e47d77baee..72d7a7c909 100644
> --- a/builtin/merge.c
> +++ b/builtin/merge.c
> @@ -449,7 +449,7 @@ static void finish(struct commit *head_commit,
>  			 * We ignore errors in 'gc --auto', since the
>  			 * user should see them.
>  			 */
> -			close_all_packs(the_repository->objects);
> +			close_object_store(the_repository->objects);
>  			run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);

Obviously yet another `git gc --auto`, so yes, we need to close the object
store handles we have.

Check.

>  		}
>  	}
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 7c7bc13e91..ed30fcd633 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -328,7 +328,7 @@ static int finish_rebase(struct rebase_options *opts)
>
>  	delete_ref(NULL, "REBASE_HEAD", NULL, REF_NO_DEREF);
>  	apply_autostash(opts);
> -	close_all_packs(the_repository->objects);
> +	close_object_store(the_repository->objects);
>  	/*
>  	 * We ignore errors in 'gc --auto', since the
>  	 * user should see them.

Yet another `git gc --auto`.

Check.

> diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
> index d58b7750b6..92cd1f508c 100644
> --- a/builtin/receive-pack.c
> +++ b/builtin/receive-pack.c
> @@ -2032,7 +2032,7 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
>  			proc.git_cmd = 1;
>  			proc.argv = argv_gc_auto;
>
> -			close_all_packs(the_repository->objects);
> +			close_object_store(the_repository->objects);
>  			if (!start_command(&proc)) {

This `proc` refers to another `git gc --auto` (see a couple lines above,
still within the hunk).

Check.

>  				if (use_sideband)
>  					copy_to_sideband(proc.err, -1, NULL);
> diff --git a/builtin/repack.c b/builtin/repack.c
> index 67f8978043..4de8b6600c 100644
> --- a/builtin/repack.c
> +++ b/builtin/repack.c
> @@ -419,7 +419,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
>  	if (!names.nr && !po_args.quiet)
>  		printf_ln(_("Nothing new to pack."));
>
> -	close_all_packs(the_repository->objects);
> +	close_object_store(the_repository->objects);
>
>  	/*
>  	 * Ok we have prepared all new packfiles.

Ah, the joys of un-dynamic patch review. What you, dear reader, cannot see
in this hunk is that the code comment at the end continues thusly:

         * First see if there are packs of the same name and if so
         * if we can move them out of the way (this can happen if we
         * repacked immediately after packing fully.
         */

Meaning: we're about to rename some pack files. So the pack file handles
need to be closed, all right, but what about the other object store
handles? There is no mention of the commit graph (more on that below), but
the loop following the code comment contains this:

                        if (!midx_cleared) {
                                clear_midx_file(the_repository);
                                midx_cleared = 1;
                        }

So yes, I would give this a check.

It does puzzle me, I have to admit, that there is no (opt-in) code block
to re-write the commit graph. After all, the commit graph references the
pack files, right? So if they are repacked, it would at least be
invalidated at this point...

> diff --git a/object.c b/object.c
> index e81d47a79c..cf1a2b7086 100644
> --- a/object.c
> +++ b/object.c
> @@ -517,7 +517,7 @@ void raw_object_store_clear(struct raw_object_store *o)
>  	o->loaded_alternates = 0;
>
>  	INIT_LIST_HEAD(&o->packed_git_mru);
> -	close_all_packs(o);
> +	close_object_store(o);

We're in the middle of a function called `raw_object_store_clear()`. So...

Check.

>  	o->packed_git = NULL;
>  }
>
> diff --git a/packfile.c b/packfile.c
> index ce12bffe3e..017046fcf9 100644
> --- a/packfile.c
> +++ b/packfile.c
> @@ -337,7 +337,7 @@ void close_pack(struct packed_git *p)
>  	close_pack_index(p);
>  }
>
> -void close_all_packs(struct raw_object_store *o)
> +void close_object_store(struct raw_object_store *o)
>  {
>  	struct packed_git *p;
>
> diff --git a/packfile.h b/packfile.h
> index d70c6d9afb..e95e389eb8 100644
> --- a/packfile.h
> +++ b/packfile.h
> @@ -81,7 +81,7 @@ extern uint32_t get_pack_fanout(struct packed_git *p, uint32_t value);
>  extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned long *);
>  extern void close_pack_windows(struct packed_git *);
>  extern void close_pack(struct packed_git *);
> -extern void close_all_packs(struct raw_object_store *o);
> +extern void close_object_store(struct raw_object_store *o);
>  extern void unuse_pack(struct pack_window **);
>  extern void clear_delta_base_cache(void);
>  extern struct packed_git *add_packed_git(const char *path, size_t path_len, int local);
> --
> gitgitgadget

And this concludes my review.

Thank you!
Dscho

Re: [PATCH 3/3] packfile: close_all_packs to close_object_store

[Derrick Stolee]

On 5/20/2019 6:01 AM, Johannes Schindelin wrote:
> Hi Stolee,
> 
> *really* minor nit: the commit subject probably wants to have a "rename"
> after the colon ;-)

I did put that there, but then the subject line was too long. I'm not
opposed to putting it back.
 
> The patch looks sensible to me. Since Junio asked for a sanity check
> whether all of the call sites of `close_all_packs()` actually want to
> close the MIDX and the commit graph, too, I'll do the "speak out loud"
> type of patch review here (spoiler: all of them check out):

Thanks for the detail here!

>> diff --git a/builtin/repack.c b/builtin/repack.c
>> index 67f8978043..4de8b6600c 100644
>> --- a/builtin/repack.c
>> +++ b/builtin/repack.c
>> @@ -419,7 +419,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
>>  	if (!names.nr && !po_args.quiet)
>>  		printf_ln(_("Nothing new to pack."));
>>
>> -	close_all_packs(the_repository->objects);
>> +	close_object_store(the_repository->objects);
>>
>>  	/*
>>  	 * Ok we have prepared all new packfiles.
> 
> Ah, the joys of un-dynamic patch review. What you, dear reader, cannot see
> in this hunk is that the code comment at the end continues thusly:
> 
>          * First see if there are packs of the same name and if so
>          * if we can move them out of the way (this can happen if we
>          * repacked immediately after packing fully.
>          */
> 
> Meaning: we're about to rename some pack files. So the pack file handles
> need to be closed, all right, but what about the other object store
> handles? There is no mention of the commit graph (more on that below), but
> the loop following the code comment contains this:
> 
>                         if (!midx_cleared) {
>                                 clear_midx_file(the_repository);
>                                 midx_cleared = 1;
>                         }
> 
> So yes, I would give this a check.
> 
> It does puzzle me, I have to admit, that there is no (opt-in) code block
> to re-write the commit graph. After all, the commit graph references the
> pack files, right? So if they are repacked, it would at least be
> invalidated at this point...

The commit-graph does not directly reference the packs. The file will still be
valid, except if we GC'd some commits that it references. We have the ability
to rewrite the graph in 'git gc'.

The MIDX does reference packs by name, so it needs to be cleared before we delete
packs. This _could_ be done with more care: we only need to delete it if a pack
it references is queued for deletion. However, you can do that using the
'git multi-pack-index expire|repack' pattern currently cooking.

Thanks,
-Stolee

Re: [PATCH 3/3] packfile: close_all_packs to close_object_store

[Junio C Hamano]

Derrick Stolee <stolee@gmail.com> writes:

> On 5/20/2019 6:01 AM, Johannes Schindelin wrote:
>> Hi Stolee,
>> 
>> *really* minor nit: the commit subject probably wants to have a "rename"
>> after the colon ;-)
>
> I did put that there, but then the subject line was too long. I'm not
> opposed to putting it back.

Let me locally amend what I queued in the meantime, then.  Thanks, both.

Re: [PATCH 0/3] Close commit-graph before calling 'gc'

[Junio C Hamano]

"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:

> This series adds close_commit_graph() to close_all_packs() and then renames 
> close_all_packs() to close_object_store(). This name is more descriptive of
> its larger purpose.

OK.  Somebody needs to go though all the existing callers of
close_all_packs() to see if the above claim is true (unless you
haven't done so, that is), but I really like the general direction.

Thanks.

Re: [PATCH 0/3] Close commit-graph before calling 'gc'

[Johannes Schindelin]

Hi Junio,

On Sun, 19 May 2019, Junio C Hamano wrote:

> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > This series adds close_commit_graph() to close_all_packs() and then renames
> > close_all_packs() to close_object_store(). This name is more descriptive of
> > its larger purpose.
>
> OK.  Somebody needs to go though all the existing callers of
> close_all_packs() to see if the above claim is true (unless you
> haven't done so, that is), but I really like the general direction.

I tried to provide that in my review of 3/3.

Please note that these patches are most relevant for Windows, where
renames and deletes fail when any process has an open handle to the
file(s) in question.

Ciao,
Dscho

P.S.: Now that I think of it, if we close the object store, that's
probably also a time when we want to release the loose object cache.

Re: [PATCH 0/3] Close commit-graph before calling 'gc'

[Derrick Stolee]

On 5/18/2019 10:04 PM, Junio C Hamano wrote:
> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
>> This series adds close_commit_graph() to close_all_packs() and then renames 
>> close_all_packs() to close_object_store(). This name is more descriptive of
>> its larger purpose.
> 
> OK.  Somebody needs to go though all the existing callers of
> close_all_packs() to see if the above claim is true (unless you
> haven't done so, that is), but I really like the general direction.

Here is a full inventory. Most of the context can be found simply by
'git grep -B 10 -A 10 close_object_store' but some cases need reading
a helper function to know for sure.

About to call gc or repack:

* am
* clone
* fetch
* merge
* rebase
* receive-pack

Is about to delete packs or pack-garbage:

* gc
* repack

And in object.c, we are in the "raw_object_store_clear()" method.

Thanks,
-Stolee

Re: [PATCH 0/3] Close commit-graph before calling 'gc'

[Johannes Schindelin]

Hi Stolee,

On Fri, 17 May 2019, Derrick Stolee via GitGitGadget wrote:

> In Windows, the way we rename a lock file to replace the underlying file
> does not work when a process holds a read handle. For this reason, we call
> close_all_packs() everywhere before starting a git gc --auto subprocess. We
> also call close_commit_graph() before renaming the commit-graph lock file.
> But we don't close the commit-graph handles before running gc, which can
> cause an issue when gc.writeCommitGraph is enabled.
>
> This series adds close_commit_graph() to close_all_packs() and then renames
> close_all_packs() to close_object_store(). This name is more descriptive of
> its larger purpose.
>
> This is based on ds/commit-graph-write-refactor to avoid conflicts.

Thank you so much for jumping on my (off-list, in-team) bug report!

FWIW I integrated this series into Git for Windows v2.22.0-rc1 already.

Thanks,
Dscho