From b3cecf49eac00d62e361bf6e6e81392f5a2fb571 Mon Sep 17 00:00:00 2001 From: Neeraj Singh Date: Mon, 6 Dec 2021 22:05:04 +0000 Subject: tmp-objdir: new API for creating temporary writable databases The tmp_objdir API provides the ability to create temporary object directories, but was designed with the goal of having subprocesses access these object stores, followed by the main process migrating objects from it to the main object store or just deleting it. The subprocesses would view it as their primary datastore and write to it. Here we add the tmp_objdir_replace_primary_odb function that replaces the current process's writable "main" object directory with the specified one. The previous main object directory is restored in either tmp_objdir_migrate or tmp_objdir_destroy. For the --remerge-diff usecase, add a new `will_destroy` flag in `struct object_database` to mark ephemeral object databases that do not require fsync durability. Add 'git prune' support for removing temporary object databases, and make sure that they have a name starting with tmp_ and containing an operation-specific name. Based-on-patch-by: Elijah Newren Signed-off-by: Neeraj Singh Reviewed-by: Elijah Newren Signed-off-by: Junio C Hamano --- object-file.c | 44 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 42 insertions(+), 2 deletions(-) (limited to 'object-file.c') diff --git a/object-file.c b/object-file.c index be4f94ecf3..990381abee 100644 --- a/object-file.c +++ b/object-file.c @@ -751,6 +751,43 @@ void add_to_alternates_memory(const char *reference) '\n', NULL, 0); } +struct object_directory *set_temporary_primary_odb(const char *dir, int will_destroy) +{ + struct object_directory *new_odb; + + /* + * Make sure alternates are initialized, or else our entry may be + * overwritten when they are. + */ + prepare_alt_odb(the_repository); + + /* + * Make a new primary odb and link the old primary ODB in as an + * alternate + */ + new_odb = xcalloc(1, sizeof(*new_odb)); + new_odb->path = xstrdup(dir); + new_odb->will_destroy = will_destroy; + new_odb->next = the_repository->objects->odb; + the_repository->objects->odb = new_odb; + return new_odb->next; +} + +void restore_primary_odb(struct object_directory *restore_odb, const char *old_path) +{ + struct object_directory *cur_odb = the_repository->objects->odb; + + if (strcmp(old_path, cur_odb->path)) + BUG("expected %s as primary object store; found %s", + old_path, cur_odb->path); + + if (cur_odb->next != restore_odb) + BUG("we expect the old primary object store to be the first alternate"); + + the_repository->objects->odb = restore_odb; + free_object_directory(cur_odb); +} + /* * Compute the exact path an alternate is at and returns it. In case of * error NULL is returned and the human readable error is added to `err` @@ -1888,8 +1925,11 @@ int hash_object_file(const struct git_hash_algo *algo, const void *buf, /* Finalize a file on disk, and close it. */ static void close_loose_object(int fd) { - if (fsync_object_files) - fsync_or_die(fd, "loose object file"); + if (!the_repository->objects->odb->will_destroy) { + if (fsync_object_files) + fsync_or_die(fd, "loose object file"); + } + if (close(fd) != 0) die_errno(_("error when closing loose object file")); } -- cgit v1.2.3 From ecd81dfc79cf12cc21fc0340da8ca8fcc5aa58a7 Mon Sep 17 00:00:00 2001 From: Neeraj Singh Date: Mon, 6 Dec 2021 22:05:05 +0000 Subject: tmp-objdir: disable ref updates when replacing the primary odb When creating a subprocess with a temporary ODB, we set the GIT_QUARANTINE_ENVIRONMENT env var to tell child Git processes not to update refs, since the tmp-objdir may go away. Introduce a similar mechanism for in-process temporary ODBs when we call tmp_objdir_replace_primary_odb. Now both mechanisms set the disable_ref_updates flag on the odb, which is queried by the ref_transaction_prepare function. Peff's test case [1] was invoking ref updates via the cachetextconv setting. That particular code silently does nothing when a ref update is forbidden. See the call to notes_cache_put in fill_textconv where errors are ignored. [1] https://lore.kernel.org/git/YVOn3hDsb5pnxR53@coredump.intra.peff.net/ Reported-by: Jeff King Signed-off-by: Neeraj Singh Reviewed-by: Elijah Newren Signed-off-by: Junio C Hamano --- object-file.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'object-file.c') diff --git a/object-file.c b/object-file.c index 990381abee..f16441afb9 100644 --- a/object-file.c +++ b/object-file.c @@ -767,6 +767,12 @@ struct object_directory *set_temporary_primary_odb(const char *dir, int will_des */ new_odb = xcalloc(1, sizeof(*new_odb)); new_odb->path = xstrdup(dir); + + /* + * Disable ref updates while a temporary odb is active, since + * the objects in the database may roll back. + */ + new_odb->disable_ref_updates = 1; new_odb->will_destroy = will_destroy; new_odb->next = the_repository->objects->odb; the_repository->objects->odb = new_odb; -- cgit v1.2.3