зеркало из https://github.com/microsoft/git.git
tmp-objdir: introduce API for temporary object directories
Once objects are added to the object database by a process, they cannot easily be deleted, as we don't know what other processes may have started referencing them. We have to clean them up with git-gc, which will apply the usual reachability and grace-period checks. This patch provides an alternative: it helps callers create a temporary directory inside the object directory, and a temporary environment which can be passed to sub-programs to ask them to write there (the original object directory remains accessible as an alternate of the temporary one). See tmp-objdir.h for details on the API. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
Junio C Hamano
Родитель
526f108a27
Коммит
2564d994c9
1
Makefile
1
Makefile
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@ -831,6 +831,7 @@ LIB_OBJS += submodule-config.o
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LIB_OBJS += symlinks.o
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LIB_OBJS += tag.o
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LIB_OBJS += tempfile.o
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LIB_OBJS += tmp-objdir.o
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LIB_OBJS += trace.o
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LIB_OBJS += trailer.o
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LIB_OBJS += transport.o
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@ -0,0 +1,273 @@
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#include "cache.h"
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#include "tmp-objdir.h"
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#include "dir.h"
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#include "sigchain.h"
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#include "string-list.h"
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#include "strbuf.h"
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#include "argv-array.h"
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struct tmp_objdir {
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struct strbuf path;
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struct argv_array env;
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};
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/*
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* Allow only one tmp_objdir at a time in a running process, which simplifies
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* our signal/atexit cleanup routines. It's doubtful callers will ever need
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* more than one, and we can expand later if so. You can have many such
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* tmp_objdirs simultaneously in many processes, of course.
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*/
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static struct tmp_objdir *the_tmp_objdir;
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static void tmp_objdir_free(struct tmp_objdir *t)
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{
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strbuf_release(&t->path);
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argv_array_clear(&t->env);
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free(t);
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}
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static int tmp_objdir_destroy_1(struct tmp_objdir *t, int on_signal)
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{
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int err;
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if (!t)
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return 0;
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if (t == the_tmp_objdir)
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the_tmp_objdir = NULL;
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/*
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* This may use malloc via strbuf_grow(), but we should
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* have pre-grown t->path sufficiently so that this
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* doesn't happen in practice.
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*/
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err = remove_dir_recursively(&t->path, 0);
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/*
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* When we are cleaning up due to a signal, we won't bother
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* freeing memory; it may cause a deadlock if the signal
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* arrived while libc's allocator lock is held.
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*/
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if (!on_signal)
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tmp_objdir_free(t);
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return err;
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}
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int tmp_objdir_destroy(struct tmp_objdir *t)
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{
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return tmp_objdir_destroy_1(t, 0);
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}
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static void remove_tmp_objdir(void)
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{
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tmp_objdir_destroy(the_tmp_objdir);
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}
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static void remove_tmp_objdir_on_signal(int signo)
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{
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tmp_objdir_destroy_1(the_tmp_objdir, 1);
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sigchain_pop(signo);
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raise(signo);
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}
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/*
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* These env_* functions are for setting up the child environment; the
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* "replace" variant overrides the value of any existing variable with that
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* "key". The "append" variant puts our new value at the end of a list,
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* separated by PATH_SEP (which is what separate values in
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* GIT_ALTERNATE_OBJECT_DIRECTORIES).
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*/
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static void env_append(struct argv_array *env, const char *key, const char *val)
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{
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const char *old = getenv(key);
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if (!old)
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argv_array_pushf(env, "%s=%s", key, val);
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else
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argv_array_pushf(env, "%s=%s%c%s", key, old, PATH_SEP, val);
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}
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static void env_replace(struct argv_array *env, const char *key, const char *val)
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{
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argv_array_pushf(env, "%s=%s", key, val);
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}
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static int setup_tmp_objdir(const char *root)
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{
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char *path;
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int ret = 0;
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path = xstrfmt("%s/pack", root);
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ret = mkdir(path, 0777);
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free(path);
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return ret;
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}
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struct tmp_objdir *tmp_objdir_create(void)
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{
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static int installed_handlers;
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struct tmp_objdir *t;
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if (the_tmp_objdir)
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die("BUG: only one tmp_objdir can be used at a time");
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t = xmalloc(sizeof(*t));
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strbuf_init(&t->path, 0);
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argv_array_init(&t->env);
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strbuf_addf(&t->path, "%s/incoming-XXXXXX", get_object_directory());
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/*
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* Grow the strbuf beyond any filename we expect to be placed in it.
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* If tmp_objdir_destroy() is called by a signal handler, then
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* we should be able to use the strbuf to remove files without
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* having to call malloc.
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*/
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strbuf_grow(&t->path, 1024);
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if (!mkdtemp(t->path.buf)) {
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/* free, not destroy, as we never touched the filesystem */
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tmp_objdir_free(t);
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return NULL;
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}
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the_tmp_objdir = t;
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if (!installed_handlers) {
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atexit(remove_tmp_objdir);
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sigchain_push_common(remove_tmp_objdir_on_signal);
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installed_handlers++;
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}
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if (setup_tmp_objdir(t->path.buf)) {
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tmp_objdir_destroy(t);
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return NULL;
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}
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env_append(&t->env, ALTERNATE_DB_ENVIRONMENT,
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absolute_path(get_object_directory()));
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env_replace(&t->env, DB_ENVIRONMENT, absolute_path(t->path.buf));
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return t;
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}
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/*
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* Make sure we copy packfiles and their associated metafiles in the correct
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* order. All of these ends_with checks are slightly expensive to do in
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* the midst of a sorting routine, but in practice it shouldn't matter.
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* We will have a relatively small number of packfiles to order, and loose
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* objects exit early in the first line.
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*/
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static int pack_copy_priority(const char *name)
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{
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if (!starts_with(name, "pack"))
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return 0;
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if (ends_with(name, ".keep"))
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return 1;
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if (ends_with(name, ".pack"))
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return 2;
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if (ends_with(name, ".idx"))
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return 3;
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return 4;
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}
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static int pack_copy_cmp(const char *a, const char *b)
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{
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return pack_copy_priority(a) - pack_copy_priority(b);
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}
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static int read_dir_paths(struct string_list *out, const char *path)
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{
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DIR *dh;
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struct dirent *de;
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dh = opendir(path);
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if (!dh)
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return -1;
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while ((de = readdir(dh)))
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if (!is_dot_or_dotdot(de->d_name))
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string_list_append(out, de->d_name);
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closedir(dh);
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return 0;
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}
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static int migrate_paths(struct strbuf *src, struct strbuf *dst);
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static int migrate_one(struct strbuf *src, struct strbuf *dst)
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{
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struct stat st;
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if (stat(src->buf, &st) < 0)
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return -1;
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if (S_ISDIR(st.st_mode)) {
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if (!mkdir(dst->buf, 0777)) {
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if (adjust_shared_perm(dst->buf))
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return -1;
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} else if (errno != EEXIST)
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return -1;
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return migrate_paths(src, dst);
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}
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return finalize_object_file(src->buf, dst->buf);
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}
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static int migrate_paths(struct strbuf *src, struct strbuf *dst)
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{
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size_t src_len = src->len, dst_len = dst->len;
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struct string_list paths = STRING_LIST_INIT_DUP;
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int i;
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int ret = 0;
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if (read_dir_paths(&paths, src->buf) < 0)
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return -1;
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paths.cmp = pack_copy_cmp;
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string_list_sort(&paths);
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for (i = 0; i < paths.nr; i++) {
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const char *name = paths.items[i].string;
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strbuf_addf(src, "/%s", name);
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strbuf_addf(dst, "/%s", name);
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ret |= migrate_one(src, dst);
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strbuf_setlen(src, src_len);
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strbuf_setlen(dst, dst_len);
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}
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string_list_clear(&paths, 0);
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return ret;
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}
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int tmp_objdir_migrate(struct tmp_objdir *t)
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{
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struct strbuf src = STRBUF_INIT, dst = STRBUF_INIT;
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int ret;
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if (!t)
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return 0;
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strbuf_addbuf(&src, &t->path);
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strbuf_addstr(&dst, get_object_directory());
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ret = migrate_paths(&src, &dst);
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strbuf_release(&src);
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strbuf_release(&dst);
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tmp_objdir_destroy(t);
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return ret;
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}
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const char **tmp_objdir_env(const struct tmp_objdir *t)
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{
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if (!t)
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return NULL;
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return t->env.argv;
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}
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void tmp_objdir_add_as_alternate(const struct tmp_objdir *t)
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{
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add_to_alternates_memory(t->path.buf);
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}
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@ -0,0 +1,54 @@
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#ifndef TMP_OBJDIR_H
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#define TMP_OBJDIR_H
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/*
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* This API allows you to create a temporary object directory, advertise it to
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* sub-processes via GIT_OBJECT_DIRECTORY and GIT_ALTERNATE_OBJECT_DIRECTORIES,
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* and then either migrate its object into the main object directory, or remove
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* it. The library handles unexpected signal/exit death by cleaning up the
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* temporary directory.
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*
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* Example:
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*
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* struct tmp_objdir *t = tmp_objdir_create();
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* if (!run_command_v_opt_cd_env(cmd, 0, NULL, tmp_objdir_env(t)) &&
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* !tmp_objdir_migrate(t))
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* printf("success!\n");
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* else
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* die("failed...tmp_objdir will clean up for us");
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*
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*/
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struct tmp_objdir;
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/*
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* Create a new temporary object directory; returns NULL on failure.
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*/
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struct tmp_objdir *tmp_objdir_create(void);
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/*
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* Return a list of environment strings, suitable for use with
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* child_process.env, that can be passed to child programs to make use of the
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* temporary object directory.
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*/
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const char **tmp_objdir_env(const struct tmp_objdir *);
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/*
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* Finalize a temporary object directory by migrating its objects into the main
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* object database, removing the temporary directory, and freeing any
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* associated resources.
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*/
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int tmp_objdir_migrate(struct tmp_objdir *);
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/*
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* Destroy a temporary object directory, discarding any objects it contains.
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*/
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int tmp_objdir_destroy(struct tmp_objdir *);
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/*
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* Add the temporary object directory as an alternate object store in the
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* current process.
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*/
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void tmp_objdir_add_as_alternate(const struct tmp_objdir *);
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#endif /* TMP_OBJDIR_H */
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