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files-backend.c
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3321 lines (2913 loc) · 90.8 KB
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#include "../cache.h"
#include "../config.h"
#include "../refs.h"
#include "refs-internal.h"
#include "ref-cache.h"
#include "packed-backend.h"
#include "../iterator.h"
#include "../dir-iterator.h"
#include "../lockfile.h"
#include "../object.h"
#include "../dir.h"
#include "../chdir-notify.h"
#include "worktree.h"
/*
* This backend uses the following flags in `ref_update::flags` for
* internal bookkeeping purposes. Their numerical values must not
* conflict with REF_NO_DEREF, REF_FORCE_CREATE_REFLOG, REF_HAVE_NEW,
* or REF_HAVE_OLD, which are also stored in `ref_update::flags`.
*/
/*
* Used as a flag in ref_update::flags when a loose ref is being
* pruned. This flag must only be used when REF_NO_DEREF is set.
*/
#define REF_IS_PRUNING (1 << 4)
/*
* Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
* refs (i.e., because the reference is about to be deleted anyway).
*/
#define REF_DELETING (1 << 5)
/*
* Used as a flag in ref_update::flags when the lockfile needs to be
* committed.
*/
#define REF_NEEDS_COMMIT (1 << 6)
/*
* Used as a flag in ref_update::flags when the ref_update was via an
* update to HEAD.
*/
#define REF_UPDATE_VIA_HEAD (1 << 8)
/*
* Used as a flag in ref_update::flags when a reference has been
* deleted and the ref's parent directories may need cleanup.
*/
#define REF_DELETED_RMDIR (1 << 9)
struct ref_lock {
char *ref_name;
struct lock_file lk;
struct object_id old_oid;
};
struct files_ref_store {
struct ref_store base;
unsigned int store_flags;
char *gitcommondir;
struct ref_cache *loose;
struct ref_store *packed_ref_store;
};
static void clear_loose_ref_cache(struct files_ref_store *refs)
{
if (refs->loose) {
free_ref_cache(refs->loose);
refs->loose = NULL;
}
}
/*
* Create a new submodule ref cache and add it to the internal
* set of caches.
*/
static struct ref_store *files_ref_store_create(struct repository *repo,
const char *gitdir,
unsigned int flags)
{
struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
struct ref_store *ref_store = (struct ref_store *)refs;
struct strbuf sb = STRBUF_INIT;
base_ref_store_init(ref_store, repo, gitdir, &refs_be_files);
refs->store_flags = flags;
get_common_dir_noenv(&sb, gitdir);
refs->gitcommondir = strbuf_detach(&sb, NULL);
refs->packed_ref_store =
packed_ref_store_create(repo, refs->gitcommondir, flags);
chdir_notify_reparent("files-backend $GIT_DIR", &refs->base.gitdir);
chdir_notify_reparent("files-backend $GIT_COMMONDIR",
&refs->gitcommondir);
return ref_store;
}
/*
* Die if refs is not the main ref store. caller is used in any
* necessary error messages.
*/
static void files_assert_main_repository(struct files_ref_store *refs,
const char *caller)
{
if (refs->store_flags & REF_STORE_MAIN)
return;
BUG("operation %s only allowed for main ref store", caller);
}
/*
* Downcast ref_store to files_ref_store. Die if ref_store is not a
* files_ref_store. required_flags is compared with ref_store's
* store_flags to ensure the ref_store has all required capabilities.
* "caller" is used in any necessary error messages.
*/
static struct files_ref_store *files_downcast(struct ref_store *ref_store,
unsigned int required_flags,
const char *caller)
{
struct files_ref_store *refs;
if (ref_store->be != &refs_be_files)
BUG("ref_store is type \"%s\" not \"files\" in %s",
ref_store->be->name, caller);
refs = (struct files_ref_store *)ref_store;
if ((refs->store_flags & required_flags) != required_flags)
BUG("operation %s requires abilities 0x%x, but only have 0x%x",
caller, required_flags, refs->store_flags);
return refs;
}
static void files_reflog_path_other_worktrees(struct files_ref_store *refs,
struct strbuf *sb,
const char *refname)
{
const char *real_ref;
const char *worktree_name;
int length;
if (parse_worktree_ref(refname, &worktree_name, &length, &real_ref))
BUG("refname %s is not a other-worktree ref", refname);
if (worktree_name)
strbuf_addf(sb, "%s/worktrees/%.*s/logs/%s", refs->gitcommondir,
length, worktree_name, real_ref);
else
strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir,
real_ref);
}
static void files_reflog_path(struct files_ref_store *refs,
struct strbuf *sb,
const char *refname)
{
switch (ref_type(refname)) {
case REF_TYPE_PER_WORKTREE:
case REF_TYPE_PSEUDOREF:
strbuf_addf(sb, "%s/logs/%s", refs->base.gitdir, refname);
break;
case REF_TYPE_OTHER_PSEUDOREF:
case REF_TYPE_MAIN_PSEUDOREF:
files_reflog_path_other_worktrees(refs, sb, refname);
break;
case REF_TYPE_NORMAL:
strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
break;
default:
BUG("unknown ref type %d of ref %s",
ref_type(refname), refname);
}
}
static void files_ref_path(struct files_ref_store *refs,
struct strbuf *sb,
const char *refname)
{
switch (ref_type(refname)) {
case REF_TYPE_PER_WORKTREE:
case REF_TYPE_PSEUDOREF:
strbuf_addf(sb, "%s/%s", refs->base.gitdir, refname);
break;
case REF_TYPE_MAIN_PSEUDOREF:
if (!skip_prefix(refname, "main-worktree/", &refname))
BUG("ref %s is not a main pseudoref", refname);
/* fallthrough */
case REF_TYPE_OTHER_PSEUDOREF:
case REF_TYPE_NORMAL:
strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
break;
default:
BUG("unknown ref type %d of ref %s",
ref_type(refname), refname);
}
}
/*
* Manually add refs/bisect, refs/rewritten and refs/worktree, which, being
* per-worktree, might not appear in the directory listing for
* refs/ in the main repo.
*/
static void add_per_worktree_entries_to_dir(struct ref_dir *dir, const char *dirname)
{
const char *prefixes[] = { "refs/bisect/", "refs/worktree/", "refs/rewritten/" };
int ip;
if (strcmp(dirname, "refs/"))
return;
for (ip = 0; ip < ARRAY_SIZE(prefixes); ip++) {
const char *prefix = prefixes[ip];
int prefix_len = strlen(prefix);
struct ref_entry *child_entry;
int pos;
pos = search_ref_dir(dir, prefix, prefix_len);
if (pos >= 0)
continue;
child_entry = create_dir_entry(dir->cache, prefix, prefix_len);
add_entry_to_dir(dir, child_entry);
}
}
/*
* Read the loose references from the namespace dirname into dir
* (without recursing). dirname must end with '/'. dir must be the
* directory entry corresponding to dirname.
*/
static void loose_fill_ref_dir(struct ref_store *ref_store,
struct ref_dir *dir, const char *dirname)
{
struct files_ref_store *refs =
files_downcast(ref_store, REF_STORE_READ, "fill_ref_dir");
DIR *d;
struct dirent *de;
int dirnamelen = strlen(dirname);
struct strbuf refname;
struct strbuf path = STRBUF_INIT;
size_t path_baselen;
files_ref_path(refs, &path, dirname);
path_baselen = path.len;
d = opendir(path.buf);
if (!d) {
strbuf_release(&path);
return;
}
strbuf_init(&refname, dirnamelen + 257);
strbuf_add(&refname, dirname, dirnamelen);
while ((de = readdir(d)) != NULL) {
struct object_id oid;
struct stat st;
int flag;
if (de->d_name[0] == '.')
continue;
if (ends_with(de->d_name, ".lock"))
continue;
strbuf_addstr(&refname, de->d_name);
strbuf_addstr(&path, de->d_name);
if (stat(path.buf, &st) < 0) {
; /* silently ignore */
} else if (S_ISDIR(st.st_mode)) {
strbuf_addch(&refname, '/');
add_entry_to_dir(dir,
create_dir_entry(dir->cache, refname.buf,
refname.len));
} else {
if (!refs_resolve_ref_unsafe(&refs->base,
refname.buf,
RESOLVE_REF_READING,
&oid, &flag)) {
oidclr(&oid);
flag |= REF_ISBROKEN;
} else if (is_null_oid(&oid)) {
/*
* It is so astronomically unlikely
* that null_oid is the OID of an
* actual object that we consider its
* appearance in a loose reference
* file to be repo corruption
* (probably due to a software bug).
*/
flag |= REF_ISBROKEN;
}
if (check_refname_format(refname.buf,
REFNAME_ALLOW_ONELEVEL)) {
if (!refname_is_safe(refname.buf))
die("loose refname is dangerous: %s", refname.buf);
oidclr(&oid);
flag |= REF_BAD_NAME | REF_ISBROKEN;
}
add_entry_to_dir(dir,
create_ref_entry(refname.buf, &oid, flag));
}
strbuf_setlen(&refname, dirnamelen);
strbuf_setlen(&path, path_baselen);
}
strbuf_release(&refname);
strbuf_release(&path);
closedir(d);
add_per_worktree_entries_to_dir(dir, dirname);
}
static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
{
if (!refs->loose) {
/*
* Mark the top-level directory complete because we
* are about to read the only subdirectory that can
* hold references:
*/
refs->loose = create_ref_cache(&refs->base, loose_fill_ref_dir);
/* We're going to fill the top level ourselves: */
refs->loose->root->flag &= ~REF_INCOMPLETE;
/*
* Add an incomplete entry for "refs/" (to be filled
* lazily):
*/
add_entry_to_dir(get_ref_dir(refs->loose->root),
create_dir_entry(refs->loose, "refs/", 5));
}
return refs->loose;
}
static int read_ref_internal(struct ref_store *ref_store, const char *refname,
struct object_id *oid, struct strbuf *referent,
unsigned int *type, int *failure_errno, int skip_packed_refs)
{
struct files_ref_store *refs =
files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
struct strbuf sb_contents = STRBUF_INIT;
struct strbuf sb_path = STRBUF_INIT;
const char *path;
const char *buf;
struct stat st;
int fd;
int ret = -1;
int remaining_retries = 3;
int myerr = 0;
*type = 0;
strbuf_reset(&sb_path);
files_ref_path(refs, &sb_path, refname);
path = sb_path.buf;
stat_ref:
/*
* We might have to loop back here to avoid a race
* condition: first we lstat() the file, then we try
* to read it as a link or as a file. But if somebody
* changes the type of the file (file <-> directory
* <-> symlink) between the lstat() and reading, then
* we don't want to report that as an error but rather
* try again starting with the lstat().
*
* We'll keep a count of the retries, though, just to avoid
* any confusing situation sending us into an infinite loop.
*/
if (remaining_retries-- <= 0)
goto out;
if (lstat(path, &st) < 0) {
int ignore_errno;
myerr = errno;
if (myerr != ENOENT || skip_packed_refs)
goto out;
if (refs_read_raw_ref(refs->packed_ref_store, refname, oid,
referent, type, &ignore_errno)) {
myerr = ENOENT;
goto out;
}
ret = 0;
goto out;
}
/* Follow "normalized" - ie "refs/.." symlinks by hand */
if (S_ISLNK(st.st_mode)) {
strbuf_reset(&sb_contents);
if (strbuf_readlink(&sb_contents, path, st.st_size) < 0) {
myerr = errno;
if (myerr == ENOENT || myerr == EINVAL)
/* inconsistent with lstat; retry */
goto stat_ref;
else
goto out;
}
if (starts_with(sb_contents.buf, "refs/") &&
!check_refname_format(sb_contents.buf, 0)) {
strbuf_swap(&sb_contents, referent);
*type |= REF_ISSYMREF;
ret = 0;
goto out;
}
/*
* It doesn't look like a refname; fall through to just
* treating it like a non-symlink, and reading whatever it
* points to.
*/
}
/* Is it a directory? */
if (S_ISDIR(st.st_mode)) {
int ignore_errno;
/*
* Even though there is a directory where the loose
* ref is supposed to be, there could still be a
* packed ref:
*/
if (skip_packed_refs ||
refs_read_raw_ref(refs->packed_ref_store, refname, oid,
referent, type, &ignore_errno)) {
myerr = EISDIR;
goto out;
}
ret = 0;
goto out;
}
/*
* Anything else, just open it and try to use it as
* a ref
*/
fd = open(path, O_RDONLY);
if (fd < 0) {
myerr = errno;
if (myerr == ENOENT && !S_ISLNK(st.st_mode))
/* inconsistent with lstat; retry */
goto stat_ref;
else
goto out;
}
strbuf_reset(&sb_contents);
if (strbuf_read(&sb_contents, fd, 256) < 0) {
myerr = errno;
close(fd);
goto out;
}
close(fd);
strbuf_rtrim(&sb_contents);
buf = sb_contents.buf;
ret = parse_loose_ref_contents(buf, oid, referent, type, &myerr);
out:
if (ret && !myerr)
BUG("returning non-zero %d, should have set myerr!", ret);
*failure_errno = myerr;
strbuf_release(&sb_path);
strbuf_release(&sb_contents);
errno = 0;
return ret;
}
static int files_read_raw_ref(struct ref_store *ref_store, const char *refname,
struct object_id *oid, struct strbuf *referent,
unsigned int *type, int *failure_errno)
{
return read_ref_internal(ref_store, refname, oid, referent, type, failure_errno, 0);
}
static int files_read_symbolic_ref(struct ref_store *ref_store, const char *refname,
struct strbuf *referent)
{
struct object_id oid;
int failure_errno, ret;
unsigned int type;
ret = read_ref_internal(ref_store, refname, &oid, referent, &type, &failure_errno, 1);
if (ret)
return ret;
return !(type & REF_ISSYMREF);
}
int parse_loose_ref_contents(const char *buf, struct object_id *oid,
struct strbuf *referent, unsigned int *type,
int *failure_errno)
{
const char *p;
if (skip_prefix(buf, "ref:", &buf)) {
while (isspace(*buf))
buf++;
strbuf_reset(referent);
strbuf_addstr(referent, buf);
*type |= REF_ISSYMREF;
return 0;
}
/*
* FETCH_HEAD has additional data after the sha.
*/
if (parse_oid_hex(buf, oid, &p) ||
(*p != '\0' && !isspace(*p))) {
*type |= REF_ISBROKEN;
*failure_errno = EINVAL;
return -1;
}
return 0;
}
static void unlock_ref(struct ref_lock *lock)
{
rollback_lock_file(&lock->lk);
free(lock->ref_name);
free(lock);
}
/*
* Lock refname, without following symrefs, and set *lock_p to point
* at a newly-allocated lock object. Fill in lock->old_oid, referent,
* and type similarly to read_raw_ref().
*
* The caller must verify that refname is a "safe" reference name (in
* the sense of refname_is_safe()) before calling this function.
*
* If the reference doesn't already exist, verify that refname doesn't
* have a D/F conflict with any existing references. extras and skip
* are passed to refs_verify_refname_available() for this check.
*
* If mustexist is not set and the reference is not found or is
* broken, lock the reference anyway but clear old_oid.
*
* Return 0 on success. On failure, write an error message to err and
* return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
*
* Implementation note: This function is basically
*
* lock reference
* read_raw_ref()
*
* but it includes a lot more code to
* - Deal with possible races with other processes
* - Avoid calling refs_verify_refname_available() when it can be
* avoided, namely if we were successfully able to read the ref
* - Generate informative error messages in the case of failure
*/
static int lock_raw_ref(struct files_ref_store *refs,
const char *refname, int mustexist,
const struct string_list *extras,
struct ref_lock **lock_p,
struct strbuf *referent,
unsigned int *type,
struct strbuf *err)
{
struct ref_lock *lock;
struct strbuf ref_file = STRBUF_INIT;
int attempts_remaining = 3;
int ret = TRANSACTION_GENERIC_ERROR;
int failure_errno;
assert(err);
files_assert_main_repository(refs, "lock_raw_ref");
*type = 0;
/* First lock the file so it can't change out from under us. */
*lock_p = CALLOC_ARRAY(lock, 1);
lock->ref_name = xstrdup(refname);
files_ref_path(refs, &ref_file, refname);
retry:
switch (safe_create_leading_directories(ref_file.buf)) {
case SCLD_OK:
break; /* success */
case SCLD_EXISTS:
/*
* Suppose refname is "refs/foo/bar". We just failed
* to create the containing directory, "refs/foo",
* because there was a non-directory in the way. This
* indicates a D/F conflict, probably because of
* another reference such as "refs/foo". There is no
* reason to expect this error to be transitory.
*/
if (refs_verify_refname_available(&refs->base, refname,
extras, NULL, err)) {
if (mustexist) {
/*
* To the user the relevant error is
* that the "mustexist" reference is
* missing:
*/
strbuf_reset(err);
strbuf_addf(err, "unable to resolve reference '%s'",
refname);
} else {
/*
* The error message set by
* refs_verify_refname_available() is
* OK.
*/
ret = TRANSACTION_NAME_CONFLICT;
}
} else {
/*
* The file that is in the way isn't a loose
* reference. Report it as a low-level
* failure.
*/
strbuf_addf(err, "unable to create lock file %s.lock; "
"non-directory in the way",
ref_file.buf);
}
goto error_return;
case SCLD_VANISHED:
/* Maybe another process was tidying up. Try again. */
if (--attempts_remaining > 0)
goto retry;
/* fall through */
default:
strbuf_addf(err, "unable to create directory for %s",
ref_file.buf);
goto error_return;
}
if (hold_lock_file_for_update_timeout(
&lock->lk, ref_file.buf, LOCK_NO_DEREF,
get_files_ref_lock_timeout_ms()) < 0) {
int myerr = errno;
errno = 0;
if (myerr == ENOENT && --attempts_remaining > 0) {
/*
* Maybe somebody just deleted one of the
* directories leading to ref_file. Try
* again:
*/
goto retry;
} else {
unable_to_lock_message(ref_file.buf, myerr, err);
goto error_return;
}
}
/*
* Now we hold the lock and can read the reference without
* fear that its value will change.
*/
if (files_read_raw_ref(&refs->base, refname, &lock->old_oid, referent,
type, &failure_errno)) {
if (failure_errno == ENOENT) {
if (mustexist) {
/* Garden variety missing reference. */
strbuf_addf(err, "unable to resolve reference '%s'",
refname);
goto error_return;
} else {
/*
* Reference is missing, but that's OK. We
* know that there is not a conflict with
* another loose reference because
* (supposing that we are trying to lock
* reference "refs/foo/bar"):
*
* - We were successfully able to create
* the lockfile refs/foo/bar.lock, so we
* know there cannot be a loose reference
* named "refs/foo".
*
* - We got ENOENT and not EISDIR, so we
* know that there cannot be a loose
* reference named "refs/foo/bar/baz".
*/
}
} else if (failure_errno == EISDIR) {
/*
* There is a directory in the way. It might have
* contained references that have been deleted. If
* we don't require that the reference already
* exists, try to remove the directory so that it
* doesn't cause trouble when we want to rename the
* lockfile into place later.
*/
if (mustexist) {
/* Garden variety missing reference. */
strbuf_addf(err, "unable to resolve reference '%s'",
refname);
goto error_return;
} else if (remove_dir_recursively(&ref_file,
REMOVE_DIR_EMPTY_ONLY)) {
if (refs_verify_refname_available(
&refs->base, refname,
extras, NULL, err)) {
/*
* The error message set by
* verify_refname_available() is OK.
*/
ret = TRANSACTION_NAME_CONFLICT;
goto error_return;
} else {
/*
* We can't delete the directory,
* but we also don't know of any
* references that it should
* contain.
*/
strbuf_addf(err, "there is a non-empty directory '%s' "
"blocking reference '%s'",
ref_file.buf, refname);
goto error_return;
}
}
} else if (failure_errno == EINVAL && (*type & REF_ISBROKEN)) {
strbuf_addf(err, "unable to resolve reference '%s': "
"reference broken", refname);
goto error_return;
} else {
strbuf_addf(err, "unable to resolve reference '%s': %s",
refname, strerror(failure_errno));
goto error_return;
}
/*
* If the ref did not exist and we are creating it,
* make sure there is no existing packed ref that
* conflicts with refname:
*/
if (refs_verify_refname_available(
refs->packed_ref_store, refname,
extras, NULL, err))
goto error_return;
}
ret = 0;
goto out;
error_return:
unlock_ref(lock);
*lock_p = NULL;
out:
strbuf_release(&ref_file);
return ret;
}
struct files_ref_iterator {
struct ref_iterator base;
struct ref_iterator *iter0;
struct repository *repo;
unsigned int flags;
};
static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
{
struct files_ref_iterator *iter =
(struct files_ref_iterator *)ref_iterator;
int ok;
while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
continue;
if ((iter->flags & DO_FOR_EACH_OMIT_DANGLING_SYMREFS) &&
(iter->iter0->flags & REF_ISSYMREF) &&
(iter->iter0->flags & REF_ISBROKEN))
continue;
if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
!ref_resolves_to_object(iter->iter0->refname,
iter->repo,
iter->iter0->oid,
iter->iter0->flags))
continue;
iter->base.refname = iter->iter0->refname;
iter->base.oid = iter->iter0->oid;
iter->base.flags = iter->iter0->flags;
return ITER_OK;
}
iter->iter0 = NULL;
if (ref_iterator_abort(ref_iterator) != ITER_DONE)
ok = ITER_ERROR;
return ok;
}
static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
struct object_id *peeled)
{
struct files_ref_iterator *iter =
(struct files_ref_iterator *)ref_iterator;
return ref_iterator_peel(iter->iter0, peeled);
}
static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
{
struct files_ref_iterator *iter =
(struct files_ref_iterator *)ref_iterator;
int ok = ITER_DONE;
if (iter->iter0)
ok = ref_iterator_abort(iter->iter0);
base_ref_iterator_free(ref_iterator);
return ok;
}
static struct ref_iterator_vtable files_ref_iterator_vtable = {
.advance = files_ref_iterator_advance,
.peel = files_ref_iterator_peel,
.abort = files_ref_iterator_abort,
};
static struct ref_iterator *files_ref_iterator_begin(
struct ref_store *ref_store,
const char *prefix, unsigned int flags)
{
struct files_ref_store *refs;
struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
struct files_ref_iterator *iter;
struct ref_iterator *ref_iterator;
unsigned int required_flags = REF_STORE_READ;
if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
required_flags |= REF_STORE_ODB;
refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
/*
* We must make sure that all loose refs are read before
* accessing the packed-refs file; this avoids a race
* condition if loose refs are migrated to the packed-refs
* file by a simultaneous process, but our in-memory view is
* from before the migration. We ensure this as follows:
* First, we call start the loose refs iteration with its
* `prime_ref` argument set to true. This causes the loose
* references in the subtree to be pre-read into the cache.
* (If they've already been read, that's OK; we only need to
* guarantee that they're read before the packed refs, not
* *how much* before.) After that, we call
* packed_ref_iterator_begin(), which internally checks
* whether the packed-ref cache is up to date with what is on
* disk, and re-reads it if not.
*/
loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
prefix, ref_store->repo, 1);
/*
* The packed-refs file might contain broken references, for
* example an old version of a reference that points at an
* object that has since been garbage-collected. This is OK as
* long as there is a corresponding loose reference that
* overrides it, and we don't want to emit an error message in
* this case. So ask the packed_ref_store for all of its
* references, and (if needed) do our own check for broken
* ones in files_ref_iterator_advance(), after we have merged
* the packed and loose references.
*/
packed_iter = refs_ref_iterator_begin(
refs->packed_ref_store, prefix, 0,
DO_FOR_EACH_INCLUDE_BROKEN);
overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
CALLOC_ARRAY(iter, 1);
ref_iterator = &iter->base;
base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
overlay_iter->ordered);
iter->iter0 = overlay_iter;
iter->repo = ref_store->repo;
iter->flags = flags;
return ref_iterator;
}
/*
* Callback function for raceproof_create_file(). This function is
* expected to do something that makes dirname(path) permanent despite
* the fact that other processes might be cleaning up empty
* directories at the same time. Usually it will create a file named
* path, but alternatively it could create another file in that
* directory, or even chdir() into that directory. The function should
* return 0 if the action was completed successfully. On error, it
* should return a nonzero result and set errno.
* raceproof_create_file() treats two errno values specially:
*
* - ENOENT -- dirname(path) does not exist. In this case,
* raceproof_create_file() tries creating dirname(path)
* (and any parent directories, if necessary) and calls
* the function again.
*
* - EISDIR -- the file already exists and is a directory. In this
* case, raceproof_create_file() removes the directory if
* it is empty (and recursively any empty directories that
* it contains) and calls the function again.
*
* Any other errno causes raceproof_create_file() to fail with the
* callback's return value and errno.
*
* Obviously, this function should be OK with being called again if it
* fails with ENOENT or EISDIR. In other scenarios it will not be
* called again.
*/
typedef int create_file_fn(const char *path, void *cb);
/*
* Create a file in dirname(path) by calling fn, creating leading
* directories if necessary. Retry a few times in case we are racing
* with another process that is trying to clean up the directory that
* contains path. See the documentation for create_file_fn for more
* details.
*
* Return the value and set the errno that resulted from the most
* recent call of fn. fn is always called at least once, and will be
* called more than once if it returns ENOENT or EISDIR.
*/
static int raceproof_create_file(const char *path, create_file_fn fn, void *cb)
{
/*
* The number of times we will try to remove empty directories
* in the way of path. This is only 1 because if another
* process is racily creating directories that conflict with
* us, we don't want to fight against them.
*/
int remove_directories_remaining = 1;
/*
* The number of times that we will try to create the
* directories containing path. We are willing to attempt this
* more than once, because another process could be trying to
* clean up empty directories at the same time as we are
* trying to create them.
*/
int create_directories_remaining = 3;
/* A scratch copy of path, filled lazily if we need it: */
struct strbuf path_copy = STRBUF_INIT;
int ret, save_errno;
/* Sanity check: */
assert(*path);
retry_fn:
ret = fn(path, cb);
save_errno = errno;
if (!ret)
goto out;
if (errno == EISDIR && remove_directories_remaining-- > 0) {
/*
* A directory is in the way. Maybe it is empty; try
* to remove it:
*/
if (!path_copy.len)
strbuf_addstr(&path_copy, path);
if (!remove_dir_recursively(&path_copy, REMOVE_DIR_EMPTY_ONLY))
goto retry_fn;
} else if (errno == ENOENT && create_directories_remaining-- > 0) {
/*
* Maybe the containing directory didn't exist, or
* maybe it was just deleted by a process that is
* racing with us to clean up empty directories. Try
* to create it:
*/
enum scld_error scld_result;
if (!path_copy.len)
strbuf_addstr(&path_copy, path);
do {
scld_result = safe_create_leading_directories(path_copy.buf);
if (scld_result == SCLD_OK)
goto retry_fn;
} while (scld_result == SCLD_VANISHED && create_directories_remaining-- > 0);
}
out:
strbuf_release(&path_copy);
errno = save_errno;
return ret;
}