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-rw-r--r--refs/packed-backend.c1615
1 files changed, 1615 insertions, 0 deletions
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
new file mode 100644
index 0000000..c1c71d1
--- /dev/null
+++ b/refs/packed-backend.c
@@ -0,0 +1,1615 @@
+#include "../cache.h"
+#include "../config.h"
+#include "../refs.h"
+#include "refs-internal.h"
+#include "packed-backend.h"
+#include "../iterator.h"
+#include "../lockfile.h"
+#include "../chdir-notify.h"
+
+enum mmap_strategy {
+ /*
+ * Don't use mmap() at all for reading `packed-refs`.
+ */
+ MMAP_NONE,
+
+ /*
+ * Can use mmap() for reading `packed-refs`, but the file must
+ * not remain mmapped. This is the usual option on Windows,
+ * where you cannot rename a new version of a file onto a file
+ * that is currently mmapped.
+ */
+ MMAP_TEMPORARY,
+
+ /*
+ * It is OK to leave the `packed-refs` file mmapped while
+ * arbitrary other code is running.
+ */
+ MMAP_OK
+};
+
+#if defined(NO_MMAP)
+static enum mmap_strategy mmap_strategy = MMAP_NONE;
+#elif defined(MMAP_PREVENTS_DELETE)
+static enum mmap_strategy mmap_strategy = MMAP_TEMPORARY;
+#else
+static enum mmap_strategy mmap_strategy = MMAP_OK;
+#endif
+
+struct packed_ref_store;
+
+/*
+ * A `snapshot` represents one snapshot of a `packed-refs` file.
+ *
+ * Normally, this will be a mmapped view of the contents of the
+ * `packed-refs` file at the time the snapshot was created. However,
+ * if the `packed-refs` file was not sorted, this might point at heap
+ * memory holding the contents of the `packed-refs` file with its
+ * records sorted by refname.
+ *
+ * `snapshot` instances are reference counted (via
+ * `acquire_snapshot()` and `release_snapshot()`). This is to prevent
+ * an instance from disappearing while an iterator is still iterating
+ * over it. Instances are garbage collected when their `referrers`
+ * count goes to zero.
+ *
+ * The most recent `snapshot`, if available, is referenced by the
+ * `packed_ref_store`. Its freshness is checked whenever
+ * `get_snapshot()` is called; if the existing snapshot is obsolete, a
+ * new snapshot is taken.
+ */
+struct snapshot {
+ /*
+ * A back-pointer to the packed_ref_store with which this
+ * snapshot is associated:
+ */
+ struct packed_ref_store *refs;
+
+ /* Is the `packed-refs` file currently mmapped? */
+ int mmapped;
+
+ /*
+ * The contents of the `packed-refs` file:
+ *
+ * - buf -- a pointer to the start of the memory
+ * - start -- a pointer to the first byte of actual references
+ * (i.e., after the header line, if one is present)
+ * - eof -- a pointer just past the end of the reference
+ * contents
+ *
+ * If the `packed-refs` file was already sorted, `buf` points
+ * at the mmapped contents of the file. If not, it points at
+ * heap-allocated memory containing the contents, sorted. If
+ * there were no contents (e.g., because the file didn't
+ * exist), `buf`, `start`, and `eof` are all NULL.
+ */
+ char *buf, *start, *eof;
+
+ /*
+ * What is the peeled state of the `packed-refs` file that
+ * this snapshot represents? (This is usually determined from
+ * the file's header.)
+ */
+ enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled;
+
+ /*
+ * Count of references to this instance, including the pointer
+ * from `packed_ref_store::snapshot`, if any. The instance
+ * will not be freed as long as the reference count is
+ * nonzero.
+ */
+ unsigned int referrers;
+
+ /*
+ * The metadata of the `packed-refs` file from which this
+ * snapshot was created, used to tell if the file has been
+ * replaced since we read it.
+ */
+ struct stat_validity validity;
+};
+
+/*
+ * A `ref_store` representing references stored in a `packed-refs`
+ * file. It implements the `ref_store` interface, though it has some
+ * limitations:
+ *
+ * - It cannot store symbolic references.
+ *
+ * - It cannot store reflogs.
+ *
+ * - It does not support reference renaming (though it could).
+ *
+ * On the other hand, it can be locked outside of a reference
+ * transaction. In that case, it remains locked even after the
+ * transaction is done and the new `packed-refs` file is activated.
+ */
+struct packed_ref_store {
+ struct ref_store base;
+
+ unsigned int store_flags;
+
+ /* The path of the "packed-refs" file: */
+ char *path;
+
+ /*
+ * A snapshot of the values read from the `packed-refs` file,
+ * if it might still be current; otherwise, NULL.
+ */
+ struct snapshot *snapshot;
+
+ /*
+ * Lock used for the "packed-refs" file. Note that this (and
+ * thus the enclosing `packed_ref_store`) must not be freed.
+ */
+ struct lock_file lock;
+
+ /*
+ * Temporary file used when rewriting new contents to the
+ * "packed-refs" file. Note that this (and thus the enclosing
+ * `packed_ref_store`) must not be freed.
+ */
+ struct tempfile *tempfile;
+};
+
+/*
+ * Increment the reference count of `*snapshot`.
+ */
+static void acquire_snapshot(struct snapshot *snapshot)
+{
+ snapshot->referrers++;
+}
+
+/*
+ * If the buffer in `snapshot` is active, then either munmap the
+ * memory and close the file, or free the memory. Then set the buffer
+ * pointers to NULL.
+ */
+static void clear_snapshot_buffer(struct snapshot *snapshot)
+{
+ if (snapshot->mmapped) {
+ if (munmap(snapshot->buf, snapshot->eof - snapshot->buf))
+ die_errno("error ummapping packed-refs file %s",
+ snapshot->refs->path);
+ snapshot->mmapped = 0;
+ } else {
+ free(snapshot->buf);
+ }
+ snapshot->buf = snapshot->start = snapshot->eof = NULL;
+}
+
+/*
+ * Decrease the reference count of `*snapshot`. If it goes to zero,
+ * free `*snapshot` and return true; otherwise return false.
+ */
+static int release_snapshot(struct snapshot *snapshot)
+{
+ if (!--snapshot->referrers) {
+ stat_validity_clear(&snapshot->validity);
+ clear_snapshot_buffer(snapshot);
+ free(snapshot);
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+struct ref_store *packed_ref_store_create(struct repository *repo,
+ const char *gitdir,
+ unsigned int store_flags)
+{
+ struct packed_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_packed);
+ refs->store_flags = store_flags;
+
+ strbuf_addf(&sb, "%s/packed-refs", gitdir);
+ refs->path = strbuf_detach(&sb, NULL);
+ chdir_notify_reparent("packed-refs", &refs->path);
+ return ref_store;
+}
+
+/*
+ * Downcast `ref_store` to `packed_ref_store`. Die if `ref_store` is
+ * not a `packed_ref_store`. Also die if `packed_ref_store` doesn't
+ * support at least the flags specified in `required_flags`. `caller`
+ * is used in any necessary error messages.
+ */
+static struct packed_ref_store *packed_downcast(struct ref_store *ref_store,
+ unsigned int required_flags,
+ const char *caller)
+{
+ struct packed_ref_store *refs;
+
+ if (ref_store->be != &refs_be_packed)
+ BUG("ref_store is type \"%s\" not \"packed\" in %s",
+ ref_store->be->name, caller);
+
+ refs = (struct packed_ref_store *)ref_store;
+
+ if ((refs->store_flags & required_flags) != required_flags)
+ BUG("unallowed operation (%s), requires %x, has %x\n",
+ caller, required_flags, refs->store_flags);
+
+ return refs;
+}
+
+static void clear_snapshot(struct packed_ref_store *refs)
+{
+ if (refs->snapshot) {
+ struct snapshot *snapshot = refs->snapshot;
+
+ refs->snapshot = NULL;
+ release_snapshot(snapshot);
+ }
+}
+
+static NORETURN void die_unterminated_line(const char *path,
+ const char *p, size_t len)
+{
+ if (len < 80)
+ die("unterminated line in %s: %.*s", path, (int)len, p);
+ else
+ die("unterminated line in %s: %.75s...", path, p);
+}
+
+static NORETURN void die_invalid_line(const char *path,
+ const char *p, size_t len)
+{
+ const char *eol = memchr(p, '\n', len);
+
+ if (!eol)
+ die_unterminated_line(path, p, len);
+ else if (eol - p < 80)
+ die("unexpected line in %s: %.*s", path, (int)(eol - p), p);
+ else
+ die("unexpected line in %s: %.75s...", path, p);
+
+}
+
+struct snapshot_record {
+ const char *start;
+ size_t len;
+};
+
+static int cmp_packed_ref_records(const void *v1, const void *v2)
+{
+ const struct snapshot_record *e1 = v1, *e2 = v2;
+ const char *r1 = e1->start + the_hash_algo->hexsz + 1;
+ const char *r2 = e2->start + the_hash_algo->hexsz + 1;
+
+ while (1) {
+ if (*r1 == '\n')
+ return *r2 == '\n' ? 0 : -1;
+ if (*r1 != *r2) {
+ if (*r2 == '\n')
+ return 1;
+ else
+ return (unsigned char)*r1 < (unsigned char)*r2 ? -1 : +1;
+ }
+ r1++;
+ r2++;
+ }
+}
+
+/*
+ * Compare a snapshot record at `rec` to the specified NUL-terminated
+ * refname.
+ */
+static int cmp_record_to_refname(const char *rec, const char *refname)
+{
+ const char *r1 = rec + the_hash_algo->hexsz + 1;
+ const char *r2 = refname;
+
+ while (1) {
+ if (*r1 == '\n')
+ return *r2 ? -1 : 0;
+ if (!*r2)
+ return 1;
+ if (*r1 != *r2)
+ return (unsigned char)*r1 < (unsigned char)*r2 ? -1 : +1;
+ r1++;
+ r2++;
+ }
+}
+
+/*
+ * `snapshot->buf` is not known to be sorted. Check whether it is, and
+ * if not, sort it into new memory and munmap/free the old storage.
+ */
+static void sort_snapshot(struct snapshot *snapshot)
+{
+ struct snapshot_record *records = NULL;
+ size_t alloc = 0, nr = 0;
+ int sorted = 1;
+ const char *pos, *eof, *eol;
+ size_t len, i;
+ char *new_buffer, *dst;
+
+ pos = snapshot->start;
+ eof = snapshot->eof;
+
+ if (pos == eof)
+ return;
+
+ len = eof - pos;
+
+ /*
+ * Initialize records based on a crude estimate of the number
+ * of references in the file (we'll grow it below if needed):
+ */
+ ALLOC_GROW(records, len / 80 + 20, alloc);
+
+ while (pos < eof) {
+ eol = memchr(pos, '\n', eof - pos);
+ if (!eol)
+ /* The safety check should prevent this. */
+ BUG("unterminated line found in packed-refs");
+ if (eol - pos < the_hash_algo->hexsz + 2)
+ die_invalid_line(snapshot->refs->path,
+ pos, eof - pos);
+ eol++;
+ if (eol < eof && *eol == '^') {
+ /*
+ * Keep any peeled line together with its
+ * reference:
+ */
+ const char *peeled_start = eol;
+
+ eol = memchr(peeled_start, '\n', eof - peeled_start);
+ if (!eol)
+ /* The safety check should prevent this. */
+ BUG("unterminated peeled line found in packed-refs");
+ eol++;
+ }
+
+ ALLOC_GROW(records, nr + 1, alloc);
+ records[nr].start = pos;
+ records[nr].len = eol - pos;
+ nr++;
+
+ if (sorted &&
+ nr > 1 &&
+ cmp_packed_ref_records(&records[nr - 2],
+ &records[nr - 1]) >= 0)
+ sorted = 0;
+
+ pos = eol;
+ }
+
+ if (sorted)
+ goto cleanup;
+
+ /* We need to sort the memory. First we sort the records array: */
+ QSORT(records, nr, cmp_packed_ref_records);
+
+ /*
+ * Allocate a new chunk of memory, and copy the old memory to
+ * the new in the order indicated by `records` (not bothering
+ * with the header line):
+ */
+ new_buffer = xmalloc(len);
+ for (dst = new_buffer, i = 0; i < nr; i++) {
+ memcpy(dst, records[i].start, records[i].len);
+ dst += records[i].len;
+ }
+
+ /*
+ * Now munmap the old buffer and use the sorted buffer in its
+ * place:
+ */
+ clear_snapshot_buffer(snapshot);
+ snapshot->buf = snapshot->start = new_buffer;
+ snapshot->eof = new_buffer + len;
+
+cleanup:
+ free(records);
+}
+
+/*
+ * Return a pointer to the start of the record that contains the
+ * character `*p` (which must be within the buffer). If no other
+ * record start is found, return `buf`.
+ */
+static const char *find_start_of_record(const char *buf, const char *p)
+{
+ while (p > buf && (p[-1] != '\n' || p[0] == '^'))
+ p--;
+ return p;
+}
+
+/*
+ * Return a pointer to the start of the record following the record
+ * that contains `*p`. If none is found before `end`, return `end`.
+ */
+static const char *find_end_of_record(const char *p, const char *end)
+{
+ while (++p < end && (p[-1] != '\n' || p[0] == '^'))
+ ;
+ return p;
+}
+
+/*
+ * We want to be able to compare mmapped reference records quickly,
+ * without totally parsing them. We can do so because the records are
+ * LF-terminated, and the refname should start exactly (GIT_SHA1_HEXSZ
+ * + 1) bytes past the beginning of the record.
+ *
+ * But what if the `packed-refs` file contains garbage? We're willing
+ * to tolerate not detecting the problem, as long as we don't produce
+ * totally garbled output (we can't afford to check the integrity of
+ * the whole file during every Git invocation). But we do want to be
+ * sure that we never read past the end of the buffer in memory and
+ * perform an illegal memory access.
+ *
+ * Guarantee that minimum level of safety by verifying that the last
+ * record in the file is LF-terminated, and that it has at least
+ * (GIT_SHA1_HEXSZ + 1) characters before the LF. Die if either of
+ * these checks fails.
+ */
+static void verify_buffer_safe(struct snapshot *snapshot)
+{
+ const char *start = snapshot->start;
+ const char *eof = snapshot->eof;
+ const char *last_line;
+
+ if (start == eof)
+ return;
+
+ last_line = find_start_of_record(start, eof - 1);
+ if (*(eof - 1) != '\n' || eof - last_line < the_hash_algo->hexsz + 2)
+ die_invalid_line(snapshot->refs->path,
+ last_line, eof - last_line);
+}
+
+#define SMALL_FILE_SIZE (32*1024)
+
+/*
+ * Depending on `mmap_strategy`, either mmap or read the contents of
+ * the `packed-refs` file into the snapshot. Return 1 if the file
+ * existed and was read, or 0 if the file was absent or empty. Die on
+ * errors.
+ */
+static int load_contents(struct snapshot *snapshot)
+{
+ int fd;
+ struct stat st;
+ size_t size;
+ ssize_t bytes_read;
+
+ fd = open(snapshot->refs->path, O_RDONLY);
+ if (fd < 0) {
+ if (errno == ENOENT) {
+ /*
+ * This is OK; it just means that no
+ * "packed-refs" file has been written yet,
+ * which is equivalent to it being empty,
+ * which is its state when initialized with
+ * zeros.
+ */
+ return 0;
+ } else {
+ die_errno("couldn't read %s", snapshot->refs->path);
+ }
+ }
+
+ stat_validity_update(&snapshot->validity, fd);
+
+ if (fstat(fd, &st) < 0)
+ die_errno("couldn't stat %s", snapshot->refs->path);
+ size = xsize_t(st.st_size);
+
+ if (!size) {
+ close(fd);
+ return 0;
+ } else if (mmap_strategy == MMAP_NONE || size <= SMALL_FILE_SIZE) {
+ snapshot->buf = xmalloc(size);
+ bytes_read = read_in_full(fd, snapshot->buf, size);
+ if (bytes_read < 0 || bytes_read != size)
+ die_errno("couldn't read %s", snapshot->refs->path);
+ snapshot->mmapped = 0;
+ } else {
+ snapshot->buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+ snapshot->mmapped = 1;
+ }
+ close(fd);
+
+ snapshot->start = snapshot->buf;
+ snapshot->eof = snapshot->buf + size;
+
+ return 1;
+}
+
+/*
+ * Find the place in `snapshot->buf` where the start of the record for
+ * `refname` starts. If `mustexist` is true and the reference doesn't
+ * exist, then return NULL. If `mustexist` is false and the reference
+ * doesn't exist, then return the point where that reference would be
+ * inserted, or `snapshot->eof` (which might be NULL) if it would be
+ * inserted at the end of the file. In the latter mode, `refname`
+ * doesn't have to be a proper reference name; for example, one could
+ * search for "refs/replace/" to find the start of any replace
+ * references.
+ *
+ * The record is sought using a binary search, so `snapshot->buf` must
+ * be sorted.
+ */
+static const char *find_reference_location(struct snapshot *snapshot,
+ const char *refname, int mustexist)
+{
+ /*
+ * This is not *quite* a garden-variety binary search, because
+ * the data we're searching is made up of records, and we
+ * always need to find the beginning of a record to do a
+ * comparison. A "record" here is one line for the reference
+ * itself and zero or one peel lines that start with '^'. Our
+ * loop invariant is described in the next two comments.
+ */
+
+ /*
+ * A pointer to the character at the start of a record whose
+ * preceding records all have reference names that come
+ * *before* `refname`.
+ */
+ const char *lo = snapshot->start;
+
+ /*
+ * A pointer to a the first character of a record whose
+ * reference name comes *after* `refname`.
+ */
+ const char *hi = snapshot->eof;
+
+ while (lo != hi) {
+ const char *mid, *rec;
+ int cmp;
+
+ mid = lo + (hi - lo) / 2;
+ rec = find_start_of_record(lo, mid);
+ cmp = cmp_record_to_refname(rec, refname);
+ if (cmp < 0) {
+ lo = find_end_of_record(mid, hi);
+ } else if (cmp > 0) {
+ hi = rec;
+ } else {
+ return rec;
+ }
+ }
+
+ if (mustexist)
+ return NULL;
+ else
+ return lo;
+}
+
+/*
+ * Create a newly-allocated `snapshot` of the `packed-refs` file in
+ * its current state and return it. The return value will already have
+ * its reference count incremented.
+ *
+ * A comment line of the form "# pack-refs with: " may contain zero or
+ * more traits. We interpret the traits as follows:
+ *
+ * Neither `peeled` nor `fully-peeled`:
+ *
+ * Probably no references are peeled. But if the file contains a
+ * peeled value for a reference, we will use it.
+ *
+ * `peeled`:
+ *
+ * References under "refs/tags/", if they *can* be peeled, *are*
+ * peeled in this file. References outside of "refs/tags/" are
+ * probably not peeled even if they could have been, but if we find
+ * a peeled value for such a reference we will use it.
+ *
+ * `fully-peeled`:
+ *
+ * All references in the file that can be peeled are peeled.
+ * Inversely (and this is more important), any references in the
+ * file for which no peeled value is recorded is not peelable. This
+ * trait should typically be written alongside "peeled" for
+ * compatibility with older clients, but we do not require it
+ * (i.e., "peeled" is a no-op if "fully-peeled" is set).
+ *
+ * `sorted`:
+ *
+ * The references in this file are known to be sorted by refname.
+ */
+static struct snapshot *create_snapshot(struct packed_ref_store *refs)
+{
+ struct snapshot *snapshot = xcalloc(1, sizeof(*snapshot));
+ int sorted = 0;
+
+ snapshot->refs = refs;
+ acquire_snapshot(snapshot);
+ snapshot->peeled = PEELED_NONE;
+
+ if (!load_contents(snapshot))
+ return snapshot;
+
+ /* If the file has a header line, process it: */
+ if (snapshot->buf < snapshot->eof && *snapshot->buf == '#') {
+ char *tmp, *p, *eol;
+ struct string_list traits = STRING_LIST_INIT_NODUP;
+
+ eol = memchr(snapshot->buf, '\n',
+ snapshot->eof - snapshot->buf);
+ if (!eol)
+ die_unterminated_line(refs->path,
+ snapshot->buf,
+ snapshot->eof - snapshot->buf);
+
+ tmp = xmemdupz(snapshot->buf, eol - snapshot->buf);
+
+ if (!skip_prefix(tmp, "# pack-refs with:", (const char **)&p))
+ die_invalid_line(refs->path,
+ snapshot->buf,
+ snapshot->eof - snapshot->buf);
+
+ string_list_split_in_place(&traits, p, ' ', -1);
+
+ if (unsorted_string_list_has_string(&traits, "fully-peeled"))
+ snapshot->peeled = PEELED_FULLY;
+ else if (unsorted_string_list_has_string(&traits, "peeled"))
+ snapshot->peeled = PEELED_TAGS;
+
+ sorted = unsorted_string_list_has_string(&traits, "sorted");
+
+ /* perhaps other traits later as well */
+
+ /* The "+ 1" is for the LF character. */
+ snapshot->start = eol + 1;
+
+ string_list_clear(&traits, 0);
+ free(tmp);
+ }
+
+ verify_buffer_safe(snapshot);
+
+ if (!sorted) {
+ sort_snapshot(snapshot);
+
+ /*
+ * Reordering the records might have moved a short one
+ * to the end of the buffer, so verify the buffer's
+ * safety again:
+ */
+ verify_buffer_safe(snapshot);
+ }
+
+ if (mmap_strategy != MMAP_OK && snapshot->mmapped) {
+ /*
+ * We don't want to leave the file mmapped, so we are
+ * forced to make a copy now:
+ */
+ size_t size = snapshot->eof - snapshot->start;
+ char *buf_copy = xmalloc(size);
+
+ memcpy(buf_copy, snapshot->start, size);
+ clear_snapshot_buffer(snapshot);
+ snapshot->buf = snapshot->start = buf_copy;
+ snapshot->eof = buf_copy + size;
+ }
+
+ return snapshot;
+}
+
+/*
+ * Check that `refs->snapshot` (if present) still reflects the
+ * contents of the `packed-refs` file. If not, clear the snapshot.
+ */
+static void validate_snapshot(struct packed_ref_store *refs)
+{
+ if (refs->snapshot &&
+ !stat_validity_check(&refs->snapshot->validity, refs->path))
+ clear_snapshot(refs);
+}
+
+/*
+ * Get the `snapshot` for the specified packed_ref_store, creating and
+ * populating it if it hasn't been read before or if the file has been
+ * changed (according to its `validity` field) since it was last read.
+ * On the other hand, if we hold the lock, then assume that the file
+ * hasn't been changed out from under us, so skip the extra `stat()`
+ * call in `stat_validity_check()`. This function does *not* increase
+ * the snapshot's reference count on behalf of the caller.
+ */
+static struct snapshot *get_snapshot(struct packed_ref_store *refs)
+{
+ if (!is_lock_file_locked(&refs->lock))
+ validate_snapshot(refs);
+
+ if (!refs->snapshot)
+ refs->snapshot = create_snapshot(refs);
+
+ return refs->snapshot;
+}
+
+static int packed_read_raw_ref(struct ref_store *ref_store, const char *refname,
+ struct object_id *oid, struct strbuf *referent UNUSED,
+ unsigned int *type, int *failure_errno)
+{
+ struct packed_ref_store *refs =
+ packed_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
+ struct snapshot *snapshot = get_snapshot(refs);
+ const char *rec;
+
+ *type = 0;
+
+ rec = find_reference_location(snapshot, refname, 1);
+
+ if (!rec) {
+ /* refname is not a packed reference. */
+ *failure_errno = ENOENT;
+ return -1;
+ }
+
+ if (get_oid_hex(rec, oid))
+ die_invalid_line(refs->path, rec, snapshot->eof - rec);
+
+ *type = REF_ISPACKED;
+ return 0;
+}
+
+/*
+ * This value is set in `base.flags` if the peeled value of the
+ * current reference is known. In that case, `peeled` contains the
+ * correct peeled value for the reference, which might be `null_oid`
+ * if the reference is not a tag or if it is broken.
+ */
+#define REF_KNOWS_PEELED 0x40
+
+/*
+ * An iterator over a snapshot of a `packed-refs` file.
+ */
+struct packed_ref_iterator {
+ struct ref_iterator base;
+
+ struct snapshot *snapshot;
+
+ /* The current position in the snapshot's buffer: */
+ const char *pos;
+
+ /* The end of the part of the buffer that will be iterated over: */
+ const char *eof;
+
+ /* Scratch space for current values: */
+ struct object_id oid, peeled;
+ struct strbuf refname_buf;
+
+ struct repository *repo;
+ unsigned int flags;
+};
+
+/*
+ * Move the iterator to the next record in the snapshot, without
+ * respect for whether the record is actually required by the current
+ * iteration. Adjust the fields in `iter` and return `ITER_OK` or
+ * `ITER_DONE`. This function does not free the iterator in the case
+ * of `ITER_DONE`.
+ */
+static int next_record(struct packed_ref_iterator *iter)
+{
+ const char *p = iter->pos, *eol;
+
+ strbuf_reset(&iter->refname_buf);
+
+ if (iter->pos == iter->eof)
+ return ITER_DONE;
+
+ iter->base.flags = REF_ISPACKED;
+
+ if (iter->eof - p < the_hash_algo->hexsz + 2 ||
+ parse_oid_hex(p, &iter->oid, &p) ||
+ !isspace(*p++))
+ die_invalid_line(iter->snapshot->refs->path,
+ iter->pos, iter->eof - iter->pos);
+
+ eol = memchr(p, '\n', iter->eof - p);
+ if (!eol)
+ die_unterminated_line(iter->snapshot->refs->path,
+ iter->pos, iter->eof - iter->pos);
+
+ strbuf_add(&iter->refname_buf, p, eol - p);
+ iter->base.refname = iter->refname_buf.buf;
+
+ if (check_refname_format(iter->base.refname, REFNAME_ALLOW_ONELEVEL)) {
+ if (!refname_is_safe(iter->base.refname))
+ die("packed refname is dangerous: %s",
+ iter->base.refname);
+ oidclr(&iter->oid);
+ iter->base.flags |= REF_BAD_NAME | REF_ISBROKEN;
+ }
+ if (iter->snapshot->peeled == PEELED_FULLY ||
+ (iter->snapshot->peeled == PEELED_TAGS &&
+ starts_with(iter->base.refname, "refs/tags/")))
+ iter->base.flags |= REF_KNOWS_PEELED;
+
+ iter->pos = eol + 1;
+
+ if (iter->pos < iter->eof && *iter->pos == '^') {
+ p = iter->pos + 1;
+ if (iter->eof - p < the_hash_algo->hexsz + 1 ||
+ parse_oid_hex(p, &iter->peeled, &p) ||
+ *p++ != '\n')
+ die_invalid_line(iter->snapshot->refs->path,
+ iter->pos, iter->eof - iter->pos);
+ iter->pos = p;
+
+ /*
+ * Regardless of what the file header said, we
+ * definitely know the value of *this* reference. But
+ * we suppress it if the reference is broken:
+ */
+ if ((iter->base.flags & REF_ISBROKEN)) {
+ oidclr(&iter->peeled);
+ iter->base.flags &= ~REF_KNOWS_PEELED;
+ } else {
+ iter->base.flags |= REF_KNOWS_PEELED;
+ }
+ } else {
+ oidclr(&iter->peeled);
+ }
+
+ return ITER_OK;
+}
+
+static int packed_ref_iterator_advance(struct ref_iterator *ref_iterator)
+{
+ struct packed_ref_iterator *iter =
+ (struct packed_ref_iterator *)ref_iterator;
+ int ok;
+
+ while ((ok = next_record(iter)) == ITER_OK) {
+ if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
+ !is_per_worktree_ref(iter->base.refname))
+ continue;
+
+ if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
+ !ref_resolves_to_object(iter->base.refname, iter->repo,
+ &iter->oid, iter->flags))
+ continue;
+
+ return ITER_OK;
+ }
+
+ if (ref_iterator_abort(ref_iterator) != ITER_DONE)
+ ok = ITER_ERROR;
+
+ return ok;
+}
+
+static int packed_ref_iterator_peel(struct ref_iterator *ref_iterator,
+ struct object_id *peeled)
+{
+ struct packed_ref_iterator *iter =
+ (struct packed_ref_iterator *)ref_iterator;
+
+ if (iter->repo != the_repository)
+ BUG("peeling for non-the_repository is not supported");
+
+ if ((iter->base.flags & REF_KNOWS_PEELED)) {
+ oidcpy(peeled, &iter->peeled);
+ return is_null_oid(&iter->peeled) ? -1 : 0;
+ } else if ((iter->base.flags & (REF_ISBROKEN | REF_ISSYMREF))) {
+ return -1;
+ } else {
+ return peel_object(&iter->oid, peeled) ? -1 : 0;
+ }
+}
+
+static int packed_ref_iterator_abort(struct ref_iterator *ref_iterator)
+{
+ struct packed_ref_iterator *iter =
+ (struct packed_ref_iterator *)ref_iterator;
+ int ok = ITER_DONE;
+
+ strbuf_release(&iter->refname_buf);
+ release_snapshot(iter->snapshot);
+ base_ref_iterator_free(ref_iterator);
+ return ok;
+}
+
+static struct ref_iterator_vtable packed_ref_iterator_vtable = {
+ .advance = packed_ref_iterator_advance,
+ .peel = packed_ref_iterator_peel,
+ .abort = packed_ref_iterator_abort
+};
+
+static struct ref_iterator *packed_ref_iterator_begin(
+ struct ref_store *ref_store,
+ const char *prefix, unsigned int flags)
+{
+ struct packed_ref_store *refs;
+ struct snapshot *snapshot;
+ const char *start;
+ struct packed_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 = packed_downcast(ref_store, required_flags, "ref_iterator_begin");
+
+ /*
+ * Note that `get_snapshot()` internally checks whether the
+ * snapshot is up to date with what is on disk, and re-reads
+ * it if not.
+ */
+ snapshot = get_snapshot(refs);
+
+ if (prefix && *prefix)
+ start = find_reference_location(snapshot, prefix, 0);
+ else
+ start = snapshot->start;
+
+ if (start == snapshot->eof)
+ return empty_ref_iterator_begin();
+
+ CALLOC_ARRAY(iter, 1);
+ ref_iterator = &iter->base;
+ base_ref_iterator_init(ref_iterator, &packed_ref_iterator_vtable, 1);
+
+ iter->snapshot = snapshot;
+ acquire_snapshot(snapshot);
+
+ iter->pos = start;
+ iter->eof = snapshot->eof;
+ strbuf_init(&iter->refname_buf, 0);
+
+ iter->base.oid = &iter->oid;
+
+ iter->repo = ref_store->repo;
+ iter->flags = flags;
+
+ if (prefix && *prefix)
+ /* Stop iteration after we've gone *past* prefix: */
+ ref_iterator = prefix_ref_iterator_begin(ref_iterator, prefix, 0);
+
+ return ref_iterator;
+}
+
+/*
+ * Write an entry to the packed-refs file for the specified refname.
+ * If peeled is non-NULL, write it as the entry's peeled value. On
+ * error, return a nonzero value and leave errno set at the value left
+ * by the failing call to `fprintf()`.
+ */
+static int write_packed_entry(FILE *fh, const char *refname,
+ const struct object_id *oid,
+ const struct object_id *peeled)
+{
+ if (fprintf(fh, "%s %s\n", oid_to_hex(oid), refname) < 0 ||
+ (peeled && fprintf(fh, "^%s\n", oid_to_hex(peeled)) < 0))
+ return -1;
+
+ return 0;
+}
+
+int packed_refs_lock(struct ref_store *ref_store, int flags, struct strbuf *err)
+{
+ struct packed_ref_store *refs =
+ packed_downcast(ref_store, REF_STORE_WRITE | REF_STORE_MAIN,
+ "packed_refs_lock");
+ static int timeout_configured = 0;
+ static int timeout_value = 1000;
+
+ if (!timeout_configured) {
+ git_config_get_int("core.packedrefstimeout", &timeout_value);
+ timeout_configured = 1;
+ }
+
+ /*
+ * Note that we close the lockfile immediately because we
+ * don't write new content to it, but rather to a separate
+ * tempfile.
+ */
+ if (hold_lock_file_for_update_timeout(
+ &refs->lock,
+ refs->path,
+ flags, timeout_value) < 0) {
+ unable_to_lock_message(refs->path, errno, err);
+ return -1;
+ }
+
+ if (close_lock_file_gently(&refs->lock)) {
+ strbuf_addf(err, "unable to close %s: %s", refs->path, strerror(errno));
+ rollback_lock_file(&refs->lock);
+ return -1;
+ }
+
+ /*
+ * There is a stat-validity problem might cause `update-ref -d`
+ * lost the newly commit of a ref, because a new `packed-refs`
+ * file might has the same on-disk file attributes such as
+ * timestamp, file size and inode value, but has a changed
+ * ref value.
+ *
+ * This could happen with a very small chance when
+ * `update-ref -d` is called and at the same time another
+ * `pack-refs --all` process is running.
+ *
+ * Now that we hold the `packed-refs` lock, it is important
+ * to make sure we could read the latest version of
+ * `packed-refs` file no matter we have just mmap it or not.
+ * So what need to do is clear the snapshot if we hold it
+ * already.
+ */
+ clear_snapshot(refs);
+
+ /*
+ * Now make sure that the packed-refs file as it exists in the
+ * locked state is loaded into the snapshot:
+ */
+ get_snapshot(refs);
+ return 0;
+}
+
+void packed_refs_unlock(struct ref_store *ref_store)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE,
+ "packed_refs_unlock");
+
+ if (!is_lock_file_locked(&refs->lock))
+ BUG("packed_refs_unlock() called when not locked");
+ rollback_lock_file(&refs->lock);
+}
+
+int packed_refs_is_locked(struct ref_store *ref_store)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE,
+ "packed_refs_is_locked");
+
+ return is_lock_file_locked(&refs->lock);
+}
+
+/*
+ * The packed-refs header line that we write out. Perhaps other traits
+ * will be added later.
+ *
+ * Note that earlier versions of Git used to parse these traits by
+ * looking for " trait " in the line. For this reason, the space after
+ * the colon and the trailing space are required.
+ */
+static const char PACKED_REFS_HEADER[] =
+ "# pack-refs with: peeled fully-peeled sorted \n";
+
+static int packed_init_db(struct ref_store *ref_store UNUSED,
+ struct strbuf *err UNUSED)
+{
+ /* Nothing to do. */
+ return 0;
+}
+
+/*
+ * Write the packed refs from the current snapshot to the packed-refs
+ * tempfile, incorporating any changes from `updates`. `updates` must
+ * be a sorted string list whose keys are the refnames and whose util
+ * values are `struct ref_update *`. On error, rollback the tempfile,
+ * write an error message to `err`, and return a nonzero value.
+ *
+ * The packfile must be locked before calling this function and will
+ * remain locked when it is done.
+ */
+static int write_with_updates(struct packed_ref_store *refs,
+ struct string_list *updates,
+ struct strbuf *err)
+{
+ struct ref_iterator *iter = NULL;
+ size_t i;
+ int ok;
+ FILE *out;
+ struct strbuf sb = STRBUF_INIT;
+ char *packed_refs_path;
+
+ if (!is_lock_file_locked(&refs->lock))
+ BUG("write_with_updates() called while unlocked");
+
+ /*
+ * If packed-refs is a symlink, we want to overwrite the
+ * symlinked-to file, not the symlink itself. Also, put the
+ * staging file next to it:
+ */
+ packed_refs_path = get_locked_file_path(&refs->lock);
+ strbuf_addf(&sb, "%s.new", packed_refs_path);
+ free(packed_refs_path);
+ refs->tempfile = create_tempfile(sb.buf);
+ if (!refs->tempfile) {
+ strbuf_addf(err, "unable to create file %s: %s",
+ sb.buf, strerror(errno));
+ strbuf_release(&sb);
+ return -1;
+ }
+ strbuf_release(&sb);
+
+ out = fdopen_tempfile(refs->tempfile, "w");
+ if (!out) {
+ strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s",
+ strerror(errno));
+ goto error;
+ }
+
+ if (fprintf(out, "%s", PACKED_REFS_HEADER) < 0)
+ goto write_error;
+
+ /*
+ * We iterate in parallel through the current list of refs and
+ * the list of updates, processing an entry from at least one
+ * of the lists each time through the loop. When the current
+ * list of refs is exhausted, set iter to NULL. When the list
+ * of updates is exhausted, leave i set to updates->nr.
+ */
+ iter = packed_ref_iterator_begin(&refs->base, "",
+ DO_FOR_EACH_INCLUDE_BROKEN);
+ if ((ok = ref_iterator_advance(iter)) != ITER_OK)
+ iter = NULL;
+
+ i = 0;
+
+ while (iter || i < updates->nr) {
+ struct ref_update *update = NULL;
+ int cmp;
+
+ if (i >= updates->nr) {
+ cmp = -1;
+ } else {
+ update = updates->items[i].util;
+
+ if (!iter)
+ cmp = +1;
+ else
+ cmp = strcmp(iter->refname, update->refname);
+ }
+
+ if (!cmp) {
+ /*
+ * There is both an old value and an update
+ * for this reference. Check the old value if
+ * necessary:
+ */
+ if ((update->flags & REF_HAVE_OLD)) {
+ if (is_null_oid(&update->old_oid)) {
+ strbuf_addf(err, "cannot update ref '%s': "
+ "reference already exists",
+ update->refname);
+ goto error;
+ } else if (!oideq(&update->old_oid, iter->oid)) {
+ strbuf_addf(err, "cannot update ref '%s': "
+ "is at %s but expected %s",
+ update->refname,
+ oid_to_hex(iter->oid),
+ oid_to_hex(&update->old_oid));
+ goto error;
+ }
+ }
+
+ /* Now figure out what to use for the new value: */
+ if ((update->flags & REF_HAVE_NEW)) {
+ /*
+ * The update takes precedence. Skip
+ * the iterator over the unneeded
+ * value.
+ */
+ if ((ok = ref_iterator_advance(iter)) != ITER_OK)
+ iter = NULL;
+ cmp = +1;
+ } else {
+ /*
+ * The update doesn't actually want to
+ * change anything. We're done with it.
+ */
+ i++;
+ cmp = -1;
+ }
+ } else if (cmp > 0) {
+ /*
+ * There is no old value but there is an
+ * update for this reference. Make sure that
+ * the update didn't expect an existing value:
+ */
+ if ((update->flags & REF_HAVE_OLD) &&
+ !is_null_oid(&update->old_oid)) {
+ strbuf_addf(err, "cannot update ref '%s': "
+ "reference is missing but expected %s",
+ update->refname,
+ oid_to_hex(&update->old_oid));
+ goto error;
+ }
+ }
+
+ if (cmp < 0) {
+ /* Pass the old reference through. */
+
+ struct object_id peeled;
+ int peel_error = ref_iterator_peel(iter, &peeled);
+
+ if (write_packed_entry(out, iter->refname,
+ iter->oid,
+ peel_error ? NULL : &peeled))
+ goto write_error;
+
+ if ((ok = ref_iterator_advance(iter)) != ITER_OK)
+ iter = NULL;
+ } else if (is_null_oid(&update->new_oid)) {
+ /*
+ * The update wants to delete the reference,
+ * and the reference either didn't exist or we
+ * have already skipped it. So we're done with
+ * the update (and don't have to write
+ * anything).
+ */
+ i++;
+ } else {
+ struct object_id peeled;
+ int peel_error = peel_object(&update->new_oid,
+ &peeled);
+
+ if (write_packed_entry(out, update->refname,
+ &update->new_oid,
+ peel_error ? NULL : &peeled))
+ goto write_error;
+
+ i++;
+ }
+ }
+
+ if (ok != ITER_DONE) {
+ strbuf_addstr(err, "unable to write packed-refs file: "
+ "error iterating over old contents");
+ goto error;
+ }
+
+ if (fsync_component(FSYNC_COMPONENT_REFERENCE, get_tempfile_fd(refs->tempfile)) ||
+ close_tempfile_gently(refs->tempfile)) {
+ strbuf_addf(err, "error closing file %s: %s",
+ get_tempfile_path(refs->tempfile),
+ strerror(errno));
+ strbuf_release(&sb);
+ delete_tempfile(&refs->tempfile);
+ return -1;
+ }
+
+ return 0;
+
+write_error:
+ strbuf_addf(err, "error writing to %s: %s",
+ get_tempfile_path(refs->tempfile), strerror(errno));
+
+error:
+ if (iter)
+ ref_iterator_abort(iter);
+
+ delete_tempfile(&refs->tempfile);
+ return -1;
+}
+
+int is_packed_transaction_needed(struct ref_store *ref_store,
+ struct ref_transaction *transaction)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ,
+ "is_packed_transaction_needed");
+ struct strbuf referent = STRBUF_INIT;
+ size_t i;
+ int ret;
+
+ if (!is_lock_file_locked(&refs->lock))
+ BUG("is_packed_transaction_needed() called while unlocked");
+
+ /*
+ * We're only going to bother returning false for the common,
+ * trivial case that references are only being deleted, their
+ * old values are not being checked, and the old `packed-refs`
+ * file doesn't contain any of those reference(s). This gives
+ * false positives for some other cases that could
+ * theoretically be optimized away:
+ *
+ * 1. It could be that the old value is being verified without
+ * setting a new value. In this case, we could verify the
+ * old value here and skip the update if it agrees. If it
+ * disagrees, we could either let the update go through
+ * (the actual commit would re-detect and report the
+ * problem), or come up with a way of reporting such an
+ * error to *our* caller.
+ *
+ * 2. It could be that a new value is being set, but that it
+ * is identical to the current packed value of the
+ * reference.
+ *
+ * Neither of these cases will come up in the current code,
+ * because the only caller of this function passes to it a
+ * transaction that only includes `delete` updates with no
+ * `old_id`. Even if that ever changes, false positives only
+ * cause an optimization to be missed; they do not affect
+ * correctness.
+ */
+
+ /*
+ * Start with the cheap checks that don't require old
+ * reference values to be read:
+ */
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+
+ if (update->flags & REF_HAVE_OLD)
+ /* Have to check the old value -> needed. */
+ return 1;
+
+ if ((update->flags & REF_HAVE_NEW) && !is_null_oid(&update->new_oid))
+ /* Have to set a new value -> needed. */
+ return 1;
+ }
+
+ /*
+ * The transaction isn't checking any old values nor is it
+ * setting any nonzero new values, so it still might be able
+ * to be skipped. Now do the more expensive check: the update
+ * is needed if any of the updates is a delete, and the old
+ * `packed-refs` file contains a value for that reference.
+ */
+ ret = 0;
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+ int failure_errno;
+ unsigned int type;
+ struct object_id oid;
+
+ if (!(update->flags & REF_HAVE_NEW))
+ /*
+ * This reference isn't being deleted -> not
+ * needed.
+ */
+ continue;
+
+ if (!refs_read_raw_ref(ref_store, update->refname, &oid,
+ &referent, &type, &failure_errno) ||
+ failure_errno != ENOENT) {
+ /*
+ * We have to actually delete that reference
+ * -> this transaction is needed.
+ */
+ ret = 1;
+ break;
+ }
+ }
+
+ strbuf_release(&referent);
+ return ret;
+}
+
+struct packed_transaction_backend_data {
+ /* True iff the transaction owns the packed-refs lock. */
+ int own_lock;
+
+ struct string_list updates;
+};
+
+static void packed_transaction_cleanup(struct packed_ref_store *refs,
+ struct ref_transaction *transaction)
+{
+ struct packed_transaction_backend_data *data = transaction->backend_data;
+
+ if (data) {
+ string_list_clear(&data->updates, 0);
+
+ if (is_tempfile_active(refs->tempfile))
+ delete_tempfile(&refs->tempfile);
+
+ if (data->own_lock && is_lock_file_locked(&refs->lock)) {
+ packed_refs_unlock(&refs->base);
+ data->own_lock = 0;
+ }
+
+ free(data);
+ transaction->backend_data = NULL;
+ }
+
+ transaction->state = REF_TRANSACTION_CLOSED;
+}
+
+static int packed_transaction_prepare(struct ref_store *ref_store,
+ struct ref_transaction *transaction,
+ struct strbuf *err)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
+ "ref_transaction_prepare");
+ struct packed_transaction_backend_data *data;
+ size_t i;
+ int ret = TRANSACTION_GENERIC_ERROR;
+
+ /*
+ * Note that we *don't* skip transactions with zero updates,
+ * because such a transaction might be executed for the side
+ * effect of ensuring that all of the references are peeled or
+ * ensuring that the `packed-refs` file is sorted. If the
+ * caller wants to optimize away empty transactions, it should
+ * do so itself.
+ */
+
+ CALLOC_ARRAY(data, 1);
+ string_list_init_nodup(&data->updates);
+
+ transaction->backend_data = data;
+
+ /*
+ * Stick the updates in a string list by refname so that we
+ * can sort them:
+ */
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+ struct string_list_item *item =
+ string_list_append(&data->updates, update->refname);
+
+ /* Store a pointer to update in item->util: */
+ item->util = update;
+ }
+ string_list_sort(&data->updates);
+
+ if (ref_update_reject_duplicates(&data->updates, err))
+ goto failure;
+
+ if (!is_lock_file_locked(&refs->lock)) {
+ if (packed_refs_lock(ref_store, 0, err))
+ goto failure;
+ data->own_lock = 1;
+ }
+
+ if (write_with_updates(refs, &data->updates, err))
+ goto failure;
+
+ transaction->state = REF_TRANSACTION_PREPARED;
+ return 0;
+
+failure:
+ packed_transaction_cleanup(refs, transaction);
+ return ret;
+}
+
+static int packed_transaction_abort(struct ref_store *ref_store,
+ struct ref_transaction *transaction,
+ struct strbuf *err UNUSED)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
+ "ref_transaction_abort");
+
+ packed_transaction_cleanup(refs, transaction);
+ return 0;
+}
+
+static int packed_transaction_finish(struct ref_store *ref_store,
+ struct ref_transaction *transaction,
+ struct strbuf *err)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
+ "ref_transaction_finish");
+ int ret = TRANSACTION_GENERIC_ERROR;
+ char *packed_refs_path;
+
+ clear_snapshot(refs);
+
+ packed_refs_path = get_locked_file_path(&refs->lock);
+ if (rename_tempfile(&refs->tempfile, packed_refs_path)) {
+ strbuf_addf(err, "error replacing %s: %s",
+ refs->path, strerror(errno));
+ goto cleanup;
+ }
+
+ ret = 0;
+
+cleanup:
+ free(packed_refs_path);
+ packed_transaction_cleanup(refs, transaction);
+ return ret;
+}
+
+static int packed_initial_transaction_commit(struct ref_store *ref_store UNUSED,
+ struct ref_transaction *transaction,
+ struct strbuf *err)
+{
+ return ref_transaction_commit(transaction, err);
+}
+
+static int packed_delete_refs(struct ref_store *ref_store, const char *msg,
+ struct string_list *refnames, unsigned int flags)
+{
+ struct packed_ref_store *refs =
+ packed_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
+ struct strbuf err = STRBUF_INIT;
+ struct ref_transaction *transaction;
+ struct string_list_item *item;
+ int ret;
+
+ (void)refs; /* We need the check above, but don't use the variable */
+
+ if (!refnames->nr)
+ return 0;
+
+ /*
+ * Since we don't check the references' old_oids, the
+ * individual updates can't fail, so we can pack all of the
+ * updates into a single transaction.
+ */
+
+ transaction = ref_store_transaction_begin(ref_store, &err);
+ if (!transaction)
+ return -1;
+
+ for_each_string_list_item(item, refnames) {
+ if (ref_transaction_delete(transaction, item->string, NULL,
+ flags, msg, &err)) {
+ warning(_("could not delete reference %s: %s"),
+ item->string, err.buf);
+ strbuf_reset(&err);
+ }
+ }
+
+ ret = ref_transaction_commit(transaction, &err);
+
+ if (ret) {
+ if (refnames->nr == 1)
+ error(_("could not delete reference %s: %s"),
+ refnames->items[0].string, err.buf);
+ else
+ error(_("could not delete references: %s"), err.buf);
+ }
+
+ ref_transaction_free(transaction);
+ strbuf_release(&err);
+ return ret;
+}
+
+static int packed_pack_refs(struct ref_store *ref_store UNUSED,
+ unsigned int flags UNUSED)
+{
+ /*
+ * Packed refs are already packed. It might be that loose refs
+ * are packed *into* a packed refs store, but that is done by
+ * updating the packed references via a transaction.
+ */
+ return 0;
+}
+
+static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_store UNUSED)
+{
+ return empty_ref_iterator_begin();
+}
+
+struct ref_storage_be refs_be_packed = {
+ .next = NULL,
+ .name = "packed",
+ .init = packed_ref_store_create,
+ .init_db = packed_init_db,
+ .transaction_prepare = packed_transaction_prepare,
+ .transaction_finish = packed_transaction_finish,
+ .transaction_abort = packed_transaction_abort,
+ .initial_transaction_commit = packed_initial_transaction_commit,
+
+ .pack_refs = packed_pack_refs,
+ .create_symref = NULL,
+ .delete_refs = packed_delete_refs,
+ .rename_ref = NULL,
+ .copy_ref = NULL,
+
+ .iterator_begin = packed_ref_iterator_begin,
+ .read_raw_ref = packed_read_raw_ref,
+ .read_symbolic_ref = NULL,
+
+ .reflog_iterator_begin = packed_reflog_iterator_begin,
+ .for_each_reflog_ent = NULL,
+ .for_each_reflog_ent_reverse = NULL,
+ .reflog_exists = NULL,
+ .create_reflog = NULL,
+ .delete_reflog = NULL,
+ .reflog_expire = NULL,
+};