#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 Its freshness is checked whenever * `get_snapshot()` is called; if the existing snapshot is obsolete, a * new snapshot is taken.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, 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 && ref_type(iter->base.refname) != REF_TYPE_PER_WORKTREE) 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 = { packed_ref_iterator_advance, packed_ref_iterator_peel, 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, struct strbuf *err) { /* 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 (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) { 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, 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, unsigned int flags) { /* * 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 int packed_create_symref(struct ref_store *ref_store, const char *refname, const char *target, const char *logmsg) { BUG("packed reference store does not support symrefs"); } static int packed_rename_ref(struct ref_store *ref_store, const char *oldrefname, const char *newrefname, const char *logmsg) { BUG("packed reference store does not support renaming references"); } static int packed_copy_ref(struct ref_store *ref_store, const char *oldrefname, const char *newrefname, const char *logmsg) { BUG("packed reference store does not support copying references"); } static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_store) { return empty_ref_iterator_begin(); } static int packed_for_each_reflog_ent(struct ref_store *ref_store, const char *refname, each_reflog_ent_fn fn, void *cb_data) { BUG("packed reference store does not support reflogs"); return 0; } static int packed_for_each_reflog_ent_reverse(struct ref_store *ref_store, const char *refname, each_reflog_ent_fn fn, void *cb_data) { BUG("packed reference store does not support reflogs"); return 0; } static int packed_reflog_exists(struct ref_store *ref_store, const char *refname) { BUG("packed reference store does not support reflogs"); return 0; } static int packed_create_reflog(struct ref_store *ref_store, const char *refname, struct strbuf *err) { BUG("packed reference store does not support reflogs"); } static int packed_delete_reflog(struct ref_store *ref_store, const char *refname) { BUG("packed reference store does not support reflogs"); return 0; } static int packed_reflog_expire(struct ref_store *ref_store, const char *refname, unsigned int flags, reflog_expiry_prepare_fn prepare_fn, reflog_expiry_should_prune_fn should_prune_fn, reflog_expiry_cleanup_fn cleanup_fn, void *policy_cb_data) { BUG("packed reference store does not support reflogs"); return 0; } struct ref_storage_be refs_be_packed = { NULL, "packed", packed_ref_store_create, packed_init_db, packed_transaction_prepare, packed_transaction_finish, packed_transaction_abort, packed_initial_transaction_commit, packed_pack_refs, packed_create_symref, packed_delete_refs, packed_rename_ref, packed_copy_ref, packed_ref_iterator_begin, packed_read_raw_ref, packed_reflog_iterator_begin, packed_for_each_reflog_ent, packed_for_each_reflog_ent_reverse, packed_reflog_exists, packed_create_reflog, packed_delete_reflog, packed_reflog_expire };