diff options
Diffstat (limited to 'reftable/stack.c')
| -rw-r--r-- | reftable/stack.c | 1841 |
1 files changed, 1841 insertions, 0 deletions
diff --git a/reftable/stack.c b/reftable/stack.c new file mode 100644 index 0000000000..4caf96aa1d --- /dev/null +++ b/reftable/stack.c @@ -0,0 +1,1841 @@ +/* + * Copyright 2020 Google LLC + * + * Use of this source code is governed by a BSD-style + * license that can be found in the LICENSE file or at + * https://developers.google.com/open-source/licenses/bsd + */ + +#include "stack.h" + +#include "system.h" +#include "constants.h" +#include "merged.h" +#include "reftable-error.h" +#include "reftable-record.h" +#include "reftable-merged.h" +#include "table.h" +#include "writer.h" + +static int stack_try_add(struct reftable_stack *st, + int (*write_table)(struct reftable_writer *wr, + void *arg), + void *arg); +static int stack_write_compact(struct reftable_stack *st, + struct reftable_writer *wr, + size_t first, size_t last, + struct reftable_log_expiry_config *config); +static void reftable_addition_close(struct reftable_addition *add); +static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st, + int reuse_open); + +static int stack_filename(struct reftable_buf *dest, struct reftable_stack *st, + const char *name) +{ + int err; + reftable_buf_reset(dest); + if ((err = reftable_buf_addstr(dest, st->reftable_dir)) < 0 || + (err = reftable_buf_addstr(dest, "/")) < 0 || + (err = reftable_buf_addstr(dest, name)) < 0) + return err; + return 0; +} + +static int stack_fsync(const struct reftable_write_options *opts, int fd) +{ + if (opts->fsync) + return opts->fsync(fd); + return fsync(fd); +} + +static ssize_t reftable_write_data(int fd, const void *data, size_t size) +{ + size_t total_written = 0; + const char *p = data; + + while (total_written < size) { + ssize_t bytes_written = write(fd, p, size - total_written); + if (bytes_written < 0 && (errno == EAGAIN || errno == EINTR)) + continue; + if (bytes_written < 0) + return REFTABLE_IO_ERROR; + + total_written += bytes_written; + p += bytes_written; + } + + return total_written; +} + +struct fd_writer { + const struct reftable_write_options *opts; + int fd; +}; + +static ssize_t fd_writer_write(void *arg, const void *data, size_t sz) +{ + struct fd_writer *writer = arg; + return reftable_write_data(writer->fd, data, sz); +} + +static int fd_writer_flush(void *arg) +{ + struct fd_writer *writer = arg; + return stack_fsync(writer->opts, writer->fd); +} + +int reftable_new_stack(struct reftable_stack **dest, const char *dir, + const struct reftable_write_options *_opts) +{ + struct reftable_buf list_file_name = REFTABLE_BUF_INIT; + struct reftable_write_options opts = { 0 }; + struct reftable_stack *p; + int err; + + p = reftable_calloc(1, sizeof(*p)); + if (!p) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto out; + } + + if (_opts) + opts = *_opts; + if (opts.hash_id == 0) + opts.hash_id = REFTABLE_HASH_SHA1; + + *dest = NULL; + + reftable_buf_reset(&list_file_name); + if ((err = reftable_buf_addstr(&list_file_name, dir)) < 0 || + (err = reftable_buf_addstr(&list_file_name, "/tables.list")) < 0) + goto out; + + p->list_file = reftable_buf_detach(&list_file_name); + p->list_fd = -1; + p->opts = opts; + p->reftable_dir = reftable_strdup(dir); + if (!p->reftable_dir) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto out; + } + + err = reftable_stack_reload_maybe_reuse(p, 1); + if (err < 0) + goto out; + + *dest = p; + err = 0; + +out: + if (err < 0) + reftable_stack_destroy(p); + return err; +} + +static int fd_read_lines(int fd, char ***namesp) +{ + char *buf = NULL; + int err = 0; + off_t size; + + size = lseek(fd, 0, SEEK_END); + if (size < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + err = lseek(fd, 0, SEEK_SET); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + REFTABLE_ALLOC_ARRAY(buf, size + 1); + if (!buf) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + + for (off_t total_read = 0; total_read < size; ) { + ssize_t bytes_read = read(fd, buf + total_read, size - total_read); + if (bytes_read < 0 && (errno == EAGAIN || errno == EINTR)) + continue; + if (bytes_read < 0 || !bytes_read) { + err = REFTABLE_IO_ERROR; + goto done; + } + + total_read += bytes_read; + } + buf[size] = 0; + + *namesp = parse_names(buf, size); + if (!*namesp) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + +done: + reftable_free(buf); + return err; +} + +int read_lines(const char *filename, char ***namesp) +{ + int fd = open(filename, O_RDONLY); + int err = 0; + if (fd < 0) { + if (errno == ENOENT) { + REFTABLE_CALLOC_ARRAY(*namesp, 1); + if (!*namesp) + return REFTABLE_OUT_OF_MEMORY_ERROR; + return 0; + } + + return REFTABLE_IO_ERROR; + } + err = fd_read_lines(fd, namesp); + close(fd); + return err; +} + +int reftable_stack_init_ref_iterator(struct reftable_stack *st, + struct reftable_iterator *it) +{ + return merged_table_init_iter(reftable_stack_merged_table(st), + it, REFTABLE_BLOCK_TYPE_REF); +} + +int reftable_stack_init_log_iterator(struct reftable_stack *st, + struct reftable_iterator *it) +{ + return merged_table_init_iter(reftable_stack_merged_table(st), + it, REFTABLE_BLOCK_TYPE_LOG); +} + +struct reftable_merged_table * +reftable_stack_merged_table(struct reftable_stack *st) +{ + return st->merged; +} + +static int has_name(char **names, const char *name) +{ + while (*names) { + if (!strcmp(*names, name)) + return 1; + names++; + } + return 0; +} + +/* Close and free the stack */ +void reftable_stack_destroy(struct reftable_stack *st) +{ + char **names = NULL; + int err = 0; + + if (!st) + return; + + if (st->merged) { + reftable_merged_table_free(st->merged); + st->merged = NULL; + } + + err = read_lines(st->list_file, &names); + if (err < 0) { + REFTABLE_FREE_AND_NULL(names); + } + + if (st->tables) { + struct reftable_buf filename = REFTABLE_BUF_INIT; + + for (size_t i = 0; i < st->tables_len; i++) { + const char *name = reftable_table_name(st->tables[i]); + int try_unlinking = 1; + + reftable_buf_reset(&filename); + if (names && !has_name(names, name)) { + if (stack_filename(&filename, st, name) < 0) + try_unlinking = 0; + } + reftable_table_decref(st->tables[i]); + + if (try_unlinking && filename.len) { + /* On Windows, can only unlink after closing. */ + unlink(filename.buf); + } + } + + reftable_buf_release(&filename); + st->tables_len = 0; + REFTABLE_FREE_AND_NULL(st->tables); + } + + if (st->list_fd >= 0) { + close(st->list_fd); + st->list_fd = -1; + } + + REFTABLE_FREE_AND_NULL(st->list_file); + REFTABLE_FREE_AND_NULL(st->reftable_dir); + reftable_free(st); + free_names(names); +} + +static struct reftable_table **stack_copy_tables(struct reftable_stack *st, + size_t cur_len) +{ + struct reftable_table **cur = reftable_calloc(cur_len, sizeof(*cur)); + if (!cur) + return NULL; + for (size_t i = 0; i < cur_len; i++) + cur[i] = st->tables[i]; + return cur; +} + +static int reftable_stack_reload_once(struct reftable_stack *st, + const char **names, + int reuse_open) +{ + size_t cur_len = !st->merged ? 0 : st->merged->tables_len; + struct reftable_table **cur = NULL; + struct reftable_table **reused = NULL; + struct reftable_table **new_tables = NULL; + size_t reused_len = 0, reused_alloc = 0, names_len; + size_t new_tables_len = 0; + struct reftable_merged_table *new_merged = NULL; + struct reftable_buf table_path = REFTABLE_BUF_INIT; + int err = 0; + size_t i; + + if (cur_len) { + cur = stack_copy_tables(st, cur_len); + if (!cur) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + } + + names_len = names_length(names); + + if (names_len) { + new_tables = reftable_calloc(names_len, sizeof(*new_tables)); + if (!new_tables) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + } + + while (*names) { + struct reftable_table *table = NULL; + const char *name = *names++; + + /* this is linear; we assume compaction keeps the number of + tables under control so this is not quadratic. */ + for (i = 0; reuse_open && i < cur_len; i++) { + if (cur[i] && 0 == strcmp(cur[i]->name, name)) { + table = cur[i]; + cur[i] = NULL; + + /* + * When reloading the stack fails, we end up + * releasing all new tables. This also + * includes the reused tables, even though + * they are still in used by the old stack. We + * thus need to keep them alive here, which we + * do by bumping their refcount. + */ + REFTABLE_ALLOC_GROW_OR_NULL(reused, + reused_len + 1, + reused_alloc); + if (!reused) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + reused[reused_len++] = table; + reftable_table_incref(table); + break; + } + } + + if (!table) { + struct reftable_block_source src = { NULL }; + + err = stack_filename(&table_path, st, name); + if (err < 0) + goto done; + + err = reftable_block_source_from_file(&src, + table_path.buf); + if (err < 0) + goto done; + + err = reftable_table_new(&table, &src, name); + if (err < 0) + goto done; + } + + new_tables[new_tables_len] = table; + new_tables_len++; + } + + /* success! */ + err = reftable_merged_table_new(&new_merged, new_tables, + new_tables_len, st->opts.hash_id); + if (err < 0) + goto done; + + /* + * Close the old, non-reused tables and proactively try to unlink + * them. This is done for systems like Windows, where the underlying + * file of such an open table wouldn't have been possible to be + * unlinked by the compacting process. + */ + for (i = 0; i < cur_len; i++) { + if (cur[i]) { + const char *name = reftable_table_name(cur[i]); + + err = stack_filename(&table_path, st, name); + if (err < 0) + goto done; + + reftable_table_decref(cur[i]); + unlink(table_path.buf); + } + } + + /* Update the stack to point to the new tables. */ + if (st->merged) + reftable_merged_table_free(st->merged); + new_merged->suppress_deletions = 1; + st->merged = new_merged; + + if (st->tables) + reftable_free(st->tables); + st->tables = new_tables; + st->tables_len = new_tables_len; + new_tables = NULL; + new_tables_len = 0; + + /* + * Decrement the refcount of reused tables again. This only needs to + * happen on the successful case, because on the unsuccessful one we + * decrement their refcount via `new_tables`. + */ + for (i = 0; i < reused_len; i++) + reftable_table_decref(reused[i]); + +done: + for (i = 0; i < new_tables_len; i++) + reftable_table_decref(new_tables[i]); + reftable_free(new_tables); + reftable_free(reused); + reftable_free(cur); + reftable_buf_release(&table_path); + return err; +} + +/* return negative if a before b. */ +static int tv_cmp(struct timeval *a, struct timeval *b) +{ + time_t diff = a->tv_sec - b->tv_sec; + int udiff = a->tv_usec - b->tv_usec; + + if (diff != 0) + return diff; + + return udiff; +} + +static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st, + int reuse_open) +{ + char **names = NULL, **names_after = NULL; + struct timeval deadline; + int64_t delay = 0; + int tries = 0, err; + int fd = -1; + + err = gettimeofday(&deadline, NULL); + if (err < 0) + goto out; + deadline.tv_sec += 3; + + while (1) { + struct timeval now; + + err = gettimeofday(&now, NULL); + if (err < 0) + goto out; + + /* + * Only look at deadlines after the first few times. This + * simplifies debugging in GDB. + */ + tries++; + if (tries > 3 && tv_cmp(&now, &deadline) >= 0) + goto out; + + fd = open(st->list_file, O_RDONLY); + if (fd < 0) { + if (errno != ENOENT) { + err = REFTABLE_IO_ERROR; + goto out; + } + + REFTABLE_CALLOC_ARRAY(names, 1); + if (!names) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto out; + } + } else { + err = fd_read_lines(fd, &names); + if (err < 0) + goto out; + } + + err = reftable_stack_reload_once(st, (const char **) names, reuse_open); + if (!err) + break; + if (err != REFTABLE_NOT_EXIST_ERROR) + goto out; + + /* + * REFTABLE_NOT_EXIST_ERROR can be caused by a concurrent + * writer. Check if there was one by checking if the name list + * changed. + */ + err = read_lines(st->list_file, &names_after); + if (err < 0) + goto out; + if (names_equal((const char **) names_after, + (const char **) names)) { + err = REFTABLE_NOT_EXIST_ERROR; + goto out; + } + + free_names(names); + names = NULL; + free_names(names_after); + names_after = NULL; + close(fd); + fd = -1; + + delay = delay + (delay * reftable_rand()) / UINT32_MAX + 1; + poll(NULL, 0, delay); + } + +out: + /* + * Invalidate the stat cache. It is sufficient to only close the file + * descriptor and keep the cached stat info because we never use the + * latter when the former is negative. + */ + if (st->list_fd >= 0) { + close(st->list_fd); + st->list_fd = -1; + } + + /* + * Cache stat information in case it provides a useful signal to us. + * According to POSIX, "The st_ino and st_dev fields taken together + * uniquely identify the file within the system." That being said, + * Windows is not POSIX compliant and we do not have these fields + * available. So the information we have there is insufficient to + * determine whether two file descriptors point to the same file. + * + * While we could fall back to using other signals like the file's + * mtime, those are not sufficient to avoid races. We thus refrain from + * using the stat cache on such systems and fall back to the secondary + * caching mechanism, which is to check whether contents of the file + * have changed. + * + * On other systems which are POSIX compliant we must keep the file + * descriptor open. This is to avoid a race condition where two + * processes access the reftable stack at the same point in time: + * + * 1. A reads the reftable stack and caches its stat info. + * + * 2. B updates the stack, appending a new table to "tables.list". + * This will both use a new inode and result in a different file + * size, thus invalidating A's cache in theory. + * + * 3. B decides to auto-compact the stack and merges two tables. The + * file size now matches what A has cached again. Furthermore, the + * filesystem may decide to recycle the inode number of the file + * we have replaced in (2) because it is not in use anymore. + * + * 4. A reloads the reftable stack. Neither the inode number nor the + * file size changed. If the timestamps did not change either then + * we think the cached copy of our stack is up-to-date. + * + * By keeping the file descriptor open the inode number cannot be + * recycled, mitigating the race. + */ + if (!err && fd >= 0 && !fstat(fd, &st->list_st) && + st->list_st.st_dev && st->list_st.st_ino) { + st->list_fd = fd; + fd = -1; + } + + if (fd >= 0) + close(fd); + free_names(names); + free_names(names_after); + + if (st->opts.on_reload) + st->opts.on_reload(st->opts.on_reload_payload); + + return err; +} + +/* -1 = error + 0 = up to date + 1 = changed. */ +static int stack_uptodate(struct reftable_stack *st) +{ + char **names = NULL; + int err; + + /* + * When we have cached stat information available then we use it to + * verify whether the file has been rewritten. + * + * Note that we explicitly do not want to use `stat_validity_check()` + * and friends here because they may end up not comparing the `st_dev` + * and `st_ino` fields. These functions thus cannot guarantee that we + * indeed still have the same file. + */ + if (st->list_fd >= 0) { + struct stat list_st; + + if (stat(st->list_file, &list_st) < 0) { + /* + * It's fine for "tables.list" to not exist. In that + * case, we have to refresh when the loaded stack has + * any tables. + */ + if (errno == ENOENT) + return !!st->tables_len; + return REFTABLE_IO_ERROR; + } + + /* + * When "tables.list" refers to the same file we can assume + * that it didn't change. This is because we always use + * rename(3P) to update the file and never write to it + * directly. + */ + if (st->list_st.st_dev == list_st.st_dev && + st->list_st.st_ino == list_st.st_ino) + return 0; + } + + err = read_lines(st->list_file, &names); + if (err < 0) + return err; + + for (size_t i = 0; i < st->tables_len; i++) { + if (!names[i]) { + err = 1; + goto done; + } + + if (strcmp(st->tables[i]->name, names[i])) { + err = 1; + goto done; + } + } + + if (names[st->merged->tables_len]) { + err = 1; + goto done; + } + +done: + free_names(names); + return err; +} + +int reftable_stack_reload(struct reftable_stack *st) +{ + int err = stack_uptodate(st); + if (err > 0) + return reftable_stack_reload_maybe_reuse(st, 1); + return err; +} + +int reftable_stack_add(struct reftable_stack *st, + int (*write)(struct reftable_writer *wr, void *arg), + void *arg) +{ + int err = stack_try_add(st, write, arg); + if (err < 0) { + if (err == REFTABLE_OUTDATED_ERROR) { + /* Ignore error return, we want to propagate + REFTABLE_OUTDATED_ERROR. + */ + reftable_stack_reload(st); + } + return err; + } + + return 0; +} + +static int format_name(struct reftable_buf *dest, uint64_t min, uint64_t max) +{ + char buf[100]; + uint32_t rnd = reftable_rand(); + snprintf(buf, sizeof(buf), "0x%012" PRIx64 "-0x%012" PRIx64 "-%08x", + min, max, rnd); + reftable_buf_reset(dest); + return reftable_buf_addstr(dest, buf); +} + +struct reftable_addition { + struct reftable_flock tables_list_lock; + struct reftable_stack *stack; + + char **new_tables; + size_t new_tables_len, new_tables_cap; + uint64_t next_update_index; +}; + +#define REFTABLE_ADDITION_INIT {0} + +static int reftable_stack_init_addition(struct reftable_addition *add, + struct reftable_stack *st, + unsigned int flags) +{ + struct reftable_buf lock_file_name = REFTABLE_BUF_INIT; + int err; + + add->stack = st; + + err = flock_acquire(&add->tables_list_lock, st->list_file, + st->opts.lock_timeout_ms); + if (err < 0) { + if (errno == EEXIST) { + err = REFTABLE_LOCK_ERROR; + } else { + err = REFTABLE_IO_ERROR; + } + goto done; + } + if (st->opts.default_permissions) { + if (chmod(add->tables_list_lock.path, + st->opts.default_permissions) < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + err = stack_uptodate(st); + if (err < 0) + goto done; + if (err > 0 && flags & REFTABLE_STACK_NEW_ADDITION_RELOAD) { + err = reftable_stack_reload_maybe_reuse(add->stack, 1); + if (err) + goto done; + } + if (err > 0) { + err = REFTABLE_OUTDATED_ERROR; + goto done; + } + + add->next_update_index = reftable_stack_next_update_index(st); +done: + if (err) + reftable_addition_close(add); + reftable_buf_release(&lock_file_name); + return err; +} + +static void reftable_addition_close(struct reftable_addition *add) +{ + struct reftable_buf nm = REFTABLE_BUF_INIT; + size_t i; + + for (i = 0; i < add->new_tables_len; i++) { + if (!stack_filename(&nm, add->stack, add->new_tables[i])) + unlink(nm.buf); + reftable_free(add->new_tables[i]); + add->new_tables[i] = NULL; + } + reftable_free(add->new_tables); + add->new_tables = NULL; + add->new_tables_len = 0; + add->new_tables_cap = 0; + + flock_release(&add->tables_list_lock); + reftable_buf_release(&nm); +} + +void reftable_addition_destroy(struct reftable_addition *add) +{ + if (!add) { + return; + } + reftable_addition_close(add); + reftable_free(add); +} + +int reftable_addition_commit(struct reftable_addition *add) +{ + struct reftable_buf table_list = REFTABLE_BUF_INIT; + int err = 0; + size_t i; + + if (add->new_tables_len == 0) + goto done; + + for (i = 0; i < add->stack->merged->tables_len; i++) { + if ((err = reftable_buf_addstr(&table_list, add->stack->tables[i]->name)) < 0 || + (err = reftable_buf_addstr(&table_list, "\n")) < 0) + goto done; + } + for (i = 0; i < add->new_tables_len; i++) { + if ((err = reftable_buf_addstr(&table_list, add->new_tables[i])) < 0 || + (err = reftable_buf_addstr(&table_list, "\n")) < 0) + goto done; + } + + err = reftable_write_data(add->tables_list_lock.fd, + table_list.buf, table_list.len); + reftable_buf_release(&table_list); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + err = stack_fsync(&add->stack->opts, add->tables_list_lock.fd); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + err = flock_commit(&add->tables_list_lock); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + /* success, no more state to clean up. */ + for (i = 0; i < add->new_tables_len; i++) + reftable_free(add->new_tables[i]); + reftable_free(add->new_tables); + add->new_tables = NULL; + add->new_tables_len = 0; + add->new_tables_cap = 0; + + err = reftable_stack_reload_maybe_reuse(add->stack, 1); + if (err) + goto done; + + if (!add->stack->opts.disable_auto_compact) { + /* + * Auto-compact the stack to keep the number of tables in + * control. It is possible that a concurrent writer is already + * trying to compact parts of the stack, which would lead to a + * `REFTABLE_LOCK_ERROR` because parts of the stack are locked + * already. This is a benign error though, so we ignore it. + */ + err = reftable_stack_auto_compact(add->stack); + if (err < 0 && err != REFTABLE_LOCK_ERROR) + goto done; + err = 0; + } + +done: + reftable_addition_close(add); + return err; +} + +int reftable_stack_new_addition(struct reftable_addition **dest, + struct reftable_stack *st, + unsigned int flags) +{ + int err = 0; + struct reftable_addition empty = REFTABLE_ADDITION_INIT; + + REFTABLE_CALLOC_ARRAY(*dest, 1); + if (!*dest) + return REFTABLE_OUT_OF_MEMORY_ERROR; + + **dest = empty; + err = reftable_stack_init_addition(*dest, st, flags); + if (err) { + reftable_free(*dest); + *dest = NULL; + } + return err; +} + +static int stack_try_add(struct reftable_stack *st, + int (*write_table)(struct reftable_writer *wr, + void *arg), + void *arg) +{ + struct reftable_addition add = REFTABLE_ADDITION_INIT; + int err = reftable_stack_init_addition(&add, st, 0); + if (err < 0) + goto done; + + err = reftable_addition_add(&add, write_table, arg); + if (err < 0) + goto done; + + err = reftable_addition_commit(&add); +done: + reftable_addition_close(&add); + return err; +} + +int reftable_addition_add(struct reftable_addition *add, + int (*write_table)(struct reftable_writer *wr, + void *arg), + void *arg) +{ + struct reftable_buf temp_tab_file_name = REFTABLE_BUF_INIT; + struct reftable_buf tab_file_name = REFTABLE_BUF_INIT; + struct reftable_buf next_name = REFTABLE_BUF_INIT; + struct reftable_writer *wr = NULL; + struct reftable_tmpfile tab_file = REFTABLE_TMPFILE_INIT; + struct fd_writer writer = { + .opts = &add->stack->opts, + }; + int err = 0; + + reftable_buf_reset(&next_name); + + err = format_name(&next_name, add->next_update_index, add->next_update_index); + if (err < 0) + goto done; + + err = stack_filename(&temp_tab_file_name, add->stack, next_name.buf); + if (err < 0) + goto done; + + err = reftable_buf_addstr(&temp_tab_file_name, ".temp.XXXXXX"); + if (err < 0) + goto done; + + err = tmpfile_from_pattern(&tab_file, temp_tab_file_name.buf); + if (err < 0) + goto done; + if (add->stack->opts.default_permissions) { + if (chmod(tab_file.path, + add->stack->opts.default_permissions)) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + writer.fd = tab_file.fd; + err = reftable_writer_new(&wr, fd_writer_write, fd_writer_flush, + &writer, &add->stack->opts); + if (err < 0) + goto done; + + err = write_table(wr, arg); + if (err < 0) + goto done; + + err = reftable_writer_close(wr); + if (err == REFTABLE_EMPTY_TABLE_ERROR) { + err = 0; + goto done; + } + if (err < 0) + goto done; + + err = tmpfile_close(&tab_file); + if (err < 0) + goto done; + + if (wr->min_update_index < add->next_update_index) { + err = REFTABLE_API_ERROR; + goto done; + } + + err = format_name(&next_name, wr->min_update_index, wr->max_update_index); + if (err < 0) + goto done; + + err = reftable_buf_addstr(&next_name, ".ref"); + if (err < 0) + goto done; + + err = stack_filename(&tab_file_name, add->stack, next_name.buf); + if (err < 0) + goto done; + + /* + On windows, this relies on rand() picking a unique destination name. + Maybe we should do retry loop as well? + */ + err = tmpfile_rename(&tab_file, tab_file_name.buf); + if (err < 0) + goto done; + + REFTABLE_ALLOC_GROW_OR_NULL(add->new_tables, add->new_tables_len + 1, + add->new_tables_cap); + if (!add->new_tables) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + add->new_tables[add->new_tables_len++] = reftable_buf_detach(&next_name); + +done: + tmpfile_delete(&tab_file); + reftable_buf_release(&temp_tab_file_name); + reftable_buf_release(&tab_file_name); + reftable_buf_release(&next_name); + reftable_writer_free(wr); + return err; +} + +uint64_t reftable_stack_next_update_index(struct reftable_stack *st) +{ + int sz = st->merged->tables_len; + if (sz > 0) + return reftable_table_max_update_index(st->tables[sz - 1]) + + 1; + return 1; +} + +static int stack_compact_locked(struct reftable_stack *st, + size_t first, size_t last, + struct reftable_log_expiry_config *config, + struct reftable_tmpfile *tab_file_out) +{ + struct reftable_buf next_name = REFTABLE_BUF_INIT; + struct reftable_buf tab_file_path = REFTABLE_BUF_INIT; + struct reftable_writer *wr = NULL; + struct fd_writer writer= { + .opts = &st->opts, + }; + struct reftable_tmpfile tab_file = REFTABLE_TMPFILE_INIT; + int err = 0; + + err = format_name(&next_name, reftable_table_min_update_index(st->tables[first]), + reftable_table_max_update_index(st->tables[last])); + if (err < 0) + goto done; + + err = stack_filename(&tab_file_path, st, next_name.buf); + if (err < 0) + goto done; + + err = reftable_buf_addstr(&tab_file_path, ".temp.XXXXXX"); + if (err < 0) + goto done; + + err = tmpfile_from_pattern(&tab_file, tab_file_path.buf); + if (err < 0) + goto done; + + if (st->opts.default_permissions && + chmod(tab_file.path, st->opts.default_permissions) < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + writer.fd = tab_file.fd; + err = reftable_writer_new(&wr, fd_writer_write, fd_writer_flush, + &writer, &st->opts); + if (err < 0) + goto done; + + err = stack_write_compact(st, wr, first, last, config); + if (err < 0) + goto done; + + err = reftable_writer_close(wr); + if (err < 0) + goto done; + + err = tmpfile_close(&tab_file); + if (err < 0) + goto done; + + *tab_file_out = tab_file; + tab_file = REFTABLE_TMPFILE_INIT; + +done: + tmpfile_delete(&tab_file); + reftable_writer_free(wr); + reftable_buf_release(&next_name); + reftable_buf_release(&tab_file_path); + return err; +} + +static int stack_write_compact(struct reftable_stack *st, + struct reftable_writer *wr, + size_t first, size_t last, + struct reftable_log_expiry_config *config) +{ + struct reftable_merged_table *mt = NULL; + struct reftable_iterator it = { NULL }; + struct reftable_ref_record ref = { NULL }; + struct reftable_log_record log = { NULL }; + size_t subtabs_len = last - first + 1; + uint64_t entries = 0; + int err = 0; + + for (size_t i = first; i <= last; i++) + st->stats.bytes += st->tables[i]->size; + err = reftable_writer_set_limits(wr, st->tables[first]->min_update_index, + st->tables[last]->max_update_index); + if (err < 0) + goto done; + + err = reftable_merged_table_new(&mt, st->tables + first, subtabs_len, + st->opts.hash_id); + if (err < 0) + goto done; + + err = merged_table_init_iter(mt, &it, REFTABLE_BLOCK_TYPE_REF); + if (err < 0) + goto done; + + err = reftable_iterator_seek_ref(&it, ""); + if (err < 0) + goto done; + + while (1) { + err = reftable_iterator_next_ref(&it, &ref); + if (err > 0) { + err = 0; + break; + } + if (err < 0) + goto done; + + if (first == 0 && reftable_ref_record_is_deletion(&ref)) { + continue; + } + + err = reftable_writer_add_ref(wr, &ref); + if (err < 0) + goto done; + entries++; + } + reftable_iterator_destroy(&it); + + err = merged_table_init_iter(mt, &it, REFTABLE_BLOCK_TYPE_LOG); + if (err < 0) + goto done; + + err = reftable_iterator_seek_log(&it, ""); + if (err < 0) + goto done; + + while (1) { + err = reftable_iterator_next_log(&it, &log); + if (err > 0) { + err = 0; + break; + } + if (err < 0) + goto done; + if (first == 0 && reftable_log_record_is_deletion(&log)) { + continue; + } + + if (config && config->min_update_index > 0 && + log.update_index < config->min_update_index) { + continue; + } + + if (config && config->time > 0 && + log.value.update.time < config->time) { + continue; + } + + err = reftable_writer_add_log(wr, &log); + if (err < 0) + goto done; + entries++; + } + +done: + reftable_iterator_destroy(&it); + if (mt) + reftable_merged_table_free(mt); + reftable_ref_record_release(&ref); + reftable_log_record_release(&log); + st->stats.entries_written += entries; + return err; +} + +enum stack_compact_range_flags { + /* + * Perform a best-effort compaction. That is, even if we cannot lock + * all tables in the specified range, we will try to compact the + * remaining slice. + */ + STACK_COMPACT_RANGE_BEST_EFFORT = (1 << 0), +}; + +/* + * Compact all tables in the range `[first, last)` into a single new table. + * + * This function returns `0` on success or a code `< 0` on failure. When the + * stack or any of the tables in the specified range are already locked then + * this function returns `REFTABLE_LOCK_ERROR`. This is a benign error that + * callers can either ignore, or they may choose to retry compaction after some + * amount of time. + */ +static int stack_compact_range(struct reftable_stack *st, + size_t first, size_t last, + struct reftable_log_expiry_config *expiry, + unsigned int flags) +{ + struct reftable_buf tables_list_buf = REFTABLE_BUF_INIT; + struct reftable_buf new_table_name = REFTABLE_BUF_INIT; + struct reftable_buf new_table_path = REFTABLE_BUF_INIT; + struct reftable_buf table_name = REFTABLE_BUF_INIT; + struct reftable_flock tables_list_lock = REFTABLE_FLOCK_INIT; + struct reftable_flock *table_locks = NULL; + struct reftable_tmpfile new_table = REFTABLE_TMPFILE_INIT; + int is_empty_table = 0, err = 0; + size_t first_to_replace, last_to_replace; + size_t i, nlocks = 0; + char **names = NULL; + + if (first > last || (!expiry && first == last)) { + err = 0; + goto done; + } + + st->stats.attempts++; + + /* + * Hold the lock so that we can read "tables.list" and lock all tables + * which are part of the user-specified range. + */ + err = flock_acquire(&tables_list_lock, st->list_file, st->opts.lock_timeout_ms); + if (err < 0) { + if (errno == EEXIST) + err = REFTABLE_LOCK_ERROR; + else + err = REFTABLE_IO_ERROR; + goto done; + } + + err = stack_uptodate(st); + if (err) + goto done; + + /* + * Lock all tables in the user-provided range. This is the slice of our + * stack which we'll compact. + * + * Note that we lock tables in reverse order from last to first. The + * intent behind this is to allow a newer process to perform best + * effort compaction of tables that it has added in the case where an + * older process is still busy compacting tables which are preexisting + * from the point of view of the newer process. + */ + REFTABLE_ALLOC_ARRAY(table_locks, last - first + 1); + if (!table_locks) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + for (i = 0; i < last - first + 1; i++) + table_locks[i] = REFTABLE_FLOCK_INIT; + + for (i = last + 1; i > first; i--) { + err = stack_filename(&table_name, st, reftable_table_name(st->tables[i - 1])); + if (err < 0) + goto done; + + err = flock_acquire(&table_locks[nlocks], table_name.buf, 0); + if (err < 0) { + /* + * When the table is locked already we may do a + * best-effort compaction and compact only the tables + * that we have managed to lock so far. This of course + * requires that we have been able to lock at least two + * tables, otherwise there would be nothing to compact. + * In that case, we return a lock error to our caller. + */ + if (errno == EEXIST && last - (i - 1) >= 2 && + flags & STACK_COMPACT_RANGE_BEST_EFFORT) { + err = 0; + /* + * The subtraction is to offset the index, the + * addition is to only compact up to the table + * of the preceding iteration. They obviously + * cancel each other out, but that may be + * non-obvious when it was omitted. + */ + first = (i - 1) + 1; + break; + } else if (errno == EEXIST) { + err = REFTABLE_LOCK_ERROR; + goto done; + } else { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + /* + * We need to close the lockfiles as we might otherwise easily + * run into file descriptor exhaustion when we compress a lot + * of tables. + */ + err = flock_close(&table_locks[nlocks++]); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + /* + * We have locked all tables in our range and can thus release the + * "tables.list" lock while compacting the locked tables. This allows + * concurrent updates to the stack to proceed. + */ + err = flock_release(&tables_list_lock); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + /* + * Compact the now-locked tables into a new table. Note that compacting + * these tables may end up with an empty new table in case tombstones + * end up cancelling out all refs in that range. + */ + err = stack_compact_locked(st, first, last, expiry, &new_table); + if (err < 0) { + if (err != REFTABLE_EMPTY_TABLE_ERROR) + goto done; + is_empty_table = 1; + } + + /* + * Now that we have written the new, compacted table we need to re-lock + * "tables.list". We'll then replace the compacted range of tables with + * the new table. + */ + err = flock_acquire(&tables_list_lock, st->list_file, st->opts.lock_timeout_ms); + if (err < 0) { + if (errno == EEXIST) + err = REFTABLE_LOCK_ERROR; + else + err = REFTABLE_IO_ERROR; + goto done; + } + + if (st->opts.default_permissions) { + if (chmod(tables_list_lock.path, + st->opts.default_permissions) < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + /* + * As we have unlocked the stack while compacting our slice of tables + * it may have happened that a concurrently running process has updated + * the stack while we were compacting. In that case, we need to check + * whether the tables that we have just compacted still exist in the + * stack in the exact same order as we have compacted them. + * + * If they do exist, then it is fine to continue and replace those + * tables with our compacted version. If they don't, then we need to + * abort. + */ + err = stack_uptodate(st); + if (err < 0) + goto done; + if (err > 0) { + ssize_t new_offset = -1; + int fd; + + fd = open(st->list_file, O_RDONLY); + if (fd < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + err = fd_read_lines(fd, &names); + close(fd); + if (err < 0) + goto done; + + /* + * Search for the offset of the first table that we have + * compacted in the updated "tables.list" file. + */ + for (size_t i = 0; names[i]; i++) { + if (strcmp(names[i], st->tables[first]->name)) + continue; + + /* + * We have found the first entry. Verify that all the + * subsequent tables we have compacted still exist in + * the modified stack in the exact same order as we + * have compacted them. + */ + for (size_t j = 1; j < last - first + 1; j++) { + const char *old = first + j < st->merged->tables_len ? + st->tables[first + j]->name : NULL; + const char *new = names[i + j]; + + /* + * If some entries are missing or in case the tables + * have changed then we need to bail out. Again, this + * shouldn't ever happen because we have locked the + * tables we are compacting. + */ + if (!old || !new || strcmp(old, new)) { + err = REFTABLE_OUTDATED_ERROR; + goto done; + } + } + + new_offset = i; + break; + } + + /* + * In case we didn't find our compacted tables in the stack we + * need to bail out. In theory, this should have never happened + * because we locked the tables we are compacting. + */ + if (new_offset < 0) { + err = REFTABLE_OUTDATED_ERROR; + goto done; + } + + /* + * We have found the new range that we want to replace, so + * let's update the range of tables that we want to replace. + */ + first_to_replace = new_offset; + last_to_replace = last + (new_offset - first); + } else { + /* + * `fd_read_lines()` uses a `NULL` sentinel to indicate that + * the array is at its end. As we use `free_names()` to free + * the array, we need to include this sentinel value here and + * thus have to allocate `tables_len + 1` many entries. + */ + REFTABLE_CALLOC_ARRAY(names, st->merged->tables_len + 1); + if (!names) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + + for (size_t i = 0; i < st->merged->tables_len; i++) { + names[i] = reftable_strdup(st->tables[i]->name); + if (!names[i]) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + } + first_to_replace = first; + last_to_replace = last; + } + + /* + * If the resulting compacted table is not empty, then we need to move + * it into place now. + */ + if (!is_empty_table) { + err = format_name(&new_table_name, st->tables[first]->min_update_index, + st->tables[last]->max_update_index); + if (err < 0) + goto done; + + err = reftable_buf_addstr(&new_table_name, ".ref"); + if (err < 0) + goto done; + + err = stack_filename(&new_table_path, st, new_table_name.buf); + if (err < 0) + goto done; + + err = tmpfile_rename(&new_table, new_table_path.buf); + if (err < 0) + goto done; + } + + /* + * Write the new "tables.list" contents with the compacted table we + * have just written. In case the compacted table became empty we + * simply skip writing it. + */ + for (i = 0; i < first_to_replace; i++) { + if ((err = reftable_buf_addstr(&tables_list_buf, names[i])) < 0 || + (err = reftable_buf_addstr(&tables_list_buf, "\n")) < 0) + goto done; + } + if (!is_empty_table) { + if ((err = reftable_buf_addstr(&tables_list_buf, new_table_name.buf)) < 0 || + (err = reftable_buf_addstr(&tables_list_buf, "\n")) < 0) + goto done; + } + for (i = last_to_replace + 1; names[i]; i++) { + if ((err = reftable_buf_addstr(&tables_list_buf, names[i])) < 0 || + (err = reftable_buf_addstr(&tables_list_buf, "\n")) < 0) + goto done; + } + + err = reftable_write_data(tables_list_lock.fd, + tables_list_buf.buf, tables_list_buf.len); + if (err < 0) { + err = REFTABLE_IO_ERROR; + unlink(new_table_path.buf); + goto done; + } + + err = stack_fsync(&st->opts, tables_list_lock.fd); + if (err < 0) { + err = REFTABLE_IO_ERROR; + unlink(new_table_path.buf); + goto done; + } + + err = flock_commit(&tables_list_lock); + if (err < 0) { + err = REFTABLE_IO_ERROR; + unlink(new_table_path.buf); + goto done; + } + + /* + * Reload the stack before deleting the compacted tables. We can only + * delete the files after we closed them on Windows, so this needs to + * happen first. + */ + err = reftable_stack_reload_maybe_reuse(st, first < last); + if (err < 0) + goto done; + + /* + * Delete the old tables. They may still be in use by concurrent + * readers, so it is expected that unlinking tables may fail. + */ + for (i = 0; i < nlocks; i++) { + struct reftable_flock *table_lock = &table_locks[i]; + + reftable_buf_reset(&table_name); + err = reftable_buf_add(&table_name, table_lock->path, + strlen(table_lock->path) - strlen(".lock")); + if (err) + continue; + + unlink(table_name.buf); + } + +done: + flock_release(&tables_list_lock); + for (i = 0; table_locks && i < nlocks; i++) + flock_release(&table_locks[i]); + reftable_free(table_locks); + + tmpfile_delete(&new_table); + reftable_buf_release(&new_table_name); + reftable_buf_release(&new_table_path); + reftable_buf_release(&tables_list_buf); + reftable_buf_release(&table_name); + free_names(names); + + if (err == REFTABLE_LOCK_ERROR) + st->stats.failures++; + + return err; +} + +int reftable_stack_compact_all(struct reftable_stack *st, + struct reftable_log_expiry_config *config) +{ + size_t last = st->merged->tables_len ? st->merged->tables_len - 1 : 0; + return stack_compact_range(st, 0, last, config, 0); +} + +static int segment_size(struct segment *s) +{ + return s->end - s->start; +} + +struct segment suggest_compaction_segment(uint64_t *sizes, size_t n, + uint8_t factor) +{ + struct segment seg = { 0 }; + uint64_t bytes; + size_t i; + + if (!factor) + factor = DEFAULT_GEOMETRIC_FACTOR; + + /* + * If there are no tables or only a single one then we don't have to + * compact anything. The sequence is geometric by definition already. + */ + if (n <= 1) + return seg; + + /* + * Find the ending table of the compaction segment needed to restore the + * geometric sequence. Note that the segment end is exclusive. + * + * To do so, we iterate backwards starting from the most recent table + * until a valid segment end is found. If the preceding table is smaller + * than the current table multiplied by the geometric factor (2), the + * compaction segment end has been identified. + * + * Tables after the ending point are not added to the byte count because + * they are already valid members of the geometric sequence. Due to the + * properties of a geometric sequence, it is not possible for the sum of + * these tables to exceed the value of the ending point table. + * + * Example table size sequence requiring no compaction: + * 64, 32, 16, 8, 4, 2, 1 + * + * Example table size sequence where compaction segment end is set to + * the last table. Since the segment end is exclusive, the last table is + * excluded during subsequent compaction and the table with size 3 is + * the final table included: + * 64, 32, 16, 8, 4, 3, 1 + */ + for (i = n - 1; i > 0; i--) { + if (sizes[i - 1] < sizes[i] * factor) { + seg.end = i + 1; + bytes = sizes[i]; + break; + } + } + + /* + * Find the starting table of the compaction segment by iterating + * through the remaining tables and keeping track of the accumulated + * size of all tables seen from the segment end table. The previous + * table is compared to the accumulated size because the tables from the + * segment end are merged backwards recursively. + * + * Note that we keep iterating even after we have found the first + * starting point. This is because there may be tables in the stack + * preceding that first starting point which violate the geometric + * sequence. + * + * Example compaction segment start set to table with size 32: + * 128, 32, 16, 8, 4, 3, 1 + */ + for (; i > 0; i--) { + uint64_t curr = bytes; + bytes += sizes[i - 1]; + + if (sizes[i - 1] < curr * factor) { + seg.start = i - 1; + seg.bytes = bytes; + } + } + + return seg; +} + +static uint64_t *stack_table_sizes_for_compaction(struct reftable_stack *st) +{ + int version = (st->opts.hash_id == REFTABLE_HASH_SHA1) ? 1 : 2; + int overhead = header_size(version) - 1; + uint64_t *sizes; + + REFTABLE_CALLOC_ARRAY(sizes, st->merged->tables_len); + if (!sizes) + return NULL; + + for (size_t i = 0; i < st->merged->tables_len; i++) + sizes[i] = st->tables[i]->size - overhead; + + return sizes; +} + +int reftable_stack_auto_compact(struct reftable_stack *st) +{ + struct segment seg; + uint64_t *sizes; + + if (st->merged->tables_len < 2) + return 0; + + sizes = stack_table_sizes_for_compaction(st); + if (!sizes) + return REFTABLE_OUT_OF_MEMORY_ERROR; + + seg = suggest_compaction_segment(sizes, st->merged->tables_len, + st->opts.auto_compaction_factor); + reftable_free(sizes); + + if (segment_size(&seg) > 0) + return stack_compact_range(st, seg.start, seg.end - 1, + NULL, STACK_COMPACT_RANGE_BEST_EFFORT); + + return 0; +} + +struct reftable_compaction_stats * +reftable_stack_compaction_stats(struct reftable_stack *st) +{ + return &st->stats; +} + +int reftable_stack_read_ref(struct reftable_stack *st, const char *refname, + struct reftable_ref_record *ref) +{ + struct reftable_iterator it = { 0 }; + int ret; + + ret = reftable_merged_table_init_ref_iterator(st->merged, &it); + if (ret) + goto out; + + ret = reftable_iterator_seek_ref(&it, refname); + if (ret) + goto out; + + ret = reftable_iterator_next_ref(&it, ref); + if (ret) + goto out; + + if (strcmp(ref->refname, refname) || + reftable_ref_record_is_deletion(ref)) { + reftable_ref_record_release(ref); + ret = 1; + goto out; + } + +out: + reftable_iterator_destroy(&it); + return ret; +} + +int reftable_stack_read_log(struct reftable_stack *st, const char *refname, + struct reftable_log_record *log) +{ + struct reftable_iterator it = {0}; + int err; + + err = reftable_stack_init_log_iterator(st, &it); + if (err) + goto done; + + err = reftable_iterator_seek_log(&it, refname); + if (err) + goto done; + + err = reftable_iterator_next_log(&it, log); + if (err) + goto done; + + if (strcmp(log->refname, refname) || + reftable_log_record_is_deletion(log)) { + err = 1; + goto done; + } + +done: + if (err) { + reftable_log_record_release(log); + } + reftable_iterator_destroy(&it); + return err; +} + +static int is_table_name(const char *s) +{ + const char *dot = strrchr(s, '.'); + return dot && !strcmp(dot, ".ref"); +} + +static void remove_maybe_stale_table(struct reftable_stack *st, uint64_t max, + const char *name) +{ + int err = 0; + uint64_t update_idx = 0; + struct reftable_block_source src = { NULL }; + struct reftable_table *table = NULL; + struct reftable_buf table_path = REFTABLE_BUF_INIT; + + err = stack_filename(&table_path, st, name); + if (err < 0) + goto done; + + err = reftable_block_source_from_file(&src, table_path.buf); + if (err < 0) + goto done; + + err = reftable_table_new(&table, &src, name); + if (err < 0) + goto done; + + update_idx = reftable_table_max_update_index(table); + reftable_table_decref(table); + + if (update_idx <= max) { + unlink(table_path.buf); + } +done: + reftable_buf_release(&table_path); +} + +static int reftable_stack_clean_locked(struct reftable_stack *st) +{ + uint64_t max = reftable_merged_table_max_update_index( + reftable_stack_merged_table(st)); + DIR *dir = opendir(st->reftable_dir); + struct dirent *d = NULL; + if (!dir) { + return REFTABLE_IO_ERROR; + } + + while ((d = readdir(dir))) { + int found = 0; + if (!is_table_name(d->d_name)) + continue; + + for (size_t i = 0; !found && i < st->tables_len; i++) + found = !strcmp(reftable_table_name(st->tables[i]), d->d_name); + if (found) + continue; + + remove_maybe_stale_table(st, max, d->d_name); + } + + closedir(dir); + return 0; +} + +int reftable_stack_clean(struct reftable_stack *st) +{ + struct reftable_addition *add = NULL; + int err = reftable_stack_new_addition(&add, st, 0); + if (err < 0) { + goto done; + } + + err = reftable_stack_reload(st); + if (err < 0) { + goto done; + } + + err = reftable_stack_clean_locked(st); + +done: + reftable_addition_destroy(add); + return err; +} + +enum reftable_hash reftable_stack_hash_id(struct reftable_stack *st) +{ + return reftable_merged_table_hash_id(st->merged); +} |