diff options
Diffstat (limited to 'reftable/stack.c')
| -rw-r--r-- | reftable/stack.c | 1518 |
1 files changed, 1518 insertions, 0 deletions
diff --git a/reftable/stack.c b/reftable/stack.c new file mode 100644 index 0000000..80266bc --- /dev/null +++ b/reftable/stack.c @@ -0,0 +1,1518 @@ +/* +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 "../write-or-die.h" +#include "system.h" +#include "merged.h" +#include "reader.h" +#include "refname.h" +#include "reftable-error.h" +#include "reftable-record.h" +#include "reftable-merged.h" +#include "writer.h" +#include "tempfile.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 int stack_check_addition(struct reftable_stack *st, + const char *new_tab_name); +static void reftable_addition_close(struct reftable_addition *add); +static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st, + int reuse_open); + +static void stack_filename(struct strbuf *dest, struct reftable_stack *st, + const char *name) +{ + strbuf_reset(dest); + strbuf_addstr(dest, st->reftable_dir); + strbuf_addstr(dest, "/"); + strbuf_addstr(dest, name); +} + +static ssize_t reftable_fd_write(void *arg, const void *data, size_t sz) +{ + int *fdp = (int *)arg; + return write_in_full(*fdp, data, sz); +} + +static int reftable_fd_flush(void *arg) +{ + int *fdp = (int *)arg; + + return fsync_component(FSYNC_COMPONENT_REFERENCE, *fdp); +} + +int reftable_new_stack(struct reftable_stack **dest, const char *dir, + struct reftable_write_options config) +{ + struct reftable_stack *p = reftable_calloc(1, sizeof(*p)); + struct strbuf list_file_name = STRBUF_INIT; + int err = 0; + + if (config.hash_id == 0) { + config.hash_id = GIT_SHA1_FORMAT_ID; + } + + *dest = NULL; + + strbuf_reset(&list_file_name); + strbuf_addstr(&list_file_name, dir); + strbuf_addstr(&list_file_name, "/tables.list"); + + p->list_file = strbuf_detach(&list_file_name, NULL); + p->list_fd = -1; + p->reftable_dir = xstrdup(dir); + p->config = config; + + err = reftable_stack_reload_maybe_reuse(p, 1); + if (err < 0) { + reftable_stack_destroy(p); + } else { + *dest = p; + } + return err; +} + +static int fd_read_lines(int fd, char ***namesp) +{ + off_t size = lseek(fd, 0, SEEK_END); + char *buf = NULL; + int err = 0; + 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 (read_in_full(fd, buf, size) != size) { + err = REFTABLE_IO_ERROR; + goto done; + } + buf[size] = 0; + + parse_names(buf, size, namesp); + +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); + return 0; + } + + return REFTABLE_IO_ERROR; + } + err = fd_read_lines(fd, namesp); + close(fd); + return err; +} + +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->merged) { + reftable_merged_table_free(st->merged); + st->merged = NULL; + } + + err = read_lines(st->list_file, &names); + if (err < 0) { + FREE_AND_NULL(names); + } + + if (st->readers) { + int i = 0; + struct strbuf filename = STRBUF_INIT; + for (i = 0; i < st->readers_len; i++) { + const char *name = reader_name(st->readers[i]); + strbuf_reset(&filename); + if (names && !has_name(names, name)) { + stack_filename(&filename, st, name); + } + reftable_reader_free(st->readers[i]); + + if (filename.len) { + /* On Windows, can only unlink after closing. */ + unlink(filename.buf); + } + } + strbuf_release(&filename); + st->readers_len = 0; + FREE_AND_NULL(st->readers); + } + + if (st->list_fd >= 0) { + close(st->list_fd); + st->list_fd = -1; + } + + FREE_AND_NULL(st->list_file); + FREE_AND_NULL(st->reftable_dir); + reftable_free(st); + free_names(names); +} + +static struct reftable_reader **stack_copy_readers(struct reftable_stack *st, + int cur_len) +{ + struct reftable_reader **cur = reftable_calloc(cur_len, sizeof(*cur)); + int i = 0; + for (i = 0; i < cur_len; i++) { + cur[i] = st->readers[i]; + } + return cur; +} + +static int reftable_stack_reload_once(struct reftable_stack *st, char **names, + int reuse_open) +{ + size_t cur_len = !st->merged ? 0 : st->merged->stack_len; + struct reftable_reader **cur = stack_copy_readers(st, cur_len); + size_t names_len = names_length(names); + struct reftable_reader **new_readers = + reftable_calloc(names_len, sizeof(*new_readers)); + struct reftable_table *new_tables = + reftable_calloc(names_len, sizeof(*new_tables)); + size_t new_readers_len = 0; + struct reftable_merged_table *new_merged = NULL; + struct strbuf table_path = STRBUF_INIT; + int err = 0; + size_t i; + + while (*names) { + struct reftable_reader *rd = NULL; + 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)) { + rd = cur[i]; + cur[i] = NULL; + break; + } + } + + if (!rd) { + struct reftable_block_source src = { NULL }; + stack_filename(&table_path, st, name); + + err = reftable_block_source_from_file(&src, + table_path.buf); + if (err < 0) + goto done; + + err = reftable_new_reader(&rd, &src, name); + if (err < 0) + goto done; + } + + new_readers[new_readers_len] = rd; + reftable_table_from_reader(&new_tables[new_readers_len], rd); + new_readers_len++; + } + + /* success! */ + err = reftable_new_merged_table(&new_merged, new_tables, + new_readers_len, st->config.hash_id); + if (err < 0) + goto done; + + new_tables = NULL; + st->readers_len = new_readers_len; + if (st->merged) { + merged_table_release(st->merged); + reftable_merged_table_free(st->merged); + } + if (st->readers) { + reftable_free(st->readers); + } + st->readers = new_readers; + new_readers = NULL; + new_readers_len = 0; + + new_merged->suppress_deletions = 1; + st->merged = new_merged; + for (i = 0; i < cur_len; i++) { + if (cur[i]) { + const char *name = reader_name(cur[i]); + stack_filename(&table_path, st, name); + + reader_close(cur[i]); + reftable_reader_free(cur[i]); + + /* On Windows, can only unlink after closing. */ + unlink(table_path.buf); + } + } + +done: + for (i = 0; i < new_readers_len; i++) { + reader_close(new_readers[i]); + reftable_reader_free(new_readers[i]); + } + reftable_free(new_readers); + reftable_free(new_tables); + reftable_free(cur); + strbuf_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); + } else { + err = fd_read_lines(fd, &names); + if (err < 0) + goto out; + } + + err = reftable_stack_reload_once(st, 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(names_after, 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 * rand()) / RAND_MAX + 1; + sleep_millisec(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); + return err; +} + +/* -1 = error + 0 = up to date + 1 = changed. */ +static int stack_uptodate(struct reftable_stack *st) +{ + char **names = NULL; + int err; + int i = 0; + + /* + * 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 readers. + */ + if (errno == ENOENT) + return !!st->readers_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 (i = 0; i < st->readers_len; i++) { + if (!names[i]) { + err = 1; + goto done; + } + + if (strcmp(st->readers[i]->name, names[i])) { + err = 1; + goto done; + } + } + + if (names[st->merged->stack_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 void format_name(struct strbuf *dest, uint64_t min, uint64_t max) +{ + char buf[100]; + uint32_t rnd = (uint32_t)git_rand(); + snprintf(buf, sizeof(buf), "0x%012" PRIx64 "-0x%012" PRIx64 "-%08x", + min, max, rnd); + strbuf_reset(dest); + strbuf_addstr(dest, buf); +} + +struct reftable_addition { + struct tempfile *lock_file; + 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) +{ + struct strbuf lock_file_name = STRBUF_INIT; + int err = 0; + add->stack = st; + + strbuf_addf(&lock_file_name, "%s.lock", st->list_file); + + add->lock_file = create_tempfile(lock_file_name.buf); + if (!add->lock_file) { + if (errno == EEXIST) { + err = REFTABLE_LOCK_ERROR; + } else { + err = REFTABLE_IO_ERROR; + } + goto done; + } + if (st->config.default_permissions) { + if (chmod(add->lock_file->filename.buf, st->config.default_permissions) < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + err = stack_uptodate(st); + if (err < 0) + 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); + } + strbuf_release(&lock_file_name); + return err; +} + +static void reftable_addition_close(struct reftable_addition *add) +{ + struct strbuf nm = STRBUF_INIT; + size_t i; + + for (i = 0; i < add->new_tables_len; i++) { + 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; + + delete_tempfile(&add->lock_file); + strbuf_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 strbuf table_list = STRBUF_INIT; + int lock_file_fd = get_tempfile_fd(add->lock_file); + int err = 0; + size_t i; + + if (add->new_tables_len == 0) + goto done; + + for (i = 0; i < add->stack->merged->stack_len; i++) { + strbuf_addstr(&table_list, add->stack->readers[i]->name); + strbuf_addstr(&table_list, "\n"); + } + for (i = 0; i < add->new_tables_len; i++) { + strbuf_addstr(&table_list, add->new_tables[i]); + strbuf_addstr(&table_list, "\n"); + } + + err = write_in_full(lock_file_fd, table_list.buf, table_list.len); + strbuf_release(&table_list); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + fsync_component_or_die(FSYNC_COMPONENT_REFERENCE, lock_file_fd, + get_tempfile_path(add->lock_file)); + + err = rename_tempfile(&add->lock_file, add->stack->list_file); + 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->config.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) +{ + int err = 0; + struct reftable_addition empty = REFTABLE_ADDITION_INIT; + REFTABLE_CALLOC_ARRAY(*dest, 1); + **dest = empty; + err = reftable_stack_init_addition(*dest, st); + 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); + 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 strbuf temp_tab_file_name = STRBUF_INIT; + struct strbuf tab_file_name = STRBUF_INIT; + struct strbuf next_name = STRBUF_INIT; + struct reftable_writer *wr = NULL; + struct tempfile *tab_file = NULL; + int err = 0; + int tab_fd; + + strbuf_reset(&next_name); + format_name(&next_name, add->next_update_index, add->next_update_index); + + stack_filename(&temp_tab_file_name, add->stack, next_name.buf); + strbuf_addstr(&temp_tab_file_name, ".temp.XXXXXX"); + + tab_file = mks_tempfile(temp_tab_file_name.buf); + if (!tab_file) { + err = REFTABLE_IO_ERROR; + goto done; + } + if (add->stack->config.default_permissions) { + if (chmod(get_tempfile_path(tab_file), + add->stack->config.default_permissions)) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + tab_fd = get_tempfile_fd(tab_file); + + wr = reftable_new_writer(reftable_fd_write, reftable_fd_flush, &tab_fd, + &add->stack->config); + 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 = close_tempfile_gently(tab_file); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + err = stack_check_addition(add->stack, get_tempfile_path(tab_file)); + if (err < 0) + goto done; + + if (wr->min_update_index < add->next_update_index) { + err = REFTABLE_API_ERROR; + goto done; + } + + format_name(&next_name, wr->min_update_index, wr->max_update_index); + strbuf_addstr(&next_name, ".ref"); + stack_filename(&tab_file_name, add->stack, next_name.buf); + + /* + On windows, this relies on rand() picking a unique destination name. + Maybe we should do retry loop as well? + */ + err = rename_tempfile(&tab_file, tab_file_name.buf); + if (err < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + REFTABLE_ALLOC_GROW(add->new_tables, add->new_tables_len + 1, + add->new_tables_cap); + add->new_tables[add->new_tables_len++] = strbuf_detach(&next_name, NULL); +done: + delete_tempfile(&tab_file); + strbuf_release(&temp_tab_file_name); + strbuf_release(&tab_file_name); + strbuf_release(&next_name); + reftable_writer_free(wr); + return err; +} + +uint64_t reftable_stack_next_update_index(struct reftable_stack *st) +{ + int sz = st->merged->stack_len; + if (sz > 0) + return reftable_reader_max_update_index(st->readers[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 tempfile **tab_file_out) +{ + struct strbuf next_name = STRBUF_INIT; + struct strbuf tab_file_path = STRBUF_INIT; + struct reftable_writer *wr = NULL; + struct tempfile *tab_file; + int tab_fd, err = 0; + + format_name(&next_name, + reftable_reader_min_update_index(st->readers[first]), + reftable_reader_max_update_index(st->readers[last])); + stack_filename(&tab_file_path, st, next_name.buf); + strbuf_addstr(&tab_file_path, ".temp.XXXXXX"); + + tab_file = mks_tempfile(tab_file_path.buf); + if (!tab_file) { + err = REFTABLE_IO_ERROR; + goto done; + } + tab_fd = get_tempfile_fd(tab_file); + + if (st->config.default_permissions && + chmod(get_tempfile_path(tab_file), st->config.default_permissions) < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + + wr = reftable_new_writer(reftable_fd_write, reftable_fd_flush, + &tab_fd, &st->config); + 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 = close_tempfile_gently(tab_file); + if (err < 0) + goto done; + + *tab_file_out = tab_file; + tab_file = NULL; + +done: + delete_tempfile(&tab_file); + reftable_writer_free(wr); + strbuf_release(&next_name); + strbuf_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) +{ + size_t subtabs_len = last - first + 1; + struct reftable_table *subtabs = reftable_calloc( + last - first + 1, sizeof(*subtabs)); + struct reftable_merged_table *mt = NULL; + struct reftable_iterator it = { NULL }; + struct reftable_ref_record ref = { NULL }; + struct reftable_log_record log = { NULL }; + uint64_t entries = 0; + int err = 0; + + for (size_t i = first, j = 0; i <= last; i++) { + struct reftable_reader *t = st->readers[i]; + reftable_table_from_reader(&subtabs[j++], t); + st->stats.bytes += t->size; + } + reftable_writer_set_limits(wr, st->readers[first]->min_update_index, + st->readers[last]->max_update_index); + + err = reftable_new_merged_table(&mt, subtabs, subtabs_len, + st->config.hash_id); + if (err < 0) { + reftable_free(subtabs); + goto done; + } + + err = reftable_merged_table_seek_ref(mt, &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 = reftable_merged_table_seek_log(mt, &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) { + merged_table_release(mt); + reftable_merged_table_free(mt); + } + reftable_ref_record_release(&ref); + reftable_log_record_release(&log); + st->stats.entries_written += entries; + return err; +} + +/* + * 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) +{ + struct strbuf tables_list_buf = STRBUF_INIT; + struct strbuf new_table_name = STRBUF_INIT; + struct strbuf new_table_path = STRBUF_INIT; + struct strbuf table_name = STRBUF_INIT; + struct lock_file tables_list_lock = LOCK_INIT; + struct lock_file *table_locks = NULL; + struct tempfile *new_table = NULL; + int is_empty_table = 0, err = 0; + size_t i; + + 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 = hold_lock_file_for_update(&tables_list_lock, st->list_file, + LOCK_NO_DEREF); + 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. + */ + REFTABLE_CALLOC_ARRAY(table_locks, last - first + 1); + for (i = first; i <= last; i++) { + stack_filename(&table_name, st, reader_name(st->readers[i])); + + err = hold_lock_file_for_update(&table_locks[i - first], + table_name.buf, LOCK_NO_DEREF); + if (err < 0) { + if (errno == EEXIST) + err = REFTABLE_LOCK_ERROR; + 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 = close_lock_file_gently(&table_locks[i - first]); + 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 = rollback_lock_file(&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 = hold_lock_file_for_update(&tables_list_lock, st->list_file, + LOCK_NO_DEREF); + if (err < 0) { + if (errno == EEXIST) + err = REFTABLE_LOCK_ERROR; + else + err = REFTABLE_IO_ERROR; + goto done; + } + + if (st->config.default_permissions) { + if (chmod(get_lock_file_path(&tables_list_lock), + st->config.default_permissions) < 0) { + err = REFTABLE_IO_ERROR; + goto done; + } + } + + /* + * If the resulting compacted table is not empty, then we need to move + * it into place now. + */ + if (!is_empty_table) { + format_name(&new_table_name, st->readers[first]->min_update_index, + st->readers[last]->max_update_index); + strbuf_addstr(&new_table_name, ".ref"); + stack_filename(&new_table_path, st, new_table_name.buf); + + err = rename_tempfile(&new_table, new_table_path.buf); + if (err < 0) { + err = REFTABLE_IO_ERROR; + 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; i++) + strbuf_addf(&tables_list_buf, "%s\n", st->readers[i]->name); + if (!is_empty_table) + strbuf_addf(&tables_list_buf, "%s\n", new_table_name.buf); + for (i = last + 1; i < st->merged->stack_len; i++) + strbuf_addf(&tables_list_buf, "%s\n", st->readers[i]->name); + + err = write_in_full(get_lock_file_fd(&tables_list_lock), + tables_list_buf.buf, tables_list_buf.len); + if (err < 0) { + err = REFTABLE_IO_ERROR; + unlink(new_table_path.buf); + goto done; + } + + err = fsync_component(FSYNC_COMPONENT_REFERENCE, get_lock_file_fd(&tables_list_lock)); + if (err < 0) { + err = REFTABLE_IO_ERROR; + unlink(new_table_path.buf); + goto done; + } + + err = commit_lock_file(&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 = first; i <= last; i++) { + struct lock_file *table_lock = &table_locks[i - first]; + char *table_path = get_locked_file_path(table_lock); + unlink(table_path); + free(table_path); + } + +done: + rollback_lock_file(&tables_list_lock); + for (i = first; table_locks && i <= last; i++) + rollback_lock_file(&table_locks[i - first]); + reftable_free(table_locks); + + delete_tempfile(&new_table); + strbuf_release(&new_table_name); + strbuf_release(&new_table_path); + + strbuf_release(&tables_list_buf); + strbuf_release(&table_name); + return err; +} + +int reftable_stack_compact_all(struct reftable_stack *st, + struct reftable_log_expiry_config *config) +{ + return stack_compact_range(st, 0, st->merged->stack_len ? + st->merged->stack_len - 1 : 0, config); +} + +static int stack_compact_range_stats(struct reftable_stack *st, + size_t first, size_t last, + struct reftable_log_expiry_config *config) +{ + int err = stack_compact_range(st, first, last, config); + if (err == REFTABLE_LOCK_ERROR) + st->stats.failures++; + return err; +} + +static int segment_size(struct segment *s) +{ + return s->end - s->start; +} + +struct segment suggest_compaction_segment(uint64_t *sizes, size_t n) +{ + struct segment seg = { 0 }; + uint64_t bytes; + size_t i; + + /* + * 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] * 2) { + 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 * 2) { + seg.start = i - 1; + seg.bytes = bytes; + } + } + + return seg; +} + +static uint64_t *stack_table_sizes_for_compaction(struct reftable_stack *st) +{ + uint64_t *sizes = + reftable_calloc(st->merged->stack_len, sizeof(*sizes)); + int version = (st->config.hash_id == GIT_SHA1_FORMAT_ID) ? 1 : 2; + int overhead = header_size(version) - 1; + int i = 0; + for (i = 0; i < st->merged->stack_len; i++) { + sizes[i] = st->readers[i]->size - overhead; + } + return sizes; +} + +int reftable_stack_auto_compact(struct reftable_stack *st) +{ + uint64_t *sizes = stack_table_sizes_for_compaction(st); + struct segment seg = + suggest_compaction_segment(sizes, st->merged->stack_len); + reftable_free(sizes); + if (segment_size(&seg) > 0) + return stack_compact_range_stats(st, seg.start, seg.end - 1, + NULL); + + 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_table tab = { NULL }; + reftable_table_from_merged_table(&tab, reftable_stack_merged_table(st)); + return reftable_table_read_ref(&tab, refname, ref); +} + +int reftable_stack_read_log(struct reftable_stack *st, const char *refname, + struct reftable_log_record *log) +{ + struct reftable_iterator it = { NULL }; + struct reftable_merged_table *mt = reftable_stack_merged_table(st); + int err = reftable_merged_table_seek_log(mt, &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 stack_check_addition(struct reftable_stack *st, + const char *new_tab_name) +{ + int err = 0; + struct reftable_block_source src = { NULL }; + struct reftable_reader *rd = NULL; + struct reftable_table tab = { NULL }; + struct reftable_ref_record *refs = NULL; + struct reftable_iterator it = { NULL }; + int cap = 0; + int len = 0; + int i = 0; + + if (st->config.skip_name_check) + return 0; + + err = reftable_block_source_from_file(&src, new_tab_name); + if (err < 0) + goto done; + + err = reftable_new_reader(&rd, &src, new_tab_name); + if (err < 0) + goto done; + + err = reftable_reader_seek_ref(rd, &it, ""); + if (err > 0) { + err = 0; + goto done; + } + if (err < 0) + goto done; + + while (1) { + struct reftable_ref_record ref = { NULL }; + err = reftable_iterator_next_ref(&it, &ref); + if (err > 0) + break; + if (err < 0) + goto done; + + REFTABLE_ALLOC_GROW(refs, len + 1, cap); + refs[len++] = ref; + } + + reftable_table_from_merged_table(&tab, reftable_stack_merged_table(st)); + + err = validate_ref_record_addition(tab, refs, len); + +done: + for (i = 0; i < len; i++) { + reftable_ref_record_release(&refs[i]); + } + + free(refs); + reftable_iterator_destroy(&it); + reftable_reader_free(rd); + 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_reader *rd = NULL; + struct strbuf table_path = STRBUF_INIT; + stack_filename(&table_path, st, name); + + err = reftable_block_source_from_file(&src, table_path.buf); + if (err < 0) + goto done; + + err = reftable_new_reader(&rd, &src, name); + if (err < 0) + goto done; + + update_idx = reftable_reader_max_update_index(rd); + reftable_reader_free(rd); + + if (update_idx <= max) { + unlink(table_path.buf); + } +done: + strbuf_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 i = 0; + int found = 0; + if (!is_table_name(d->d_name)) + continue; + + for (i = 0; !found && i < st->readers_len; i++) { + found = !strcmp(reader_name(st->readers[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); + 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; +} + +int reftable_stack_print_directory(const char *stackdir, uint32_t hash_id) +{ + struct reftable_stack *stack = NULL; + struct reftable_write_options cfg = { .hash_id = hash_id }; + struct reftable_merged_table *merged = NULL; + struct reftable_table table = { NULL }; + + int err = reftable_new_stack(&stack, stackdir, cfg); + if (err < 0) + goto done; + + merged = reftable_stack_merged_table(stack); + reftable_table_from_merged_table(&table, merged); + err = reftable_table_print(&table); +done: + if (stack) + reftable_stack_destroy(stack); + return err; +} |