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1830 lines (1568 loc) · 44.5 KB
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Copy pathstack.c
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1830 lines (1568 loc) · 44.5 KB
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/*
* 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_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 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 fsync(writer->fd);
}
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;
err = 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);
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;
}
static int reftable_stack_reload_maybe_reuse(struct reftable_stack *st,
int reuse_open)
{
char **names = NULL, **names_after = NULL;
uint64_t deadline;
int64_t delay = 0;
int tries = 0, err;
int fd = -1;
deadline = reftable_time_ms() + 3000;
while (1) {
uint64_t now = reftable_time_ms();
/*
* Only look at deadlines after the first few times. This
* simplifies debugging in GDB.
*/
tries++;
if (tries > 3 && now >= deadline)
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;
}
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;
}
/*
* Check whether the given stack is up-to-date with what we have in memory.
* Returns 0 if so, 1 if the stack is out-of-date or a negative error code
* otherwise.
*/
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;
}
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;
};
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);
}
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;
memset(add, 0, sizeof(*add));
add->stack = st;
err = flock_acquire(&add->tables_list_lock, st->list_file,
st->opts.lock_timeout_ms);
if (err < 0)
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 int stack_try_add(struct reftable_stack *st,
int (*write_table)(struct reftable_writer *wr,
void *arg),
void *arg, unsigned flags)
{
struct reftable_addition add;
int err;
err = reftable_stack_init_addition(&add, st, flags);
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_stack_add(struct reftable_stack *st,
int (*write)(struct reftable_writer *wr, void *arg),
void *arg, unsigned flags)
{
int err = stack_try_add(st, write, arg, flags);
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);
}
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 = fsync(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. Similarly, the stack may have been rewritten by a
* concurrent writer, which causes `REFTABLE_OUTDATED_ERROR`.
* Both of these errors are benign, so we simply ignore them.
*/
err = reftable_stack_auto_compact(add->stack);
if (err < 0 && err != REFTABLE_LOCK_ERROR &&
err != REFTABLE_OUTDATED_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;
REFTABLE_CALLOC_ARRAY(*dest, 1);
if (!*dest)
return REFTABLE_OUT_OF_MEMORY_ERROR;
err = reftable_stack_init_addition(*dest, st, flags);
if (err) {
reftable_free(*dest);
*dest = NULL;
}
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_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) {
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