journal: implement parallel traversal in client

1 files changed, 1191 insertions, 0 deletions

diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
new file mode 100644
index 0000000000..37e2e37eb1
--- /dev/null
+++ b/src/journal/journal-file.c
@@ -0,0 +1,1191 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2011 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/mman.h>
+#include <errno.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <sys/statvfs.h>
+#include <fcntl.h>
+#include <stddef.h>
+
+#include "journal-def.h"
+#include "journal-file.h"
+#include "lookup3.h"
+
+#define DEFAULT_ARENA_MAX_SIZE (16ULL*1024ULL*1024ULL*1024ULL)
+#define DEFAULT_ARENA_MIN_SIZE (256ULL*1024ULL)
+#define DEFAULT_ARENA_KEEP_FREE (1ULL*1024ULL*1024ULL)
+
+#define DEFAULT_HASH_TABLE_SIZE (2047ULL*16ULL)
+#define DEFAULT_BISECT_TABLE_SIZE ((DEFAULT_ARENA_MAX_SIZE/(64ULL*1024ULL))*8ULL)
+
+#define DEFAULT_WINDOW_SIZE (128ULL*1024ULL*1024ULL)
+
+static const char signature[] = { 'L', 'P', 'K', 'S', 'H', 'H', 'R', 'H' };
+
+#define ALIGN64(x) (((x) + 7ULL) & ~7ULL)
+
+void journal_file_close(JournalFile *f) {
+        assert(f);
+
+        if (f->fd >= 0)
+                close_nointr_nofail(f->fd);
+
+        if (f->header)
+                munmap(f->header, PAGE_ALIGN(sizeof(Header)));
+
+        if (f->hash_table_window)
+                munmap(f->hash_table_window, f->hash_table_window_size);
+
+        if (f->bisect_table_window)
+                munmap(f->bisect_table_window, f->bisect_table_window_size);
+
+        if (f->window)
+                munmap(f->window, f->window_size);
+
+        free(f->path);
+        free(f);
+}
+
+static int journal_file_init_header(JournalFile *f) {
+        Header h;
+        ssize_t k;
+        int r;
+
+        assert(f);
+
+        zero(h);
+        memcpy(h.signature, signature, 8);
+        h.arena_offset = htole64(ALIGN64(sizeof(h)));
+        h.arena_max_size = htole64(DEFAULT_ARENA_MAX_SIZE);
+        h.arena_min_size = htole64(DEFAULT_ARENA_MIN_SIZE);
+        h.arena_keep_free = htole64(DEFAULT_ARENA_KEEP_FREE);
+
+        r = sd_id128_randomize(&h.file_id);
+        if (r < 0)
+                return r;
+
+        h.seqnum_id = h.file_id;
+
+        k = pwrite(f->fd, &h, sizeof(h), 0);
+        if (k < 0)
+                return -errno;
+
+        if (k != sizeof(h))
+                return -EIO;
+
+        return 0;
+}
+
+static int journal_file_refresh_header(JournalFile *f) {
+        int r;
+
+        assert(f);
+
+        r = sd_id128_get_machine(&f->header->machine_id);
+        if (r < 0)
+                return r;
+
+        r = sd_id128_get_boot(&f->header->boot_id);
+        if (r < 0)
+                return r;
+
+        f->header->state = htole32(STATE_ONLINE);
+        return 0;
+}
+
+static int journal_file_verify_header(JournalFile *f) {
+        assert(f);
+
+        if (memcmp(f->header, signature, 8))
+                return -EBADMSG;
+
+        if (f->header->incompatible_flags != 0)
+                return -EPROTONOSUPPORT;
+
+        if ((uint64_t) f->last_stat.st_size < (le64toh(f->header->arena_offset) + le64toh(f->header->arena_size)))
+                return -ENODATA;
+
+        if (f->writable) {
+                uint32_t state;
+                sd_id128_t machine_id;
+                int r;
+
+                r = sd_id128_get_machine(&machine_id);
+                if (r < 0)
+                        return r;
+
+                if (!sd_id128_equal(machine_id, f->header->machine_id))
+                        return -EHOSTDOWN;
+
+                state = le32toh(f->header->state);
+
+                if (state == STATE_ONLINE)
+                        log_debug("Journal file %s is already online. Assuming unclean closing. Ignoring.", f->path);
+                else if (state == STATE_ARCHIVED)
+                        return -ESHUTDOWN;
+                else if (state != STATE_OFFLINE)
+                        log_debug("Journal file %s has unknown state %u. Ignoring.", f->path, state);
+        }
+
+        return 0;
+}
+
+static int journal_file_allocate(JournalFile *f, uint64_t offset, uint64_t size) {
+        uint64_t asize;
+        uint64_t old_size, new_size;
+
+        assert(f);
+
+        if (offset < le64toh(f->header->arena_offset))
+                return -EINVAL;
+
+        new_size = PAGE_ALIGN(offset + size);
+
+        /* We assume that this file is not sparse, and we know that
+         * for sure, since we alway call posix_fallocate()
+         * ourselves */
+
+        old_size =
+                le64toh(f->header->arena_offset) +
+                le64toh(f->header->arena_size);
+
+        if (old_size >= new_size)
+                return 0;
+
+        asize = new_size - le64toh(f->header->arena_offset);
+
+        if (asize > le64toh(f->header->arena_min_size)) {
+                struct statvfs svfs;
+
+                if (fstatvfs(f->fd, &svfs) >= 0) {
+                        uint64_t available;
+
+                        available = svfs.f_bfree * svfs.f_bsize;
+
+                        if (available >= f->header->arena_keep_free)
+                                available -= f->header->arena_keep_free;
+                        else
+                                available = 0;
+
+                        if (new_size - old_size > available)
+                                return -E2BIG;
+                }
+        }
+
+        if (asize > le64toh(f->header->arena_max_size))
+                return -E2BIG;
+
+        if (posix_fallocate(f->fd, 0, new_size) < 0)
+                return -errno;
+
+        if (fstat(f->fd, &f->last_stat) < 0)
+                return -errno;
+
+        f->header->arena_size = htole64(asize);
+
+        return 0;
+}
+
+static int journal_file_map(
+                JournalFile *f,
+                uint64_t offset,
+                uint64_t size,
+                void **_window,
+                uint64_t *_woffset,
+                uint64_t *_wsize,
+                void **ret) {
+
+        uint64_t woffset, wsize;
+        void *window;
+
+        assert(f);
+        assert(size > 0);
+        assert(ret);
+
+        woffset = offset & ~((uint64_t) page_size() - 1ULL);
+        wsize = size + (offset - woffset);
+        wsize = PAGE_ALIGN(wsize);
+
+        window = mmap(NULL, wsize, f->prot, MAP_SHARED, f->fd, woffset);
+        if (window == MAP_FAILED)
+                return -errno;
+
+        if (_window)
+                *_window = window;
+
+        if (_woffset)
+                *_woffset = woffset;
+
+        if (_wsize)
+                *_wsize = wsize;
+
+        *ret = (uint8_t*) window + (offset - woffset);
+
+        return 0;
+}
+
+static int journal_file_move_to(JournalFile *f, uint64_t offset, uint64_t size, void **ret) {
+        void *p;
+        uint64_t delta;
+        int r;
+
+        assert(f);
+        assert(ret);
+
+        if (_likely_(f->window &&
+                     f->window_offset <= offset &&
+                     f->window_offset+f->window_size >= offset + size)) {
+
+                *ret = (uint8_t*) f->window + (offset - f->window_offset);
+                return 0;
+        }
+
+        if (f->window) {
+                if (munmap(f->window, f->window_size) < 0)
+                        return -errno;
+
+                f->window = NULL;
+                f->window_size = f->window_offset = 0;
+        }
+
+        if (size < DEFAULT_WINDOW_SIZE) {
+                /* If the default window size is larger then what was
+                 * asked for extend the mapping a bit in the hope to
+                 * minimize needed remappings later on. We add half
+                 * the window space before and half behind the
+                 * requested mapping */
+
+                delta = PAGE_ALIGN((DEFAULT_WINDOW_SIZE - size) / 2);
+
+                if (offset < delta)
+                        delta = offset;
+
+                offset -= delta;
+                size += (DEFAULT_WINDOW_SIZE - delta);
+        } else
+                delta = 0;
+
+        r = journal_file_map(f,
+                             offset, size,
+                             &f->window, &f->window_offset, &f->window_size,
+                             & p);
+
+        if (r < 0)
+                return r;
+
+        *ret = (uint8_t*) p + delta;
+        return 0;
+}
+
+static bool verify_hash(Object *o) {
+        uint64_t t;
+
+        assert(o);
+
+        t = le64toh(o->object.type);
+        if (t == OBJECT_DATA) {
+                uint64_t s, h1, h2;
+
+                s = le64toh(o->object.size);
+
+                h1 = le64toh(o->data.hash);
+                h2 = hash64(o->data.payload, s - offsetof(Object, data.payload));
+
+                return h1 == h2;
+        }
+
+        return true;
+}
+
+int journal_file_move_to_object(JournalFile *f, uint64_t offset, int type, Object **ret) {
+        int r;
+        void *t;
+        Object *o;
+        uint64_t s;
+
+        assert(f);
+        assert(ret);
+
+        r = journal_file_move_to(f, offset, sizeof(ObjectHeader), &t);
+        if (r < 0)
+                return r;
+
+        o = (Object*) t;
+        s = le64toh(o->object.size);
+
+        if (s < sizeof(ObjectHeader))
+                return -EBADMSG;
+
+        if (type >= 0 && le64toh(o->object.type) != type)
+                return -EBADMSG;
+
+        if (s > sizeof(ObjectHeader)) {
+                r = journal_file_move_to(f, offset, s, &t);
+                if (r < 0)
+                        return r;
+
+                o = (Object*) t;
+        }
+
+        if (!verify_hash(o))
+                return -EBADMSG;
+
+        *ret = o;
+        return 0;
+}
+
+static uint64_t journal_file_seqnum(JournalFile *f) {
+        uint64_t r;
+
+        assert(f);
+
+        r = le64toh(f->header->seqnum) + 1;
+        f->header->seqnum = htole64(r);
+
+        return r;
+}
+
+static int journal_file_append_object(JournalFile *f, uint64_t size, Object **ret, uint64_t *offset) {
+        int r;
+        uint64_t p;
+        Object *tail, *o;
+        void *t;
+
+        assert(f);
+        assert(size >= sizeof(ObjectHeader));
+        assert(offset);
+        assert(ret);
+
+        p = le64toh(f->header->tail_object_offset);
+
+        if (p == 0)
+                p = le64toh(f->header->arena_offset);
+        else {
+                r = journal_file_move_to_object(f, p, -1, &tail);
+                if (r < 0)
+                        return r;
+
+                p += ALIGN64(le64toh(tail->object.size));
+        }
+
+        r = journal_file_allocate(f, p, size);
+        if (r < 0)
+                return r;
+
+        r = journal_file_move_to(f, p, size, &t);
+        if (r < 0)
+                return r;
+
+        o = (Object*) t;
+
+        zero(o->object);
+        o->object.type = htole64(OBJECT_UNUSED);
+        zero(o->object.reserved);
+        o->object.size = htole64(size);
+
+        f->header->tail_object_offset = htole64(p);
+        if (f->header->head_object_offset == 0)
+                f->header->head_object_offset = htole64(p);
+
+        f->header->n_objects = htole64(le64toh(f->header->n_objects) + 1);
+
+        *ret = o;
+        *offset = p;
+
+        return 0;
+}
+
+static int journal_file_setup_hash_table(JournalFile *f) {
+        uint64_t s, p;
+        Object *o;
+        int r;
+
+        assert(f);
+
+        s = DEFAULT_HASH_TABLE_SIZE;
+        r = journal_file_append_object(f, offsetof(Object, hash_table.table) + s, &o, &p);
+        if (r < 0)
+                return r;
+
+        o->object.type = htole64(OBJECT_HASH_TABLE);
+        memset(o->hash_table.table, 0, s);
+
+        f->header->hash_table_offset = htole64(p + offsetof(Object, hash_table.table));
+        f->header->hash_table_size = htole64(s);
+
+        return 0;
+}
+
+static int journal_file_setup_bisect_table(JournalFile *f) {
+        uint64_t s, p;
+        Object *o;
+        int r;
+
+        assert(f);
+
+        s = DEFAULT_BISECT_TABLE_SIZE;
+        r = journal_file_append_object(f, offsetof(Object, bisect_table.table) + s, &o, &p);
+        if (r < 0)
+                return r;
+
+        o->object.type = htole64(OBJECT_BISECT_TABLE);
+        memset(o->bisect_table.table, 0, s);
+
+        f->header->bisect_table_offset = htole64(p + offsetof(Object, bisect_table.table));
+        f->header->bisect_table_size = htole64(s);
+
+        return 0;
+}
+
+static int journal_file_map_hash_table(JournalFile *f) {
+        uint64_t s, p;
+        void *t;
+        int r;
+
+        assert(f);
+
+        p = le64toh(f->header->hash_table_offset);
+        s = le64toh(f->header->hash_table_size);
+
+        r = journal_file_map(f,
+                             p, s,
+                             &f->hash_table_window, NULL, &f->hash_table_window_size,
+                             &t);
+        if (r < 0)
+                return r;
+
+        f->hash_table = t;
+        return 0;
+}
+
+static int journal_file_map_bisect_table(JournalFile *f) {
+        uint64_t s, p;
+        void *t;
+        int r;
+
+        assert(f);
+
+        p = le64toh(f->header->bisect_table_offset);
+        s = le64toh(f->header->bisect_table_size);
+
+        r = journal_file_map(f,
+                             p, s,
+                             &f->bisect_table_window, NULL, &f->bisect_table_window_size,
+                             &t);
+
+        if (r < 0)
+                return r;
+
+        f->bisect_table = t;
+        return 0;
+}
+
+static int journal_file_link_data(JournalFile *f, Object *o, uint64_t offset, uint64_t hash_index) {
+        uint64_t p;
+        int r;
+
+        assert(f);
+        assert(o);
+        assert(offset > 0);
+        assert(o->object.type == htole64(OBJECT_DATA));
+
+        o->data.head_entry_offset = o->data.tail_entry_offset = 0;
+        o->data.next_hash_offset = 0;
+
+        p = le64toh(f->hash_table[hash_index].tail_hash_offset);
+        if (p == 0) {
+                /* Only entry in the hash table is easy */
+
+                o->data.prev_hash_offset = 0;
+                f->hash_table[hash_index].head_hash_offset = htole64(offset);
+        } else {
+                o->data.prev_hash_offset = htole64(p);
+
+                /* Temporarily move back to the previous data object,
+                 * to patch in pointer */
+
+                r = journal_file_move_to_object(f, p, OBJECT_DATA, &o);
+                if (r < 0)
+                        return r;
+
+                o->data.next_hash_offset = offset;
+
+                r = journal_file_move_to_object(f, offset, OBJECT_DATA, &o);
+                if (r < 0)
+                        return r;
+        }
+
+        f->hash_table[hash_index].tail_hash_offset = htole64(offset);
+
+        return 0;
+}
+
+static int journal_file_append_data(JournalFile *f, const void *data, uint64_t size, Object **ret, uint64_t *offset) {
+        uint64_t hash, h, p, np;
+        uint64_t osize;
+        Object *o;
+        int r;
+
+        assert(f);
+        assert(data || size == 0);
+
+        osize = offsetof(Object, data.payload) + size;
+
+        hash = hash64(data, size);
+        h = hash % (le64toh(f->header->hash_table_size) / sizeof(HashItem));
+        p = le64toh(f->hash_table[h].head_hash_offset);
+
+        while (p != 0) {
+                /* Look for this data object in the hash table */
+
+                r = journal_file_move_to_object(f, p, OBJECT_DATA, &o);
+                if (r < 0)
+                        return r;
+
+                if (le64toh(o->object.size) == osize &&
+                    memcmp(o->data.payload, data, size) == 0) {
+
+                        if (le64toh(o->data.hash) != hash)
+                                return -EBADMSG;
+
+                        if (ret)
+                                *ret = o;
+
+                        if (offset)
+                                *offset = p;
+
+                        return 0;
+                }
+
+                p = le64toh(o->data.next_hash_offset);
+        }
+
+        r = journal_file_append_object(f, osize, &o, &np);
+        if (r < 0)
+                return r;
+
+        o->object.type = htole64(OBJECT_DATA);
+        o->data.hash = htole64(hash);
+        memcpy(o->data.payload, data, size);
+
+        r = journal_file_link_data(f, o, np, h);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = o;
+
+        if (offset)
+                *offset = np;
+
+        return 0;
+}
+
+uint64_t journal_file_entry_n_items(Object *o) {
+        assert(o);
+        assert(o->object.type == htole64(OBJECT_ENTRY));
+
+        return (le64toh(o->object.size) - offsetof(Object, entry.items)) / sizeof(EntryItem);
+}
+
+static int journal_file_link_entry_item(JournalFile *f, Object *o, uint64_t offset, uint64_t i) {
+        uint64_t p, q;
+        int r;
+        assert(f);
+        assert(o);
+        assert(offset > 0);
+
+        p = le64toh(o->entry.items[i].object_offset);
+        if (p == 0)
+                return -EINVAL;
+
+        o->entry.items[i].next_entry_offset = 0;
+
+        /* Move to the data object */
+        r = journal_file_move_to_object(f, p, OBJECT_DATA, &o);
+        if (r < 0)
+                return r;
+
+        q = le64toh(o->data.tail_entry_offset);
+        o->data.tail_entry_offset = htole64(offset);
+
+        if (q == 0)
+                o->data.head_entry_offset = htole64(offset);
+        else {
+                uint64_t n, j;
+
+                /* Move to previous entry */
+                r = journal_file_move_to_object(f, q, OBJECT_ENTRY, &o);
+                if (r < 0)
+                        return r;
+
+                n = journal_file_entry_n_items(o);
+                for (j = 0; j < n; j++)
+                        if (le64toh(o->entry.items[j].object_offset) == p)
+                                break;
+
+                if (j >= n)
+                        return -EBADMSG;
+
+                o->entry.items[j].next_entry_offset = offset;
+        }
+
+        /* Move back to original entry */
+        r = journal_file_move_to_object(f, offset, OBJECT_ENTRY, &o);
+        if (r < 0)
+                return r;
+
+        o->entry.items[i].prev_entry_offset = q;
+        return 0;
+}
+
+static int journal_file_link_entry(JournalFile *f, Object *o, uint64_t offset) {
+        uint64_t p, i, n, k, a, b;
+        int r;
+
+        assert(f);
+        assert(o);
+        assert(offset > 0);
+        assert(o->object.type == htole64(OBJECT_ENTRY));
+
+        /* Link up the entry itself */
+        p = le64toh(f->header->tail_entry_offset);
+
+        o->entry.prev_entry_offset = f->header->tail_entry_offset;
+        o->entry.next_entry_offset = 0;
+
+        if (p == 0)
+                f->header->head_entry_offset = htole64(offset);
+        else {
+                /* Temporarily move back to the previous entry, to
+                 * patch in pointer */
+
+                r = journal_file_move_to_object(f, p, OBJECT_ENTRY, &o);
+                if (r < 0)
+                        return r;
+
+                o->entry.next_entry_offset = htole64(offset);
+
+                r = journal_file_move_to_object(f, offset, OBJECT_ENTRY, &o);
+                if (r < 0)
+                        return r;
+        }
+
+        f->header->tail_entry_offset = htole64(offset);
+
+        /* Link up the items */
+        n = journal_file_entry_n_items(o);
+        for (i = 0; i < n; i++) {
+                r = journal_file_link_entry_item(f, o, offset, i);
+                if (r < 0)
+                        return r;
+        }
+
+        /* Link up the entry in the bisect table */
+        n = le64toh(f->header->bisect_table_size) / sizeof(uint64_t);
+        k = le64toh(f->header->arena_max_size) / n;
+
+        a = (le64toh(f->header->last_bisect_offset) + k - 1) / k;
+        b = offset / k;
+
+        for (; a <= b; a++)
+                f->bisect_table[a] = htole64(offset);
+
+        f->header->last_bisect_offset = htole64(offset + le64toh(o->object.size));
+
+        return 0;
+}
+
+static int journal_file_append_entry_internal(
+                JournalFile *f,
+                const dual_timestamp *ts,
+                uint64_t xor_hash,
+                const EntryItem items[], unsigned n_items,
+                Object **ret, uint64_t *offset) {
+        uint64_t np;
+        uint64_t osize;
+        Object *o;
+        int r;
+
+        assert(f);
+        assert(items || n_items == 0);
+
+        osize = offsetof(Object, entry.items) + (n_items * sizeof(EntryItem));
+
+        r = journal_file_append_object(f, osize, &o, &np);
+        if (r < 0)
+                return r;
+
+        o->object.type = htole64(OBJECT_ENTRY);
+        o->entry.seqnum = htole64(journal_file_seqnum(f));
+        memcpy(o->entry.items, items, n_items * sizeof(EntryItem));
+        o->entry.realtime = ts ? htole64(ts->realtime) : 0;
+        o->entry.monotonic = ts ? htole64(ts->monotonic) : 0;
+        o->entry.xor_hash = htole64(xor_hash);
+        o->entry.boot_id = f->header->boot_id;
+
+        r = journal_file_link_entry(f, o, np);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = o;
+
+        if (offset)
+                *offset = np;
+
+        return 0;
+}
+
+int journal_file_append_entry(JournalFile *f, const dual_timestamp *ts, const struct iovec iovec[], unsigned n_iovec, Object **ret, uint64_t *offset) {
+        unsigned i;
+        EntryItem *items;
+        int r;
+        uint64_t xor_hash = 0;
+
+        assert(f);
+        assert(iovec || n_iovec == 0);
+
+        items = new(EntryItem, n_iovec);
+        if (!items)
+                return -ENOMEM;
+
+        for (i = 0; i < n_iovec; i++) {
+                uint64_t p;
+                Object *o;
+
+                r = journal_file_append_data(f, iovec[i].iov_base, iovec[i].iov_len, &o, &p);
+                if (r < 0)
+                        goto finish;
+
+                xor_hash ^= le64toh(o->data.hash);
+                items[i].object_offset = htole64(p);
+        }
+
+        r = journal_file_append_entry_internal(f, ts, xor_hash, items, n_iovec, ret, offset);
+
+finish:
+        free(items);
+
+        return r;
+}
+
+int journal_file_move_to_entry(JournalFile *f, uint64_t seqnum, Object **ret, uint64_t *offset) {
+        Object *o;
+        uint64_t lower, upper, p, n, k;
+        int r;
+
+        assert(f);
+
+        n = le64toh(f->header->bisect_table_size) / sizeof(uint64_t);
+        k = le64toh(f->header->arena_max_size) / n;
+
+        lower = 0;
+        upper = le64toh(f->header->last_bisect_offset)/k+1;
+
+        while (lower < upper) {
+                k = (upper + lower) / 2;
+                p = le64toh(f->bisect_table[k]);
+
+                if (p == 0) {
+                        upper = k;
+                        continue;
+                }
+
+                r = journal_file_move_to_object(f, p, OBJECT_ENTRY, &o);
+                if (r < 0)
+                        return r;
+
+                if (o->entry.seqnum == seqnum) {
+                        if (ret)
+                                *ret = o;
+
+                        if (offset)
+                                *offset = p;
+
+                        return 1;
+                } else if (seqnum < o->entry.seqnum)
+                        upper = k;
+                else if (seqnum > o->entry.seqnum)
+                        lower = k+1;
+        }
+
+        assert(lower == upper);
+
+        if (lower <= 0)
+                return 0;
+
+        /* The object we are looking for is between
+         * bisect_table[lower-1] and bisect_table[lower] */
+
+        p = le64toh(f->bisect_table[lower-1]);
+
+        for (;;) {
+                r = journal_file_move_to_object(f, p, OBJECT_ENTRY, &o);
+                if (r < 0)
+                        return r;
+
+                if (o->entry.seqnum == seqnum) {
+                        if (ret)
+                                *ret = o;
+
+                        if (offset)
+                                *offset = p;
+
+                        return 1;
+
+                } if (seqnum < o->entry.seqnum)
+                        return 0;
+
+                if (o->entry.next_entry_offset == 0)
+                        return 0;
+
+                p = le64toh(o->entry.next_entry_offset);
+        }
+
+        return 0;
+}
+
+int journal_file_next_entry(JournalFile *f, Object *o, Object **ret, uint64_t *offset) {
+        uint64_t np;
+        int r;
+
+        assert(f);
+
+        if (!o)
+                np = le64toh(f->header->head_entry_offset);
+        else {
+                if (le64toh(o->object.type) != OBJECT_ENTRY)
+                        return -EINVAL;
+
+                np = le64toh(o->entry.next_entry_offset);
+        }
+
+        if (np == 0)
+                return 0;
+
+        r = journal_file_move_to_object(f, np, OBJECT_ENTRY, &o);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = o;
+
+        if (offset)
+                *offset = np;
+
+        return 1;
+}
+
+int journal_file_prev_entry(JournalFile *f, Object *o, Object **ret, uint64_t *offset) {
+        uint64_t np;
+        int r;
+
+        assert(f);
+
+        if (!o)
+                np = le64toh(f->header->tail_entry_offset);
+        else {
+                if (le64toh(o->object.type) != OBJECT_ENTRY)
+                        return -EINVAL;
+
+                np = le64toh(o->entry.prev_entry_offset);
+        }
+
+        if (np == 0)
+                return 0;
+
+        r = journal_file_move_to_object(f, np, OBJECT_ENTRY, &o);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = o;
+
+        if (offset)
+                *offset = np;
+
+        return 1;
+}
+
+int journal_file_find_first_entry(JournalFile *f, const void *data, uint64_t size, Object **ret, uint64_t *offset) {
+        uint64_t p, osize, hash, h;
+        int r;
+
+        assert(f);
+        assert(data || size == 0);
+
+        osize = offsetof(Object, data.payload) + size;
+
+        hash = hash64(data, size);
+        h = hash % (le64toh(f->header->hash_table_size) / sizeof(HashItem));
+        p = le64toh(f->hash_table[h].head_hash_offset);
+
+        while (p != 0) {
+                Object *o;
+
+                r = journal_file_move_to_object(f, p, OBJECT_DATA, &o);
+                if (r < 0)
+                        return r;
+
+                if (le64toh(o->object.size) == osize &&
+                    memcmp(o->data.payload, data, size) == 0) {
+
+                        if (le64toh(o->data.hash) != hash)
+                                return -EBADMSG;
+
+                        if (o->data.head_entry_offset == 0)
+                                return 0;
+
+                        p = le64toh(o->data.head_entry_offset);
+                        r = journal_file_move_to_object(f, p, OBJECT_ENTRY, &o);
+                        if (r < 0)
+                                return r;
+
+                        if (ret)
+                                *ret = o;
+
+                        if (offset)
+                                *offset = p;
+
+                        return 1;
+                }
+
+                p = le64toh(o->data.next_hash_offset);
+        }
+
+        return 0;
+}
+
+int journal_file_find_last_entry(JournalFile *f, const void *data, uint64_t size, Object **ret, uint64_t *offset) {
+        uint64_t p, osize, hash, h;
+        int r;
+
+        assert(f);
+        assert(data || size == 0);
+
+        osize = offsetof(Object, data.payload) + size;
+
+        hash = hash64(data, size);
+        h = hash % (le64toh(f->header->hash_table_size) / sizeof(HashItem));
+        p = le64toh(f->hash_table[h].tail_hash_offset);
+
+        while (p != 0) {
+                Object *o;
+
+                r = journal_file_move_to_object(f, p, OBJECT_DATA, &o);
+                if (r < 0)
+                        return r;
+
+                if (le64toh(o->object.size) == osize &&
+                    memcmp(o->data.payload, data, size) == 0) {
+
+                        if (le64toh(o->data.hash) != hash)
+                                return -EBADMSG;
+
+                        if (o->data.tail_entry_offset == 0)
+                                return 0;
+
+                        p = le64toh(o->data.tail_entry_offset);
+                        r = journal_file_move_to_object(f, p, OBJECT_ENTRY, &o);
+                        if (r < 0)
+                                return r;
+
+                        if (ret)
+                                *ret = o;
+
+                        if (offset)
+                                *offset = p;
+
+                        return 1;
+                }
+
+                p = le64toh(o->data.prev_hash_offset);
+        }
+
+        return 0;
+}
+
+void journal_file_dump(JournalFile *f) {
+        char a[33], b[33], c[33];
+        Object *o;
+        int r;
+        uint64_t p;
+
+        assert(f);
+
+        printf("File ID: %s\n"
+               "Machine ID: %s\n"
+               "Boot ID: %s\n"
+               "Arena size: %llu\n",
+               sd_id128_to_string(f->header->file_id, a),
+               sd_id128_to_string(f->header->machine_id, b),
+               sd_id128_to_string(f->header->boot_id, c),
+               (unsigned long long) le64toh(f->header->arena_size));
+
+        p = le64toh(f->header->head_object_offset);
+        while (p != 0) {
+                r = journal_file_move_to_object(f, p, -1, &o);
+                if (r < 0)
+                        goto fail;
+
+                switch (o->object.type) {
+
+                case OBJECT_UNUSED:
+                        printf("Type: OBJECT_UNUSED\n");
+                        break;
+
+                case OBJECT_DATA:
+                        printf("Type: OBJECT_DATA\n");
+                        break;
+
+                case OBJECT_ENTRY:
+                        printf("Type: OBJECT_ENTRY %llu\n", (unsigned long long) le64toh(o->entry.seqnum));
+                        break;
+
+                case OBJECT_HASH_TABLE:
+                        printf("Type: OBJECT_HASH_TABLE\n");
+                        break;
+
+                case OBJECT_BISECT_TABLE:
+                        printf("Type: OBJECT_BISECT_TABLE\n");
+                        break;
+                }
+
+                if (p == le64toh(f->header->tail_object_offset))
+                        p = 0;
+                else
+                        p = p + ALIGN64(le64toh(o->object.size));
+        }
+
+        return;
+fail:
+        log_error("File corrupt");
+}
+
+int journal_file_open(
+                const char *fname,
+                int flags,
+                mode_t mode,
+                JournalFile **ret) {
+
+        JournalFile *f;
+        int r;
+        bool newly_created = false;
+
+        assert(fname);
+
+        if ((flags & O_ACCMODE) != O_RDONLY &&
+            (flags & O_ACCMODE) != O_RDWR)
+                return -EINVAL;
+
+        f = new0(JournalFile, 1);
+        if (!f)
+                return -ENOMEM;
+
+        f->writable = (flags & O_ACCMODE) != O_RDONLY;
+        f->prot = prot_from_flags(flags);
+
+        f->fd = open(fname, flags|O_CLOEXEC, mode);
+        if (f->fd < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        f->path = strdup(fname);
+        if (!f->path) {
+                r = -ENOMEM;
+                goto fail;
+        }
+
+        if (fstat(f->fd, &f->last_stat) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        if (f->last_stat.st_size == 0 && f->writable) {
+                newly_created = true;
+
+                r = journal_file_init_header(f);
+                if (r < 0)
+                        goto fail;
+
+                if (fstat(f->fd, &f->last_stat) < 0) {
+                        r = -errno;
+                        goto fail;
+                }
+        }
+
+        if (f->last_stat.st_size < (off_t) sizeof(Header)) {
+                r = -EIO;
+                goto fail;
+        }
+
+        f->header = mmap(NULL, PAGE_ALIGN(sizeof(Header)), prot_from_flags(flags), MAP_SHARED, f->fd, 0);
+        if (f->header == MAP_FAILED) {
+                f->header = NULL;
+                r = -errno;
+                goto fail;
+        }
+
+        if (!newly_created) {
+                r = journal_file_verify_header(f);
+                if (r < 0)
+                        goto fail;
+        }
+
+        if (f->writable) {
+                r = journal_file_refresh_header(f);
+                if (r < 0)
+                        goto fail;
+        }
+
+        if (newly_created) {
+
+                r = journal_file_setup_hash_table(f);
+                if (r < 0)
+                        goto fail;
+
+                r = journal_file_setup_bisect_table(f);
+                if (r < 0)
+                        goto fail;
+        }
+
+        r = journal_file_map_hash_table(f);
+        if (r < 0)
+                goto fail;
+
+        r = journal_file_map_bisect_table(f);
+        if (r < 0)
+                goto fail;
+
+        if (ret)
+                *ret = f;
+
+        return 0;
+
+fail:
+        journal_file_close(f);
+
+        return r;
+}