src/lib-index/mail-cache.c

	mail-cache.c revision ba8bdb9dfc467ed2e6a988c42567fc44a28bebfc
03831d35f7499c87d51205817c93e9a8d42c4baestevel/* Copyright (c) 2003-2008 Dovecot authors, see the included COPYING file */
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "lib.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "array.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "buffer.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "hash.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "nfs-workarounds.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "file-cache.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "mmap-util.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "write-full.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include "mail-cache-private.h"
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel#include <unistd.h>
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevelvoid mail_cache_set_syscall_error(struct mail_cache *cache,
03831d35f7499c87d51205817c93e9a8d42c4baestevel                  const char *function)
03831d35f7499c87d51205817c93e9a8d42c4baestevel{
03831d35f7499c87d51205817c93e9a8d42c4baestevel    i_assert(function != NULL);
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (ENOSPACE(errno)) {
03831d35f7499c87d51205817c93e9a8d42c4baestevel        cache->index->nodiskspace = TRUE;
03831d35f7499c87d51205817c93e9a8d42c4baestevel        return;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    }
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    mail_index_set_error(cache->index,
03831d35f7499c87d51205817c93e9a8d42c4baestevel                 "%s failed with index cache file %s: %m",
03831d35f7499c87d51205817c93e9a8d42c4baestevel                 function, cache->filepath);
03831d35f7499c87d51205817c93e9a8d42c4baestevel}
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevelvoid mail_cache_set_corrupted(struct mail_cache *cache, const char *fmt, ...)
03831d35f7499c87d51205817c93e9a8d42c4baestevel{
03831d35f7499c87d51205817c93e9a8d42c4baestevel    va_list va;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    (void)unlink(cache->filepath);
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    /* mark the cache as unusable */
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->hdr = NULL;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    va_start(va, fmt);
03831d35f7499c87d51205817c93e9a8d42c4baestevel    T_BEGIN {
03831d35f7499c87d51205817c93e9a8d42c4baestevel        mail_index_set_error(cache->index,
03831d35f7499c87d51205817c93e9a8d42c4baestevel                     "Corrupted index cache file %s: %s",
03831d35f7499c87d51205817c93e9a8d42c4baestevel                     cache->filepath,
03831d35f7499c87d51205817c93e9a8d42c4baestevel                     t_strdup_vprintf(fmt, va));
03831d35f7499c87d51205817c93e9a8d42c4baestevel    } T_END;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    va_end(va);
03831d35f7499c87d51205817c93e9a8d42c4baestevel}
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevelvoid mail_cache_file_close(struct mail_cache *cache)
03831d35f7499c87d51205817c93e9a8d42c4baestevel{
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (cache->mmap_base != NULL) {
03831d35f7499c87d51205817c93e9a8d42c4baestevel        if (munmap(cache->mmap_base, cache->mmap_length) < 0)
03831d35f7499c87d51205817c93e9a8d42c4baestevel            mail_cache_set_syscall_error(cache, "munmap()");
03831d35f7499c87d51205817c93e9a8d42c4baestevel    }
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (cache->file_cache != NULL)
03831d35f7499c87d51205817c93e9a8d42c4baestevel        file_cache_set_fd(cache->file_cache, -1);
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->mmap_base = NULL;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->data = NULL;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->hdr = NULL;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->mmap_length = 0;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->last_field_header_offset = 0;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (cache->file_lock != NULL)
03831d35f7499c87d51205817c93e9a8d42c4baestevel        file_lock_free(&cache->file_lock);
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->locked = FALSE;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (cache->fd != -1) {
03831d35f7499c87d51205817c93e9a8d42c4baestevel        if (close(cache->fd) < 0)
03831d35f7499c87d51205817c93e9a8d42c4baestevel            mail_cache_set_syscall_error(cache, "close()");
03831d35f7499c87d51205817c93e9a8d42c4baestevel        cache->fd = -1;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    }
03831d35f7499c87d51205817c93e9a8d42c4baestevel}
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevelstatic void mail_cache_init_file_cache(struct mail_cache *cache)
03831d35f7499c87d51205817c93e9a8d42c4baestevel{
03831d35f7499c87d51205817c93e9a8d42c4baestevel    struct stat st;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (cache->file_cache == NULL)
03831d35f7499c87d51205817c93e9a8d42c4baestevel        return;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    file_cache_set_fd(cache->file_cache, cache->fd);
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (fstat(cache->fd, &st) == 0)
03831d35f7499c87d51205817c93e9a8d42c4baestevel        file_cache_set_size(cache->file_cache, st.st_size);
03831d35f7499c87d51205817c93e9a8d42c4baestevel    else if (errno != ESTALE)
03831d35f7499c87d51205817c93e9a8d42c4baestevel        mail_cache_set_syscall_error(cache, "fstat()");
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->st_ino = st.st_ino;
03831d35f7499c87d51205817c93e9a8d42c4baestevel    cache->st_dev = st.st_dev;
03831d35f7499c87d51205817c93e9a8d42c4baestevel}
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevelstatic bool mail_cache_need_reopen(struct mail_cache *cache)
03831d35f7499c87d51205817c93e9a8d42c4baestevel{
03831d35f7499c87d51205817c93e9a8d42c4baestevel    struct stat st;
03831d35f7499c87d51205817c93e9a8d42c4baestevel
03831d35f7499c87d51205817c93e9a8d42c4baestevel    if (MAIL_CACHE_IS_UNUSABLE(cache)) {
03831d35f7499c87d51205817c93e9a8d42c4baestevel        if (cache->need_compress_file_seq != 0) {
03831d35f7499c87d51205817c93e9a8d42c4baestevel            /* we're waiting for compression */
03831d35f7499c87d51205817c93e9a8d42c4baestevel            return FALSE;
03831d35f7499c87d51205817c93e9a8d42c4baestevel        }
03831d35f7499c87d51205817c93e9a8d42c4baestevel        if (MAIL_INDEX_IS_IN_MEMORY(cache->index)) {
03831d35f7499c87d51205817c93e9a8d42c4baestevel            /* disabled */
03831d35f7499c87d51205817c93e9a8d42c4baestevel            return FALSE;
03831d35f7499c87d51205817c93e9a8d42c4baestevel        }
03831d35f7499c87d51205817c93e9a8d42c4baestevel    }
03831d35f7499c87d51205817c93e9a8d42c4baestevel
    if (cache->fd == -1)
        return TRUE;

    /* see if the file has changed */
    if (cache->index->nfs_flush) {
        i_assert(!cache->locked);
        nfs_flush_file_handle_cache(cache->filepath);
    }
    if (nfs_safe_stat(cache->filepath, &st) < 0) {
        mail_cache_set_syscall_error(cache, "stat()");
        return TRUE;
    }

    if (st.st_ino != cache->st_ino ||
        !CMP_DEV_T(st.st_dev, cache->st_dev)) {
        /* file changed */
        return TRUE;
    }

    if (cache->index->nfs_flush) {
        /* if the old file has been deleted, the new file may have
           the same inode as the old one. we'll catch this here by
           checking if fstat() fails with ESTALE */
        if (fstat(cache->fd, &st) < 0) {
            if (errno == ESTALE)
                return TRUE;
            mail_cache_set_syscall_error(cache, "fstat()");
            return FALSE;
        }
    }
    return FALSE;
}

int mail_cache_reopen(struct mail_cache *cache)
{
    struct mail_index_view *view;
    const struct mail_index_ext *ext;

    i_assert(!cache->locked);

    if (!mail_cache_need_reopen(cache)) {
        /* reopening does no good */
        return 0;
    }

    mail_cache_file_close(cache);

    cache->fd = nfs_safe_open(cache->filepath,
                  cache->index->readonly ? O_RDONLY : O_RDWR);
    if (cache->fd == -1) {
        if (errno == ENOENT)
            cache->need_compress_file_seq = 0;
        else
            mail_cache_set_syscall_error(cache, "open()");
        return -1;
    }

    mail_cache_init_file_cache(cache);

    if (mail_cache_map(cache, 0, 0) < 0)
        return -1;

    if (mail_cache_header_fields_read(cache) < 0)
        return -1;

    view = mail_index_view_open(cache->index);
    ext = mail_index_view_get_ext(view, cache->ext_id);
    if (ext == NULL || cache->hdr->file_seq != ext->reset_id) {
        /* still different - maybe a race condition or maybe the
           file_seq really is corrupted. either way, this shouldn't
           happen often so we'll just mark cache to be compressed
           later which fixes this. */
        cache->need_compress_file_seq = cache->hdr->file_seq;
        mail_index_view_close(&view);
        return 0;
    }

    mail_index_view_close(&view);
    i_assert(!MAIL_CACHE_IS_UNUSABLE(cache));
    return 1;
}

static bool mail_cache_verify_header(struct mail_cache *cache)
{
    const struct mail_cache_header *hdr = cache->data;

    /* check that the header is still ok */
    if (cache->mmap_length < sizeof(struct mail_cache_header)) {
        mail_cache_set_corrupted(cache, "File too small");
        return FALSE;
    }

    if (hdr->version != MAIL_CACHE_VERSION) {
        /* version changed - upgrade silently */
        (void)unlink(cache->filepath);
        return FALSE;
    }
    if (hdr->compat_sizeof_uoff_t != sizeof(uoff_t)) {
        /* architecture change - handle silently(?) */
        (void)unlink(cache->filepath);
        return FALSE;
    }

    if (hdr->indexid != cache->index->indexid) {
        /* index id changed - handle silently */
        (void)unlink(cache->filepath);
        return FALSE;
    }
    if (hdr->file_seq == 0) {
        mail_cache_set_corrupted(cache, "file_seq is 0");
        return FALSE;
    }

    /* only check the header if we're locked */
    if (!cache->locked)
        return TRUE;

    if (hdr->used_file_size < sizeof(struct mail_cache_header)) {
        mail_cache_set_corrupted(cache, "used_file_size too small");
        return FALSE;
    }
    if ((hdr->used_file_size % sizeof(uint32_t)) != 0) {
        mail_cache_set_corrupted(cache, "used_file_size not aligned");
        return FALSE;
    }

    if (cache->mmap_base != NULL &&
        hdr->used_file_size > cache->mmap_length) {
        mail_cache_set_corrupted(cache, "used_file_size too large");
        return FALSE;
    }
    return TRUE;
}

int mail_cache_map(struct mail_cache *cache, size_t offset, size_t size)
{
    ssize_t ret;

    cache->remap_counter++;

    if (size == 0)
        size = sizeof(struct mail_cache_header);

    if (cache->file_cache != NULL) {
        cache->data = NULL;
        cache->hdr = NULL;

        ret = file_cache_read(cache->file_cache, offset, size);
        if (ret < 0) {
                        /* In case of ESTALE we'll simply fail without error
                           messages. The caller will then just have to
                           fallback to generating the value itself.

                           We can't simply reopen the cache flie, because
                           using it requires also having updated file
                           offsets. */
                        if (errno != ESTALE)
                                mail_cache_set_syscall_error(cache, "read()");
            return -1;
        }

        cache->data = file_cache_get_map(cache->file_cache,
                         &cache->mmap_length);

        if (offset == 0) {
            if (!mail_cache_verify_header(cache)) {
                cache->need_compress_file_seq =
                    !MAIL_CACHE_IS_UNUSABLE(cache) &&
                    cache->hdr->file_seq != 0 ?
                    cache->hdr->file_seq : 0;
                return -1;
            }
            memcpy(&cache->hdr_ro_copy, cache->data,
                   sizeof(cache->hdr_ro_copy));
        }
        cache->hdr = &cache->hdr_ro_copy;
        return 0;
    }

    if (offset < cache->mmap_length &&
        size <= cache->mmap_length - offset) {
        /* already mapped */
        return 0;
    }

    if (cache->mmap_base != NULL) {
        if (munmap(cache->mmap_base, cache->mmap_length) < 0)
            mail_cache_set_syscall_error(cache, "munmap()");
    } else {
        if (cache->fd == -1) {
            /* unusable, waiting for compression or
               index is in memory */
            i_assert(cache->need_compress_file_seq != 0 ||
                 MAIL_INDEX_IS_IN_MEMORY(cache->index));
            return -1;
        }
    }

    /* map the whole file */
    cache->hdr = NULL;
    cache->mmap_length = 0;

    cache->mmap_base = mmap_ro_file(cache->fd, &cache->mmap_length);
    if (cache->mmap_base == MAP_FAILED) {
        cache->mmap_base = NULL;
        cache->data = NULL;
        mail_cache_set_syscall_error(cache, "mmap()");
        return -1;
    }
    cache->data = cache->mmap_base;

    if (!mail_cache_verify_header(cache)) {
        cache->need_compress_file_seq =
            !MAIL_CACHE_IS_UNUSABLE(cache) &&
            cache->hdr->file_seq != 0 ?
            cache->hdr->file_seq : 0;
        return -1;
    }

    cache->hdr = cache->data;
    return 0;
}

static int mail_cache_try_open(struct mail_cache *cache)
{
    cache->opened = TRUE;

    if (MAIL_INDEX_IS_IN_MEMORY(cache->index))
        return 0;

    cache->fd = nfs_safe_open(cache->filepath,
                  cache->index->readonly ? O_RDONLY : O_RDWR);
    if (cache->fd == -1) {
        if (errno == ENOENT) {
            cache->need_compress_file_seq = 0;
            return 0;
        }

        mail_cache_set_syscall_error(cache, "open()");
        return -1;
    }

    mail_cache_init_file_cache(cache);

    if (mail_cache_map(cache, 0, sizeof(struct mail_cache_header)) < 0)
        return -1;

    return 1;
}

int mail_cache_open_and_verify(struct mail_cache *cache)
{
    int ret;

    ret = mail_cache_try_open(cache);
    if (ret > 0)
        ret = mail_cache_header_fields_read(cache);
    if (ret < 0) {
        /* failed for some reason - doesn't really matter,
           it's disabled for now. */
        mail_cache_file_close(cache);
    }
    return ret;
}

static struct mail_cache *mail_cache_alloc(struct mail_index *index)
{
    struct mail_cache *cache;

    cache = i_new(struct mail_cache, 1);
    cache->index = index;
    cache->fd = -1;
    cache->filepath =
        i_strconcat(index->filepath, MAIL_CACHE_FILE_SUFFIX, NULL);
    cache->field_pool = pool_alloconly_create("Cache fields", 1024);
    cache->field_name_hash =
        hash_create(default_pool, cache->field_pool, 0,
                strcase_hash, (hash_cmp_callback_t *)strcasecmp);

    cache->dotlock_settings.use_excl_lock = index->use_excl_dotlocks;
    cache->dotlock_settings.nfs_flush = index->nfs_flush;
    cache->dotlock_settings.timeout = MAIL_CACHE_LOCK_TIMEOUT;
    cache->dotlock_settings.stale_timeout = MAIL_CACHE_LOCK_CHANGE_TIMEOUT;

    if (!MAIL_INDEX_IS_IN_MEMORY(index)) {
        if (index->mmap_disable)
            cache->file_cache = file_cache_new(-1);
    }

    cache->ext_id =
        mail_index_ext_register(index, "cache", 0,
                    sizeof(uint32_t), sizeof(uint32_t));
    mail_index_register_expunge_handler(index, cache->ext_id, FALSE,
                        mail_cache_expunge_handler, cache);
    mail_index_register_sync_handler(index, cache->ext_id,
                     mail_cache_sync_handler,
                                         MAIL_INDEX_SYNC_HANDLER_FILE |
                                         MAIL_INDEX_SYNC_HANDLER_HEAD |
                     (cache->file_cache == NULL ? 0 :
                      MAIL_INDEX_SYNC_HANDLER_VIEW));

    if (cache->file_cache != NULL) {
        mail_index_register_sync_lost_handler(index,
            mail_cache_sync_lost_handler);
    }
    return cache;
}

struct mail_cache *mail_cache_open_or_create(struct mail_index *index)
{
    struct mail_cache *cache;

    cache = mail_cache_alloc(index);
    return cache;
}

struct mail_cache *mail_cache_create(struct mail_index *index)
{
    struct mail_cache *cache;

    cache = mail_cache_alloc(index);
    if (!MAIL_INDEX_IS_IN_MEMORY(index)) {
        if (unlink(cache->filepath) < 0 && errno != ENOENT)
            mail_cache_set_syscall_error(cache, "unlink()");
    }
    return cache;
}

void mail_cache_free(struct mail_cache **_cache)
{
    struct mail_cache *cache = *_cache;

    *_cache = NULL;
    if (cache->file_cache != NULL) {
        mail_index_unregister_sync_lost_handler(cache->index,
            mail_cache_sync_lost_handler);

        file_cache_free(&cache->file_cache);
    }

    mail_index_unregister_expunge_handler(cache->index, cache->ext_id);
    mail_index_unregister_sync_handler(cache->index, cache->ext_id);

    mail_cache_file_close(cache);

    hash_destroy(&cache->field_name_hash);
    pool_unref(&cache->field_pool);
    i_free(cache->field_file_map);
    i_free(cache->file_field_map);
    i_free(cache->fields);
    i_free(cache->filepath);
    i_free(cache);
}

static int mail_cache_lock_file(struct mail_cache *cache)
{
    int ret;

    if (cache->index->lock_method != FILE_LOCK_METHOD_DOTLOCK) {
        i_assert(cache->file_lock == NULL);
        ret = mail_index_lock_fd(cache->index, cache->filepath,
                     cache->fd, F_WRLCK,
                     MAIL_CACHE_LOCK_TIMEOUT,
                     &cache->file_lock);
    } else {
        i_assert(cache->dotlock == NULL);
        ret = file_dotlock_create(&cache->dotlock_settings,
                      cache->filepath, 0, &cache->dotlock);
        if (ret < 0) {
            mail_cache_set_syscall_error(cache,
                             "file_dotlock_create()");
        }
    }

    if (ret <= 0)
        return ret;

    mail_index_flush_read_cache(cache->index, cache->filepath, cache->fd,
                    TRUE);
    return 1;
}

static void mail_cache_unlock_file(struct mail_cache *cache)
{
    if (cache->index->lock_method != FILE_LOCK_METHOD_DOTLOCK)
        file_unlock(&cache->file_lock);
    else
        (void)file_dotlock_delete(&cache->dotlock);
}

int mail_cache_lock(struct mail_cache *cache, bool require_same_reset_id)
{
    const struct mail_index_ext *ext;
    struct mail_index_view *iview;
    uint32_t reset_id;
    int i, ret;

    i_assert(!cache->locked);

    if (!cache->opened)
        (void)mail_cache_open_and_verify(cache);

    if (MAIL_CACHE_IS_UNUSABLE(cache) ||
        MAIL_INDEX_IS_IN_MEMORY(cache->index))
        return 0;

    iview = mail_index_view_open(cache->index);
    ext = mail_index_view_get_ext(iview, cache->ext_id);
    reset_id = ext == NULL ? 0 : ext->reset_id;
    mail_index_view_close(&iview);

    if (ext == NULL && require_same_reset_id) {
        /* cache not used */
        return 0;
    }

    for (i = 0; i < 3; i++) {
        if (cache->hdr->file_seq != reset_id &&
            (require_same_reset_id || i == 0)) {
            /* we want the latest cache file */
            if (reset_id < cache->hdr->file_seq) {
                /* either we're still waiting for index to
                   catch up with a cache compression, or
                   that catching up is never going to happen */
                ret = 0;
                break;
            }
            ret = mail_cache_reopen(cache);
            if (ret < 0 || (ret == 0 && require_same_reset_id))
                break;
        }

        ret = mail_cache_lock_file(cache);
        if (ret <= 0)
            break;
        cache->locked = TRUE;

        if (cache->hdr->file_seq == reset_id ||
            !require_same_reset_id) {
            /* got it */
            break;
        }

        /* okay, so it was just compressed. try again. */
        (void)mail_cache_unlock(cache);
        ret = 0;
    }

    if (ret > 0) {
        /* make sure our header is up to date */
        if (cache->file_cache != NULL) {
            file_cache_invalidate(cache->file_cache, 0,
                          sizeof(struct mail_cache_header));
        }
        if (mail_cache_map(cache, 0, 0) == 0)
            cache->hdr_copy = *cache->hdr;
        else {
            (void)mail_cache_unlock(cache);
            ret = -1;
        }
    }

    i_assert((ret <= 0 && !cache->locked) || (ret > 0 && cache->locked));
    return ret;
}

static void mail_cache_update_need_compress(struct mail_cache *cache)
{
    const struct mail_cache_header *hdr = cache->hdr;
    unsigned int cont_percentage;
    uoff_t max_del_space;

        cont_percentage = hdr->continued_record_count * 100 /
        (cache->index->map->rec_map->records_count == 0 ? 1 :
         cache->index->map->rec_map->records_count);
    if (cont_percentage >= MAIL_CACHE_COMPRESS_CONTINUED_PERCENTAGE &&
        hdr->used_file_size >= MAIL_CACHE_COMPRESS_MIN_SIZE) {
        /* too many continued rows, compress */
        cache->need_compress_file_seq = hdr->file_seq;
    }

    /* see if we've reached the max. deleted space in file */
    max_del_space = hdr->used_file_size / 100 *
        MAIL_CACHE_COMPRESS_PERCENTAGE;
    if (hdr->deleted_space >= max_del_space &&
        hdr->used_file_size >= MAIL_CACHE_COMPRESS_MIN_SIZE)
        cache->need_compress_file_seq = hdr->file_seq;
}

int mail_cache_unlock(struct mail_cache *cache)
{
    int ret = 0;

    i_assert(cache->locked);

    if (cache->field_header_write_pending)
                ret = mail_cache_header_fields_update(cache);

    cache->locked = FALSE;

    if (MAIL_CACHE_IS_UNUSABLE(cache)) {
        /* we found it to be broken during the lock. just clean up. */
        cache->hdr_modified = FALSE;
        return -1;
    }

    if (cache->hdr_modified) {
        cache->hdr_modified = FALSE;
        if (mail_cache_write(cache, &cache->hdr_copy,
                     sizeof(cache->hdr_copy), 0) < 0)
            ret = -1;
        cache->hdr_ro_copy = cache->hdr_copy;
        mail_cache_update_need_compress(cache);
    }

    if (cache->index->nfs_flush) {
        if (fdatasync(cache->fd) < 0)
            mail_cache_set_syscall_error(cache, "fdatasync()");
    }

    mail_cache_unlock_file(cache);
    return ret;
}

int mail_cache_write(struct mail_cache *cache, const void *data, size_t size,
             uoff_t offset)
{
    if (pwrite_full(cache->fd, data, size, offset) < 0) {
        mail_cache_set_syscall_error(cache, "pwrite_full()");
        return -1;
    }

    if (cache->file_cache != NULL) {
        file_cache_write(cache->file_cache, data, size, offset);

        /* data pointer may change if file cache was grown */
        cache->data = file_cache_get_map(cache->file_cache,
                         &cache->mmap_length);
    }
    return 0;
}

struct mail_cache_view *
mail_cache_view_open(struct mail_cache *cache, struct mail_index_view *iview)
{
    struct mail_cache_view *view;

    view = i_new(struct mail_cache_view, 1);
    view->cache = cache;
    view->view = iview;
    view->cached_exists_buf =
        buffer_create_dynamic(default_pool,
                      cache->file_fields_count + 10);
    return view;
}

void mail_cache_view_close(struct mail_cache_view *view)
{
    i_assert(view->trans_view == NULL);

    if (view->cache->field_header_write_pending)
                (void)mail_cache_header_fields_update(view->cache);

    buffer_free(&view->cached_exists_buf);
    i_free(view);
}

uint32_t mail_cache_get_first_new_seq(struct mail_index_view *view)
{
    const struct mail_index_header *idx_hdr;
    uint32_t first_new_seq, message_count;

    idx_hdr = mail_index_get_header(view);
    if (idx_hdr->day_first_uid[7] == 0)
        return 1;

    if (!mail_index_lookup_seq_range(view, idx_hdr->day_first_uid[7],
                     (uint32_t)-1, &first_new_seq,
                     &message_count)) {
        /* all messages are too old */
        return message_count+1;
    }
    return first_new_seq;
}