src/lib-index/mail-cache-compress.c

	mail-cache-compress.c revision de9b2ee7878a73346ba0eee34798abb22ffcfcb6
/* Copyright (c) 2003-2012 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "ostream.h"
#include "nfs-workarounds.h"
#include "read-full.h"
#include "close-keep-errno.h"
#include "file-dotlock.h"
#include "file-cache.h"
#include "file-set-size.h"
#include "mail-cache-private.h"

#include <sys/stat.h>

struct mail_cache_copy_context {
    struct mail_cache *cache;

    buffer_t *buffer, *field_seen;
    ARRAY_DEFINE(bitmask_pos, unsigned int);
    uint32_t *field_file_map;

    uint8_t field_seen_value;
    bool new_msg;
};

static void
mail_cache_merge_bitmask(struct mail_cache_copy_context *ctx,
             const struct mail_cache_iterate_field *field)
{
    unsigned char *dest;
    unsigned int i, *pos;

    pos = array_idx_modifiable(&ctx->bitmask_pos, field->field_idx);
    if (*pos == 0) {
        /* we decided to drop this field */
        return;
    }

    dest = buffer_get_space_unsafe(ctx->buffer, *pos, field->size);
    for (i = 0; i < field->size; i++)
        dest[i] |= ((const unsigned char*)field->data)[i];
}

static void
mail_cache_compress_field(struct mail_cache_copy_context *ctx,
              const struct mail_cache_iterate_field *field)
{
        struct mail_cache_field *cache_field;
    enum mail_cache_decision_type dec;
    uint32_t file_field_idx, size32;
    uint8_t *field_seen;

    file_field_idx = ctx->field_file_map[field->field_idx];
    if (file_field_idx == (uint32_t)-1)
        return;

    cache_field = &ctx->cache->fields[field->field_idx].field;

    field_seen = buffer_get_space_unsafe(ctx->field_seen,
                         field->field_idx, 1);
    if (*field_seen == ctx->field_seen_value) {
        /* duplicate */
        if (cache_field->type == MAIL_CACHE_FIELD_BITMASK)
            mail_cache_merge_bitmask(ctx, field);
        return;
    }
    *field_seen = ctx->field_seen_value;

    dec = cache_field->decision & ~MAIL_CACHE_DECISION_FORCED;
    if (ctx->new_msg) {
        if (dec == MAIL_CACHE_DECISION_NO)
            return;
    } else {
        if (dec != MAIL_CACHE_DECISION_YES)
            return;
    }

    buffer_append(ctx->buffer, &file_field_idx, sizeof(file_field_idx));

    if (cache_field->field_size == (unsigned int)-1) {
        size32 = (uint32_t)field->size;
        buffer_append(ctx->buffer, &size32, sizeof(size32));
    }

    if (cache_field->type == MAIL_CACHE_FIELD_BITMASK) {
        /* remember the position in case we need to update it */
        unsigned int pos = ctx->buffer->used;

        array_idx_set(&ctx->bitmask_pos, field->field_idx, &pos);
    }
    buffer_append(ctx->buffer, field->data, field->size);
    if ((field->size & 3) != 0)
        buffer_append_zero(ctx->buffer, 4 - (field->size & 3));
}

static uint32_t
get_next_file_seq(struct mail_cache *cache, struct mail_index_view *view)
{
    const struct mail_index_ext *ext;
    uint32_t file_seq;

    ext = mail_index_view_get_ext(view, cache->ext_id);
    file_seq = ext != NULL ? ext->reset_id + 1 : (uint32_t)ioloop_time;

    if (cache->hdr != NULL && file_seq <= cache->hdr->file_seq)
        file_seq = cache->hdr->file_seq + 1;

    return file_seq != 0 ? file_seq : 1;
}

static void
mail_cache_compress_get_fields(struct mail_cache_copy_context *ctx,
                   unsigned int used_fields_count)
{
    struct mail_cache *cache = ctx->cache;
    struct mail_cache_field *field;
    unsigned int i, j, idx;

    /* Make mail_cache_header_fields_get() return the fields in
       the same order as we saved them. */
    memcpy(cache->field_file_map, ctx->field_file_map,
           sizeof(uint32_t) * cache->fields_count);

    /* reverse mapping */
    cache->file_fields_count = used_fields_count;
    i_free(cache->file_field_map);
    cache->file_field_map = used_fields_count == 0 ? NULL :
        i_new(unsigned int, used_fields_count);
    for (i = j = 0; i < cache->fields_count; i++) {
        idx = cache->field_file_map[i];
        if (idx != (uint32_t)-1) {
            i_assert(idx < used_fields_count &&
                 cache->file_field_map != NULL &&
                 cache->file_field_map[idx] == 0);
            cache->file_field_map[idx] = i;
            j++;
        }

        /* change permanent decisions to temporary decisions.
           if they're still permanent they'll get updated later. */
        field = &cache->fields[i].field;
        if (field->decision == MAIL_CACHE_DECISION_YES)
            field->decision = MAIL_CACHE_DECISION_TEMP;
    }
    i_assert(j == used_fields_count);

    buffer_set_used_size(ctx->buffer, 0);
    mail_cache_header_fields_get(cache, ctx->buffer);
}

static int
mail_cache_copy(struct mail_cache *cache, struct mail_index_transaction *trans,
        int fd, uint32_t *file_seq_r,
        ARRAY_TYPE(uint32_t) *ext_offsets)
{
        struct mail_cache_copy_context ctx;
    struct mail_cache_lookup_iterate_ctx iter;
    struct mail_cache_iterate_field field;
    struct mail_index_view *view;
    struct mail_cache_view *cache_view;
    const struct mail_index_header *idx_hdr;
    struct mail_cache_header hdr;
    struct mail_cache_record cache_rec;
    struct ostream *output;
    uint32_t message_count, seq, first_new_seq, ext_offset;
    unsigned int i, used_fields_count, orig_fields_count;
    time_t max_drop_time;

    view = mail_index_transaction_get_view(trans);
    cache_view = mail_cache_view_open(cache, view);
    output = o_stream_create_fd_file(fd, 0, FALSE);

    memset(&hdr, 0, sizeof(hdr));
    hdr.version = MAIL_CACHE_VERSION;
    hdr.compat_sizeof_uoff_t = sizeof(uoff_t);
    hdr.indexid = cache->index->indexid;
    hdr.file_seq = get_next_file_seq(cache, view);
    o_stream_send(output, &hdr, sizeof(hdr));

    memset(&ctx, 0, sizeof(ctx));
    ctx.cache = cache;
    ctx.buffer = buffer_create_dynamic(default_pool, 4096);
    ctx.field_seen = buffer_create_dynamic(default_pool, 64);
    ctx.field_seen_value = 0;
    ctx.field_file_map = t_new(uint32_t, cache->fields_count + 1);
    t_array_init(&ctx.bitmask_pos, 32);

    /* @UNSAFE: drop unused fields and create a field mapping for
       used fields */
    idx_hdr = mail_index_get_header(view);
    max_drop_time = idx_hdr->day_stamp == 0 ? 0 :
        idx_hdr->day_stamp - MAIL_CACHE_FIELD_DROP_SECS;

    orig_fields_count = cache->fields_count;
    if (cache->file_fields_count == 0) {
        /* creating the initial cache file. add all fields. */
        for (i = 0; i < orig_fields_count; i++)
            ctx.field_file_map[i] = i;
        used_fields_count = i;
    } else {
        for (i = used_fields_count = 0; i < orig_fields_count; i++) {
            struct mail_cache_field_private *priv =
                &cache->fields[i];
            enum mail_cache_decision_type dec =
                priv->field.decision;

            /* if the decision isn't forced and this field hasn't
               been accessed for a while, drop it */
            if ((dec & MAIL_CACHE_DECISION_FORCED) == 0 &&
                priv->field.last_used < max_drop_time &&
                !priv->adding) {
                dec = MAIL_CACHE_DECISION_NO;
                priv->field.decision = dec;
            }

            /* drop all fields we don't want */
            if ((dec & ~MAIL_CACHE_DECISION_FORCED) ==
                MAIL_CACHE_DECISION_NO && !priv->adding) {
                priv->used = FALSE;
                priv->field.last_used = 0;
            }

            ctx.field_file_map[i] = !priv->used ?
                (uint32_t)-1 : used_fields_count++;
        }
    }

    /* get sequence of first message which doesn't need its temp fields
       removed. */
    first_new_seq = mail_cache_get_first_new_seq(view);
    message_count = mail_index_view_get_messages_count(view);

    i_array_init(ext_offsets, message_count);
    for (seq = 1; seq <= message_count; seq++) {
        if (mail_index_transaction_is_expunged(trans, seq)) {
            (void)array_append_space(ext_offsets);
            continue;
        }

        ctx.new_msg = seq >= first_new_seq;
        buffer_set_used_size(ctx.buffer, 0);

        if (++ctx.field_seen_value == 0) {
            memset(buffer_get_modifiable_data(ctx.field_seen, NULL),
                   0, buffer_get_size(ctx.field_seen));
            ctx.field_seen_value++;
        }

        memset(&cache_rec, 0, sizeof(cache_rec));
        buffer_append(ctx.buffer, &cache_rec, sizeof(cache_rec));

        mail_cache_lookup_iter_init(cache_view, seq, &iter);
        while (mail_cache_lookup_iter_next(&iter, &field) > 0)
            mail_cache_compress_field(&ctx, &field);

        cache_rec.size = buffer_get_used_size(ctx.buffer);
        if (cache_rec.size == sizeof(cache_rec)) {
            /* nothing cached */
            ext_offset = 0;
        } else {
            ext_offset = output->offset;
            buffer_write(ctx.buffer, 0, &cache_rec,
                     sizeof(cache_rec));
            o_stream_send(output, ctx.buffer->data, cache_rec.size);
        }

        array_append(ext_offsets, &ext_offset, 1);
    }
    i_assert(orig_fields_count == cache->fields_count);

    hdr.field_header_offset = mail_index_uint32_to_offset(output->offset);
    mail_cache_compress_get_fields(&ctx, used_fields_count);
    o_stream_send(output, ctx.buffer->data, ctx.buffer->used);

    hdr.used_file_size = output->offset;
    buffer_free(&ctx.buffer);
    buffer_free(&ctx.field_seen);

    o_stream_seek(output, 0);
    o_stream_send(output, &hdr, sizeof(hdr));

    mail_cache_view_close(&cache_view);

    if (o_stream_flush(output) < 0) {
        errno = output->stream_errno;
        mail_cache_set_syscall_error(cache, "o_stream_flush()");
        o_stream_destroy(&output);
        array_free(ext_offsets);
        return -1;
    }

    if (hdr.used_file_size < MAIL_CACHE_INITIAL_SIZE) {
        /* grow the file some more. doesn't matter if it fails */
        (void)file_set_size(fd, MAIL_CACHE_INITIAL_SIZE);
    }

    o_stream_destroy(&output);

    if (cache->index->fsync_mode == FSYNC_MODE_ALWAYS) {
        if (fdatasync(fd) < 0) {
            mail_cache_set_syscall_error(cache, "fdatasync()");
            array_free(ext_offsets);
            return -1;
        }
    }

    *file_seq_r = hdr.file_seq;
    return 0;
}

static int mail_cache_compress_has_file_changed(struct mail_cache *cache)
{
    struct mail_cache_header hdr;
    unsigned int i;
    int fd, ret;

    for (i = 0;; i++) {
        fd = nfs_safe_open(cache->filepath, O_RDONLY);
        if (fd == -1) {
            if (errno == ENOENT)
                return 0;

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

        ret = read_full(fd, &hdr, sizeof(hdr));
        close_keep_errno(fd);

        if (ret >= 0) {
            if (ret == 0)
                return 0;
            if (cache->need_compress_file_seq == 0) {
                /* previously it didn't exist */
                return 1;
            }
            return hdr.file_seq != cache->need_compress_file_seq;
        } else if (errno != ESTALE || i >= NFS_ESTALE_RETRY_COUNT) {
            mail_cache_set_syscall_error(cache, "read()");
            return -1;
        }
    }
}

static int mail_cache_compress_locked(struct mail_cache *cache,
                      struct mail_index_transaction *trans,
                      bool *unlock)
{
    struct dotlock *dotlock;
    struct stat st;
    mode_t old_mask;
    uint32_t file_seq, old_offset;
    ARRAY_TYPE(uint32_t) ext_offsets;
    const uint32_t *offsets;
    const void *data;
    unsigned int i, count;
    int fd, ret;

    /* get the latest info on fields */
    if (mail_cache_header_fields_read(cache) < 0)
        return -1;

    old_mask = umask(cache->index->mode ^ 0666);
    fd = file_dotlock_open(&cache->dotlock_settings, cache->filepath,
                   DOTLOCK_CREATE_FLAG_NONBLOCK, &dotlock);
    umask(old_mask);

    if (fd == -1) {
        if (errno != EAGAIN)
            mail_cache_set_syscall_error(cache, "file_dotlock_open()");
        return -1;
    }

    if ((ret = mail_cache_compress_has_file_changed(cache)) != 0) {
        if (ret < 0)
            return -1;

        /* was just compressed, forget this */
        cache->need_compress_file_seq = 0;
        file_dotlock_delete(&dotlock);

        if (*unlock) {
            (void)mail_cache_unlock(cache);
            *unlock = FALSE;
        }

        return mail_cache_reopen(cache);
    }

    mail_index_fchown(cache->index, fd,
              file_dotlock_get_lock_path(dotlock));

    if (mail_cache_copy(cache, trans, fd, &file_seq, &ext_offsets) < 0) {
        /* the fields may have been updated in memory already.
           reverse those changes by re-reading them from file. */
        if (mail_cache_header_fields_read(cache) < 0)
            return -1;
        (void)file_dotlock_delete(&dotlock);
        return -1;
    }

    if (fstat(fd, &st) < 0) {
        mail_cache_set_syscall_error(cache, "fstat()");
        (void)file_dotlock_delete(&dotlock);
        return -1;
    }

    if (file_dotlock_replace(&dotlock,
                 DOTLOCK_REPLACE_FLAG_DONT_CLOSE_FD) < 0) {
        mail_cache_set_syscall_error(cache,
                         "file_dotlock_replace()");
        (void)close(fd);
        array_free(&ext_offsets);
        return -1;
    }

    /* once we're sure that the compression was successful,
       update the offsets */
    mail_index_ext_reset(trans, cache->ext_id, file_seq, TRUE);
    offsets = array_get(&ext_offsets, &count);
    for (i = 0; i < count; i++) {
        if (offsets[i] != 0) {
            mail_index_update_ext(trans, i + 1, cache->ext_id,
                          &offsets[i], &old_offset);
        }
    }
    array_free(&ext_offsets);

    if (*unlock) {
        (void)mail_cache_unlock(cache);
        *unlock = FALSE;
    }

    mail_cache_file_close(cache);
    cache->fd = fd;
    cache->st_ino = st.st_ino;
    cache->st_dev = st.st_dev;
    cache->field_header_write_pending = FALSE;

    if (cache->file_cache != NULL)
        file_cache_set_fd(cache->file_cache, cache->fd);

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

    cache->need_compress_file_seq = 0;
    return 0;
}

int mail_cache_compress(struct mail_cache *cache,
            struct mail_index_transaction *trans)
{
    bool unlock = FALSE;
    int ret;

    i_assert(!cache->compressing);

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

    /* compression isn't very efficient with small read()s */
    if (cache->map_with_read) {
        cache->map_with_read = FALSE;
        if (cache->read_buf != NULL)
            buffer_set_used_size(cache->read_buf, 0);
        cache->hdr = NULL;
        cache->mmap_length = 0;
    }

    if (cache->index->lock_method == FILE_LOCK_METHOD_DOTLOCK) {
        /* we're using dotlocking, cache file creation itself creates
           the dotlock file we need. */
        if (!MAIL_CACHE_IS_UNUSABLE(cache)) {
            mail_index_flush_read_cache(cache->index,
                            cache->filepath, cache->fd,
                            FALSE);
        }
    } else {
        switch (mail_cache_try_lock(cache)) {
        case -1:
            return -1;
        case 0:
            /* couldn't lock, either it's broken or doesn't exist.
               just start creating it. */
            break;
        default:
            /* locking succeeded. */
            unlock = TRUE;
        }
    }
    cache->compressing = TRUE;
    ret = mail_cache_compress_locked(cache, trans, &unlock);
    cache->compressing = FALSE;
    if (unlock) {
        if (mail_cache_unlock(cache) < 0)
            ret = -1;
    }
    return ret;
}

bool mail_cache_need_compress(struct mail_cache *cache)
{
    return cache->need_compress_file_seq != 0 &&
        (cache->index->flags & MAIL_INDEX_OPEN_FLAG_SAVEONLY) == 0 &&
        !cache->index->readonly;
}