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Message-ID: <CALTww2-+0h2Pxq0PJLZQxcoYpMJuiKuv6CZQ3kgX5PeqBkxKsQ@mail.gmail.com>
Date: Thu, 29 May 2025 15:03:50 +0800
From: Xiao Ni <xni@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: hch@....de, colyli@...nel.org, song@...nel.org, yukuai3@...wei.com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-raid@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
johnny.chenyi@...wei.com
Subject: Re: [PATCH 18/23] md/md-llbitmap: implement APIs to mange bitmap lifetime
Hi Kuai
Is it better to put this patch before patch15. I'm reading patch15.
But I need to read this patch first to understand how llbitmap is
created and loaded. Then I can go to read the io related part.
Regards
Xiao
On Sat, May 24, 2025 at 2:18 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> Include following APIs:
> - llbitmap_create
> - llbitmap_resize
> - llbitmap_load
> - llbitmap_destroy
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
> drivers/md/md-llbitmap.c | 322 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 322 insertions(+)
>
> diff --git a/drivers/md/md-llbitmap.c b/drivers/md/md-llbitmap.c
> index 4d5f9a139a25..23283c4f7263 100644
> --- a/drivers/md/md-llbitmap.c
> +++ b/drivers/md/md-llbitmap.c
> @@ -689,4 +689,326 @@ static void llbitmap_resume(struct llbitmap *llbitmap, int page_idx)
> wake_up(&pctl->wait);
> }
>
> +static int llbitmap_check_support(struct mddev *mddev)
> +{
> + if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
> + pr_notice("md/llbitmap: %s: array with journal cannot have bitmap\n",
> + mdname(mddev));
> + return -EBUSY;
> + }
> +
> + if (mddev->bitmap_info.space == 0) {
> + if (mddev->bitmap_info.default_space == 0) {
> + pr_notice("md/llbitmap: %s: no space for bitmap\n",
> + mdname(mddev));
> + return -ENOSPC;
> + }
> + }
> +
> + if (!mddev->persistent) {
> + pr_notice("md/llbitmap: %s: array must be persistent\n",
> + mdname(mddev));
> + return -EOPNOTSUPP;
> + }
> +
> + if (mddev->bitmap_info.file) {
> + pr_notice("md/llbitmap: %s: doesn't support bitmap file\n",
> + mdname(mddev));
> + return -EOPNOTSUPP;
> + }
> +
> + if (mddev->bitmap_info.external) {
> + pr_notice("md/llbitmap: %s: doesn't support external metadata\n",
> + mdname(mddev));
> + return -EOPNOTSUPP;
> + }
> +
> + if (mddev_is_dm(mddev)) {
> + pr_notice("md/llbitmap: %s: doesn't support dm-raid\n",
> + mdname(mddev));
> + return -EOPNOTSUPP;
> + }
> +
> + return 0;
> +}
> +
> +static int llbitmap_init(struct llbitmap *llbitmap)
> +{
> + struct mddev *mddev = llbitmap->mddev;
> + sector_t blocks = mddev->resync_max_sectors;
> + unsigned long chunksize = MIN_CHUNK_SIZE;
> + unsigned long chunks = DIV_ROUND_UP(blocks, chunksize);
> + unsigned long space = mddev->bitmap_info.space << SECTOR_SHIFT;
> + int ret;
> +
> + while (chunks > space) {
> + chunksize = chunksize << 1;
> + chunks = DIV_ROUND_UP(blocks, chunksize);
> + }
> +
> + llbitmap->chunkshift = ffz(~chunksize);
> + llbitmap->chunksize = chunksize;
> + llbitmap->chunks = chunks;
> + mddev->bitmap_info.daemon_sleep = DEFAULT_DAEMON_SLEEP;
> +
> + ret = llbitmap_cache_pages(llbitmap);
> + if (ret)
> + return ret;
> +
> + llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1, BitmapActionInit);
> + return 0;
> +}
> +
> +static int llbitmap_read_sb(struct llbitmap *llbitmap)
> +{
> + struct mddev *mddev = llbitmap->mddev;
> + unsigned long daemon_sleep;
> + unsigned long chunksize;
> + unsigned long events;
> + struct page *sb_page;
> + bitmap_super_t *sb;
> + int ret = -EINVAL;
> +
> + if (!mddev->bitmap_info.offset) {
> + pr_err("md/llbitmap: %s: no super block found", mdname(mddev));
> + return -EINVAL;
> + }
> +
> + sb_page = llbitmap_read_page(llbitmap, 0);
> + if (IS_ERR(sb_page)) {
> + pr_err("md/llbitmap: %s: read super block failed",
> + mdname(mddev));
> + ret = -EIO;
> + goto out;
> + }
> +
> + sb = kmap_local_page(sb_page);
> + if (sb->magic != cpu_to_le32(BITMAP_MAGIC)) {
> + pr_err("md/llbitmap: %s: invalid super block magic number",
> + mdname(mddev));
> + goto out_put_page;
> + }
> +
> + if (sb->version != cpu_to_le32(BITMAP_MAJOR_LOCKLESS)) {
> + pr_err("md/llbitmap: %s: invalid super block version",
> + mdname(mddev));
> + goto out_put_page;
> + }
> +
> + if (memcmp(sb->uuid, mddev->uuid, 16)) {
> + pr_err("md/llbitmap: %s: bitmap superblock UUID mismatch\n",
> + mdname(mddev));
> + goto out_put_page;
> + }
> +
> + if (mddev->bitmap_info.space == 0) {
> + int room = le32_to_cpu(sb->sectors_reserved);
> +
> + if (room)
> + mddev->bitmap_info.space = room;
> + else
> + mddev->bitmap_info.space = mddev->bitmap_info.default_space;
> + }
> + llbitmap->flags = le32_to_cpu(sb->state);
> + if (test_and_clear_bit(BITMAP_FIRST_USE, &llbitmap->flags)) {
> + ret = llbitmap_init(llbitmap);
> + goto out_put_page;
> + }
> +
> + chunksize = le32_to_cpu(sb->chunksize);
> + if (!is_power_of_2(chunksize)) {
> + pr_err("md/llbitmap: %s: chunksize not a power of 2",
> + mdname(mddev));
> + goto out_put_page;
> + }
> +
> + if (chunksize < DIV_ROUND_UP(mddev->resync_max_sectors,
> + mddev->bitmap_info.space << SECTOR_SHIFT)) {
> + pr_err("md/llbitmap: %s: chunksize too small %lu < %llu / %lu",
> + mdname(mddev), chunksize, mddev->resync_max_sectors,
> + mddev->bitmap_info.space);
> + goto out_put_page;
> + }
> +
> + daemon_sleep = le32_to_cpu(sb->daemon_sleep);
> + if (daemon_sleep < 1 || daemon_sleep > MAX_SCHEDULE_TIMEOUT / HZ) {
> + pr_err("md/llbitmap: %s: daemon sleep %lu period out of range",
> + mdname(mddev), daemon_sleep);
> + goto out_put_page;
> + }
> +
> + events = le64_to_cpu(sb->events);
> + if (events < mddev->events) {
> + pr_warn("md/llbitmap :%s: bitmap file is out of date (%lu < %llu) -- forcing full recovery",
> + mdname(mddev), events, mddev->events);
> + set_bit(BITMAP_STALE, &llbitmap->flags);
> + }
> +
> + sb->sync_size = cpu_to_le64(mddev->resync_max_sectors);
> + mddev->bitmap_info.chunksize = chunksize;
> + mddev->bitmap_info.daemon_sleep = daemon_sleep;
> +
> + llbitmap->chunksize = chunksize;
> + llbitmap->chunks = DIV_ROUND_UP(mddev->resync_max_sectors, chunksize);
> + llbitmap->chunkshift = ffz(~chunksize);
> + ret = llbitmap_cache_pages(llbitmap);
> +
> +out_put_page:
> + __free_page(sb_page);
> +out:
> + kunmap_local(sb);
> + return ret;
> +}
> +
> +static void llbitmap_pending_timer_fn(struct timer_list *t)
> +{
> + struct llbitmap *llbitmap = from_timer(llbitmap, t, pending_timer);
> +
> + if (work_busy(&llbitmap->daemon_work)) {
> + pr_warn("daemon_work not finished\n");
> + set_bit(BITMAP_DAEMON_BUSY, &llbitmap->flags);
> + return;
> + }
> +
> + queue_work(md_llbitmap_io_wq, &llbitmap->daemon_work);
> +}
> +
> +static void md_llbitmap_daemon_fn(struct work_struct *work)
> +{
> + struct llbitmap *llbitmap =
> + container_of(work, struct llbitmap, daemon_work);
> + unsigned long start;
> + unsigned long end;
> + bool restart;
> + int idx;
> +
> + if (llbitmap->mddev->degraded)
> + return;
> +
> +retry:
> + start = 0;
> + end = min(llbitmap->chunks, PAGE_SIZE - BITMAP_SB_SIZE) - 1;
> + restart = false;
> +
> + for (idx = 0; idx < llbitmap->nr_pages; idx++) {
> + struct llbitmap_page_ctl *pctl = llbitmap->pctl[idx];
> +
> + if (idx > 0) {
> + start = end + 1;
> + end = min(end + PAGE_SIZE, llbitmap->chunks - 1);
> + }
> +
> + if (!test_bit(LLPageFlush, &pctl->flags) &&
> + time_before(jiffies, pctl->expire)) {
> + restart = true;
> + continue;
> + }
> +
> + llbitmap_suspend(llbitmap, idx);
> + llbitmap_state_machine(llbitmap, start, end, BitmapActionDaemon);
> + llbitmap_resume(llbitmap, idx);
> + }
> +
> + /*
> + * If the daemon took a long time to finish, retry to prevent missing
> + * clearing dirty bits.
> + */
> + if (test_and_clear_bit(BITMAP_DAEMON_BUSY, &llbitmap->flags))
> + goto retry;
> +
> + /* If some page is dirty but not expired, setup timer again */
> + if (restart)
> + mod_timer(&llbitmap->pending_timer,
> + jiffies + llbitmap->mddev->bitmap_info.daemon_sleep * HZ);
> +}
> +
> +static int llbitmap_create(struct mddev *mddev)
> +{
> + struct llbitmap *llbitmap;
> + int ret;
> +
> + ret = llbitmap_check_support(mddev);
> + if (ret)
> + return ret;
> +
> + llbitmap = kzalloc(sizeof(*llbitmap), GFP_KERNEL);
> + if (!llbitmap)
> + return -ENOMEM;
> +
> + llbitmap->mddev = mddev;
> + llbitmap->io_size = bdev_logical_block_size(mddev->gendisk->part0);
> + llbitmap->bits_per_page = PAGE_SIZE / llbitmap->io_size;
> +
> + timer_setup(&llbitmap->pending_timer, llbitmap_pending_timer_fn, 0);
> + INIT_WORK(&llbitmap->daemon_work, md_llbitmap_daemon_fn);
> + atomic_set(&llbitmap->behind_writes, 0);
> + init_waitqueue_head(&llbitmap->behind_wait);
> +
> + mutex_lock(&mddev->bitmap_info.mutex);
> + mddev->bitmap = llbitmap;
> + ret = llbitmap_read_sb(llbitmap);
> + mutex_unlock(&mddev->bitmap_info.mutex);
> + if (ret)
> + goto err_out;
> +
> + return 0;
> +
> +err_out:
> + kfree(llbitmap);
> + return ret;
> +}
> +
> +static int llbitmap_resize(struct mddev *mddev, sector_t blocks, int chunksize)
> +{
> + struct llbitmap *llbitmap = mddev->bitmap;
> + unsigned long chunks;
> +
> + if (chunksize == 0)
> + chunksize = llbitmap->chunksize;
> +
> + /* If there is enough space, leave the chunksize unchanged. */
> + chunks = DIV_ROUND_UP(blocks, chunksize);
> + while (chunks > mddev->bitmap_info.space << SECTOR_SHIFT) {
> + chunksize = chunksize << 1;
> + chunks = DIV_ROUND_UP(blocks, chunksize);
> + }
> +
> + llbitmap->chunkshift = ffz(~chunksize);
> + llbitmap->chunksize = chunksize;
> + llbitmap->chunks = chunks;
> +
> + return 0;
> +}
> +
> +static int llbitmap_load(struct mddev *mddev)
> +{
> + enum llbitmap_action action = BitmapActionReload;
> + struct llbitmap *llbitmap = mddev->bitmap;
> +
> + if (test_and_clear_bit(BITMAP_STALE, &llbitmap->flags))
> + action = BitmapActionStale;
> +
> + llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1, action);
> + return 0;
> +}
> +
> +static void llbitmap_destroy(struct mddev *mddev)
> +{
> + struct llbitmap *llbitmap = mddev->bitmap;
> +
> + if (!llbitmap)
> + return;
> +
> + mutex_lock(&mddev->bitmap_info.mutex);
> +
> + timer_delete_sync(&llbitmap->pending_timer);
> + flush_workqueue(md_llbitmap_io_wq);
> + flush_workqueue(md_llbitmap_unplug_wq);
> +
> + mddev->bitmap = NULL;
> + llbitmap_free_pages(llbitmap);
> + kfree(llbitmap);
> + mutex_unlock(&mddev->bitmap_info.mutex);
> +}
> +
> #endif /* CONFIG_MD_LLBITMAP */
> --
> 2.39.2
>
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