On Fri, Aug 19, 2016 at 03:34:02PM -0700, Song Liu wrote:
> In current r5cache, when the journal device is broken, the raid
> array is forced in readonly mode. There is no way to remove the
> "journal feature", and thus make the array read-write without
> journal.
>
> This patch provides sysfs entry r5c_cache_mode that can be used
> to remove journal feature.
>
> r5c_cache_mode has 4 different values:
> * no-cache;
> * write-through (write journal only);
> * write-back (w/ write cache feature, which will be added soon);
> * broken-cache (journal missing or Faulty)
>
> By writing into r5c_cache_mode, the array can transit from
> broken-cache to no-cache, which removes journal feature for the
> array.
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
> drivers/md/raid5-cache.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
> drivers/md/raid5.c | 5 ++++
> drivers/md/raid5.h | 6 +++++
> 3 files changed, 75 insertions(+)
>
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 5504ce2..508d470 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -40,6 +40,16 @@
> */
> #define R5L_POOL_SIZE 4
>
> +enum r5c_cache_mode {
> + R5C_MODE_NO_CACHE = 0,
> + R5C_MODE_WRITE_THROUGH = 1,
> + R5C_MODE_WRITE_BACK = 2,
> + R5C_MODE_BROKEN_CACHE = 3,
The idea of setting different modes makes sense.
But this is a little confusing. The first three are modes, the last one is status.
We can't set BROKEN_CACHE mode, right?
> +};
> +
> +static char *r5c_cache_mode_str[] = {"no-cache", "write-through",
> + "write-back", "broken-cache"};
> +
> struct r5l_log {
> struct md_rdev *rdev;
>
> @@ -97,6 +107,8 @@ struct r5l_log {
>
> bool need_cache_flush;
> bool in_teardown;
> +
> + enum r5c_cache_mode cache_mode;
> };
>
> /*
> @@ -1193,6 +1205,56 @@ ioerr:
> return ret;
> }
>
> +ssize_t r5c_show_cache_mode(struct mddev *mddev, char *page)
> +{
> + struct r5conf *conf = mddev->private;
> + int val = 0;
> + int ret = 0;
> +
> + if (conf->log)
> + val = conf->log->cache_mode;
> + else if (test_bit(MD_HAS_JOURNAL, &mddev->flags))
> + val = R5C_MODE_BROKEN_CACHE;
> + ret += snprintf(page, PAGE_SIZE - ret, "%d: %s\n",
> + val, r5c_cache_mode_str[val]);
> + return ret;
> +}
> +
> +ssize_t r5c_store_cache_mode(struct mddev *mddev, const char *page, size_t len)
> +{
> + struct r5conf *conf = mddev->private;
> + struct r5l_log *log = conf->log;
> + int val;
> +
> + if (kstrtoint(page, 10, &val))
> + return -EINVAL;
> + if (!log && val != R5C_MODE_NO_CACHE)
> + return -EINVAL;
> + /* currently only support write through (write journal) */
> + if (val < R5C_MODE_NO_CACHE || val > R5C_MODE_WRITE_THROUGH)
> + return -EINVAL;
> + if (val == R5C_MODE_NO_CACHE) {
> + if (conf->log &&
> + !test_bit(Faulty, &log->rdev->flags)) {
> + pr_err("md/raid:%s: journal device is in use, cannot remove it\n",
> + mdname(mddev));
> + return -EINVAL;
> + }
> + }
> +
> + spin_lock_irq(&conf->device_lock);
> + if (log)
> + conf->log->cache_mode = val;
> + if (val == R5C_MODE_NO_CACHE) {
> + clear_bit(MD_HAS_JOURNAL, &mddev->flags);
> + set_bit(MD_UPDATE_SB_FLAGS, &mddev->flags);
If the journal disk is Faulty and we clear HAS_JOURNAL, what's role of journal
disk?
This sounds incomplete. If we assemble the array and journal disk is missing,
can we set the mode to NO_CACHE and allow the array writeable?
> + }
> + spin_unlock_irq(&conf->device_lock);
> + pr_info("%s: setting r5c cache mode to %d: %s\n",
> + mdname(mddev), val, r5c_cache_mode_str[val]);
> + return len;
> +}
> +
> int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
> {
> struct request_queue *q = bdev_get_queue(rdev->bdev);
> @@ -1246,6 +1308,8 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
> INIT_LIST_HEAD(&log->no_space_stripes);
> spin_lock_init(&log->no_space_stripes_lock);
>
> + log->cache_mode = R5C_MODE_WRITE_THROUGH;
> +
> if (r5l_load_log(log))
> goto error;
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 2119e09..665d853 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -6230,6 +6230,10 @@ raid5_group_thread_cnt = __ATTR(group_thread_cnt, S_IRUGO | S_IWUSR,
> raid5_show_group_thread_cnt,
> raid5_store_group_thread_cnt);
>
> +static struct md_sysfs_entry
> +r5c_cache_mode = __ATTR(r5c_cache_mode, S_IRUGO | S_IWUSR,
> + r5c_show_cache_mode, r5c_store_cache_mode);
> +
> static struct attribute *raid5_attrs[] = {
> &raid5_stripecache_size.attr,
> &raid5_stripecache_active.attr,
> @@ -6237,6 +6241,7 @@ static struct attribute *raid5_attrs[] = {
> &raid5_group_thread_cnt.attr,
> &raid5_skip_copy.attr,
> &raid5_rmw_level.attr,
> + &r5c_cache_mode.attr,
> NULL,
> };
> static struct attribute_group raid5_attrs_group = {
> diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
> index 517d4b6..ace9675 100644
> --- a/drivers/md/raid5.h
> +++ b/drivers/md/raid5.h
> @@ -635,4 +635,10 @@ extern void r5l_stripe_write_finished(struct stripe_head *sh);
> extern int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio);
> extern void r5l_quiesce(struct r5l_log *log, int state);
> extern bool r5l_log_disk_error(struct r5conf *conf);
> +
> +
> +extern ssize_t r5c_show_cache_mode(struct mddev *mddev, char *page);
> +extern ssize_t
> +r5c_store_cache_mode(struct mddev *mddev, const char *page, size_t len);
Instead of export two functions, you can move r5c_cache_mode sysfs entry to raid5-cache.c
and export it.
Thanks,
Shaohua
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