md/r5cache: sysfs entry journal_mode

With write cache, journal_mode is the knob to switch between
write-back and write-through.

Below is an example:

root@virt-test:~/# cat /sys/block/md0/md/journal_mode
[write-through] write-back
root@virt-test:~/# echo write-back > /sys/block/md0/md/journal_mode
root@virt-test:~/# cat /sys/block/md0/md/journal_mode
write-through [write-back]

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 7dec2a04ca2608ac145f6e9a07ee706643748ac3..b9ad0e8fcf679240d675b5a1a6db26fcba52f9d7 100644 (file)
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -60,6 +60,8 @@ enum r5c_journal_mode {
        R5C_JOURNAL_MODE_WRITE_BACK = 1,
 };
 
+static char *r5c_journal_mode_str[] = {"write-through",
+                                      "write-back"};
 /*
  * raid5 cache state machine
  *
@@ -1617,6 +1619,69 @@ static void r5l_write_super(struct r5l_log *log, sector_t cp)
        set_bit(MD_CHANGE_DEVS, &mddev->flags);
 }
 
+static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
+{
+       struct r5conf *conf = mddev->private;
+       int ret;
+
+       if (!conf->log)
+               return 0;
+
+       switch (conf->log->r5c_journal_mode) {
+       case R5C_JOURNAL_MODE_WRITE_THROUGH:
+               ret = snprintf(
+                       page, PAGE_SIZE, "[%s] %s\n",
+                       r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_THROUGH],
+                       r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_BACK]);
+               break;
+       case R5C_JOURNAL_MODE_WRITE_BACK:
+               ret = snprintf(
+                       page, PAGE_SIZE, "%s [%s]\n",
+                       r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_THROUGH],
+                       r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_BACK]);
+               break;
+       default:
+               ret = 0;
+       }
+       return ret;
+}
+
+static ssize_t r5c_journal_mode_store(struct mddev *mddev,
+                                     const char *page, size_t length)
+{
+       struct r5conf *conf = mddev->private;
+       struct r5l_log *log = conf->log;
+       int val = -1, i;
+       int len = length;
+
+       if (!log)
+               return -ENODEV;
+
+       if (len && page[len - 1] == '\n')
+               len -= 1;
+       for (i = 0; i < ARRAY_SIZE(r5c_journal_mode_str); i++)
+               if (strlen(r5c_journal_mode_str[i]) == len &&
+                   strncmp(page, r5c_journal_mode_str[i], len) == 0) {
+                       val = i;
+                       break;
+               }
+       if (val < R5C_JOURNAL_MODE_WRITE_THROUGH ||
+           val > R5C_JOURNAL_MODE_WRITE_BACK)
+               return -EINVAL;
+
+       mddev_suspend(mddev);
+       conf->log->r5c_journal_mode = val;
+       mddev_resume(mddev);
+
+       pr_debug("md/raid:%s: setting r5c cache mode to %d: %s\n",
+                mdname(mddev), val, r5c_journal_mode_str[val]);
+       return length;
+}
+
+struct md_sysfs_entry
+r5c_journal_mode = __ATTR(journal_mode, 0644,
+                         r5c_journal_mode_show, r5c_journal_mode_store);
+
 /*
  * Try handle write operation in caching phase. This function should only
  * be called in write-back mode.

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 90638ba6781233728dcf3b6a3327fc2b5e2da60a..17cf98e933072b1c0c213df22bb87a2d7b944555 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6319,6 +6319,7 @@ static struct attribute *raid5_attrs[] =  {
        &raid5_group_thread_cnt.attr,
        &raid5_skip_copy.attr,
        &raid5_rmw_level.attr,
+       &r5c_journal_mode.attr,
        NULL,
 };
 static struct attribute_group raid5_attrs_group = {

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 35b4c0f0a850e26f731507a008104ac3c78c9db4..a698113c6188b4888023b673261c075c55f2af1a 100644 (file)
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -773,4 +773,5 @@ extern void r5c_make_stripe_write_out(struct stripe_head *sh);
 extern void r5c_flush_cache(struct r5conf *conf, int num);
 extern void r5c_check_stripe_cache_usage(struct r5conf *conf);
 extern void r5c_check_cached_full_stripe(struct r5conf *conf);
+extern struct md_sysfs_entry r5c_journal_mode;
 #endif