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Commit 2c7da14b authored by Song Liu's avatar Song Liu Committed by Shaohua Li
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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: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent a39f7afd

drivers/md/raid5-cache.c

+65 −0
Original line number Diff line number Diff line
@@ -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.

drivers/md/raid5.c

+1 −0
Original line number Diff line number Diff line
@@ -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 = {

drivers/md/raid5.h

+1 −0
Original line number Diff line number Diff line
@@ -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