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Commit 43a70507 authored by NeilBrown's avatar NeilBrown
Browse files

md: support updating bitmap parameters via sysfs. 



A new attribute directory 'bitmap' in 'md' is created which
contains files for configuring the bitmap.
'location' identifies where the bitmap is, either 'none',
or 'file' or 'sector offset from metadata'.
Writing 'location' can create or remove a bitmap.
Adding a 'file' bitmap this way is not yet supported.
'chunksize' and 'time_base' must be set before 'location'
can be set.

'chunksize' can be set before creating a bitmap, but is
currently always over-ridden by the bitmap superblock.

'time_base' and 'backlog' can be updated at any time.


Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Reviewed-by: default avatarAndre Noll <maan@systemlinux.org>
parent 72e02075

Documentation/md.txt

+29 −0
Original line number Diff line number Diff line
@@ -296,6 +296,35 @@ All md devices contain: 
     active-idle

         like active, but no writes have been seen for a while (safe_mode_delay).



  bitmap/location

     This indicates where the write-intent bitmap for the array is

     stored.

     It can be one of "none", "file" or "[+-]N".

     "file" may later be extended to "file:/file/name"

     "[+-]N" means that many sectors from the start of the metadata.

       This is replicated on all devices.  For arrays with externally

       managed metadata, the offset is from the beginning of the

       device.

  bitmap/chunksize

     The size, in bytes, of the chunk which will be represented by a

     single bit.  For RAID456, it is a portion of an individual

     device. For RAID10, it is a portion of the array.  For RAID1, it

     is both (they come to the same thing).

  bitmap/time_base

     The time, in seconds, between looking for bits in the bitmap to

     be cleared. In the current implementation, a bit will be cleared

     between 2 and 3 times "time_base" after all the covered blocks

     are known to be in-sync.

  bitmap/backlog

     When write-mostly devices are active in a RAID1, write requests

     to those devices proceed in the background - the filesystem (or

     other user of the device) does not have to wait for them.

     'backlog' sets a limit on the number of concurrent background

     writes.  If there are more than this, new writes will by

     synchronous.

     

     

     



As component devices are added to an md array, they appear in the 'md'

directory as new directories named

drivers/md/bitmap.c

+205 −0
Original line number Diff line number Diff line
@@ -510,6 +510,9 @@ void bitmap_update_sb(struct bitmap *bitmap) 
		bitmap->events_cleared = bitmap->mddev->events;

		sb->events_cleared = cpu_to_le64(bitmap->events_cleared);

	}

	/* Just in case these have been changed via sysfs: */

	sb->daemon_sleep = cpu_to_le32(bitmap->mddev->bitmap_info.daemon_sleep/HZ);

	sb->write_behind = cpu_to_le32(bitmap->mddev->bitmap_info.max_write_behind);

	kunmap_atomic(sb, KM_USER0);

	write_page(bitmap, bitmap->sb_page, 1);

}
@@ -1714,6 +1717,208 @@ int bitmap_create(mddev_t *mddev) 
	return err;

}



static ssize_t

location_show(mddev_t *mddev, char *page)

{

	ssize_t len;

	if (mddev->bitmap_info.file) {

		len = sprintf(page, "file");

	} else if (mddev->bitmap_info.offset) {

		len = sprintf(page, "%+lld", (long long)mddev->bitmap_info.offset);

	} else

		len = sprintf(page, "none");

	len += sprintf(page+len, "\n");

	return len;

}



static ssize_t

location_store(mddev_t *mddev, const char *buf, size_t len)

{



	if (mddev->pers) {

		if (!mddev->pers->quiesce)

			return -EBUSY;

		if (mddev->recovery || mddev->sync_thread)

			return -EBUSY;

	}



	if (mddev->bitmap || mddev->bitmap_info.file ||

	    mddev->bitmap_info.offset) {

		/* bitmap already configured.  Only option is to clear it */

		if (strncmp(buf, "none", 4) != 0)

			return -EBUSY;

		if (mddev->pers) {

			mddev->pers->quiesce(mddev, 1);

			bitmap_destroy(mddev);

			mddev->pers->quiesce(mddev, 0);

		}

		mddev->bitmap_info.offset = 0;

		if (mddev->bitmap_info.file) {

			struct file *f = mddev->bitmap_info.file;

			mddev->bitmap_info.file = NULL;

			restore_bitmap_write_access(f);

			fput(f);

		}

	} else {

		/* No bitmap, OK to set a location */

		long long offset;

		if (strncmp(buf, "none", 4) == 0)

			/* nothing to be done */;

		else if (strncmp(buf, "file:", 5) == 0) {

			/* Not supported yet */

			return -EINVAL;

		} else {

			int rv;

			if (buf[0] == '+')

				rv = strict_strtoll(buf+1, 10, &offset);

			else

				rv = strict_strtoll(buf, 10, &offset);

			if (rv)

				return rv;

			if (offset == 0)

				return -EINVAL;

			if (mddev->major_version == 0 &&

			    offset != mddev->bitmap_info.default_offset)

				return -EINVAL;

			mddev->bitmap_info.offset = offset;

			if (mddev->pers) {

				mddev->pers->quiesce(mddev, 1);

				rv = bitmap_create(mddev);

				if (rv) {

					bitmap_destroy(mddev);

					mddev->bitmap_info.offset = 0;

				}

				mddev->pers->quiesce(mddev, 0);

				if (rv)

					return rv;

			}

		}

	}

	if (!mddev->external) {

		/* Ensure new bitmap info is stored in

		 * metadata promptly.

		 */

		set_bit(MD_CHANGE_DEVS, &mddev->flags);

		md_wakeup_thread(mddev->thread);

	}

	return len;

}



static struct md_sysfs_entry bitmap_location =

__ATTR(location, S_IRUGO|S_IWUSR, location_show, location_store);



static ssize_t

timeout_show(mddev_t *mddev, char *page)

{

	ssize_t len;

	unsigned long secs = mddev->bitmap_info.daemon_sleep / HZ;

	unsigned long jifs = mddev->bitmap_info.daemon_sleep % HZ;

	

	len = sprintf(page, "%lu", secs);

	if (jifs)

		len += sprintf(page+len, ".%03u", jiffies_to_msecs(jifs));

	len += sprintf(page+len, "\n");

	return len;

}



static ssize_t

timeout_store(mddev_t *mddev, const char *buf, size_t len)

{

	/* timeout can be set at any time */

	unsigned long timeout;

	int rv = strict_strtoul_scaled(buf, &timeout, 4);

	if (rv)

		return rv;



	/* just to make sure we don't overflow... */

	if (timeout >= LONG_MAX / HZ)

		return -EINVAL;



	timeout = timeout * HZ / 10000;



	if (timeout >= MAX_SCHEDULE_TIMEOUT)

		timeout = MAX_SCHEDULE_TIMEOUT-1;

	if (timeout < 1)

		timeout = 1;

	mddev->bitmap_info.daemon_sleep = timeout;

	if (mddev->thread) {

		/* if thread->timeout is MAX_SCHEDULE_TIMEOUT, then

		 * the bitmap is all clean and we don't need to

		 * adjust the timeout right now

		 */

		if (mddev->thread->timeout < MAX_SCHEDULE_TIMEOUT) {

			mddev->thread->timeout = timeout;

			md_wakeup_thread(mddev->thread);

		}

	}

	return len;

}



static struct md_sysfs_entry bitmap_timeout =

__ATTR(time_base, S_IRUGO|S_IWUSR, timeout_show, timeout_store);



static ssize_t

backlog_show(mddev_t *mddev, char *page)

{

	return sprintf(page, "%lu\n", mddev->bitmap_info.max_write_behind);

}



static ssize_t

backlog_store(mddev_t *mddev, const char *buf, size_t len)

{

	unsigned long backlog;

	int rv = strict_strtoul(buf, 10, &backlog);

	if (rv)

		return rv;

	if (backlog > COUNTER_MAX)

		return -EINVAL;

	mddev->bitmap_info.max_write_behind = backlog;

	return len;

}



static struct md_sysfs_entry bitmap_backlog =

__ATTR(backlog, S_IRUGO|S_IWUSR, backlog_show, backlog_store);



static ssize_t

chunksize_show(mddev_t *mddev, char *page)

{

	return sprintf(page, "%lu\n", mddev->bitmap_info.chunksize);

}



static ssize_t

chunksize_store(mddev_t *mddev, const char *buf, size_t len)

{

	/* Can only be changed when no bitmap is active */

	int rv;

	unsigned long csize;

	if (mddev->bitmap)

		return -EBUSY;

	rv = strict_strtoul(buf, 10, &csize);

	if (rv)

		return rv;

	if (csize < 512 ||

	    !is_power_of_2(csize))

		return -EINVAL;

	mddev->bitmap_info.chunksize = csize;

	return len;

}



static struct md_sysfs_entry bitmap_chunksize =

__ATTR(chunksize, S_IRUGO|S_IWUSR, chunksize_show, chunksize_store);



static struct attribute *md_bitmap_attrs[] = {

	&bitmap_location.attr,

	&bitmap_timeout.attr,

	&bitmap_backlog.attr,

	&bitmap_chunksize.attr,

	NULL

};

struct attribute_group md_bitmap_group = {

	.name = "bitmap",

	.attrs = md_bitmap_attrs,

};





/* the bitmap API -- for raid personalities */

EXPORT_SYMBOL(bitmap_startwrite);

EXPORT_SYMBOL(bitmap_endwrite);

drivers/md/md.c

+4 −1
Original line number Diff line number Diff line
@@ -4018,6 +4018,7 @@ static void mddev_delayed_delete(struct work_struct *ws) 
		mddev->sysfs_action = NULL;

		mddev->private = NULL;

	}

	sysfs_remove_group(&mddev->kobj, &md_bitmap_group);

	kobject_del(&mddev->kobj);

	kobject_put(&mddev->kobj);

}
@@ -4109,6 +4110,8 @@ static int md_alloc(dev_t dev, char *name) 
		       disk->disk_name);

		error = 0;

	}

	if (sysfs_create_group(&mddev->kobj, &md_bitmap_group))

		printk(KERN_DEBUG "pointless warning\n");

 abort:

	mutex_unlock(&disks_mutex);

	if (!error) {
@@ -4434,7 +4437,7 @@ static int deny_bitmap_write_access(struct file * file) 
	return 0;

}



static void restore_bitmap_write_access(struct file *file)

void restore_bitmap_write_access(struct file *file)

{

	struct inode *inode = file->f_mapping->host;

drivers/md/md.h

+2 −1
Original line number Diff line number Diff line
@@ -372,7 +372,7 @@ struct md_sysfs_entry { 
	ssize_t (*show)(mddev_t *, char *);

	ssize_t (*store)(mddev_t *, const char *, size_t);

};



extern struct attribute_group md_bitmap_group;



static inline char * mdname (mddev_t * mddev)

{
@@ -465,5 +465,6 @@ extern int md_check_no_bitmap(mddev_t *mddev); 
extern int md_integrity_register(mddev_t *mddev);

extern void md_integrity_add_rdev(mdk_rdev_t *rdev, mddev_t *mddev);

extern int strict_strtoul_scaled(const char *cp, unsigned long *res, int scale);

extern void restore_bitmap_write_access(struct file *file);



#endif /* _MD_MD_H */