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Commit 3009a62f authored by David Sterba's avatar David Sterba
Browse files

btrfs: track running balance in a simpler way 



Currently fs_info::balance_running is 0 or 1 and does not use the
semantics of atomics. The pause and cancel check for 0, that can happen
only after __btrfs_balance exits for whatever reason.

Parallel calls to balance ioctl may enter btrfs_ioctl_balance multiple
times but will block on the balance_mutex that protects the
fs_info::flags bit.

Reviewed-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent dccdb07b

fs/btrfs/ctree.h

+6 −1
Original line number Diff line number Diff line
@@ -739,6 +739,12 @@ struct btrfs_delayed_root; 
 */

#define BTRFS_FS_NEED_ASYNC_COMMIT		17



/*

 * Indicate that balance has been set up from the ioctl and is in the main

 * phase. The fs_info::balance_ctl is initialized.

 */

#define BTRFS_FS_BALANCE_RUNNING		18



struct btrfs_fs_info {

	u8 fsid[BTRFS_FSID_SIZE];

	u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
@@ -1003,7 +1009,6 @@ struct btrfs_fs_info { 
	/* restriper state */

	spinlock_t balance_lock;

	struct mutex balance_mutex;

	atomic_t balance_running;

	atomic_t balance_pause_req;

	atomic_t balance_cancel_req;

	struct btrfs_balance_control *balance_ctl;

fs/btrfs/disk-io.c

+0 −1
Original line number Diff line number Diff line
@@ -2164,7 +2164,6 @@ static void btrfs_init_balance(struct btrfs_fs_info *fs_info) 
{

	spin_lock_init(&fs_info->balance_lock);

	mutex_init(&fs_info->balance_mutex);

	atomic_set(&fs_info->balance_running, 0);

	atomic_set(&fs_info->balance_pause_req, 0);

	atomic_set(&fs_info->balance_cancel_req, 0);

	fs_info->balance_ctl = NULL;

fs/btrfs/ioctl.c

+3 −3
Original line number Diff line number Diff line
@@ -4312,7 +4312,7 @@ void update_ioctl_balance_args(struct btrfs_fs_info *fs_info, int lock, 


	bargs->flags = bctl->flags;



	if (atomic_read(&fs_info->balance_running))

	if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags))

		bargs->state |= BTRFS_BALANCE_STATE_RUNNING;

	if (atomic_read(&fs_info->balance_pause_req))

		bargs->state |= BTRFS_BALANCE_STATE_PAUSE_REQ;
@@ -4364,7 +4364,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg) 
	mutex_lock(&fs_info->balance_mutex);

	if (fs_info->balance_ctl) {

		/* this is either (2) or (3) */

		if (!atomic_read(&fs_info->balance_running)) {

		if (!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {

			mutex_unlock(&fs_info->balance_mutex);

			/*

			 * Lock released to allow other waiters to continue,
@@ -4373,7 +4373,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg) 
			mutex_lock(&fs_info->balance_mutex);



			if (fs_info->balance_ctl &&

			    !atomic_read(&fs_info->balance_running)) {

			    !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {

				/* this is (3) */

				need_unlock = false;

				goto locked;

fs/btrfs/volumes.c

+10 −8
Original line number Diff line number Diff line
@@ -3907,13 +3907,14 @@ int btrfs_balance(struct btrfs_balance_control *bctl, 
		spin_unlock(&fs_info->balance_lock);

	}



	atomic_inc(&fs_info->balance_running);

	ASSERT(!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));

	set_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);

	mutex_unlock(&fs_info->balance_mutex);



	ret = __btrfs_balance(fs_info);



	mutex_lock(&fs_info->balance_mutex);

	atomic_dec(&fs_info->balance_running);

	clear_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);



	if (bargs) {

		memset(bargs, 0, sizeof(*bargs));
@@ -4061,16 +4062,16 @@ int btrfs_pause_balance(struct btrfs_fs_info *fs_info) 
		return -ENOTCONN;

	}



	if (atomic_read(&fs_info->balance_running)) {

	if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {

		atomic_inc(&fs_info->balance_pause_req);

		mutex_unlock(&fs_info->balance_mutex);



		wait_event(fs_info->balance_wait_q,

			   atomic_read(&fs_info->balance_running) == 0);

			   !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));



		mutex_lock(&fs_info->balance_mutex);

		/* we are good with balance_ctl ripped off from under us */

		BUG_ON(atomic_read(&fs_info->balance_running));

		BUG_ON(test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));

		atomic_dec(&fs_info->balance_pause_req);

	} else {

		ret = -ENOTCONN;
@@ -4096,10 +4097,10 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info) 
	 * if we are running just wait and return, balance item is

	 * deleted in btrfs_balance in this case

	 */

	if (atomic_read(&fs_info->balance_running)) {

	if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {

		mutex_unlock(&fs_info->balance_mutex);

		wait_event(fs_info->balance_wait_q,

			   atomic_read(&fs_info->balance_running) == 0);

			   !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));

		mutex_lock(&fs_info->balance_mutex);

	} else {

		mutex_unlock(&fs_info->balance_mutex);
@@ -4115,7 +4116,8 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info) 
		}

	}



	BUG_ON(fs_info->balance_ctl || atomic_read(&fs_info->balance_running));

	BUG_ON(fs_info->balance_ctl ||

		test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));

	atomic_dec(&fs_info->balance_cancel_req);

	mutex_unlock(&fs_info->balance_mutex);

	return 0;