Commit e9fd2c05 authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: fix ->free_chunk_space math in btrfs_shrink_device 



There are two bugs in how we adjust ->free_chunk_space in
btrfs_shrink_device.  First we're removing the entire diff between
new_size and old_size from ->free_chunk_space.  This only works if we're
reducing the free area, which we could potentially not be.  So adjust
the math to only subtract the diff in the free space from
->free_chunk_space.

Additionally in the error case we're unconditionally adding the diff
back into ->free_chunk_space, which we need to only do if this device is
writeable.

Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent efba1454

fs/btrfs/volumes.c

+17 −3
Original line number Diff line number Diff line
@@ -4722,6 +4722,7 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) 
	u64 old_size = btrfs_device_get_total_bytes(device);

	u64 diff;

	u64 start;

	u64 free_diff = 0;



	new_size = round_down(new_size, fs_info->sectorsize);

	start = new_size;
@@ -4747,7 +4748,19 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) 
	btrfs_device_set_total_bytes(device, new_size);

	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {

		device->fs_devices->total_rw_bytes -= diff;

		atomic64_sub(diff, &fs_info->free_chunk_space);



		/*

		 * The new free_chunk_space is new_size - used, so we have to

		 * subtract the delta of the old free_chunk_space which included

		 * old_size - used.  If used > new_size then just subtract this

		 * entire device's free space.

		 */

		if (device->bytes_used < new_size)

			free_diff = (old_size - device->bytes_used) -

				    (new_size - device->bytes_used);

		else

			free_diff = old_size - device->bytes_used;

		atomic64_sub(free_diff, &fs_info->free_chunk_space);

	}



	/*
@@ -4882,9 +4895,10 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) 
	if (ret) {

		mutex_lock(&fs_info->chunk_mutex);

		btrfs_device_set_total_bytes(device, old_size);

		if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))

		if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {

			device->fs_devices->total_rw_bytes += diff;

		atomic64_add(diff, &fs_info->free_chunk_space);

			atomic64_add(free_diff, &fs_info->free_chunk_space);

		}

		mutex_unlock(&fs_info->chunk_mutex);

	}

	return ret;