Commit 61d0d0d2 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: Handle pending/pinned chunks before blockgroup relocation during device shrink 



During device shrink pinned/pending chunks (i.e. those which have been
deleted/created respectively, in the current transaction and haven't
touched disk) need to be accounted when doing device shrink. Presently
this happens after the main relocation loop in btrfs_shrink_device,
which could lead to making another go in the body of the function.

Since there is no hard requirement to perform pinned/pending chunks
handling after the relocation loop, move the code before it. This leads
to simplifying the code flow around - i.e. no need to use 'goto again'.

A notable side effect of this change is that modification of the
device's size requires a transaction to be started and committed before
the relocation loop starts. This is necessary to ensure that relocation
process sees the shrunk device size.

Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent bbbf7243

fs/btrfs/volumes.c

+23 −32
Original line number Original line Diff line number Diff line
@@ -4720,15 +4720,16 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) 
	int slot;

	int slot;

	int failed = 0;

	int failed = 0;

	bool retried = false;

	bool retried = false;

	bool checked_pending_chunks = false;

	struct extent_buffer *l;

	struct extent_buffer *l;

	struct btrfs_key key;

	struct btrfs_key key;

	struct btrfs_super_block *super_copy = fs_info->super_copy;

	struct btrfs_super_block *super_copy = fs_info->super_copy;

	u64 old_total = btrfs_super_total_bytes(super_copy);

	u64 old_total = btrfs_super_total_bytes(super_copy);

	u64 old_size = btrfs_device_get_total_bytes(device);

	u64 old_size = btrfs_device_get_total_bytes(device);

	u64 diff;

	u64 diff;

	u64 start;





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

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

	start = new_size;

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

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





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

	if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
@@ -4740,6 +4741,12 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) 




	path->reada = READA_BACK;

	path->reada = READA_BACK;





	trans = btrfs_start_transaction(root, 0);

	if (IS_ERR(trans)) {

		btrfs_free_path(path);

		return PTR_ERR(trans);

	}



	mutex_lock(&fs_info->chunk_mutex);

	mutex_lock(&fs_info->chunk_mutex);





	btrfs_device_set_total_bytes(device, new_size);

	btrfs_device_set_total_bytes(device, new_size);
@@ -4747,7 +4754,21 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) 
		device->fs_devices->total_rw_bytes -= diff;

		device->fs_devices->total_rw_bytes -= diff;

		atomic64_sub(diff, &fs_info->free_chunk_space);

		atomic64_sub(diff, &fs_info->free_chunk_space);

	}

	}



	/*

	 * Once the device's size has been set to the new size, ensure all

	 * in-memory chunks are synced to disk so that the loop below sees them

	 * and relocates them accordingly.

	 */

	if (contains_pending_extent(trans->transaction, device, &start, diff)) {

		mutex_unlock(&fs_info->chunk_mutex);

		mutex_unlock(&fs_info->chunk_mutex);

		ret = btrfs_commit_transaction(trans);

		if (ret)

			goto done;

	} else {

		mutex_unlock(&fs_info->chunk_mutex);

		btrfs_end_transaction(trans);

	}





again:

again:

	key.objectid = device->devid;

	key.objectid = device->devid;
@@ -4838,36 +4859,6 @@ again: 
	}

	}





	mutex_lock(&fs_info->chunk_mutex);

	mutex_lock(&fs_info->chunk_mutex);



	/*

	 * We checked in the above loop all device extents that were already in

	 * the device tree. However before we have updated the device's

	 * total_bytes to the new size, we might have had chunk allocations that

	 * have not complete yet (new block groups attached to transaction

	 * handles), and therefore their device extents were not yet in the

	 * device tree and we missed them in the loop above. So if we have any

	 * pending chunk using a device extent that overlaps the device range

	 * that we can not use anymore, commit the current transaction and

	 * repeat the search on the device tree - this way we guarantee we will

	 * not have chunks using device extents that end beyond 'new_size'.

	 */

	if (!checked_pending_chunks) {

		u64 start = new_size;

		u64 len = old_size - new_size;



		if (contains_pending_extent(trans->transaction, device,

					    &start, len)) {

			mutex_unlock(&fs_info->chunk_mutex);

			checked_pending_chunks = true;

			failed = 0;

			retried = false;

			ret = btrfs_commit_transaction(trans);

			if (ret)

				goto done;

			goto again;

		}

	}



	btrfs_device_set_disk_total_bytes(device, new_size);

	btrfs_device_set_disk_total_bytes(device, new_size);

	if (list_empty(&device->post_commit_list))

	if (list_empty(&device->post_commit_list))

		list_add_tail(&device->post_commit_list,

		list_add_tail(&device->post_commit_list,

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