Commit 3b4ffa40 authored by Naohiro Aota's avatar Naohiro Aota Committed by David Sterba
Browse files

btrfs: refactor find_free_dev_extent_start() 



Factor out two functions from find_free_dev_extent_start().
dev_extent_search_start() decides the starting position of the search.
dev_extent_hole_check() checks if a hole found is suitable for device
extent allocation.

These functions also have the switch-cases to change the allocation
behavior depending on the policy.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent c4a816c6

fs/btrfs/volumes.c

+58 −20
Original line number Diff line number Diff line
@@ -1381,6 +1381,59 @@ static bool contains_pending_extent(struct btrfs_device *device, u64 *start, 
	return false;

}



static u64 dev_extent_search_start(struct btrfs_device *device, u64 start)

{

	switch (device->fs_devices->chunk_alloc_policy) {

	case BTRFS_CHUNK_ALLOC_REGULAR:

		/*

		 * We don't want to overwrite the superblock on the drive nor

		 * any area used by the boot loader (grub for example), so we

		 * make sure to start at an offset of at least 1MB.

		 */

		return max_t(u64, start, SZ_1M);

	default:

		BUG();

	}

}



/**

 * dev_extent_hole_check - check if specified hole is suitable for allocation

 * @device:	the device which we have the hole

 * @hole_start: starting position of the hole

 * @hole_size:	the size of the hole

 * @num_bytes:	the size of the free space that we need

 *

 * This function may modify @hole_start and @hole_end to reflect the suitable

 * position for allocation. Returns 1 if hole position is updated, 0 otherwise.

 */

static bool dev_extent_hole_check(struct btrfs_device *device, u64 *hole_start,

				  u64 *hole_size, u64 num_bytes)

{

	bool changed = false;

	u64 hole_end = *hole_start + *hole_size;



	/*

	 * Check before we set max_hole_start, otherwise we could end up

	 * sending back this offset anyway.

	 */

	if (contains_pending_extent(device, hole_start, *hole_size)) {

		if (hole_end >= *hole_start)

			*hole_size = hole_end - *hole_start;

		else

			*hole_size = 0;

		changed = true;

	}



	switch (device->fs_devices->chunk_alloc_policy) {

	case BTRFS_CHUNK_ALLOC_REGULAR:

		/* No extra check */

		break;

	default:

		BUG();

	}



	return changed;

}



/*

 * find_free_dev_extent_start - find free space in the specified device
@@ -1427,12 +1480,7 @@ static int find_free_dev_extent_start(struct btrfs_device *device, 
	int slot;

	struct extent_buffer *l;



	/*

	 * We don't want to overwrite the superblock on the drive nor any area

	 * used by the boot loader (grub for example), so we make sure to start

	 * at an offset of at least 1MB.

	 */

	search_start = max_t(u64, search_start, SZ_1M);

	search_start = dev_extent_search_start(device, search_start);



	path = btrfs_alloc_path();

	if (!path)
@@ -1490,18 +1538,8 @@ again: 


		if (key.offset > search_start) {

			hole_size = key.offset - search_start;



			/*

			 * Have to check before we set max_hole_start, otherwise

			 * we could end up sending back this offset anyway.

			 */

			if (contains_pending_extent(device, &search_start,

						    hole_size)) {

				if (key.offset >= search_start)

					hole_size = key.offset - search_start;

				else

					hole_size = 0;

			}

			dev_extent_hole_check(device, &search_start, &hole_size,

					      num_bytes);



			if (hole_size > max_hole_size) {

				max_hole_start = search_start;
@@ -1540,8 +1578,8 @@ next: 
	 */

	if (search_end > search_start) {

		hole_size = search_end - search_start;



		if (contains_pending_extent(device, &search_start, hole_size)) {

		if (dev_extent_hole_check(device, &search_start, &hole_size,

					  num_bytes)) {

			btrfs_release_path(path);

			goto again;

		}

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