Commit de11cc12 authored by Li Zefan's avatar Li Zefan
Browse files

Btrfs: don't pre-allocate btrfs bio 



We pre-allocate a btrfs bio with fixed size, and then may re-allocate
memory if we find stripes are bigger than the fixed size. But this
pre-allocation is not necessary.

Also we don't have to calcuate the stripe number twice.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
parent 125ccb0a

fs/btrfs/volumes.c

+21 −46
Original line number Diff line number Diff line
@@ -2897,26 +2897,13 @@ static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw, 
	u64 stripe_nr;

	u64 stripe_nr_orig;

	u64 stripe_nr_end;

	int stripes_allocated = 8;

	int stripes_required = 1;

	int stripe_index;

	int i;

	int ret = 0;

	int num_stripes;

	int max_errors = 0;

	struct btrfs_bio *bbio = NULL;



	if (bbio_ret && !(rw & (REQ_WRITE | REQ_DISCARD)))

		stripes_allocated = 1;

again:

	if (bbio_ret) {

		bbio = kzalloc(btrfs_bio_size(stripes_allocated),

				GFP_NOFS);

		if (!bbio)

			return -ENOMEM;



		atomic_set(&bbio->error, 0);

	}



	read_lock(&em_tree->lock);

	em = lookup_extent_mapping(em_tree, logical, *length);

	read_unlock(&em_tree->lock);
@@ -2935,32 +2922,6 @@ again: 
	if (mirror_num > map->num_stripes)

		mirror_num = 0;



	/* if our btrfs_bio struct is too small, back off and try again */

	if (rw & REQ_WRITE) {

		if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |

				 BTRFS_BLOCK_GROUP_DUP)) {

			stripes_required = map->num_stripes;

			max_errors = 1;

		} else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {

			stripes_required = map->sub_stripes;

			max_errors = 1;

		}

	}

	if (rw & REQ_DISCARD) {

		if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |

				 BTRFS_BLOCK_GROUP_RAID1 |

				 BTRFS_BLOCK_GROUP_DUP |

				 BTRFS_BLOCK_GROUP_RAID10)) {

			stripes_required = map->num_stripes;

		}

	}

	if (bbio_ret && (rw & (REQ_WRITE | REQ_DISCARD)) &&

	    stripes_allocated < stripes_required) {

		stripes_allocated = map->num_stripes;

		free_extent_map(em);

		kfree(bbio);

		goto again;

	}

	stripe_nr = offset;

	/*

	 * stripe_nr counts the total number of stripes we have to stride
@@ -3055,6 +3016,13 @@ again: 
	}

	BUG_ON(stripe_index >= map->num_stripes);



	bbio = kzalloc(btrfs_bio_size(num_stripes), GFP_NOFS);

	if (!bbio) {

		ret = -ENOMEM;

		goto out;

	}

	atomic_set(&bbio->error, 0);



	if (rw & REQ_DISCARD) {

		for (i = 0; i < num_stripes; i++) {

			bbio->stripes[i].physical =
@@ -3151,15 +3119,22 @@ again: 
			stripe_index++;

		}

	}

	if (bbio_ret) {



	if (rw & REQ_WRITE) {

		if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |

				 BTRFS_BLOCK_GROUP_RAID10 |

				 BTRFS_BLOCK_GROUP_DUP)) {

			max_errors = 1;

		}

	}



	*bbio_ret = bbio;

	bbio->num_stripes = num_stripes;

	bbio->max_errors = max_errors;

	bbio->mirror_num = mirror_num;

	}

out:

	free_extent_map(em);

	return 0;

	return ret;

}



int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,

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