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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: Li Zefan <lizf@cn.fujitsu.com>
This commit is contained in:
Li Zefan 2011-12-01 12:55:47 +08:00
parent 125ccb0ae6
commit de11cc12df
1 changed files with 21 additions and 46 deletions
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67
fs/btrfs/volumes.c
View File

@ -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) {
*bbio_ret = bbio;
bbio->num_stripes = num_stripes;
bbio->max_errors = max_errors;
bbio->mirror_num = mirror_num;
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,