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btrfs: simplify checks when adding excluded ranges 

Adresses held in 'logical' array are always guaranteed to fall within
the boundaries of the block group. That is, 'start' can never be
smaller than cache->start. This invariant follows from the way the
address are calculated in btrfs_rmap_block:

    stripe_nr = physical - map->stripes[i].physical;
    stripe_nr = div64_u64(stripe_nr, map->stripe_len);
    bytenr = chunk_start + stripe_nr * io_stripe_size;

I.e it's always some IO stripe within the given chunk.

Exploit this invariant to simplify the body of the loop by removing the
unnecessary 'if' since its 'else' part is the one always executed.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Nikolay Borisov 2020-04-03 16:40:35 +03:00 committed by David Sterba
parent 9e22b92598
commit 96f9b0f2fa
1 changed files with 4 additions and 17 deletions
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21
fs/btrfs/block-group.c
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@ -1741,25 +1741,12 @@ static int exclude_super_stripes(struct btrfs_block_group *cache)
return ret;
while (nr--) {
u64 start, len;
if (logical[nr] > cache->start + cache->length)
continue;
if (logical[nr] + stripe_len <= cache->start)
continue;
start = logical[nr];
if (start < cache->start) {
start = cache->start;
len = (logical[nr] + stripe_len) - start;
} else {
len = min_t(u64, stripe_len,
cache->start + cache->length - start);
}
u64 len = min_t(u64, stripe_len,
cache->start + cache->length - logical[nr]);
cache->bytes_super += len;
ret = btrfs_add_excluded_extent(fs_info, start, len);
ret = btrfs_add_excluded_extent(fs_info, logical[nr],
len);
if (ret) {
kfree(logical);
return ret;