Commit 96f9b0f2 authored Apr 03, 2020 by Nikolay Borisov Committed by David Sterba Jul 27, 2020

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>

parent 9e22b925

fs/btrfs/block-group.c

+4 −17

Original line number	Diff line number	Diff line
		@@ -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;

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