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[RESEND,2/2] btrfs: Remove dead code exclude_super_stripes

Message ID 20200403134035.8875-2-nborisov@suse.com (mailing list archive)
State New, archived
Headers show
Series [RESEND,1/2] btrfs: Read stripe len directly in btrfs_rmap_block | expand

Commit Message

Nikolay Borisov April 3, 2020, 1:40 p.m. UTC 
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>
---
 fs/btrfs/block-group.c | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

--
2.17.1
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Patch

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index d0dbaa470b88..7b96ded820f9 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1712,25 +1712,12 @@  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;