btrfs: rename member 'trimming' of block group to a more generic name

Back in 2014, commit 04216820fe83d5 ("Btrfs: fix race between fs trimming
and block group remove/allocation"), I added the 'trimming' member to the
block group structure. Its purpose was to prevent races between trimming
and block group deletion/allocation by pinning the block group in a way
that prevents its logical address and device extents from being reused
while trimming is in progress for a block group, so that if another task
deletes the block group and then another task allocates a new block group
that gets the same logical address and device extents while the trimming
task is still in progress.

After the previous fix for scrub (patch "btrfs: fix a race between scrub
and block group removal/allocation"), scrub now also has the same needs that
trimming has, so the member name 'trimming' no longer makes sense.
Since there is already a 'pinned' member in the block group that refers
to space reservations (pinned bytes), rename the member to 'frozen',
add a comment on top of it to describe its general purpose and rename
the helpers to increment and decrement the counter as well, to match
the new member name.

The next patch in the series will move the helpers into a more suitable
file (from free-space-cache.c to block-group.c).

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 13 insertions, 12 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 3613da065a73..e9cfe9da6bbe 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3762,12 +3762,12 @@ out:
 	return ret;
 }
 
-void btrfs_get_block_group_trimming(struct btrfs_block_group *cache)
+void btrfs_freeze_block_group(struct btrfs_block_group *cache)
 {
-	atomic_inc(&cache->trimming);
+	atomic_inc(&cache->frozen);
 }
 
-void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
+void btrfs_unfreeze_block_group(struct btrfs_block_group *block_group)
 {
 	struct btrfs_fs_info *fs_info = block_group->fs_info;
 	struct extent_map_tree *em_tree;
@@ -3775,7 +3775,7 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
 	bool cleanup;
 
 	spin_lock(&block_group->lock);
-	cleanup = (atomic_dec_and_test(&block_group->trimming) &&
+	cleanup = (atomic_dec_and_test(&block_group->frozen) &&
 		   block_group->removed);
 	spin_unlock(&block_group->lock);
 
@@ -3795,8 +3795,9 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
 		free_extent_map(em);
 
 		/*
-		 * We've left one free space entry and other tasks trimming
-		 * this block group have left 1 entry each one. Free them.
+		 * We may have left one free space entry and other possible
+		 * tasks trimming this block group have left 1 entry each one.
+		 * Free them if any.
 		 */
 		__btrfs_remove_free_space_cache(block_group->free_space_ctl);
 	}
@@ -3816,7 +3817,7 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-	btrfs_get_block_group_trimming(block_group);
+	btrfs_freeze_block_group(block_group);
 	spin_unlock(&block_group->lock);
 
 	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, false);
@@ -3829,7 +3830,7 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 	if (rem)
 		reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
 out:
-	btrfs_put_block_group_trimming(block_group);
+	btrfs_unfreeze_block_group(block_group);
 	return ret;
 }
 
@@ -3846,11 +3847,11 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-	btrfs_get_block_group_trimming(block_group);
+	btrfs_freeze_block_group(block_group);
 	spin_unlock(&block_group->lock);
 
 	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, async);
-	btrfs_put_block_group_trimming(block_group);
+	btrfs_unfreeze_block_group(block_group);
 
 	return ret;
 }
@@ -3868,13 +3869,13 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-	btrfs_get_block_group_trimming(block_group);
+	btrfs_freeze_block_group(block_group);
 	spin_unlock(&block_group->lock);
 
 	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, maxlen,
 			   async);
 
-	btrfs_put_block_group_trimming(block_group);
+	btrfs_unfreeze_block_group(block_group);
 
 	return ret;
 }