erofs: convert workstn to XArray

XArray has friendly APIs and it will replace the old radix
tree in the near future.

This convert makes use of __xa_cmpxchg when inserting on
a just inserted item by other thread. In detail, instead
of totally looking up again as what we did for the old
radix tree, it will try to legitimize the current in-tree
item in the XArray therefore more effective.

In addition, naming is rather a challenge for non-English
speaker like me. The basic idea of workstn is to provide
a runtime sparse array with items arranged in the physical
block number order. Such items (was called workgroup) can be
used to record compress clusters or for later new features.

However, both workgroup and workstn seem not good names from
whatever point of view, so I'd like to rename them as pslot
and managed_pslots to stand for physical slots. This patch
handles the second as a part of the radix tree convert.

Cc: Matthew Wilcox <willy@infradead.org>
Link: https://lore.kernel.org/r/20200220024642.91529-1-gaoxiang25@huawei.com
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index c4c6dcdc89ad..5eead7fdc7a6 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -52,8 +52,8 @@ struct erofs_sb_info {
 	struct list_head list;
 	struct mutex umount_mutex;
 
-	/* the dedicated workstation for compression */
-	struct radix_tree_root workstn_tree;
+	/* managed XArray arranged in physical block number */
+	struct xarray managed_pslots;
 
 	/* threshold for decompression synchronously */
 	unsigned int max_sync_decompress_pages;
@@ -402,8 +402,8 @@ static inline void *erofs_get_pcpubuf(unsigned int pagenr)
 int erofs_workgroup_put(struct erofs_workgroup *grp);
 struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
 					     pgoff_t index);
-int erofs_register_workgroup(struct super_block *sb,
-			     struct erofs_workgroup *grp);
+struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
+					       struct erofs_workgroup *grp);
 void erofs_workgroup_free_rcu(struct erofs_workgroup *grp);
 void erofs_shrinker_register(struct super_block *sb);
 void erofs_shrinker_unregister(struct super_block *sb);