Btrfs: Start btree concurrency work.

The allocation trees and the chunk trees are serialized via their own
dedicated mutexes.  This means allocation location is still not very
fine grained.

The main FS btree is protected by locks on each block in the btree.  Locks
are taken top / down, and as processing finishes on a given level of the
tree, the lock is released after locking the lower level.

The end result of a search is now a path where only the lowest level
is locked.  Releasing or freeing the path drops any locks held.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 0 insertions, 8 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 17c508a941eb..bd15cdcaba95 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2889,7 +2889,6 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree,
 
         for (i = 0; i < num_pages; i++) {
                 page = extent_buffer_page(eb, i);
-                lock_page(page);
                 if (i == 0)
                         set_page_extent_head(page, eb->len);
                 else
@@ -2907,7 +2906,6 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree,
                         end  = start + PAGE_CACHE_SIZE - 1;
                         if (test_range_bit(tree, start, end,
                                            EXTENT_DIRTY, 0)) {
-                                unlock_page(page);
                                 continue;
                         }
                 }
@@ -2919,7 +2917,6 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree,
                                                 PAGECACHE_TAG_DIRTY);
                 }
                 read_unlock_irq(&page->mapping->tree_lock);
-                unlock_page(page);
         }
         return 0;
 }
@@ -2948,17 +2945,12 @@ int set_extent_buffer_dirty(struct extent_io_tree *tree,
                  * on us if the page isn't already dirty.
                  */
                 if (i == 0) {
-                        lock_page(page);
                         set_page_extent_head(page, eb->len);
                 } else if (PagePrivate(page) &&
                            page->private != EXTENT_PAGE_PRIVATE) {
-                        lock_page(page);
                         set_page_extent_mapped(page);
-                        unlock_page(page);
                 }
                 __set_page_dirty_nobuffers(extent_buffer_page(eb, i));
-                if (i == 0)
-                        unlock_page(page);
         }
         return set_extent_dirty(tree, eb->start,
                                 eb->start + eb->len - 1, GFP_NOFS);