Btrfs: Use a mutex in the extent buffer for tree block locking

This replaces the use of the page cache lock bit for locking, which wasn't
suitable for block size < page size and couldn't be used recursively.

The mutexes alone don't fix either problem, but they are the first step.

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

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 32bb4ed3723d..7380449cb5b3 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2690,6 +2690,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
         eb = kmem_cache_zalloc(extent_buffer_cache, mask);
         eb->start = start;
         eb->len = len;
+        mutex_init(&eb->mutex);
         spin_lock_irqsave(&leak_lock, flags);
         list_add(&eb->leak_list, &buffers);
         spin_unlock_irqrestore(&leak_lock, flags);
@@ -2837,6 +2838,7 @@ 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
@@ -2854,6 +2856,7 @@ 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;
                         }
                 }
@@ -2865,6 +2868,7 @@ 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;
 }
@@ -2893,12 +2897,17 @@ 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);