Btrfs: Avoid fragmentation from parallel delalloc filling

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

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index f91f28e..7fd4eb7 100644 (file)
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1033,11 +1033,11 @@ out:
 EXPORT_SYMBOL(find_first_extent_bit);
 
 u64 find_lock_delalloc_range(struct extent_map_tree *tree,
-                            u64 start, u64 lock_start, u64 *end, u64 max_bytes)
+                            u64 *start, u64 *end, u64 max_bytes)
 {
        struct rb_node *node;
        struct extent_state *state;
-       u64 cur_start = start;
+       u64 cur_start = *start;
        u64 found = 0;
        u64 total_bytes = 0;
 
@@ -1054,27 +1054,43 @@ search_again:
 
        while(1) {
                state = rb_entry(node, struct extent_state, rb_node);
-               if (state->start != cur_start) {
+               if (found && state->start != cur_start) {
                        goto out;
                }
                if (!(state->state & EXTENT_DELALLOC)) {
                        goto out;
                }
-               if (state->start >= lock_start) {
-                       if (state->state & EXTENT_LOCKED) {
-                               DEFINE_WAIT(wait);
-                               atomic_inc(&state->refs);
-                               prepare_to_wait(&state->wq, &wait,
-                                               TASK_UNINTERRUPTIBLE);
-                               write_unlock_irq(&tree->lock);
-                               schedule();
-                               write_lock_irq(&tree->lock);
-                               finish_wait(&state->wq, &wait);
-                               free_extent_state(state);
-                               goto search_again;
+               if (!found) {
+                       struct extent_state *prev_state;
+                       struct rb_node *prev_node = node;
+                       while(1) {
+                               prev_node = rb_prev(prev_node);
+                               if (!prev_node)
+                                       break;
+                               prev_state = rb_entry(prev_node,
+                                                     struct extent_state,
+                                                     rb_node);
+                               if (!(prev_state->state & EXTENT_DELALLOC))
+                                       break;
+                               state = prev_state;
+                               node = prev_node;
                        }
-                       state->state |= EXTENT_LOCKED;
                }
+               if (state->state & EXTENT_LOCKED) {
+                       DEFINE_WAIT(wait);
+                       atomic_inc(&state->refs);
+                       prepare_to_wait(&state->wq, &wait,
+                                       TASK_UNINTERRUPTIBLE);
+                       write_unlock_irq(&tree->lock);
+                       schedule();
+                       write_lock_irq(&tree->lock);
+                       finish_wait(&state->wq, &wait);
+                       free_extent_state(state);
+                       goto search_again;
+               }
+               state->state |= EXTENT_LOCKED;
+               if (!found)
+                       *start = state->start;
                found++;
                *end = state->end;
                cur_start = state->end + 1;
@@ -1695,6 +1711,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
        struct extent_page_data *epd = data;
        struct extent_map_tree *tree = epd->tree;
        u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+       u64 delalloc_start;
        u64 page_end = start + PAGE_CACHE_SIZE - 1;
        u64 end;
        u64 cur = start;
@@ -1729,25 +1746,23 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 
        set_page_extent_mapped(page);
 
-       lock_extent(tree, start, page_end, GFP_NOFS);
-       nr_delalloc = find_lock_delalloc_range(tree, start, page_end + 1,
-                                              &delalloc_end,
-                                              128 * 1024 * 1024);
-       if (nr_delalloc) {
-               tree->ops->fill_delalloc(inode, start, delalloc_end);
-               if (delalloc_end >= page_end + 1) {
-                       clear_extent_bit(tree, page_end + 1, delalloc_end,
-                                        EXTENT_LOCKED | EXTENT_DELALLOC,
-                                        1, 0, GFP_NOFS);
-               }
-               clear_extent_bit(tree, start, page_end, EXTENT_DELALLOC,
-                                0, 0, GFP_NOFS);
-               if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0)) {
-                       printk("found delalloc bits after clear extent_bit\n");
-               }
-       } else if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0)) {
-               printk("found delalloc bits after find_delalloc_range returns 0\n");
+       delalloc_start = start;
+       delalloc_end = 0;
+       while(delalloc_end < page_end) {
+               nr_delalloc = find_lock_delalloc_range(tree, &delalloc_start,
+                                                      &delalloc_end,
+                                                      128 * 1024 * 1024);
+               if (nr_delalloc <= 0)
+                       break;
+               tree->ops->fill_delalloc(inode, delalloc_start,
+                                        delalloc_end);
+               clear_extent_bit(tree, delalloc_start,
+                                delalloc_end,
+                                EXTENT_LOCKED | EXTENT_DELALLOC,
+                                1, 0, GFP_NOFS);
+               delalloc_start = delalloc_end + 1;
        }
+       lock_extent(tree, start, page_end, GFP_NOFS);
 
        end = page_end;
        if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0)) {