1 files changed, 55 insertions, 29 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 782f3bc4651d..02d05817cbdf 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1277,7 +1277,12 @@ int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		      unsigned bits, gfp_t mask)
 {
-	return clear_extent_bit(tree, start, end, bits, 0, 0, NULL, mask);
+	int wake = 0;
+
+	if (bits & EXTENT_LOCKED)
+		wake = 1;
+
+	return clear_extent_bit(tree, start, end, bits, wake, 0, NULL, mask);
 }
 
 int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
@@ -2767,8 +2772,6 @@ static int __must_check submit_one_bio(int rw, struct bio *bio,
 	else
 		btrfsic_submit_bio(rw, bio);
 
-	if (bio_flagged(bio, BIO_EOPNOTSUPP))
-		ret = -EOPNOTSUPP;
 	bio_put(bio);
 	return ret;
 }
@@ -4492,6 +4495,8 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		}
 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
 			flags |= FIEMAP_EXTENT_ENCODED;
+		if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
+			flags |= FIEMAP_EXTENT_UNWRITTEN;
 
 		free_extent_map(em);
 		em = NULL;
@@ -4560,36 +4565,37 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
 	do {
 		index--;
 		page = eb->pages[index];
-		if (page && mapped) {
+		if (!page)
+			continue;
+		if (mapped)
 			spin_lock(&page->mapping->private_lock);
+		/*
+		 * We do this since we'll remove the pages after we've
+		 * removed the eb from the radix tree, so we could race
+		 * and have this page now attached to the new eb.  So
+		 * only clear page_private if it's still connected to
+		 * this eb.
+		 */
+		if (PagePrivate(page) &&
+		    page->private == (unsigned long)eb) {
+			BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
+			BUG_ON(PageDirty(page));
+			BUG_ON(PageWriteback(page));
 			/*
-			 * We do this since we'll remove the pages after we've
-			 * removed the eb from the radix tree, so we could race
-			 * and have this page now attached to the new eb.  So
-			 * only clear page_private if it's still connected to
-			 * this eb.
+			 * We need to make sure we haven't be attached
+			 * to a new eb.
 			 */
-			if (PagePrivate(page) &&
-			    page->private == (unsigned long)eb) {
-				BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
-				BUG_ON(PageDirty(page));
-				BUG_ON(PageWriteback(page));
-				/*
-				 * We need to make sure we haven't be attached
-				 * to a new eb.
-				 */
-				ClearPagePrivate(page);
-				set_page_private(page, 0);
-				/* One for the page private */
-				page_cache_release(page);
-			}
-			spin_unlock(&page->mapping->private_lock);
-
-		}
-		if (page) {
-			/* One for when we alloced the page */
+			ClearPagePrivate(page);
+			set_page_private(page, 0);
+			/* One for the page private */
 			page_cache_release(page);
 		}
+
+		if (mapped)
+			spin_unlock(&page->mapping->private_lock);
+
+		/* One for when we alloced the page */
+		page_cache_release(page);
 	} while (index != 0);
 }
 
@@ -4771,6 +4777,25 @@ struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
 			       start >> PAGE_CACHE_SHIFT);
 	if (eb && atomic_inc_not_zero(&eb->refs)) {
 		rcu_read_unlock();
+		/*
+		 * Lock our eb's refs_lock to avoid races with
+		 * free_extent_buffer. When we get our eb it might be flagged
+		 * with EXTENT_BUFFER_STALE and another task running
+		 * free_extent_buffer might have seen that flag set,
+		 * eb->refs == 2, that the buffer isn't under IO (dirty and
+		 * writeback flags not set) and it's still in the tree (flag
+		 * EXTENT_BUFFER_TREE_REF set), therefore being in the process
+		 * of decrementing the extent buffer's reference count twice.
+		 * So here we could race and increment the eb's reference count,
+		 * clear its stale flag, mark it as dirty and drop our reference
+		 * before the other task finishes executing free_extent_buffer,
+		 * which would later result in an attempt to free an extent
+		 * buffer that is dirty.
+		 */
+		if (test_bit(EXTENT_BUFFER_STALE, &eb->bflags)) {
+			spin_lock(&eb->refs_lock);
+			spin_unlock(&eb->refs_lock);
+		}
 		mark_extent_buffer_accessed(eb, NULL);
 		return eb;
 	}
@@ -4870,6 +4895,7 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 				mark_extent_buffer_accessed(exists, p);
 				goto free_eb;
 			}
+			exists = NULL;
 
 			/*
 			 * Do this so attach doesn't complain and we need to
@@ -4933,12 +4959,12 @@ again:
 	return eb;
 
 free_eb:
+	WARN_ON(!atomic_dec_and_test(&eb->refs));
 	for (i = 0; i < num_pages; i++) {
 		if (eb->pages[i])
 			unlock_page(eb->pages[i]);
 	}
 
-	WARN_ON(!atomic_dec_and_test(&eb->refs));
 	btrfs_release_extent_buffer(eb);
 	return exists;
 }