1 files changed, 25 insertions, 8 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 2be00e873e92..15b925142793 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -531,6 +531,14 @@ int btrfs_dirty_pages(struct inode *inode, struct page **pages,
 
 	end_of_last_block = start_pos + num_bytes - 1;
 
+	/*
+	 * The pages may have already been dirty, clear out old accounting so
+	 * we can set things up properly
+	 */
+	clear_extent_bit(&BTRFS_I(inode)->io_tree, start_pos, end_of_last_block,
+			 EXTENT_DIRTY | EXTENT_DELALLOC |
+			 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 0, 0, cached);
+
 	if (!btrfs_is_free_space_inode(BTRFS_I(inode))) {
 		if (start_pos >= isize &&
 		    !(BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC)) {
@@ -1500,18 +1508,27 @@ lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
 		}
 		if (ordered)
 			btrfs_put_ordered_extent(ordered);
-		clear_extent_bit(&inode->io_tree, start_pos, last_pos,
-				 EXTENT_DIRTY | EXTENT_DELALLOC |
-				 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
-				 0, 0, cached_state);
+
 		*lockstart = start_pos;
 		*lockend = last_pos;
 		ret = 1;
 	}
 
+	/*
+	 * It's possible the pages are dirty right now, but we don't want
+	 * to clean them yet because copy_from_user may catch a page fault
+	 * and we might have to fall back to one page at a time.  If that
+	 * happens, we'll unlock these pages and we'd have a window where
+	 * reclaim could sneak in and drop the once-dirty page on the floor
+	 * without writing it.
+	 *
+	 * We have the pages locked and the extent range locked, so there's
+	 * no way someone can start IO on any dirty pages in this range.
+	 *
+	 * We'll call btrfs_dirty_pages() later on, and that will flip around
+	 * delalloc bits and dirty the pages as required.
+	 */
 	for (i = 0; i < num_pages; i++) {
-		if (clear_page_dirty_for_io(pages[i]))
-			account_page_redirty(pages[i]);
 		set_page_extent_mapped(pages[i]);
 		WARN_ON(!PageLocked(pages[i]));
 	}
@@ -2544,7 +2561,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 	}
 
 	ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, rsv,
-				      min_size, 0);
+				      min_size, false);
 	BUG_ON(ret);
 	trans->block_rsv = rsv;
 
@@ -2594,7 +2611,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 		}
 
 		ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv,
-					      rsv, min_size, 0);
+					      rsv, min_size, false);
 		BUG_ON(ret);	/* shouldn't happen */
 		trans->block_rsv = rsv;