Btrfs: report error after failure inlining extent in compressed write path

If cow_file_range_inline() failed, when called from compress_file_range(),
we were tagging the locked page for writeback, end its writeback and unlock it,
but not marking it with an error nor setting AS_EIO in inode's mapping flags.

This made it impossible for a caller of filemap_fdatawrite_range (writepages)
or filemap_fdatawait_range() to know that an error happened. And the return
value of compress_file_range() is useless because it's returned to a workqueue
task and not to the task calling filemap_fdatawrite_range (writepages).

This change applies on top of the previous patchset starting at the patch
titled:

    "[1/5] Btrfs: set page and mapping error on compressed write failure"

Which changed extent_clear_unlock_delalloc() to use SetPageError and
mapping_set_error().

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/inode.c

@@ -527,7 +527,10 @@ cont:
 		if (ret <= 0) {
 			unsigned long clear_flags = EXTENT_DELALLOC |
 				EXTENT_DEFRAG;
+			unsigned long page_error_op;
+
 			clear_flags |= (ret < 0) ? EXTENT_DO_ACCOUNTING : 0;
+			page_error_op = ret < 0 ? PAGE_SET_ERROR : 0;
 
 			/*
 			 * inline extent creation worked or returned error,
@@ -538,6 +541,7 @@ cont:
 						     clear_flags, PAGE_UNLOCK |
 						     PAGE_CLEAR_DIRTY |
 						     PAGE_SET_WRITEBACK |
+						     page_error_op |
 						     PAGE_END_WRITEBACK);
 			goto free_pages_out;
 		}