btrfs: move ordered extent cleanup to where they are allocated

The ordered extent cleanup is hard to grasp because it doesn't follow
the common cleanup-asap pattern.

E.g. run_delalloc_nocow() and cow_file_range() allocate one or more
ordered extent, but if any error is hit, the cleanup is done later inside
btrfs_run_delalloc_range().

To change the existing delayed cleanup:

- Update the comment on error handling of run_delalloc_nocow()
  There are in fact 3 different cases other than 2 if we are doing
  ordered extents cleanup inside run_delalloc_nocow():

  1) @cow_start and @cow_end not set
     No fallback to COW at all.
     Before @cur_offset we need to cleanup the OE and page dirty.
     After @cur_offset just clear all involved page and extent flags.

  2) @cow_start set but @cow_end not set.
     This means we failed before even calling fallback_to_cow().
     It's just a variant of case 1), where it's @cow_start splitting
     the two parts (and we should just ignore @cur_offset since it's
     advanced without any new ordered extent).

  3) @cow_start and @cow_end both set
     This means fallback_to_cow() failed, meaning [start, cow_start)
     needs the regular OE and dirty folio cleanup, and skip range
     [cow_start, cow_end) as cow_file_range() has done the cleanup,
     and eventually cleanup [cow_end, end) range.

- Only reset @cow_start after fallback_to_cow() succeeded
  As above case 2) and 3) are both relying on @cow_start to determine
  the cleanup range.

- Move btrfs_cleanup_ordered_extents() into run_delalloc_nocow(),
  cow_file_range() and nocow_one_range()

  For cow_file_range() it's pretty straightforward and easy.

  For run_delalloc_nocow() refer to the above 3 different error cases.

  For nocow_one_range() if we hit an error, we need to cleanup the
  ordered extents by ourselves.
  And then it will fallback to case 1), since @cur_offset is not yet
  advanced, the existing cleanup will co-operate with nocow_one_range()
  well.

- Remove the btrfs_cleanup_ordered_extents() inside submit_uncompressed_range()
  As failed cow_file_range() will do all the proper cleanup now.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -1090,7 +1090,6 @@ static void submit_uncompressed_range(struct btrfs_inode *inode,
 			       &wbc, false);
 	wbc_detach_inode(&wbc);
 	if (ret < 0) {
-		btrfs_cleanup_ordered_extents(inode, start, end - start + 1);
 		if (locked_folio)
 			btrfs_folio_end_lock(inode->root->fs_info, locked_folio,
 					     start, async_extent->ram_size);
@@ -1272,10 +1271,7 @@ u64 btrfs_get_extent_allocation_hint(struct btrfs_inode *inode, u64 start,
  * - Else all pages except for @locked_folio are unlocked.
  *
  * When a failure happens in the second or later iteration of the
- * while-loop, the ordered extents created in previous iterations are kept
+ * while-loop, the ordered extents created in previous iterations are cleaned up.
- * intact. So, the caller must clean them up by calling
- * btrfs_cleanup_ordered_extents(). See btrfs_run_delalloc_range() for
- * example.
  */
 static noinline int cow_file_range(struct btrfs_inode *inode,
 				   struct folio *locked_folio, u64 start,
@@ -1492,11 +1488,9 @@ out_unlock:
 
 	/*
 	 * For the range (1). We have already instantiated the ordered extents
-	 * for this region. They are cleaned up by
+	 * for this region, thus we need to cleanup those ordered extents.
-	 * btrfs_cleanup_ordered_extents() in e.g,
-	 * btrfs_run_delalloc_range().
 	 * EXTENT_DELALLOC_NEW | EXTENT_DEFRAG | EXTENT_CLEAR_META_RESV
-	 * are also handled by the cleanup function.
+	 * are also handled by the ordered extents cleanup.
 	 *
 	 * So here we only clear EXTENT_LOCKED and EXTENT_DELALLOC flag, and
 	 * finish the writeback of the involved folios, which will be never submitted.
@@ -1507,6 +1501,8 @@ out_unlock:
 
 		if (!locked_folio)
 			mapping_set_error(inode->vfs_inode.i_mapping, ret);
+
+		btrfs_cleanup_ordered_extents(inode, orig_start, start - orig_start);
 		extent_clear_unlock_delalloc(inode, orig_start, start - 1,
 					     locked_folio, NULL, clear_bits, page_ops);
 	}
@@ -2024,12 +2020,14 @@ static int nocow_one_range(struct btrfs_inode *inode, struct folio *locked_folio
 				     EXTENT_LOCKED | EXTENT_DELALLOC |
 				     EXTENT_CLEAR_DATA_RESV,
 				     PAGE_UNLOCK | PAGE_SET_ORDERED);
-
 	/*
-	 * btrfs_reloc_clone_csums() error, now we're OK to call error handler,
+	 * On error, we need to cleanup the ordered extents we created.
-	 * as metadata for created ordered extent will only be freed by
+	 *
-	 * btrfs_finish_ordered_io().
+	 * We do not clear the folio Dirty flags because they are set and
+	 * cleaered by the caller.
 	 */
+	if (ret < 0)
+		btrfs_cleanup_ordered_extents(inode, file_pos, end);
 	return ret;
 }
 
@@ -2208,12 +2206,12 @@ must_cow:
 		if (cow_start != (u64)-1) {
 			ret = fallback_to_cow(inode, locked_folio, cow_start,
 					      found_key.offset - 1);
-			cow_start = (u64)-1;
 			if (ret) {
 				cow_end = found_key.offset - 1;
 				btrfs_dec_nocow_writers(nocow_bg);
 				goto error;
 			}
+			cow_start = (u64)-1;
 		}
 
 		ret = nocow_one_range(inode, locked_folio, &cached_state,
@@ -2231,11 +2229,11 @@ must_cow:
 
 	if (cow_start != (u64)-1) {
 		ret = fallback_to_cow(inode, locked_folio, cow_start, end);
-		cow_start = (u64)-1;
 		if (ret) {
 			cow_end = end;
 			goto error;
 		}
+		cow_start = (u64)-1;
 	}
 
 	btrfs_free_path(path);
@@ -2249,27 +2247,44 @@ error:
 	 *    start         cur_offset             end
 	 *    |/////////////|                      |
 	 *
+	 *    In this case, cow_start should be (u64)-1.
+	 *
 	 *    For range [start, cur_offset) the folios are already unlocked (except
 	 *    @locked_folio), EXTENT_DELALLOC already removed.
-	 *    Only need to clear the dirty flag as they will never be submitted.
+	 *    Need to clear the dirty flags and finish the ordered extents.
-	 *    Ordered extent and extent maps are handled by
-	 *    btrfs_mark_ordered_io_finished() inside run_delalloc_range().
 	 *
-	 * 2) Failed with error from fallback_to_cow()
+	 * 2) Failed with error before calling fallback_to_cow()
-	 *    start         cur_offset  cow_end    end
+	 *
+	 *    start         cow_start              end
+	 *    |/////////////|                      |
+	 *
+	 *    In this case, only @cow_start is set, @cur_offset is between
+	 *    [cow_start, end)
+	 *
+	 *    It's mostly the same as case 1), just replace @cur_offset with
+	 *    @cow_start.
+	 *
+	 * 3) Failed with error from fallback_to_cow()
+	 *
+	 *    start         cow_start   cow_end    end
 	 *    |/////////////|-----------|          |
 	 *
-	 *    For range [start, cur_offset) it's the same as case 1).
+	 *    In this case, both @cow_start and @cow_end is set.
-	 *    But for range [cur_offset, cow_end), the folios have dirty flag
-	 *    cleared and unlocked, EXTENT_DEALLLOC cleared by cow_file_range().
 	 *
-	 *    Thus we should not call extent_clear_unlock_delalloc() on range
+	 *    For range [start, cow_start) it's the same as case 1).
-	 *    [cur_offset, cow_end), as the folios are already unlocked.
+	 *    But for range [cow_start, cow_end), all the cleanup is handled by
+	 *    cow_file_range(), we should not touch anything in that range.
 	 *
-	 * So clear the folio dirty flags for [start, cur_offset) first.
+	 * So for all above cases, if @cow_start is set, cleanup ordered extents
+	 * for range [start, @cow_start), other wise cleanup range [start, @cur_offset).
 	 */
-	if (cur_offset > start)
+	if (cow_start != (u64)-1)
+		cur_offset = cow_start;
+
+	if (cur_offset > start) {
+		btrfs_cleanup_ordered_extents(inode, start, cur_offset - start);
 		cleanup_dirty_folios(inode, locked_folio, start, cur_offset - 1, ret);
+	}
 
 	/*
 	 * If an error happened while a COW region is outstanding, cur_offset
@@ -2334,7 +2349,7 @@ int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct folio *locked_fol
 
 	if (should_nocow(inode, start, end)) {
 		ret = run_delalloc_nocow(inode, locked_folio, start, end);
-		goto out;
+		return ret;
 	}
 
 	if (btrfs_inode_can_compress(inode) &&
@@ -2348,10 +2363,6 @@ int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct folio *locked_fol
 	else
 		ret = cow_file_range(inode, locked_folio, start, end, NULL,
 				     false, false);
-
-out:
-	if (ret < 0)
-		btrfs_cleanup_ordered_extents(inode, start, end - start + 1);
 	return ret;
 }