2 files changed, 104 insertions, 7 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 643243a0a010..cc4c55c0733c 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1226,13 +1226,23 @@ static inline void contiguous_readpages(struct page *pages[], int nr_pages,
 static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 		struct page *page, struct writeback_control *wbc)
 {
+	struct btrfs_fs_info *fs_info = inode_to_fs_info(&inode->vfs_inode);
+	struct folio *folio = page_folio(page);
+	const bool is_subpage = btrfs_is_subpage(fs_info, page->mapping);
 	const u64 page_start = page_offset(page);
 	const u64 page_end = page_start + PAGE_SIZE - 1;
+	/*
+	 * Save the last found delalloc end. As the delalloc end can go beyond
+	 * page boundary, thus we cannot rely on subpage bitmap to locate the
+	 * last delalloc end.
+	 */
+	u64 last_delalloc_end = 0;
 	u64 delalloc_start = page_start;
 	u64 delalloc_end = page_end;
 	u64 delalloc_to_write = 0;
 	int ret = 0;
 
+	/* Lock all (subpage) delalloc ranges inside the page first. */
 	while (delalloc_start < page_end) {
 		delalloc_end = page_end;
 		if (!find_lock_delalloc_range(&inode->vfs_inode, page,
@@ -1240,15 +1250,95 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 			delalloc_start = delalloc_end + 1;
 			continue;
 		}
-
-		ret = btrfs_run_delalloc_range(inode, page, delalloc_start,
-					       delalloc_end, wbc);
-		if (ret < 0)
-			return ret;
-
+		btrfs_folio_set_writer_lock(fs_info, folio, delalloc_start,
+					    min(delalloc_end, page_end) + 1 -
+					    delalloc_start);
+		last_delalloc_end = delalloc_end;
 		delalloc_start = delalloc_end + 1;
 	}
+	delalloc_start = page_start;
+
+	if (!last_delalloc_end)
+		goto out;
+
+	/* Run the delalloc ranges for the above locked ranges. */
+	while (delalloc_start < page_end) {
+		u64 found_start;
+		u32 found_len;
+		bool found;
+
+		if (!is_subpage) {
+			/*
+			 * For non-subpage case, the found delalloc range must
+			 * cover this page and there must be only one locked
+			 * delalloc range.
+			 */
+			found_start = page_start;
+			found_len = last_delalloc_end + 1 - found_start;
+			found = true;
+		} else {
+			found = btrfs_subpage_find_writer_locked(fs_info, folio,
+					delalloc_start, &found_start, &found_len);
+		}
+		if (!found)
+			break;
+		/*
+		 * The subpage range covers the last sector, the delalloc range may
+		 * end beyond the page boundary, use the saved delalloc_end
+		 * instead.
+		 */
+		if (found_start + found_len >= page_end)
+			found_len = last_delalloc_end + 1 - found_start;
+
+		if (ret >= 0) {
+			/* No errors hit so far, run the current delalloc range. */
+			ret = btrfs_run_delalloc_range(inode, page, found_start,
+						       found_start + found_len - 1,
+						       wbc);
+		} else {
+			/*
+			 * We've hit an error during previous delalloc range,
+			 * have to cleanup the remaining locked ranges.
+			 */
+			unlock_extent(&inode->io_tree, found_start,
+				      found_start + found_len - 1, NULL);
+			__unlock_for_delalloc(&inode->vfs_inode, page, found_start,
+					      found_start + found_len - 1);
+		}
+
+		/*
+		 * We can hit btrfs_run_delalloc_range() with >0 return value.
+		 *
+		 * This happens when either the IO is already done and page
+		 * unlocked (inline) or the IO submission and page unlock would
+		 * be handled as async (compression).
+		 *
+		 * Inline is only possible for regular sectorsize for now.
+		 *
+		 * Compression is possible for both subpage and regular cases,
+		 * but even for subpage compression only happens for page aligned
+		 * range, thus the found delalloc range must go beyond current
+		 * page.
+		 */
+		if (ret > 0)
+			ASSERT(!is_subpage || found_start + found_len >= page_end);
+
+		/*
+		 * Above btrfs_run_delalloc_range() may have unlocked the page,
+		 * thus for the last range, we cannot touch the page anymore.
+		 */
+		if (found_start + found_len >= last_delalloc_end + 1)
+			break;
 
+		delalloc_start = found_start + found_len;
+	}
+	if (ret < 0)
+		return ret;
+out:
+	if (last_delalloc_end)
+		delalloc_end = last_delalloc_end;
+	else
+		delalloc_end = page_end;
 	/*
 	 * delalloc_end is already one less than the total length, so
 	 * we don't subtract one from PAGE_SIZE
@@ -1520,7 +1610,8 @@ done:
 					       PAGE_SIZE, !ret);
 		mapping_set_error(page->mapping, ret);
 	}
-	unlock_page(page);
+
+	btrfs_folio_end_all_writers(inode_to_fs_info(inode), folio);
 	ASSERT(ret <= 0);
 	return ret;
 }
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index 93ae7b7367d5..fc7db52e8f58 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -864,6 +864,7 @@ out:
  */
 void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct folio *folio)
 {
+	struct btrfs_subpage *subpage = folio_get_private(folio);
 	u64 folio_start = folio_pos(folio);
 	u64 cur = folio_start;
 
@@ -873,6 +874,11 @@ void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct fol
 		return;
 	}
 
+	/* The page has no new delalloc range locked on it. Just plain unlock. */
+	if (atomic_read(&subpage->writers) == 0) {
+		folio_unlock(folio);
+		return;
+	}
 	while (cur < folio_start + PAGE_SIZE) {
 		u64 found_start;
 		u32 found_len;