Merge branch 'no-rebase-mnt_ns_tree_remove'

Bring in the fix for removing a mount namespace from the mount namespace
rbtree and list.

Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 18 insertions, 1 deletions

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index c9b3821957f7..cb4f97833dc3 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -448,8 +448,25 @@ void btrfs_subpage_set_writeback(const struct btrfs_fs_info *fs_info,
 
 	spin_lock_irqsave(&bfs->lock, flags);
 	bitmap_set(bfs->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
+
+	/*
+	 * Don't clear the TOWRITE tag when starting writeback on a still-dirty
+	 * folio. Doing so can cause WB_SYNC_ALL writepages() to overlook it,
+	 * assume writeback is complete, and exit too early — violating sync
+	 * ordering guarantees.
+	 */
 	if (!folio_test_writeback(folio))
-		folio_start_writeback(folio);
+		__folio_start_writeback(folio, true);
+	if (!folio_test_dirty(folio)) {
+		struct address_space *mapping = folio_mapping(folio);
+		XA_STATE(xas, &mapping->i_pages, folio->index);
+		unsigned long flags;
+
+		xas_lock_irqsave(&xas, flags);
+		xas_load(&xas);
+		xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
+		xas_unlock_irqrestore(&xas, flags);
+	}
 	spin_unlock_irqrestore(&bfs->lock, flags);
 }