2 files changed, 74 insertions, 0 deletions
diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index 2bf2e82b2ad79f..d72292e40f9b9f 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -150,6 +150,34 @@ static inline bool netfs_is_cache_enabled(struct netfs_inode *ctx)
 }
 
 /*
+ * Get a ref on a netfs group attached to a dirty page (e.g. a ceph snap).
+ */
+static inline struct netfs_group *netfs_get_group(struct netfs_group *netfs_group)
+{
+	if (netfs_group)
+		refcount_inc(&netfs_group->ref);
+	return netfs_group;
+}
+
+/*
+ * Dispose of a netfs group attached to a dirty page (e.g. a ceph snap).
+ */
+static inline void netfs_put_group(struct netfs_group *netfs_group)
+{
+	if (netfs_group && refcount_dec_and_test(&netfs_group->ref))
+		netfs_group->free(netfs_group);
+}
+
+/*
+ * Dispose of a netfs group attached to a dirty page (e.g. a ceph snap).
+ */
+static inline void netfs_put_group_many(struct netfs_group *netfs_group, int nr)
+{
+	if (netfs_group && refcount_sub_and_test(nr, &netfs_group->ref))
+		netfs_group->free(netfs_group);
+}
+
+/*
  * fscache-cache.c
  */
 #ifdef CONFIG_PROC_FS
diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 5d545073fe03ca..eeb44abe59c523 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -177,9 +177,55 @@ EXPORT_SYMBOL(netfs_clear_inode_writeback);
  */
 void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
 {
+	struct netfs_folio *finfo = NULL;
+	size_t flen = folio_size(folio);
+
 	_enter("{%lx},%zx,%zx", folio_index(folio), offset, length);
 
 	folio_wait_fscache(folio);
+
+	if (!folio_test_private(folio))
+		return;
+
+	finfo = netfs_folio_info(folio);
+
+	if (offset == 0 && length >= flen)
+		goto erase_completely;
+
+	if (finfo) {
+		/* We have a partially uptodate page from a streaming write. */
+		unsigned int fstart = finfo->dirty_offset;
+		unsigned int fend = fstart + finfo->dirty_len;
+		unsigned int end = offset + length;
+
+		if (offset >= fend)
+			return;
+		if (end <= fstart)
+			return;
+		if (offset <= fstart && end >= fend)
+			goto erase_completely;
+		if (offset <= fstart && end > fstart)
+			goto reduce_len;
+		if (offset > fstart && end >= fend)
+			goto move_start;
+		/* A partial write was split.  The caller has already zeroed
+		 * it, so just absorb the hole.
+		 */
+	}
+	return;
+
+erase_completely:
+	netfs_put_group(netfs_folio_group(folio));
+	folio_detach_private(folio);
+	folio_clear_uptodate(folio);
+	kfree(finfo);
+	return;
+reduce_len:
+	finfo->dirty_len = offset + length - finfo->dirty_offset;
+	return;
+move_start:
+	finfo->dirty_len -= offset - finfo->dirty_offset;
+	finfo->dirty_offset = offset;
 }
 EXPORT_SYMBOL(netfs_invalidate_folio);