From: Hugh Dickins <hughd@xxxxxxxxxx> Subject: mm: remove nrexceptional from inode: remove BUG_ON clear_inode()'s BUG_ON(!mapping_empty(&inode->i_data)) is unsafe: we know of two ways in which nodes can and do (on rare occasions) get left behind. Until those are fixed, do not BUG_ON() nor even WARN_ON(). Yes, this will then leak those nodes (or the next user of the struct inode may use them); but this has been happening for years, and the new BUG_ON(!mapping_empty) was only guilty of revealing that. A proper fix will follow, but no hurry. Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2104292229380.16080@eggly.anvils Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/inode.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/fs/inode.c~mm-remove-nrexceptional-from-inode-remove-bug_on +++ a/fs/inode.c @@ -529,7 +529,14 @@ void clear_inode(struct inode *inode) */ xa_lock_irq(&inode->i_data.i_pages); BUG_ON(inode->i_data.nrpages); - BUG_ON(!mapping_empty(&inode->i_data)); + /* + * Almost always, mapping_empty(&inode->i_data) here; but there are + * two known and long-standing ways in which nodes may get left behind + * (when deep radix-tree node allocation failed partway; or when THP + * collapse_file() failed). Until those two known cases are cleaned up, + * or a cleanup function is called here, do not BUG_ON(!mapping_empty), + * nor even WARN_ON(!mapping_empty). + */ xa_unlock_irq(&inode->i_data.i_pages); BUG_ON(!list_empty(&inode->i_data.private_list)); BUG_ON(!(inode->i_state & I_FREEING)); _
