From: Barry Song v-songbaohua@oppo.com

Since commit 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space"), we can plug multiple pages then unplug them all together. That means iov_iter_count(iter) could be way bigger than PAGE_SIZE, it actually equals the size of iov_iter_npages(iter, INT_MAX).

Note this issue has nothing to do with large folios as we don't support THP_SWPOUT to non-block devices.

Fixes: 2282679fb20b ("mm: submit multipage write for SWP_FS_OPS swap-space") Reported-by: Christoph Hellwig hch@lst.de Closes: https://lore.kernel.org/linux-mm/20240617053201.GA16852@lst.de/ Cc: NeilBrown neilb@suse.de Cc: Anna Schumaker anna@kernel.org Cc: Steve French sfrench@samba.org Cc: Trond Myklebust trondmy@kernel.org Cc: Chuanhua Han hanchuanhua@oppo.com Cc: Ryan Roberts ryan.roberts@arm.com Cc: Chris Li chrisl@kernel.org Cc: "Huang, Ying" ying.huang@intel.com Cc: Jeff Layton jlayton@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Barry Song v-songbaohua@oppo.com --- fs/nfs/direct.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index bb2f583eb28b..a1bfa86f467a 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -141,7 +141,7 @@ int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter) { ssize_t ret;

- VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE); + VM_WARN_ON(iov_iter_count(iter) != iov_iter_npages(iter, INT_MAX) * PAGE_SIZE);

if (iov_iter_rw(iter) == READ) ret = nfs_file_direct_read(iocb, iter, true);