On Mon, Apr 21, 2025 at 10:50:30AM +0000, 陈涛涛 Taotao Chen wrote: > diff --git a/mm/filemap.c b/mm/filemap.c > index 7b90cbeb4a1a..9174b6310f0b 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -4087,7 +4087,11 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i) > size_t offset; /* Offset into folio */ > size_t bytes; /* Bytes to write to folio */ > size_t copied; /* Bytes copied from user */ > - void *fsdata = NULL; > + /* > + * Initialize fsdata with iocb flags pointer so that filesystems > + * can check ki_flags (like IOCB_DONTCACHE) in write operations. > + */ > + void *fsdata = &iocb->ki_flags; Unfortunately, this is't safe. There may very well be code paths which depend on fsdata being initialized to NULL before calling write_begin(). In fact in the patch 2/3 in this series, ext4_write_end() will get confused in the non-delayed allocation case, since ext4_write_begin() doesn't force fsdata to be not be &iocb->ki_flags, and this will cause ext4_write_end() to potentially get confused and do the wrong thing. I understand that it would be a lot more inconvenient change the function signature of write_begin() to pass through iocb->ki_fags via a new parameter. But I think that probably is the best way to go. Cheers, - Ted
