On Mon, Feb 27, 2023 at 01:13:30AM +0530, Ritesh Harjani (IBM) wrote: > +++ b/fs/iomap/buffered-io.c > @@ -535,11 +535,16 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos, > size_t from = offset_in_folio(folio, pos), to = from + len; > size_t poff, plen; > > + if (pos <= folio_pos(folio) && > + pos + len >= folio_pos(folio) + folio_size(folio)) > + return 0; > + > + iop = iomap_page_create(iter->inode, folio, iter->flags); > + > if (folio_test_uptodate(folio)) > return 0; > folio_clear_error(folio); > > - iop = iomap_page_create(iter->inode, folio, iter->flags); > if ((iter->flags & IOMAP_NOWAIT) && !iop && nr_blocks > 1) > return -EAGAIN; Don't you want to move the -EAGAIN check up too? Otherwise an io_uring write will dirty the entire folio rather than a block. It occurs to me (even though I was the one who suggested the current check) that pos <= folio_pos etc is actually a bit tighter than necessary. We could get away with: if (pos < folio_pos(folio) + block_size && pos + len > folio_pos(folio) + folio_size(folio) - block_size) since that will also cause the entire folio to be dirtied. Not sure if it's worth it.
