Re: [PATCH 3/3] iomap: use filemap_range_needs_writeback() for O_DIRECT reads
From: Christoph Hellwig <hch@infradead.org>
Date: 2021-02-09 07:52:08
Also in:
linux-fsdevel
On Mon, Feb 08, 2021 at 07:30:08PM -0700, Jens Axboe wrote:
quoted hunk ↗ jump to hunk
+ if (iocb->ki_flags & IOCB_NOWAIT) { + if (filemap_range_needs_writeback(mapping, pos, end)) { + ret = -EAGAIN; + goto out_free_dio; + } + flags |= IOMAP_NOWAIT; + } if (iter_is_iovec(iter)) dio->flags |= IOMAP_DIO_DIRTY; } else { + if (iocb->ki_flags & IOCB_NOWAIT) { + if (filemap_range_has_page(mapping, pos, end)) { + ret = -EAGAIN; + goto out_free_dio; + } + flags |= IOMAP_NOWAIT; + } + flags |= IOMAP_WRITE; dio->flags |= IOMAP_DIO_WRITE;@@ -478,14 +493,6 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, dio->flags |= IOMAP_DIO_WRITE_FUA; } - if (iocb->ki_flags & IOCB_NOWAIT) { - if (filemap_range_has_page(mapping, pos, end)) { - ret = -EAGAIN; - goto out_free_dio; - } - flags |= IOMAP_NOWAIT; - }
looking at this I really hate the scheme with the potential racyness and duplicated page looksups. Why can't we pass a nonblock flag to filemap_write_and_wait_range and invalidate_inode_pages2_range that makes them return -EAGAIN when they would block to clean this whole mess up?