On Wed, Nov 04, 2020 at 08:42:12PM +0000, Matthew Wilcox (Oracle) wrote:
> Use AOP_TRUNCATED_PAGE to indicate that no error occurred, but the
> page we looked up is no longer valid.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Reviewed-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> ---
> mm/filemap.c | 42 +++++++++++++++++++-----------------------
> 1 file changed, 19 insertions(+), 23 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 25945fefdd39..93c054f51677 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2231,24 +2231,21 @@ static int filemap_read_page(struct file *file, struct address_space *mapping,
> return error;
> }
>
> +static int filemap_update_page(struct kiocb *iocb,
> + struct address_space *mapping, struct iov_iter *iter,
> + struct page *page, loff_t pos, loff_t count)
> {
> struct inode *inode = mapping->host;
> int error;
>
> if (iocb->ki_flags & IOCB_WAITQ) {
> error = lock_page_async(page, iocb->ki_waitq);
> + if (error)
> + goto error;
> } else {
> if (!trylock_page(page)) {
> put_and_wait_on_page_locked(page, TASK_KILLABLE);
> + return AOP_TRUNCATED_PAGE;
> }
> }
>
> @@ -2267,25 +2264,24 @@ static struct page *filemap_update_page(struct kiocb *iocb, struct file *filp,
> goto readpage;
> uptodate:
> unlock_page(page);
> + return 0;
>
> readpage:
> if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) {
> unlock_page(page);
> + error = -EAGAIN;
> + } else {
> + error = filemap_read_page(iocb->ki_filp, mapping, page);
> + if (!error)
> + return 0;
> }
> +error:
> put_page(page);
> + return error;
> truncated:
> unlock_page(page);
> put_page(page);
> + return AOP_TRUNCATED_PAGE;
We could still consolidate the page unlocking by having another label.
Or even better move the put_page into the caller like I did in my
series, which would conceputally fit in pretty nicely here:
> + err = filemap_update_page(iocb, mapping, iter, page,
> pg_pos, pg_count);
> + if (err)
> pvec->nr--;
But otherwise this looks good:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
