On Fri, Aug 02, 2019 at 05:00:37PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> In case of a IOMAP_COW, read a page from the srcmap before
> performing a write on the page.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/iomap/buffered-io.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f27756c0b31c..a96cc26eec92 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -581,7 +581,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
>
> static int
> iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> - struct page **pagep, struct iomap *iomap)
> + struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
> {
> const struct iomap_page_ops *page_ops = iomap->page_ops;
> pgoff_t index = pos >> PAGE_SHIFT;
> @@ -607,6 +607,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
>
> if (iomap->type == IOMAP_INLINE)
> iomap_read_inline_data(inode, page, iomap);
> + else if (iomap->type == IOMAP_COW)
> + status = __iomap_write_begin(inode, pos, len, page, srcmap);
> else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
> status = __block_write_begin_int(page, pos, len, NULL, iomap);
> else
This looks busted w.r.t. IOMAP_F_BUFFER_HEAD. i.e. What's to stop
someone returning iomap->type == IOMAP_COW, iomap->flags &
IOMAP_F_BUFFER_HEAD?
In which case we can't call __iomap_write_begin(), right?
I'm with Darrick on CONFIG_IOMAP_DEBUG here - we need to start
locking down invalid behaviour and invalid combinations with asserts
that tell developers they've broken something.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
