On Tue, Oct 08, 2019 at 09:15:13AM +0200, Christoph Hellwig wrote:
> Use the existing iomap write_begin code to read the pages unshared
> by iomap_file_unshare. That avoids the extra ->readpage call and
> extent tree lookup currently done by read_mapping_page.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/iomap/buffered-io.c | 49 ++++++++++++++----------------------------
> 1 file changed, 16 insertions(+), 33 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index d5abd8e5dca7..ac1bbed71a9b 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -548,6 +548,10 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage,
> EXPORT_SYMBOL_GPL(iomap_migrate_page);
> #endif /* CONFIG_MIGRATION */
>
> +enum {
> + IOMAP_WRITE_F_UNSHARE = (1 << 0),
> +};
> +
> static void
> iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
> {
> @@ -577,7 +581,7 @@ iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
> }
>
> static int
> -__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
> +__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> struct page *page, struct iomap *iomap)
> {
> struct iomap_page *iop = iomap_page_create(inode, page);
> @@ -596,11 +600,14 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
> if (plen == 0)
> break;
>
> - if ((from <= poff || from >= poff + plen) &&
> + if (!(flags & IOMAP_WRITE_F_UNSHARE) &&
> + (from <= poff || from >= poff + plen) &&
> (to <= poff || to >= poff + plen))
> continue;
>
> if (iomap_block_needs_zeroing(inode, iomap, block_start)) {
> + if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
> + return -EIO;
> zero_user_segments(page, poff, from, to, poff + plen);
> iomap_set_range_uptodate(page, poff, plen);
> continue;
> @@ -646,7 +653,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
> status = __block_write_begin_int(page, pos, len, NULL, iomap);
> else
> - status = __iomap_write_begin(inode, pos, len, page, iomap);
> + status = __iomap_write_begin(inode, pos, len, flags, page,
> + iomap);
>
> if (unlikely(status))
> goto out_unlock;
> @@ -869,22 +877,6 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
> }
> EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
>
> -static struct page *
> -__iomap_read_page(struct inode *inode, loff_t offset)
> -{
> - struct address_space *mapping = inode->i_mapping;
> - struct page *page;
> -
> - page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
> - if (IS_ERR(page))
> - return page;
> - if (!PageUptodate(page)) {
> - put_page(page);
> - return ERR_PTR(-EIO);
> - }
> - return page;
> -}
> -
> static loff_t
> iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> struct iomap *iomap)
> @@ -900,24 +892,15 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> return length;
>
> do {
> - struct page *page, *rpage;
> - unsigned long offset; /* Offset into pagecache page */
> - unsigned long bytes; /* Bytes to write to page */
> -
> - offset = offset_in_page(pos);
> - bytes = min_t(loff_t, PAGE_SIZE - offset, length);
> -
> - rpage = __iomap_read_page(inode, pos);
> - if (IS_ERR(rpage))
> - return PTR_ERR(rpage);
> + unsigned long offset = offset_in_page(pos);
> + unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
> + struct page *page;
>
> - status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
> - put_page(rpage);
> + status = iomap_write_begin(inode, pos, bytes,
> + IOMAP_WRITE_F_UNSHARE, &page, iomap);
> if (unlikely(status))
> return status;
>
> - WARN_ON_ONCE(!PageUptodate(page));
> -
> status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
> if (unlikely(status <= 0)) {
> if (WARN_ON_ONCE(status == 0))
> --
> 2.20.1
>
