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Subject[PATCH 7/8] swap: use direct I/O for SWP_FILE swap_readpage
Date
On Mon, Nov 17, 2014 at 07:48:17AM -0800, Christoph Hellwig wrote:
> With the new iov_iter infrastructure that supprots direct I/O to kernel
> pages please get rid of the ->readpage hack first. I'm still utterly
> disapoined that this crap ever got merged.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
---
mm/page_io.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index 4741248..956307c 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -346,12 +346,33 @@ int swap_readpage(struct page *page)
}

if (sis->flags & SWP_FILE) {
+ struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
+ struct iov_iter to;
+ struct bio_vec bv = {
+ .bv_page = page,
+ .bv_len = PAGE_SIZE,
+ .bv_offset = 0,
+ };
+
+ iov_iter_bvec(&to, ITER_BVEC | READ, &bv, 1, PAGE_SIZE);

- ret = mapping->a_ops->readpage(swap_file, page);
- if (!ret)
+ init_sync_kiocb(&kiocb, swap_file);
+ kiocb.ki_pos = page_file_offset(page);
+ kiocb.ki_nbytes = PAGE_SIZE;
+
+ ret = mapping->a_ops->direct_IO(READ, &kiocb, &to,
+ kiocb.ki_pos);
+ if (ret == PAGE_SIZE) {
+ SetPageUptodate(page);
count_vm_event(PSWPIN);
+ ret = 0;
+ } else {
+ ClearPageUptodate(page);
+ SetPageError(page);
+ }
+ unlock_page(page);
return ret;
}

--
2.1.3


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