[CRIU] [PATCHv0] page-xfer: fix wrong hole address offset

[Eugene Batalov]

From: Fyodor <bocharovfedor at gmail.com>

CRIU doesn't save vaddr of each anon shmem page in anon shared mem pagemap img.
It saves page offset from the beginning of anon shared memory area.
CRIU calls page_xfer_dump_pages() with non zero @off argument
to convert dumper virtual addresses to such offsets.

The problem is in page_xfer_dump_pages() code. It substracts @off
only for pages in pagemap but not for holes in pagemap.
Bug is fixed in this patch.
This patch is just a copy-paste of valid code path for pages to code path for holes.

Bug is not currently reproduced in CRIU because:
1. Only anon shmem provides non-zero @off value to page_xfer_dump_pages()
2. Anon shared memory doesn't create holes in its pagemap (for now)

This bugfix is a preparation for anon shared memory deduplication patchset.

Signed-off-by: Fyodor Bocharov <fbocharov at yandex.ru>
Signed-off-by: Eugene Batalov <eabatalov89 at gmail.com>
---
 page-xfer.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/page-xfer.c b/page-xfer.c
index f7da2d2..cb6073a 100644
--- a/page-xfer.c
+++ b/page-xfer.c
@@ -699,6 +699,8 @@ int page_xfer_dump_pages(struct page_xfer *xfer, struct page_pipe *pp,
 			struct iovec *iov = &ppb->iov[i];
 
 			while (hole && (hole->iov_base < iov->iov_base)) {
+				BUG_ON(hole->iov_base < (void *)off);
+				hole->iov_base -= off;
 				pr_debug("\th %p [%u]\n", hole->iov_base,
 						(unsigned int)(hole->iov_len / PAGE_SIZE));
 				if (xfer->write_hole(xfer, hole))
@@ -722,6 +724,8 @@ int page_xfer_dump_pages(struct page_xfer *xfer, struct page_pipe *pp,
 	}
 
 	while (hole) {
+		BUG_ON(hole->iov_base < (void *)off);
+		hole->iov_base -= off;
 		pr_debug("\th* %p [%u]\n", hole->iov_base,
 				(unsigned int)(hole->iov_len / PAGE_SIZE));
 		if (xfer->write_hole(xfer, hole))
-- 
1.9.1