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lazy-pages: make uffd_io_complete more robust

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Make sure we handle various corner cases:
* we received less pages than requested
* the request was capped because of unmap/remap etc
* the process has exited underneath us

Currently we are freeing the request once we've found the address to use
with uffd_copy(). Instead, let's keep the request object around, use it to
properly calculate number of pages we pass to uffd_copy() and then re-add
tailing range (if any) to the IOVs list.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
This commit is contained in:
Mike Rapoport 2018-05-09 18:03:49 +03:00 committed by Andrei Vagin
parent 00ce9b52aa
commit 850095dad4
1 changed files with 22 additions and 8 deletions
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30
criu/uffd.c
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@ -845,7 +845,7 @@ static int uffd_io_complete(struct page_read *pr, unsigned long img_addr, int nr
{
struct lazy_pages_info *lpi;
unsigned long addr = 0;
int req_pages;
int req_pages, ret;
struct lazy_iov *req;
lpi = container_of(pr, struct lazy_pages_info, pr);
@ -861,25 +861,39 @@ static int uffd_io_complete(struct page_read *pr, unsigned long img_addr, int nr
list_for_each_entry(req, &lpi->reqs, l) {
if (req->img_start == img_addr) {
addr = req->start;
list_del(&req->l);
xfree(req);
break;
}
}
/* the request may be already gone because if uname/remove */
/* the request may be already gone because if unmap/remove */
if (!addr)
return 0;
/*
* by the time we get the pages from the remote source, parts
* of the request may already be gone because of
* UFFD_EVENT_{REMAP,REMOVE,UNMAP}
* By the time we get the pages from the remote source, parts
* of the request may already be gone because of unmap/remove
* OTOH, the remote side may send less pages than we requested.
* Make sure we are not trying to uffd_copy more memory than
* we should.
*/
req_pages = (req->end - req->start) / PAGE_SIZE;
nr = min(nr, req_pages);
return uffd_copy(lpi, addr, nr);
ret = uffd_copy(lpi, addr, nr);
if (ret < 0)
return ret;
/* recheck if the process exited, it may be detected in uffd_copy */
if (lpi->exited)
return 0;
/*
* Since the completed request length may differ from the
* actual data we've received we re-insert the request to IOVs
* list and let drop_iovs do the range math, free memory etc.
*/
iov_list_insert(req, &lpi->iovs);
return drop_iovs(lpi, addr, nr * PAGE_SIZE);
}
static int uffd_zero(struct lazy_pages_info *lpi, __u64 address, int nr_pages)