[CRIU] [PATCH 08/10] uffd: Don't carry void *page through the callstack

[Pavel Emelyanov]

Since all #PFs are serialized with a mutex it seems reasonable
to have a global page_szie() buffer nearby.

Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
---
 criu/uffd.c | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/criu/uffd.c b/criu/uffd.c
index 96b5ec0..25e13ab 100644
--- a/criu/uffd.c
+++ b/criu/uffd.c
@@ -46,6 +46,7 @@
 #define LAZY_PAGES_SOCK_NAME	"lazy-pages.socket"
 
 static mutex_t *lazy_sock_mutex;
+static void *aux_page;
 
 struct lazy_pages_info {
 	int pid;
@@ -375,21 +376,20 @@ struct uffd_pages_struct {
 	int flags;
 };
 
-static int uffd_copy_page(struct lazy_pages_info *lpi, __u64 address,
-			  void *dest)
+static int uffd_copy_page(struct lazy_pages_info *lpi, __u64 address)
 {
 	struct uffdio_copy uffdio_copy;
 	int rc;
 
 	if (opts.use_page_server)
-		rc = get_remote_pages(lpi->pid, address, 1, dest);
+		rc = get_remote_pages(lpi->pid, address, 1, aux_page);
 	else
-		rc = get_page(lpi, address, dest);
+		rc = get_page(lpi, address, aux_page);
 	if (rc <= 0)
 		return rc;
 
 	uffdio_copy.dst = address;
-	uffdio_copy.src = (unsigned long) dest;
+	uffdio_copy.src = (unsigned long) aux_page;
 	uffdio_copy.len = page_size();
 	uffdio_copy.mode = 0;
 	uffdio_copy.copy = 0;
@@ -437,12 +437,11 @@ static int uffd_zero_page(struct lazy_pages_info *lpi, __u64 address)
 	return ps;
 }
 
-static int uffd_handle_page(struct lazy_pages_info *lpi, __u64 address,
-			    void *dest)
+static int uffd_handle_page(struct lazy_pages_info *lpi, __u64 address)
 {
 	int rc;
 
-	rc = uffd_copy_page(lpi, address, dest);
+	rc = uffd_copy_page(lpi, address);
 	if (rc == 0)
 		rc = uffd_zero_page(lpi, address);
 
@@ -518,7 +517,7 @@ static int collect_uffd_pages(struct page_read *pr, struct lazy_pages_info *lpi)
 	return 0;
 }
 
-static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
+static int handle_remaining_pages(struct lazy_pages_info *lpi)
 {
 	struct uffd_pages_struct *uffd_pages;
 	int rc;
@@ -529,7 +528,7 @@ static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
 		if (uffd_pages->flags & UFFD_FLAG_SENT)
 			continue;
 
-		rc = uffd_handle_page(lpi, uffd_pages->addr, dest);
+		rc = uffd_handle_page(lpi, uffd_pages->addr);
 		if (rc < 0) {
 			pr_err("Error during UFFD copy\n");
 			return -1;
@@ -542,13 +541,12 @@ static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
 }
 
 
-static int handle_regular_pages(struct lazy_pages_info *lpi, void *dest,
-				__u64 address)
+static int handle_regular_pages(struct lazy_pages_info *lpi, __u64 address)
 {
 	int rc;
 	struct uffd_pages_struct *uffd_pages;
 
-	rc = uffd_handle_page(lpi, address, dest);
+	rc = uffd_handle_page(lpi, address);
 	if (rc < 0) {
 		pr_err("Error during UFFD copy\n");
 		return -1;
@@ -647,7 +645,7 @@ out:
 	return ret;
 }
 
-static int handle_user_fault(struct lazy_pages_info *lpi, void *dest)
+static int handle_user_fault(struct lazy_pages_info *lpi)
 {
 	struct uffd_msg msg;
 	__u64 flags;
@@ -686,7 +684,7 @@ static int handle_user_fault(struct lazy_pages_info *lpi, void *dest)
 	flags = msg.arg.pagefault.flags;
 	pr_debug("msg.arg.pagefault.flags 0x%llx\n", flags);
 
-	ret = handle_regular_pages(lpi, dest, address);
+	ret = handle_regular_pages(lpi, address);
 	if (ret < 0) {
 		pr_err("Error during regular page copy\n");
 		return -1;
@@ -718,13 +716,12 @@ static int handle_requests(int epollfd, struct epoll_event *events)
 	struct lazy_pages_info *lpi;
 	int ret = -1;
 	unsigned long ps;
-	void *dest;
 	int i;
 
 	/* All operations will be done on page size */
 	ps = page_size();
-	dest = xmalloc(ps);
-	if (!dest)
+	aux_page = xmalloc(ps);
+	if (!aux_page)
 		return ret;
 
 	while (1) {
@@ -748,14 +745,14 @@ static int handle_requests(int epollfd, struct epoll_event *events)
 			int err;
 
 			lpi = (struct lazy_pages_info *)events[i].data.ptr;
-			err = handle_user_fault(lpi, dest);
+			err = handle_user_fault(lpi);
 			if (err < 0)
 				goto out;
 		}
 	}
 	pr_debug("Handle remaining pages\n");
 	list_for_each_entry(lpi, &lpis, l) {
-		ret = handle_remaining_pages(lpi, dest);
+		ret = handle_remaining_pages(lpi);
 		if (ret < 0) {
 			pr_err("Error during remaining page copy\n");
 			ret = 1;
@@ -767,7 +764,7 @@ static int handle_requests(int epollfd, struct epoll_event *events)
 		ret += lazy_pages_summary(lpi);
 
 out:
-	free(dest);
+	free(aux_page);
 	return ret;
 
 }
-- 
2.5.0