lazy-pages: extend the page_read with ability to read remote pages

Currently lazy-pages daemon uses either pr->read_pages or get_remote_pages
to get actual page data from local images or remote server. From now on,
page_read will be completely responsible for getting the page data.

travis-ci: success for uffd: A new set of improvements
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/include/pagemap.h

@@ -53,6 +53,8 @@ struct page_read {
 	int (*sync)(struct page_read *pr);
 	int (*seek_pagemap)(struct page_read *pr, unsigned long vaddr);
 	void (*reset)(struct page_read *pr);
+	int (*maybe_read_page)(struct page_read *pr, unsigned long vaddr,
+			       int nr, void *buf, unsigned flags);
 
 	/* Whether or not pages can be read in PIE code */
 	bool pieok;
@@ -72,7 +74,8 @@ struct page_read {
 
 	struct iovec bunch;		/* record consequent neighbour
 					   iovecs to punch together */
-	unsigned id; /* for logging */
+	unsigned id;			/* for logging */
+	int pid;			/* PID of the process */
 
 	PagemapEntry **pmes;
 	int nr_pmes;
@@ -90,6 +93,7 @@ struct page_read {
 
 #define PR_TYPE_MASK	0x3
 #define PR_MOD		0x4	/* Will need to modify */
+#define PR_REMOTE	0x8
 
 /*
  * -1 -- error

criu/pagemap.c

@@ -12,6 +12,8 @@
 #include "pagemap.h"
 #include "restorer.h"
 #include "rst-malloc.h"
+#include "page-xfer.h"
+
 #include "fault-injection.h"
 #include "xmalloc.h"
 #include "protobuf.h"
@@ -393,8 +395,8 @@ int pagemap_enqueue_iovec(struct page_read *pr, void *buf,
 	return 0;
 }
 
-static int maybe_read_page(struct page_read *pr, unsigned long vaddr,
-		int nr, void *buf, unsigned flags)
+static int maybe_read_page_local(struct page_read *pr, unsigned long vaddr,
+				 int nr, void *buf, unsigned flags)
 {
 	int ret;
 	unsigned long len = nr * PAGE_SIZE;
@@ -409,6 +411,19 @@ static int maybe_read_page(struct page_read *pr, unsigned long vaddr,
 	return ret;
 }
 
+static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
+				  int nr, void *buf, unsigned flags)
+{
+	int ret;
+
+	if (flags & PR_ASYNC)
+		ret = -1;	/* not yet supported */
+	else
+		ret = get_remote_pages(pr->pid, vaddr, nr, buf);
+
+	return ret;
+}
+
 static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr,
 			     void *buf, unsigned flags)
 {
@@ -422,7 +437,7 @@ static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr,
 		/* zero mappings should be skipped by get_pagemap */
 		BUG();
 	} else {
-		if (maybe_read_page(pr, vaddr, nr, buf, flags) < 0)
+		if (pr->maybe_read_page(pr, vaddr, nr, buf, flags) < 0)
 			return -1;
 	}
 
@@ -678,6 +693,7 @@ int open_page_read_at(int dfd, int pid, struct page_read *pr, int pr_flags)
 {
 	int flags, i_typ;
 	static unsigned ids = 1;
+	bool remote = pr_flags & PR_REMOTE;
 
 	if (opts.auto_dedup)
 		pr_flags |= PR_MOD;
@@ -741,11 +757,19 @@ int open_page_read_at(int dfd, int pid, struct page_read *pr, int pr_flags)
 	pr->seek_pagemap = seek_pagemap;
 	pr->reset = reset_pagemap;
 	pr->id = ids++;
-	if (!pr->parent)
-		pr->pieok = true;
+	pr->pid = pid;
+
+	if (remote)
+		pr->maybe_read_page = maybe_read_page_remote;
+	else {
+		pr->maybe_read_page = maybe_read_page_local;
+		if (!pr->parent && !opts.lazy_pages)
+			pr->pieok = true;
+	}
 
-	pr_debug("Opened page read %u (parent %u)\n",
-			pr->id, pr->parent ? pr->parent->id : 0);
+	pr_debug("Opened %s page read %u (parent %u)\n",
+		 remote ? "remote" : "local", pr->id,
+		 pr->parent ? pr->parent->id : 0);
 
 	return 1;
 }

criu/uffd.c

@@ -452,6 +452,7 @@ static int ud_open(int client, struct lazy_pages_info **_lpi)
 	struct lazy_pages_info *lpi;
 	int ret = -1;
 	int uffd_flags;
+	int pr_flags = PR_TASK;
 
 	lpi = lpi_init();
 	if (!lpi)
@@ -485,7 +486,9 @@ static int ud_open(int client, struct lazy_pages_info **_lpi)
 	uffd_flags = fcntl(lpi->lpfd.fd, F_GETFD, NULL);
 	pr_debug("uffd_flags are 0x%x\n", uffd_flags);
 
-	ret = open_page_read(lpi->pid, &lpi->pr, PR_TASK);
+	if (opts.use_page_server)
+		pr_flags |= PR_REMOTE;
+	ret = open_page_read(lpi->pid, &lpi->pr, pr_flags);
 	if (ret <= 0) {
 		ret = -1;
 		goto out;
@@ -579,11 +582,7 @@ static int uffd_handle_pages(struct lazy_pages_info *lpi, __u64 address, int nr)
 	if (pagemap_zero(lpi->pr.pe))
 		return uffd_zero(lpi, address, nr);
 
-	if (opts.use_page_server)
-		ret = get_remote_pages(lpi->pid, address, nr, lpi->buf);
-	else
-		ret = lpi->pr.read_pages(&lpi->pr, address, nr, lpi->buf, 0);
-
+	ret = lpi->pr.read_pages(&lpi->pr, address, nr, lpi->buf, 0);
 	if (ret <= 0) {
 		pr_err("%d: failed reading pages at %llx\n", lpi->pid, address);
 		return ret;