[CRIU] [PATCH v6 3/3] Try to include userfaultfd with criu (part 2)
Adrian Reber
adrian at lisas.de
Tue Mar 15 06:21:13 PDT 2016
From: Adrian Reber <areber at redhat.com>
This is a first try to include userfaultfd with criu. Right now it
still requires a "normal" checkpoint. After checkpointing the
application it can be restored with the help of userfaultfd.
All restored pages with MAP_ANONYMOUS and MAP_PRIVATE set are marked as
being handled by userfaultfd.
As soon as the process is restored it blocks on the first memory access
and waits for pages being transferred by userfaultfd.
To handle the required pages a new criu command has been added. For a
userfaultfd supported restore the first step is to start the
'lazy-pages' server:
criu lazy-pages -v4 -D /tmp/3/ --address /tmp/userfault.socket
This waits on a unix domain socket (defined using the --address option)
to receive a userfaultfd file descriptor from a '--lazy-pages' enabled
'criu restore':
criu restore -D /tmp/3 -j -v4 --lazy-pages \
--address /tmp/userfault.socket
In the first step the VDSO pages are pushed from the lazy-pages server
into the restored process. After that the lazy-pages server waits on the
UFFD FD for a UFFD requested page. If there are no requests received
during a period of 5 seconds the lazy-pages server switches into a mode
where the remaining, non-transferred pages are copied into the
destination process. After all remaining pages have been copied the
lazy-pages server exits.
The first page that usually is requested is a VDSO page. The process
currently used for restoring has two VDSO pages, but only one is
requested
via userfaultfd. In the second part where the remaining pages are copied
into the process, the second VDSO page is also copied into the process
as it has not been requested previously. Unfortunately, even as this
page has not been requested before, it is not accepted by userfaultfd.
EINVAL is returned. The reason for EINVAL is not understood and
therefore
the VDSO pages are copied first into the process, then switching to
request
mode and copying the pages which are requested via userfaultfd. To
decide at which point the VDSO pages can be copied into the process, the
lazy-pages server is currently waiting for the first page requested via
userfaultfd. This is one of the VDSO pages. To not copy a page a second
time, which is unnecessary and not possible, there is now a check to see
if the page has been transferred previously.
The use case to use usefaultfd with a checkpointed process on a remote
machine will probably benefit from the current work related to
image-cache and image-proxy.
For the final implementation it would be nice to have a restore running
in uffd mode on one system which requests the memory pages over the
network from another system which is running 'criu checkpoint' also in
uffd mode. This way the pages need to be copied only 'once' from the
checkpoint process to the uffd restore process.
TODO:
* Contains still many debug outputs which need to be cleaned up.
* Maybe transfer the dump directory FD also via unix domain sockets
so that the 'uffd'/'lazy-pages' server can keep running without
the need to specify the dump directory with '-D'
* Keep the lazy-pages server running after all pages have been
transferred and start waiting for new connections to serve.
* Resurrect the non-cooperative patch set, as once the restored task
fork()'s or calls mremap() the whole thing becomes broken.
* Figure out if current VDSO handling is correct.
* Figure out when and how zero pages need to be inserted via uffd.
v2:
* provide option '--lazy-pages' to enable uffd style restore
* use send_fd()/recv_fd() provided by criu (instead of own
implementation)
* do not install the uffd as service_fd
* use named constants for MAP_ANONYMOUS
* do not restore memory pages and then later mark them as uffd
handled
* remove function find_pages() to search in pages-<id>.img;
now using criu functions to find the necessary pages;
for each new page search the pages-<id>.img file is opened
* only check the UFFDIO_API once
* trying to protect uffd code by CONFIG_UFFD;
use make UFFD=1 to compile criu with this patch
v3:
* renamed the server mode from 'uffd' -> 'lazy-pages'
* switched client and server roles transferring the UFFD FD
* the criu part running in lazy-pages server mode is now
waiting for connections
* the criu restore process connects to the lazy-pages server
to pass the UFFD FD
* before UFFD copying anything else the VDSO pages are copied
as it fails to copy unused VDSO pages once the process is running.
this was necessary to be able to copy all pages.
* if there are no more UFFD messages for 5 seconds the lazy-pages
server switches in copy mode to copy all remaining pages, which
have not been requested yet, into the restored process
* check the UFFDIO_API at the correct place
* close UFFD FD in the restorer to remove open UFFD FD in the
restored process
v4:
* removed unnecessary madvise() calls ; it seemed necessary when
first running tests with uffd; it actually is not necessary
* auto-detect if build-system provides linux/userfaultfd.h
header.
* simplify unix domain socket setup and communication.
* use --address to specify the location of the used
unix domain socket.
v5:
* split the userfaultfd patch in multiple smaller patches
* introduced vma_can_be_lazy() function to check if a page
can be handled by uffd
* moved uffd related code from cr-restore.c to uffd.c
* handle failure to register a memory page of the restored process
with userfaultfd
v6:
* get PID of to be restored process from the 'criu restore' process;
first the PID is transferred and then the UFFD
Signed-off-by: Adrian Reber <areber at redhat.com>
---
criu/cr-restore.c | 21 +++++++++++
criu/crtools.c | 14 ++++++++
criu/include/cr_options.h | 1 +
criu/include/restorer.h | 2 ++
criu/include/uffd.h | 6 ++++
criu/include/vma.h | 9 +++++
criu/pie/restorer.c | 77 ++++++++++++++++++++++++++++++++++++++---
criu/uffd.c | 88 +++++++++++++++++++++++++++++++++++++++++++++--
8 files changed, 210 insertions(+), 8 deletions(-)
diff --git a/criu/cr-restore.c b/criu/cr-restore.c
index 9950fa1..2299e95 100644
--- a/criu/cr-restore.c
+++ b/criu/cr-restore.c
@@ -19,6 +19,7 @@
#include <sys/shm.h>
#include <sys/mount.h>
#include <sys/prctl.h>
+#include <sys/syscall.h>
#include <sched.h>
@@ -76,6 +77,8 @@
#include "seccomp.h"
#include "bitmap.h"
#include "fault-injection.h"
+#include "uffd.h"
+
#include "parasite-syscall.h"
#include "protobuf.h"
@@ -415,6 +418,7 @@ static int restore_priv_vma_content(void)
unsigned int nr_shared = 0;
unsigned int nr_droped = 0;
unsigned int nr_compared = 0;
+ unsigned int nr_lazy = 0;
unsigned long va;
struct page_read pr;
@@ -469,6 +473,17 @@ static int restore_priv_vma_content(void)
p = decode_pointer((off) * PAGE_SIZE +
vma->premmaped_addr);
+ /*
+ * This means that userfaultfd is used to load the pages
+ * on demand.
+ */
+ if (opts.lazy_pages && vma_entry_can_be_lazy(vma->e)) {
+ pr_debug("Lazy restore skips %lx\n", vma->e->start);
+ pr.skip_pages(&pr, PAGE_SIZE);
+ nr_lazy++;
+ continue;
+ }
+
set_bit(off, vma->page_bitmap);
if (vma->ppage_bitmap) { /* inherited vma */
clear_bit(off, vma->ppage_bitmap);
@@ -557,6 +572,7 @@ err_read:
pr_info("nr_restored_pages: %d\n", nr_restored);
pr_info("nr_shared_pages: %d\n", nr_shared);
pr_info("nr_droped_pages: %d\n", nr_droped);
+ pr_info("nr_lazy: %d\n", nr_lazy);
return 0;
@@ -3231,6 +3247,11 @@ static int sigreturn_restore(pid_t pid, CoreEntry *core)
strncpy(task_args->comm, core->tc->comm, sizeof(task_args->comm));
+ if (!opts.lazy_pages)
+ task_args->uffd = -1;
+ else
+ if (setup_uffd(task_args, pid) != 0)
+ goto err;
/*
* Fill up per-thread data.
diff --git a/criu/crtools.c b/criu/crtools.c
index 763b5fd..2e85cb8 100644
--- a/criu/crtools.c
+++ b/criu/crtools.c
@@ -319,6 +319,9 @@ int main(int argc, char *argv[], char *envp[])
{ "external", required_argument, 0, 1073 },
{ "empty-ns", required_argument, 0, 1074 },
{ "unshare", required_argument, 0, 1075 },
+#ifdef CONFIG_HAS_UFFD
+ { "lazy-pages", no_argument, 0, 1076 },
+#endif
{ },
};
@@ -572,6 +575,11 @@ int main(int argc, char *argv[], char *envp[])
if (parse_unshare_arg(optarg))
return -1;
break;
+#ifdef CONFIG_HAS_UFFD
+ case 1076:
+ opts.lazy_pages = true;
+ break;
+#endif
case 'M':
{
char *aux;
@@ -813,6 +821,12 @@ usage:
" --unshare FLAGS what namespaces to unshare when restoring\n"
" --freeze-cgroup\n"
" use cgroup freezer to collect processes\n"
+#ifdef CONFIG_HAS_UFFD
+" --lazy-pages restore pages on demand\n"
+" this requires running a second instance of criu\n"
+" in lazy-pages mode: 'criu lazy-pages -D DIR'\n"
+" --lazy-pages and lazy-pages mode require userfaultfd\n"
+#endif
"\n"
"* Special resources support:\n"
" -x|--" USK_EXT_PARAM "inode,.." " allow external unix connections (optionally can be assign socket's inode that allows one-sided dump)\n"
diff --git a/criu/include/cr_options.h b/criu/include/cr_options.h
index c1e8fbc..918bb4d 100644
--- a/criu/include/cr_options.h
+++ b/criu/include/cr_options.h
@@ -108,6 +108,7 @@ struct cr_options {
char *lsm_profile;
unsigned int timeout;
unsigned int empty_ns;
+ bool lazy_pages;
};
extern struct cr_options opts;
diff --git a/criu/include/restorer.h b/criu/include/restorer.h
index 9896aa1..86236b0 100644
--- a/criu/include/restorer.h
+++ b/criu/include/restorer.h
@@ -124,6 +124,8 @@ struct task_restore_args {
int logfd;
unsigned int loglevel;
+ int uffd;
+
/* threads restoration */
int nr_threads; /* number of threads */
thread_restore_fcall_t clone_restore_fn; /* helper address for clone() call */
diff --git a/criu/include/uffd.h b/criu/include/uffd.h
index d5a043b..6c931e2 100644
--- a/criu/include/uffd.h
+++ b/criu/include/uffd.h
@@ -2,6 +2,7 @@
#define __CR_UFFD_H_
#include "config.h"
+#include "restorer.h"
#ifdef CONFIG_HAS_UFFD
@@ -11,6 +12,11 @@
#ifndef __NR_userfaultfd
#error "missing __NR_userfaultfd definition"
#endif
+
+extern int setup_uffd(struct task_restore_args *task_args, int pid);
+#else
+static inline int setup_uffd(struct task_restore_args *task_args, int pid) { return 0; }
+
#endif /* CONFIG_HAS_UFFD */
#endif /* __CR_UFFD_H_ */
diff --git a/criu/include/vma.h b/criu/include/vma.h
index 247c5a3..28b77b5 100644
--- a/criu/include/vma.h
+++ b/criu/include/vma.h
@@ -7,6 +7,8 @@
#include "images/vma.pb-c.h"
+#include <sys/mman.h>
+
struct vm_area_list {
struct list_head h;
unsigned nr;
@@ -107,4 +109,11 @@ static inline bool vma_area_is_private(struct vma_area *vma,
return vma_entry_is_private(vma->e, task_size);
}
+static inline bool vma_entry_can_be_lazy(VmaEntry *e)
+{
+ return ((e->flags & MAP_ANONYMOUS) &&
+ (e->flags & MAP_PRIVATE) &&
+ !(vma_entry_is(e, VMA_AREA_VSYSCALL)));
+}
+
#endif /* __CR_VMA_H__ */
diff --git a/criu/pie/restorer.c b/criu/pie/restorer.c
index f7bde75..4a009f4 100644
--- a/criu/pie/restorer.c
+++ b/criu/pie/restorer.c
@@ -25,6 +25,7 @@
#include "image.h"
#include "sk-inet.h"
#include "vma.h"
+#include "uffd.h"
#include "crtools.h"
#include "lock.h"
@@ -567,8 +568,50 @@ static void rst_tcp_socks_all(struct task_restore_args *ta)
rst_tcp_repair_off(&ta->tcp_socks[i]);
}
-static int vma_remap(unsigned long src, unsigned long dst, unsigned long len)
+
+
+
+static int enable_uffd(int uffd, unsigned long addr, unsigned long len)
{
+ /*
+ * If uffd == -1, this means that userfaultfd is not enabled
+ * or it is not available.
+ */
+ if (uffd == -1)
+ return 0;
+#ifdef CONFIG_HAS_UFFD
+ int rc;
+ struct uffdio_register uffdio_register;
+ unsigned long expected_ioctls;
+
+ uffdio_register.range.start = addr;
+ uffdio_register.range.len = len;
+ uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
+ pr_info("lazy-pages: uffdio_register.range.start 0x%lx\n", (unsigned long) uffdio_register.range.start);
+ pr_info("lazy-pages: uffdio_register.len 0x%llx\n", uffdio_register.range.len);
+ rc = sys_ioctl(uffd, UFFDIO_REGISTER, &uffdio_register);
+ pr_info("lazy-pages: ioctl UFFDIO_REGISTER rc %d\n", rc);
+ pr_info("lazy-pages: uffdio_register.range.start 0x%lx\n", (unsigned long) uffdio_register.range.start);
+ pr_info("lazy-pages: uffdio_register.len 0x%llx\n", uffdio_register.range.len);
+ if (rc != 0)
+ return -1;
+
+ expected_ioctls = (1 << _UFFDIO_WAKE) | (1 << _UFFDIO_COPY) | (1 << _UFFDIO_ZEROPAGE);
+
+ if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls) {
+ pr_err("lazy-pages: unexpected missing uffd ioctl for anon memory\n");
+ }
+
+#endif
+ return 0;
+}
+
+
+static int vma_remap(VmaEntry *vma_entry, int uffd)
+{
+ unsigned long src = vma_premmaped_start(vma_entry);
+ unsigned long dst = vma_entry->start;
+ unsigned long len = vma_entry_len(vma_entry);
unsigned long guard = 0, tmp;
pr_info("Remap %lx->%lx len %lx\n", src, dst, len);
@@ -640,6 +683,18 @@ static int vma_remap(unsigned long src, unsigned long dst, unsigned long len)
return -1;
}
+ /*
+ * If running in userfaultfd/lazy-pages mode pages with
+ * MAP_ANONYMOUS and MAP_PRIVATE are remapped but without the
+ * real content.
+ * The function enable_uffd() marks the page(s) as userfaultfd
+ * pages, so that the processes will hang until the memory is
+ * injected via userfaultfd.
+ */
+ if (vma_entry_can_be_lazy(vma_entry))
+ if (enable_uffd(uffd, dst, len) != 0)
+ return -1;
+
return 0;
}
@@ -898,6 +953,10 @@ long __export_restore_task(struct task_restore_args *args)
pr_info("Switched to the restorer %d\n", my_pid);
+ if (args->uffd > -1) {
+ pr_debug("lazy-pages: uffd %d\n", args->uffd);
+ }
+
if (vdso_do_park(&args->vdso_sym_rt, args->vdso_rt_parked_at, vdso_rt_size))
goto core_restore_end;
@@ -918,8 +977,7 @@ long __export_restore_task(struct task_restore_args *args)
if (vma_entry->start > vma_entry->shmid)
break;
- if (vma_remap(vma_premmaped_start(vma_entry),
- vma_entry->start, vma_entry_len(vma_entry)))
+ if (vma_remap(vma_entry, args->uffd))
goto core_restore_end;
}
@@ -936,11 +994,20 @@ long __export_restore_task(struct task_restore_args *args)
if (vma_entry->start < vma_entry->shmid)
break;
- if (vma_remap(vma_premmaped_start(vma_entry),
- vma_entry->start, vma_entry_len(vma_entry)))
+ if (vma_remap(vma_entry, args->uffd))
goto core_restore_end;
}
+ if (args->uffd > -1) {
+ pr_debug("lazy-pages: closing uffd %d\n", args->uffd);
+ /*
+ * All userfaultfd configuration has finished at this point.
+ * Let's close the UFFD file descriptor, so that the restored
+ * process does not have an opened UFFD FD for ever.
+ */
+ sys_close(args->uffd);
+ }
+
/*
* OK, lets try to map new one.
*/
diff --git a/criu/uffd.c b/criu/uffd.c
index 6d8b286..3beae79 100644
--- a/criu/uffd.c
+++ b/criu/uffd.c
@@ -30,6 +30,90 @@
#undef LOG_PREFIX
#define LOG_PREFIX "lazy-pages: "
+static int send_uffd(int sendfd, int pid)
+{
+ int fd;
+ int len;
+ int ret = -1;
+ struct sockaddr_un sun;
+
+ if (!opts.addr) {
+ pr_info("Please specify a file name for the unix domain socket\n");
+ pr_info("used to communicate between the lazy-pages server\n");
+ pr_info("and the restore process. Use the --address option like\n");
+ pr_info("criu restore --lazy-pages --address /tmp/userfault.socket\n");
+ return -1;
+ }
+
+ if (sendfd < 0)
+ return -1;
+
+ if (strlen(opts.addr) >= sizeof(sun.sun_path)) {
+ return -1;
+ }
+
+ if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+ return -1;
+
+ memset(&sun, 0, sizeof(sun));
+ sun.sun_family = AF_UNIX;
+ strcpy(sun.sun_path, opts.addr);
+ len = offsetof(struct sockaddr_un, sun_path) + strlen(opts.addr);
+ if (connect(fd, (struct sockaddr *) &sun, len) < 0) {
+ pr_perror("connect to %s failed", opts.addr);
+ goto out;
+ }
+
+ /* The "transfer protocol" is first the pid as int and then
+ * the FD for UFFD */
+ pr_debug("Sending PID %d\n", pid);
+ if (send(fd, &pid, sizeof(pid), 0) < 0) {
+ pr_perror("PID sending error:");
+ goto out;
+ }
+
+ if (send_fd(fd, NULL, 0, sendfd) < 0) {
+ pr_perror("send_fd error:");
+ goto out;
+ }
+ ret = 0;
+out:
+ close(fd);
+ return ret;
+}
+
+/* This function is used by 'criu restore --lazy-pages' */
+int setup_uffd(struct task_restore_args *task_args, int pid)
+{
+ struct uffdio_api uffdio_api;
+ /*
+ * Open userfaulfd FD which is passed to the restorer blob and
+ * to a second process handling the userfaultfd page faults.
+ */
+ task_args->uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+
+ /*
+ * Check if the UFFD_API is the one which is expected
+ */
+ uffdio_api.api = UFFD_API;
+ uffdio_api.features = 0;
+ if (ioctl(task_args->uffd, UFFDIO_API, &uffdio_api)) {
+ pr_err("Checking for UFFDIO_API failed.\n");
+ return -1;
+ }
+ if (uffdio_api.api != UFFD_API) {
+ pr_err("Result of looking up UFFDIO_API does not match: %Lu\n", uffdio_api.api);
+ return -1;
+ }
+
+ if (send_uffd(task_args->uffd, pid) < 0) {
+ close(task_args->uffd);
+ return -1;
+ }
+
+ return 0;
+}
+
static int server_listen(struct sockaddr_un *saddr)
{
int fd;
@@ -232,9 +316,7 @@ static int collect_uffd_pages(struct page_read *pr, struct list_head *uffd_list,
* in the VMA list.
*/
if (base >= vma->e->start && base < vma->e->end) {
- if ((vma->e->flags & MAP_ANONYMOUS) &&
- (vma->e->flags & MAP_PRIVATE) &&
- !(vma_area_is(vma, VMA_AREA_VSYSCALL))) {
+ if (vma_entry_can_be_lazy(vma->e)) {
uffd_page = true;
if (vma_area_is(vma, VMA_AREA_VDSO))
uffd_vdso = true;
--
1.8.3.1
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