Punch holes in input files when restoring anonymous non-shared memory if --auto-dedup is enabled.

Submitted by Pawel Stradomski on July 24, 2018, 10:12 a.m.

Details

Message ID 00000000000008ac1d057239c6fe@google.com
State Rejected
Series "Punch holes in input files when restoring anonymous non-shared memory if --auto-dedup is enabled."
Headers show

Commit Message

Pawel Stradomski July 24, 2018, 10:12 a.m.
This reduces memory usage if image files are stored on tmpfs.

Signed-off-by: Pawel Stradomski <pstradomski@google.com>
---
 .../arch/arm/plugins/std/syscalls/syscall.def |  1 +
 .../plugins/std/syscalls/syscall-ppc64.tbl    |  1 +
 .../plugins/std/syscalls/syscall-s390.tbl     |  1 +
 .../x86/plugins/std/syscalls/syscall_32.tbl   |  1 +
 .../x86/plugins/std/syscalls/syscall_64.tbl   |  1 +
 criu/mem.c                                    | 16 +++++++++-
 criu/pie/restorer.c                           | 31 +++++++++++++++++++
 7 files changed, 51 insertions(+), 1 deletion(-)

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diff --git a/compel/arch/arm/plugins/std/syscalls/syscall.def b/compel/arch/arm/plugins/std/syscalls/syscall.def
index b68f9f2f..bcd61d4a 100644
--- a/compel/arch/arm/plugins/std/syscalls/syscall.def
+++ b/compel/arch/arm/plugins/std/syscalls/syscall.def
@@ -109,3 +109,4 @@  seccomp				277	383	(unsigned int op, unsigned int flags, const char *uargs)
 gettimeofday			169	78	(struct timeval *tv, struct timezone *tz)
 preadv_raw			69	361	(int fd, struct iovec *iov, unsigned long nr, unsigned long pos_l, unsigned long pos_h)
 userfaultfd			282	388	(int flags)
+fallocate			47	352	(int fd, int mode, loff_t offset, loff_t len)
diff --git a/compel/arch/ppc64/plugins/std/syscalls/syscall-ppc64.tbl b/compel/arch/ppc64/plugins/std/syscalls/syscall-ppc64.tbl
index fa0b034e..62e0bc1a 100644
--- a/compel/arch/ppc64/plugins/std/syscalls/syscall-ppc64.tbl
+++ b/compel/arch/ppc64/plugins/std/syscalls/syscall-ppc64.tbl
@@ -89,6 +89,7 @@  __NR_set_robust_list	300		sys_set_robust_list	(struct robust_list_head *head, si
 __NR_get_robust_list	299		sys_get_robust_list	(int pid, struct robust_list_head **head_ptr, size_t *len_ptr)
 __NR_vmsplice		285		sys_vmsplice		(int fd, const struct iovec *iov, unsigned long nr_segs, unsigned int flags)
 __NR_openat		286		sys_openat		(int dfd, const char *filename, int flags, int mode)
+__NR_fallocate		309		sys_fallocate		(int fd, int mode, loff_t offset, loff_t len)
 __NR_timerfd_settime	311		sys_timerfd_settime	(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr)
 __NR_signalfd4		313		sys_signalfd		(int fd, k_rtsigset_t *mask, size_t sizemask, int flags)
 __NR_rt_tgsigqueueinfo	322		sys_rt_tgsigqueueinfo	(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
diff --git a/compel/arch/s390/plugins/std/syscalls/syscall-s390.tbl b/compel/arch/s390/plugins/std/syscalls/syscall-s390.tbl
index bc77ae97..3521e915 100644
--- a/compel/arch/s390/plugins/std/syscalls/syscall-s390.tbl
+++ b/compel/arch/s390/plugins/std/syscalls/syscall-s390.tbl
@@ -89,6 +89,7 @@  __NR_set_robust_list	304		sys_set_robust_list	(struct robust_list_head *head, si
 __NR_get_robust_list	305		sys_get_robust_list	(int pid, struct robust_list_head **head_ptr, size_t *len_ptr)
 __NR_vmsplice		309		sys_vmsplice		(int fd, const struct iovec *iov, unsigned long nr_segs, unsigned int flags)
 __NR_openat		288		sys_openat		(int dfd, const char *filename, int flags, int mode)
+__NR_fallocate		314		sys_fallocate		(int fd, int mode, loff_t offset, loff_t len)
 __NR_timerfd_settime	320		sys_timerfd_settime	(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr)
 __NR_signalfd4		322		sys_signalfd		(int fd, k_rtsigset_t *mask, size_t sizemask, int flags)
 __NR_rt_tgsigqueueinfo	330		sys_rt_tgsigqueueinfo	(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
diff --git a/compel/arch/x86/plugins/std/syscalls/syscall_32.tbl b/compel/arch/x86/plugins/std/syscalls/syscall_32.tbl
index 9e1de281..a6c55b83 100644
--- a/compel/arch/x86/plugins/std/syscalls/syscall_32.tbl
+++ b/compel/arch/x86/plugins/std/syscalls/syscall_32.tbl
@@ -83,6 +83,7 @@  __NR_set_robust_list	311		sys_set_robust_list	(struct robust_list_head *head, si
 __NR_get_robust_list	312		sys_get_robust_list	(int pid, struct robust_list_head **head_ptr, size_t *len_ptr)
 __NR_vmsplice		316		sys_vmsplice		(int fd, const struct iovec *iov, unsigned int nr_segs, unsigned int flags)
 __NR_signalfd		321		sys_signalfd		(int ufd, const k_rtsigset_t *sigmask, size_t sigsetsize)
+__NR_fallocate		324		sys_fallocate		(int fd, int mode, loff_t offset, loff_t len)
 __NR_timerfd_settime	325		sys_timerfd_settime	(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr)
 __NR_preadv		333		sys_preadv_raw		(int fd, struct iovec *iov, unsigned long nr, unsigned long pos_l, unsigned long pos_h)
 __NR_rt_tgsigqueueinfo	335		sys_rt_tgsigqueueinfo	(pid_t tgid, pid_t pid, int sig, siginfo_t *uinfo)
diff --git a/compel/arch/x86/plugins/std/syscalls/syscall_64.tbl b/compel/arch/x86/plugins/std/syscalls/syscall_64.tbl
index 726fa797..64271514 100644
--- a/compel/arch/x86/plugins/std/syscalls/syscall_64.tbl
+++ b/compel/arch/x86/plugins/std/syscalls/syscall_64.tbl
@@ -94,6 +94,7 @@  __NR_set_robust_list		273		sys_set_robust_list	(struct robust_list_head *head, s
 __NR_get_robust_list		274		sys_get_robust_list	(int pid, struct robust_list_head **head_ptr, size_t *len_ptr)
 __NR_seccomp			317		sys_seccomp		(unsigned int op, unsigned int flags, const char *uargs)
 __NR_vmsplice			278		sys_vmsplice		(int fd, const struct iovec *iov, unsigned long nr_segs, unsigned int flags)
+__NR_fallocate			285		sys_fallocate		(int fd, int mode, loff_t offset, loff_t len)
 __NR_timerfd_settime		286		sys_timerfd_settime	(int ufd, int flags, const struct itimerspec *utmr, struct itimerspec *otmr)
 __NR_signalfd4			289		sys_signalfd		(int fd, k_rtsigset_t *mask, size_t sizemask, int flags)
 __NR_preadv			295		sys_preadv_raw		(int fd, struct iovec *iov, unsigned long nr, unsigned long pos_l, unsigned long pos_h)
diff --git a/criu/mem.c b/criu/mem.c
index d020b7fd..9e2375f8 100644
--- a/criu/mem.c
+++ b/criu/mem.c
@@ -1271,7 +1271,21 @@  static int prepare_vma_ios(struct pstree_item *t, struct task_restore_args *ta)
 {
 	struct cr_img *pages;
 
-	pages = open_image(CR_FD_PAGES, O_RSTR, rsti(t)->pages_img_id);
+	/* if auto-dedup is on we need RDWR mode to be able to punch holes
+	 * in the input files (in restorer.c)
+	 */
+	pages = open_image(CR_FD_PAGES, opts.auto_dedup ? O_RDWR : O_RSTR,
+				rsti(t)->pages_img_id);
+	/* When running inside namespace we might lack privileges to open the file
+	 * for writing.
+	 * TODO: use userns_call to do the opening instead of downgrading to opening
+	 * read-only.
+	 */
+	if (!pages && opts.auto_dedup) {
+		pr_warn("Failed to open image read-write, trying read-only instead. auto-dedup won't work\n");
+		pages = open_image(CR_FD_PAGES, O_RSTR, rsti(t)->pages_img_id);
+	}
+
 	if (!pages)
 		return -1;
 
diff --git a/criu/pie/restorer.c b/criu/pie/restorer.c
index f990e9b7..7c70d02a 100644
--- a/criu/pie/restorer.c
+++ b/criu/pie/restorer.c
@@ -50,6 +50,15 @@ 
 #define PR_SET_PDEATHSIG 1
 #endif
 
+#ifndef FALLOC_FL_KEEP_SIZE
+#define FALLOC_FL_KEEP_SIZE     0x01
+#endif
+
+#ifndef FALLOC_FL_PUNCH_HOLE
+#define FALLOC_FL_PUNCH_HOLE    0x02
+#endif
+
+
 #define sys_prctl_safe(opcode, val1, val2, val3)			\
 	({								\
 		long __ret = sys_prctl(opcode, val1, val2, val3, 0);	\
@@ -646,6 +655,14 @@  static unsigned long restore_mapping(VmaEntry *vma_entry)
 			!(vma_entry->status & VMA_NO_PROT_WRITE))
 		prot |= PROT_WRITE;
 
+	/* TODO: Drop MAP_LOCKED bit and restore it after reading memory.
+	 *
+	 * Code below tries to limit memory usage by running fallocate()
+	 * after each preadv() to avoid doubling memory usage (once in
+	 * image files, once in process). Unfortunately, MAP_LOCKED defeats
+	 * that mechanism as it causes the process to be charged for memory
+	 * immediately upon mmap, not later, upon preadv().
+	 */
 	pr_debug("\tmmap(%"PRIx64" -> %"PRIx64", %x %x %d)\n",
 			vma_entry->start, vma_entry->end,
 			prot, flags, (int)vma_entry->fd);
@@ -1355,6 +1372,11 @@  long __export_restore_task(struct task_restore_args *args)
 		struct iovec *iovs = rio->iovs;
 		int nr = rio->nr_iovs;
 		ssize_t r;
+		int file_flags = sys_fcntl(args->vma_ios_fd, F_GETFL, 0);
+		if (file_flags < 0) {
+			pr_err("Can't check file flags\n");
+			file_flags = 0;
+		}
 
 		while (nr) {
 			pr_debug("Preadv %lx:%d... (%d iovs)\n",
@@ -1367,6 +1389,15 @@  long __export_restore_task(struct task_restore_args *args)
 			}
 
 			pr_debug("`- returned %ld\n", (long)r);
+			/* If the file is open for writing, then it means we should punch holes
+			 * in it. */
+			if (r > 0 && (file_flags & O_RDWR)) {
+				int fr = sys_fallocate(args->vma_ios_fd, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE,
+					rio->off, r);
+				if (fr < 0) {
+					pr_debug("Failed to punch holes with fallocate: %d\n", fr);
+				}
+			}
 			rio->off += r;
 			/* Advance the iovecs */
 			do {