From 4534b32c7394d9f5c9d49820f11b9f07fe41b079 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 22 Sep 2020 11:19:37 +0200
Subject: [PATCH 1/4] shutdown: fsync() before detaching loopback devices

This is a follow-up for cae1e8fb88c5a6b0960a2d0be3df8755f0c78462: we
also call the detach ioctls in the shutdown code, hence add the fsync()s
there too, just to be safe.
---
 src/shutdown/umount.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/shutdown/umount.c b/src/shutdown/umount.c
index 0eb694c1af..307944c657 100644
--- a/src/shutdown/umount.c
+++ b/src/shutdown/umount.c
@@ -387,8 +387,15 @@ static int delete_loopback(const char *device) {
         assert(device);
 
         fd = open(device, O_RDONLY|O_CLOEXEC);
-        if (fd < 0)
+        if (fd < 0) {
+                log_debug_errno(errno, "Failed to open loopback device %s: %m", device);
                 return errno == ENOENT ? 0 : -errno;
+        }
+
+        /* Loopback block devices don't sync in-flight blocks when we clear the fd, hence sync explicitly
+         * first */
+        if (fsync(fd) < 0)
+                log_debug_errno(errno, "Failed to sync loop block device %s, ignoring: %m", device);
 
         if (ioctl(fd, LOOP_CLR_FD, 0) < 0) {
                 if (errno == ENXIO) /* Nothing bound, didn't do anything */

From 1a269c4ee34a4fc98f2407996cc6bda82f3e03bf Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 22 Sep 2020 11:21:19 +0200
Subject: [PATCH 2/4] shutdown: don't compare pointers with 0

---
 src/shutdown/umount.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/shutdown/umount.c b/src/shutdown/umount.c
index 307944c657..4354485728 100644
--- a/src/shutdown/umount.c
+++ b/src/shutdown/umount.c
@@ -474,11 +474,11 @@ static int delete_dm(dev_t devnum) {
 }
 
 static int delete_md(MountPoint *m) {
-
         _cleanup_close_ int fd = -1;
 
+        assert(m);
         assert(major(m->devnum) != 0);
-        assert(m->path != 0);
+        assert(m->path);
 
         fd = open(m->path, O_RDONLY|O_CLOEXEC|O_EXCL);
         if (fd < 0)

From 32c4626c4c34a7deb9ddc5edfba98c3f171900c8 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 22 Sep 2020 11:21:27 +0200
Subject: [PATCH 3/4] shutdown: also fsync() MD devices when going down

Let's make this explicit, just in case this suffers by the same issues
as the loopback devices, and drops in-flight IO when we disassemble it.
---
 src/shutdown/umount.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/shutdown/umount.c b/src/shutdown/umount.c
index 4354485728..89b05fcc3f 100644
--- a/src/shutdown/umount.c
+++ b/src/shutdown/umount.c
@@ -484,6 +484,9 @@ static int delete_md(MountPoint *m) {
         if (fd < 0)
                 return -errno;
 
+        if (fsync(fd) < 0)
+                log_debug_errno(errno, "Failed to sync MD block device %s, ignoring: %m", m->path);
+
         if (ioctl(fd, STOP_ARRAY, NULL) < 0)
                 return -errno;
 

From e55299da4d75f1e33385f04fded002f23530de94 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 22 Sep 2020 11:23:35 +0200
Subject: [PATCH 4/4] shutdown: also fsync() DM devices before going down

Similar reasons as the previous patch.
---
 src/shutdown/umount.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/src/shutdown/umount.c b/src/shutdown/umount.c
index 89b05fcc3f..6eebaf7abc 100644
--- a/src/shutdown/umount.c
+++ b/src/shutdown/umount.c
@@ -23,6 +23,7 @@
 #include "device-util.h"
 #include "escape.h"
 #include "fd-util.h"
+#include "fs-util.h"
 #include "fstab-util.h"
 #include "libmount-util.h"
 #include "mount-setup.h"
@@ -447,27 +448,31 @@ static int delete_loopback(const char *device) {
         return -EBUSY; /* Nothing changed, the device is still attached, hence it apparently is still busy */
 }
 
-static int delete_dm(dev_t devnum) {
-
-        struct dm_ioctl dm = {
-                .version = {
-                        DM_VERSION_MAJOR,
-                        DM_VERSION_MINOR,
-                        DM_VERSION_PATCHLEVEL
-                },
-                .data_size = sizeof(dm),
-                .dev = devnum,
-        };
-
+static int delete_dm(MountPoint *m) {
         _cleanup_close_ int fd = -1;
+        int r;
 
-        assert(major(devnum) != 0);
+        assert(m);
+        assert(major(m->devnum) != 0);
+        assert(m->path);
 
         fd = open("/dev/mapper/control", O_RDWR|O_CLOEXEC);
         if (fd < 0)
                 return -errno;
 
-        if (ioctl(fd, DM_DEV_REMOVE, &dm) < 0)
+        r = fsync_path_at(AT_FDCWD, m->path);
+        if (r < 0)
+                log_debug_errno(r, "Failed to sync DM block device %s, ignoring: %m", m->path);
+
+        if (ioctl(fd, DM_DEV_REMOVE, &(struct dm_ioctl) {
+                .version = {
+                        DM_VERSION_MAJOR,
+                        DM_VERSION_MINOR,
+                        DM_VERSION_PATCHLEVEL
+                },
+                .data_size = sizeof(struct dm_ioctl),
+                .dev = m->devnum,
+        }) < 0)
                 return -errno;
 
         return 0;
@@ -702,7 +707,7 @@ static int dm_points_list_detach(MountPoint **head, bool *changed, int umount_lo
                 }
 
                 log_info("Detaching DM %s (%u:%u).", m->path, major(m->devnum), minor(m->devnum));
-                r = delete_dm(m->devnum);
+                r = delete_dm(m);
                 if (r < 0) {
                         log_full_errno(umount_log_level, r, "Could not detach DM %s: %m", m->path);
                         n_failed++;