@@ -29,6 +29,9 @@
#ifndef __NR_watch_mount
#define __NR_watch_mount -1
#endif
+#ifndef __NR_watch_sb
+#define __NR_watch_sb -1
+#endif
#define BUF_SIZE 256
@@ -87,6 +90,24 @@ static void saw_mount_change(struct watch_notification *n, size_t len)
}
+static const char *super_subtypes[256] = {
+ [NOTIFY_SUPERBLOCK_READONLY] = "readonly",
+ [NOTIFY_SUPERBLOCK_ERROR] = "error",
+ [NOTIFY_SUPERBLOCK_EDQUOT] = "edquot",
+ [NOTIFY_SUPERBLOCK_NETWORK] = "network",
+};
+
+static void saw_super_change(struct watch_notification *n, size_t len)
+{
+ struct superblock_notification *s = (struct superblock_notification *)n;
+
+ if (len < sizeof(struct superblock_notification))
+ return;
+
+ printf("SUPER %08llx change=%u[%s]\n",
+ s->sb_id, n->subtype, super_subtypes[n->subtype]);
+}
+
/*
* Consume and display events.
*/
@@ -166,6 +187,9 @@ static void consumer(int fd)
case WATCH_TYPE_MOUNT_NOTIFY:
saw_mount_change(&n.n, len);
break;
+ case WATCH_TYPE_SB_NOTIFY:
+ saw_super_change(&n.n, len);
+ break;
}
p += len;
@@ -174,7 +198,7 @@ static void consumer(int fd)
}
static struct watch_notification_filter filter = {
- .nr_filters = 2,
+ .nr_filters = 3,
.filters = {
[0] = {
.type = WATCH_TYPE_KEY_NOTIFY,
@@ -185,6 +209,14 @@ static struct watch_notification_filter filter = {
// Reject move-from notifications
.subtype_filter[0] = UINT_MAX & ~(1 << NOTIFY_MOUNT_MOVE_FROM),
},
+ [2] = {
+ .type = WATCH_TYPE_SB_NOTIFY,
+ // Only accept notification of changes to R/O state
+ .subtype_filter[0] = (1 << NOTIFY_SUPERBLOCK_READONLY),
+ // Only accept notifications of change-to-R/O
+ .info_mask = WATCH_INFO_FLAG_0,
+ .info_filter = WATCH_INFO_FLAG_0,
+ },
},
};
@@ -223,6 +255,11 @@ int main(int argc, char **argv)
exit(1);
}
+ if (syscall(__NR_watch_sb, AT_FDCWD, "/mnt", 0, fd, 0x03) == -1) {
+ perror("watch_sb");
+ exit(1);
+ }
+
consumer(fd);
exit(0);
}
The notification is run as: ./watch_test and it then watches "/mnt" for superblock notifications: # mount -t tmpfs none /mnt # ./watch_test & # mount -o remount,ro /mnt # mount -o remount,rw /mnt producing: # ./watch_test NOTIFY[000]: ty=000003 sy=00 i=03010010 SUPER 157eb57ca7 change=0[readonly] read() = 16 NOTIFY[000]: ty=000002 sy=04 i=02010010 MOUNT 000001a0 change=4[setattr] aux=0 read() = 16 NOTIFY[000]: ty=000002 sy=04 i=02010010 MOUNT 000001a0 change=4[setattr] aux=0 Signed-off-by: David Howells <dhowells@redhat.com> --- samples/watch_queue/watch_test.c | 39 +++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-)