David Howells
dhowe****@redha*****
Mon Jul 30 19:49:16 JST 2018
Tetsuo Handa <pengu****@I-lov*****> wrote: > Would you provide examples of each possible combination as a C program? > For example, if one mount point from multiple sources with different > options are possible, please describe such pattern using syscall so that > LSM modules can run it to see whether they are working as expected. One example could be overlayfs. So you might do, say: ufd = open("/overlay", O_PATH); fsfd = fsopen("overlay", 0); fsconfig(fsfd, fsconfig_set_path, "lowerdir", "/src", AT_FDCWD); fsconfig(fsfd, fsconfig_set_path, "upperdir", "upper", ufd); fsconfig(fsfd, fsconfig_set_path, "workdir", "scratch", ufd); mfd = fsmount(fsfd, 0, 0); move_mount(fsfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH); which would allow you to specify the "sources" using dirfds. Another possibility is could be ext4 with separate journal: fsfd = fsopen("ext4", 0); fsconfig(fsfd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD); fsconfig(fsfd, fsconfig_set_path, "journal_path", "/dev/sda2", AT_FDCWD); mfd = fsmount(fsfd, 0, 0); move_mount(fsfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH); And then there's bcachefs which suggests on the webpage: mount -t bcachefs /dev/sda1:/dev/sdb1 /mnt but you could then do: fsfd = fsopen("bcachefs", 0); fsconfig(fsfd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD); fsconfig(fsfd, fsconfig_set_path, "source", "/dev/sdb2", AT_FDCWD); mfd = fsmount(fsfd, 0, 0); move_mount(fsfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH); One thing I'm not certain of is whether I should allow multiple values to the same key name, or whether I should require that each key be labelled differently, possibly something like: fsconfig(fsfd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD); fsconfig(fsfd, fsconfig_set_path, "source.1", "/dev/sdb2", AT_FDCWD); David
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