diff --git a/sys-utils/mount.8 b/sys-utils/mount.8 index d18881b2c..5ec121092 100644 --- a/sys-utils/mount.8 +++ b/sys-utils/mount.8 @@ -398,6 +398,15 @@ command (then mount(8) does not read /etc/mtab), then you have to use bind flag .B mount -o remount,ro,bind .I olddir newdir .RE + +Note that +.I remount,ro,bind +will create a read-only mountpoint (VFS entry), but the original filesystem suberblock +will be still writable, it means that the +.I olddir +will be writable, but the +.I newdir +will be read-only. .RE .B The move operation. @@ -434,6 +443,11 @@ unbindable mount is a private mount which cannot be cloned through a bind operation. Detailed semantics is documented in Documentation/filesystems/sharedsubtree.txt file in the kernel source tree. +Note that Linux kernel does not allow to change more propagation flags by one +.B mount (2) +syscall and the flags cannot be mixed with another mount options. It means that +more --make-* options cannot be used together or with another mount options. + .RS .nf .BI "mount --make-shared " mountpoint diff --git a/sys-utils/mount.c b/sys-utils/mount.c index d1e2e16c7..f5df087ea 100644 --- a/sys-utils/mount.c +++ b/sys-utils/mount.c @@ -789,37 +789,37 @@ int main(int argc, char **argv) mnt_context_enable_sloppy(cxt, TRUE); break; case 'B': - oper = MS_BIND; + oper |= MS_BIND; break; case 'M': - oper = MS_MOVE; + oper |= MS_MOVE; break; case 'R': - oper = (MS_BIND | MS_REC); + oper |= (MS_BIND | MS_REC); break; case MOUNT_OPT_SHARED: - oper = MS_SHARED; + oper |= MS_SHARED; break; case MOUNT_OPT_SLAVE: - oper = MS_SLAVE; + oper |= MS_SLAVE; break; case MOUNT_OPT_PRIVATE: - oper = MS_PRIVATE; + oper |= MS_PRIVATE; break; case MOUNT_OPT_UNBINDABLE: - oper = MS_UNBINDABLE; + oper |= MS_UNBINDABLE; break; case MOUNT_OPT_RSHARED: - oper = (MS_SHARED | MS_REC); + oper |= (MS_SHARED | MS_REC); break; case MOUNT_OPT_RSLAVE: - oper = (MS_SLAVE | MS_REC); + oper |= (MS_SLAVE | MS_REC); break; case MOUNT_OPT_RPRIVATE: - oper = (MS_PRIVATE | MS_REC); + oper |= (MS_PRIVATE | MS_REC); break; case MOUNT_OPT_RUNBINDABLE: - oper = (MS_UNBINDABLE | MS_REC); + oper |= (MS_UNBINDABLE | MS_REC); break; default: usage(stderr); @@ -885,6 +885,12 @@ int main(int argc, char **argv) usage(stderr); if (oper) { + if (!is_power_of_2(oper)) + errx(MOUNT_EX_USAGE, _("propagation flags (--make-* or --bind options) are mutually exclusive")); + + if (oper != MS_BIND && mnt_context_get_options(cxt)) + errx(MOUNT_EX_USAGE, _("propagation flags (--make-* options) cannot be mixed with another mount options")); + /* MS_PROPAGATION operations, let's set the mount flags */ mnt_context_set_mflags(cxt, oper);