mount: "mount -o rw ...." should not fall back to RO mount

The reported case was an attempt to remount,rw a CD-ROM:

  mount -o remount,rw /mnt/sr0

which "succeeded" by falling back to RO:

  mount("/dev/sr0", "/mnt/sr0", 0x412862, MS_REMOUNT|MS_SILENT|MS_RELATIME, "nojoliet,check=s,map=n,blocksize"...) = -1 EROFS (Read-only file system)
  ...
  mount("/dev/sr0", "/mnt/sr0", 0x412862, MS_RDONLY|MS_REMOUNT|MS_SILENT|MS_RELATIME, "nojoliet,check=s,map=n,blocksize"...) = 0

Clearly, not what was intended!

function                                             old     new   delta
parse_mount_options                                  241     267     +26
mount_main                                          1198    1211     +13
singlemount                                         1301    1313     +12
inetd_main                                          1919    1911      -8
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(add/remove: 0/0 grow/shrink: 3/1 up/down: 51/-8)              Total: 43 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed