Hello,
To my surprise, mount("/dev/sda1", "/mnt", "vfat", MS_RDONLY, "")
followed by mount("/mnt", "/mnt", 0, MS_REMOUNT | MS_BIND, 0) succeeds,
with some IMO odd behavior:
* statfs(2) on /mnt shows /mnt as not being readonly in the s_flags
field
* The sixth column of relevant mountinfo files (but not the tenth!)
shows /mnt as being rw
* All other syscalls (AFAICT, I checked with git grep MNT_READONLY)
behave as if /mnt were readonly
Why does mount behave like this? To me it would make much more sense if
either MS_REMOUNT | MS_BIND failed on a non-bind mountpoint (my personal
preference) or if it succeeded but the mountpoint was still treated as
readonly from the perspective of all userspace interfaces.
Cheers,
Shea Levy
P.S. I am not subscribed to fsdevel or lkml, so please CC me in
responses.
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