On 08/28/10 12:05 PM, Ian Collins wrote:
On 08/28/10 11:13 AM, Robert Milkowski wrote:
Hi,
When I set readonly=on on a dataset then no new files are allowed to
be created.
However writes to already opened files are allowed.
This is rather counter intuitive - if I set a filesystem as read-only
I would expect it not to allow any modifications to it.
I think it shouldn't behave this way and it should be considered as a
bug.
What do you think?
No.
Think of this from the perspective of an application. How would write
failure be reported? open(2) returns EACCES if the file can not be
written but there isn't a corresponding return from write(2). Any
open file descriptors would have to be updated to reflect the change
of access and the application would end up with an unexpected error
return (EBADF?).
If the application has been given permission to open a file for
writing and this permission is unexpectedly revoked, strange things my
happen. The file being written would be in an inconsistent state.
I think it is better to let write operation complete and leave the
file in a consistent state.
Following on from my own reply, I think that if there is a bug, it it
letting the change occur when there are open files. Setting the
filesystem read-only is effectively remounting it (the equivalent on
other filesystems) so it should behave in the same way as an unmount in
the presence of open files.
--
Ian.
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