Joerg Schilling wrote:
> See: http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/stat.h.html
>
> "The st_ino and st_dev fields taken together uniquely identify the file
> within
> the system."
>
> The identity of an open file cannot change during the lifetime of a process.
> Note that the renamed file may be open and the process may call fstat(2)
> on the open file before and after the rename(2). As rename(2) does not change
> the content of the file, it may only affect the time stamps of the file.
>
> Note that some programs call stat/fstat on files in order to compare file
> identities. What happens if program A calls stat("file1"), then program B
> calls rename("file1", "file2") and after that, program A calls stat("file2").
> A POSIX compliant system will grant that stat("file1") and stat("file2") will
> return the same st_dev/st_ino identity.
>
>
And consider what happens if the originating zfs is exported via NFS,
and the destination isn't. If an NFS client has the subject file open,
we need to ensure the correct behavior after the move.
The Unix file system behavior (Sorry, don't have references to Posix or
RFCs here, just 25 years of experience..) would be that if a file is
moved between file systems, it is removed from the source, yet the file
storage will continue to exist until the last process which has this
file open closes. In effect, this means the file in the old location
(file system) should continue to exist indefinitely, if it is open by a
long running process. I fear if we aren't careful, we will introduce a
boat load of bugs.
Hey, here's an idea: We snapshot the file as it exists at the time of
the mv in the old file system until all referring file handles are
closed, then destroy the single file snap. I know, not easy to
implement, but that is the correct behavior, I believe.
All this said, I would love to have this "feature" introduced. Moving
large file stores between zfs file systems would be so handy! From my
own sloppiness, I've suffered dearly from the the lack of it.
Jon
--
- _____/ _____/ / - Jonathan Loran - -
- / / / IT Manager -
- _____ / _____ / / Space Sciences Laboratory, UC Berkeley
- / / / (510) 643-5146 [EMAIL PROTECTED]
- ______/ ______/ ______/ AST:7731^29u18e3
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