Wouter Verhelst <[email protected]> writes:
> On Tue, Apr 10, 2012 at 11:18:05AM -0300, Salatiel Filho wrote:
>> Hi guys , i have a doubt.
>> If i have a device , let's say /dev/sdb2 which is mounted locally read
>> only, and this same device is exported using nbd , and mounted
>> readwrite by the client. If the client writes to the Filesystem , this
>> can lead to data corruption ?
>
> Yes, as in, "reads from /dev/sdb2 on the server will probably only get
> you garbage after a while". This is because there's nothing in nbd
> telling the filesystem layer that things have changed in the block
> device it's working with, and that the data it's cached is no longer
> valid.
Worse it can potentially lead to kernel oopses and crash your system.
> There are filesystems who are written to support such a mode of
> operation (e.g., GFS2), but don't try this with "normal" filesystems
> like ext4.
>
> Also, note that "mount -o ro" will still try to write to the filesystem
> if the journal is dirty. Arguably this is a bug in the kernel.
Thereby also endangering the client that has it mounted read-write.
>> Or the local filesystem will just be unable to see the changes until
>> it is remounted ?
>
> No, it doesn't work that way.
MfG
Goswin
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