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On Thu, 05 Apr 2012 21:10:07 -0400 Phillip Susi [off-list ref] wrote:

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On 04/05/2012 07:24 PM, NeilBrown wrote:

quoted

Something wrote to the md device despite it being marked 'read-only'.
Some filesystems do that to replay their journal.  totally inexcusable
behaviour, but what can we do....

I agree... read-only means read ONLY.

quoted

I'm surprised that would happen during installation though.
But certainly the array is marked read-only, and certainly something is
writing to it, and that is the real bug.

If the block device is flagged as read only, then shouldn't it reject write attempts even if the fs or userspace issue them?

It will reject writes from user-space, and it will reject attempts to mount a
filesystem unless the filesystem is mounted "read-only".
But if a read-only mounted filesystem decides to write anyway (XFS, ext3,
ext4...) then the block layer doesn't stop it.

NeilBrown

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