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SubjectRe: Wrong DIF guard tag on ext2 write
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>>>>> "Nick" == Nick Piggin <npiggin@suse.de> writes:

Nick,

>> Filesystems will inevitably have to be integrity-aware for that to
>> work. And it will be their job to keep the data pages stable during
>> DMA.

Nick> Closing the while it is dirty, while it is being written back
Nick> window still leaves a pretty big window. Also, how do you handle
Nick> mmap writes? Write protect and checksum the destination page
Nick> after every store? Or leave some window between when the pagecache
Nick> is dirtied and when it is written back? So I don't know whether
Nick> it's worth putting a lot of effort into this case.

I'm mostly interested in the cases where the filesystem acts as a
conduit for integrity metadata from user space.

I agree the corruption windows inside the kernel are only of moderate
interest. No filesystems have added support for explicitly protecting a
bio because the block layer's function to do so automatically is just a
few function calls away.

--
Martin K. Petersen Oracle Linux Engineering


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