On Thu, Oct 03, 2024 at 08:09:32AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Remove the code in dax_unshare_iter that zeroes the destination memory
> because it's not necessary.
>
> If srcmap is unwritten, we don't have to do anything because that
> unwritten extent came from the regular file mapping, and unwritten
> extents cannot be shared. The same applies to holes.
>
> Furthermore, zeroing to unshare a mapping is just plain wrong because
> unsharing means copy on write, and we should be copying data.
>
> This is effectively a revert of commit 13dd4e04625f ("fsdax: unshare:
> zero destination if srcmap is HOLE or UNWRITTEN")
The original commit claims it fixed a bug, so I'm curious how
that happend and got fixed differently now. But manually zeroing
data on an unshare does seem very wrong to me:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
