Re: [PATCH v5 4/9] xfs: convert delayed extents to unwritten when zeroing post eof blocks

Christoph Hellwig
2024-04-27T06:59:04Z

On Fri, Apr 26, 2024 at 03:18:17PM +0800, Zhang Yi wrote:
> I've had the same idea before, I asked Dave and he explained that Linux
> could leak data beyond EOF page for some cases, e.g. mmap() can write to
> the EOF page beyond EOF without failing, and the data in that EOF page
> could be non-zeroed by mmap(), so the zeroing is still needed now.
>
> OTOH, if we free the delalloc and unwritten blocks beyond EOF blocks, he
> said it could lead to some performance problems and make thinks
> complicated to deal with the trimming of EOF block. Please see [1]
> for details and maybe Dave could explain more.

Oh well. Given that we're full in on the speculative allocations
we might as well deal with it.