Re: [PATCH] ntfs: use page allocation for resident attribute inline data

[Christoph Hellwig <hch@infradead.org>]

On Wed, Apr 22, 2026 at 01:55:40PM +0100, Matthew Wilcox wrote:
> On Wed, Apr 22, 2026 at 07:46:27PM +0900, Namjae Jeon wrote:
> > The current kmemdup() based allocation for IOMAP_INLINE can result in
> > inline_data pointer having a non-zero page offset. This causes
> > iomap_inline_data_valid() to fail the check:
> > 
> >     iomap->length <= PAGE_SIZE - offset_in_page(iomap->inline_data)
> > 
> > and triggers the kernel BUG at fs/iomap/buffered-io.c:1061.
> 
> Hang on, hang on, hang on.
> 
> First, maybe this check is too strict.  I'm sure it's true for EROFS,
> but I don't see why it should be true for everybody.  Perhaps we should
> delete this check or relax it?

I think the current check should just go.  ->iomap_inline_data is
treated as a normal linear address everywhere, so any offset in page
check is weird.

> Second, why are you calling kmemdup() to begin with?  This seems
> entirely pointless; the iomap code is going to call memcpy() on it.
> You're supposed to just be pointing into your data structures.

Yes.