From: Matthew Wilcox <willy@infradead.org>
To: "Vishal Moola (Oracle)" <vishal.moola@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
David Hildenbrand <david@redhat.com>,
Jordan Rome <linux@jordanrome.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 1/3] mm/memory.c: convert __copy_remote_vm_str() to folios
Date: Thu, 26 Jun 2025 04:02:25 +0100 [thread overview]
Message-ID: <aFy4QaXmKicMLGLR@casper.infradead.org> (raw)
In-Reply-To: <aFw5NuCbgJOBmG97@casper.infradead.org>
On Wed, Jun 25, 2025 at 07:00:22PM +0100, Matthew Wilcox wrote:
> > + folio_offset = offset_in_folio(folio, addr);
>
> Umm. Not sure this is safe. A folio might be mapped misaligned, so
> 'addr' might not give you the right offset within the folio. I think
> you might need to use addr - (vma->vm_pgoff << PAGE_SHIFT). But I'd
> defer to others here ... particularly when it comes to anonymous folios.
Sorry, this calculation is obviously wrong. It should be something like
the calculation in linear_page_index(), only without throwing away the
bottom PAGE_SHIFT bits. But that's for file VMAs only, and I'm not sure
what should be done for anon vmas. Possibly there is no way?
next prev parent reply other threads:[~2025-06-26 3:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-25 17:48 [RFC PATCH 0/3] Some remote_vm folio conversions Vishal Moola (Oracle)
2025-06-25 17:48 ` [RFC PATCH 1/3] mm/memory.c: convert __copy_remote_vm_str() to folios Vishal Moola (Oracle)
2025-06-25 18:00 ` Matthew Wilcox
2025-06-25 18:24 ` David Hildenbrand
2025-06-25 19:23 ` Vishal Moola (Oracle)
2025-06-26 3:02 ` Matthew Wilcox [this message]
2025-06-26 8:14 ` David Hildenbrand
2025-06-25 17:48 ` [RFC PATCH 2/3] mm/memory.c: convert __access_remote_vm() " Vishal Moola (Oracle)
2025-06-25 17:48 ` [RFC PATCH 3/3] mm: Remove unmap_and_put_page() Vishal Moola (Oracle)
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