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From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, ericvh@gmail.com,
	lucho@ionkov.net, viro@zeniv.linux.org.uk, jlayton@kernel.org,
	idryomov@gmail.com, mark@fasheh.com, jlbec@evilplan.org,
	joseph.qi@linux.alibaba.com,
	v9fs-developer@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, ceph-devel@vger.kernel.org,
	ocfs2-devel@oss.oracle.com, linux-btrfs@vger.kernel.org,
	clm@fb.com, josef@toxicpanda.com, dsterba@suse.com,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/7] 9P: Cast to loff_t before multiplying
Date: Wed, 7 Oct 2020 19:47:30 +0100	[thread overview]
Message-ID: <20201007184730.GW20115@casper.infradead.org> (raw)
In-Reply-To: <20201007054849.GA16556@infradead.org>

On Wed, Oct 07, 2020 at 06:48:49AM +0100, Christoph Hellwig wrote:
> > -		.range_start = vma->vm_pgoff * PAGE_SIZE,
> > +		.range_start = (loff_t)vma->vm_pgoff * PAGE_SIZE,
> 
> Given the may places where this issue shows up I think we really need
> a vma_offset or similar helper for it.  Much better than chasing missing
> casts everywhere.

Good point.  I think these patches need to go in to fix the bugs in
the various stable releases, but we should definitely have a helper
for the future.  Also, several of these patches are for non-VMA
pgoff_t.

vma_offset() is a bit weird for me -- vmas have all kinds of offsets.
vma_file_offset() would work or vma_fpos().  I tend to prefer the shorter
function name ;-)

A quick grep shows we probably want a vmf_fpos() too:

arch/powerpc/platforms/cell/spufs/file.c:       unsigned long area, offset = vmf->pgoff << PAGE_SHIFT;
arch/x86/entry/vdso/vma.c:      sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
drivers/gpu/drm/gma500/framebuffer.c:   address = vmf->address - (vmf->pgoff << PAGE_SHIFT);
drivers/scsi/cxlflash/ocxl_hw.c:        offset = vmf->pgoff << PAGE_SHIFT;

I'm sure a lot of this will never run on a 32-bit kernel or with a 4GB
file, but it's not good to have bad code around for people to copy from.


  reply	other threads:[~2020-10-07 18:47 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-04 18:04 [PATCH 0/7] Fix a pile of 4GB file problems on 32-bit Matthew Wilcox (Oracle)
2020-10-04 18:04 ` [PATCH 1/7] 9P: Cast to loff_t before multiplying Matthew Wilcox (Oracle)
2020-10-07  5:48   ` Christoph Hellwig
2020-10-07 18:47     ` Matthew Wilcox [this message]
2020-10-26 17:14   ` Dominique Martinet
2020-10-04 18:04 ` [PATCH 2/7] buffer: Promote to unsigned long long before shifting Matthew Wilcox (Oracle)
2020-10-04 18:04 ` [PATCH 3/7] ceph: " Matthew Wilcox (Oracle)
2020-10-06 11:29   ` Jeff Layton
2020-10-06 17:20   ` Jeff Layton
2020-10-04 18:04 ` [PATCH 4/7] ocfs2: " Matthew Wilcox (Oracle)
2020-10-04 18:04 ` [PATCH 5/7] btrfs: " Matthew Wilcox (Oracle)
2020-10-09 14:18   ` Josef Bacik
2020-10-26 17:02   ` David Sterba
2020-10-04 18:04 ` [PATCH 6/7] " Matthew Wilcox (Oracle)
2020-10-09 14:18   ` Josef Bacik
2020-10-26 16:35   ` David Sterba
2020-10-26 16:44     ` Matthew Wilcox
2020-10-26 17:03       ` David Sterba
2020-10-04 18:04 ` [PATCH 7/7] btrfs: Promote to unsigned long long before multiplying Matthew Wilcox (Oracle)
2020-10-26 16:21   ` David Sterba

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