linux-kernel - Re: [PATCH v3 08/13] mm: add ability to take further action in vm_area

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Message-ID: <20250916180854.GV1086830@nvidia.com>
Date: Tue, 16 Sep 2025 15:08:54 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Matthew Wilcox <willy@...radead.org>, Guo Ren <guoren@...nel.org>,
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Subject: Re: [PATCH v3 08/13] mm: add ability to take further action in
 vm_area_desc

On Tue, Sep 16, 2025 at 06:57:56PM +0100, Lorenzo Stoakes wrote:
> > > +	/*
> > > +	 * If an error occurs, unmap the VMA altogether and return an error. We
> > > +	 * only clear the newly allocated VMA, since this function is only
> > > +	 * invoked if we do NOT merge, so we only clean up the VMA we created.
> > > +	 */
> > > +	if (err) {
> > > +		const size_t len = vma_pages(vma) << PAGE_SHIFT;
> > > +
> > > +		do_munmap(current->mm, vma->vm_start, len, NULL);
> > > +
> > > +		if (action->error_hook) {
> > > +			/* We may want to filter the error. */
> > > +			err = action->error_hook(err);
> > > +
> > > +			/* The caller should not clear the error. */
> > > +			VM_WARN_ON_ONCE(!err);
> > > +		}
> > > +		return err;
> > > +	}
> > Also seems like this cleanup wants to be in a function that is not
> > protected by #ifdef nommu since the code is identical on both branches.
> 
> Not sure which cleanup you mean, this is new code :)

I mean the code I quoted right abouve that cleans up the VMA on
error.. It is always the same finishing sequence, there is no nommu
dependency in it.

Just put it all in some "finish mmap complete" function and call it in
both mmu and nommu versions.

Jason