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Mon, 09 Oct 2023 11:22:07 -0700 (PDT) Date: Mon, 9 Oct 2023 19:22:07 +0100 From: Lorenzo Stoakes To: Vlastimil Babka Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Alexander Viro , Christian Brauner , "=Liam R . Howlett" , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 4/4] mm: abstract VMA extension and merge into vma_merge_extend() helper Message-ID: References: <1ed3d1ba0069104e1685298aa2baf980c38a85ff.1696795837.git.lstoakes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 7E3D9C002D X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: xumuzoh68h119bciqq8pe169xjg9wf4i X-HE-Tag: 1696875730-375306 X-HE-Meta: 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 YsOMk85f fKwXGh9bfiV6dnpxv1elD3uSKgbN2NIUWVC0s/ofFKfeZZmZg/xG5UZhrSmdXWNTXieU+1l7I+yPS++tRZDjSVPgHtmSbWGMn6KMKHSFFgWmotcVReWog3CUjQ+9DLaFdkB17DF4CfM9nZwOo5Pi8VEE/ufwx9OK1BVm9aKnhilrlCUyEJvWz4c9I+cQsLSnnWXQevSUOuL9eooT3qYxgZTCx+t6BTu7qf/uwLfbn9kcU2IM6m9y2b72mc9c1ifxNwf6isnDjT03SPpmbXKIifuwjduupRaYQhEjRsHyp57jIDh92ACGQLTPgvvfVBsJWLUDaSV+8onJldOQSDyIylGfDXxNOWd8TulimxpQKoe29ecDMsg3YJUf/Pi8jjdlW4B6r0gEChgJyCAdAKl3zEGJG13TDJTsf5MvzDNuvDAEJHaTGrMx1o1Jzz0UCGJGq1eo0vg5ZT4cv7v7i4wHA6U7n4Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 09, 2023 at 06:30:02PM +0200, Vlastimil Babka wrote: > On 10/8/23 22:23, Lorenzo Stoakes wrote: > > mremap uses vma_merge() in the case where a VMA needs to be extended. This > > can be significantly simplified and abstracted. > > > > This makes it far easier to understand what the actual function is doing, > > avoids future mistakes in use of the confusing vma_merge() function and > > importantly allows us to make future changes to how vma_merge() is > > implemented by knowing explicitly which merge cases each invocation uses. > > > > Note that in the mremap() extend case, we perform this merge only when > > old_len == vma->vm_end - addr. The extension_start, i.e. the start of the > > extended portion of the VMA is equal to addr + old_len, i.e. vma->vm_end. > > > > With this refactoring, vma_merge() is no longer required anywhere except > > mm/mmap.c, so mark it static. > > > > Signed-off-by: Lorenzo Stoakes > > Reviewed-by: Vlastimil Babka Thanks! > > Nit: > > @@ -2546,6 +2546,24 @@ static struct vm_area_struct *vma_merge_new_vma(struct vma_iterator *vmi, > > vma->vm_userfaultfd_ctx, anon_vma_name(vma)); > > } > > > > +/* > > + * Expand vma by delta bytes, potentially merging with an immediately adjacent > > + * VMA with identical properties. > > + */ > > +struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi, > > + struct vm_area_struct *vma, > > + unsigned long delta) > > +{ > > + pgoff_t pgoff = vma->vm_pgoff + > > + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT); > > could use vma_pages() here Will update in v2. > > > + > > + /* vma is specified as prev, so case 1 or 2 will apply. */ > > + return vma_merge(vmi, vma->vm_mm, vma, vma->vm_end, vma->vm_end + delta, > > + vma->vm_flags, vma->anon_vma, vma->vm_file, pgoff, > > + vma_policy(vma), vma->vm_userfaultfd_ctx, > > + anon_vma_name(vma)); > > +} > > + > > /* > > * do_vmi_align_munmap() - munmap the aligned region from @start to @end. > > * @vmi: The vma iterator