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Message-ID: <20130514145906.GD16772@redhat.com>
Date: Tue, 14 May 2013 10:59:06 -0400
From: Vivek Goyal <vgoyal@...hat.com>
To: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc: ebiederm@...ssion.com, akpm@...ux-foundation.org, cpw@....com,
kumagai-atsushi@....nes.nec.co.jp, lisa.mitchell@...com,
kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
zhangyanfei@...fujitsu.com, jingbai.ma@...com, linux-mm@...ck.org,
Rik Van Riel <riel@...hat.com>,
Michel Lespinasse <walken@...gle.com>,
Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH v5 4/8] vmalloc: introduce remap_vmalloc_range_partial
On Tue, May 14, 2013 at 10:57:29AM +0900, HATAYAMA Daisuke wrote:
> We want to allocate ELF note segment buffer on the 2nd kernel in
> vmalloc space and remap it to user-space in order to reduce the risk
> that memory allocation fails on system with huge number of CPUs and so
> with huge ELF note segment that exceeds 11-order block size.
>
> Although there's already remap_vmalloc_range for the purpose of
> remapping vmalloc memory to user-space, we need to specify user-space
> range via vma. Mmap on /proc/vmcore needs to remap range across
> multiple objects, so the interface that requires vma to cover full
> range is problematic.
>
> This patch introduces remap_vmalloc_range_partial that receives
> user-space range as a pair of base address and size and can be used
> for mmap on /proc/vmcore case.
>
> remap_vmalloc_range is rewritten using remap_vmalloc_range_partial.
>
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
This also needs ACK of VM folks. CCing some of them.
Thanks
Vivek
> ---
>
> include/linux/vmalloc.h | 4 +++
> mm/vmalloc.c | 63 +++++++++++++++++++++++++++++++++--------------
> 2 files changed, 48 insertions(+), 19 deletions(-)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 7d5773a..dd0a2c8 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -82,6 +82,10 @@ extern void *vmap(struct page **pages, unsigned int count,
> unsigned long flags, pgprot_t prot);
> extern void vunmap(const void *addr);
>
> +extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
> + unsigned long uaddr, void *kaddr,
> + unsigned long size);
> +
> extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
> unsigned long pgoff);
> void vmalloc_sync_all(void);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 3875fa2..d9a9f4f6 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2148,42 +2148,44 @@ finished:
> }
>
> /**
> - * remap_vmalloc_range - map vmalloc pages to userspace
> - * @vma: vma to cover (map full range of vma)
> - * @addr: vmalloc memory
> - * @pgoff: number of pages into addr before first page to map
> + * remap_vmalloc_range_partial - map vmalloc pages to userspace
> + * @vma: vma to cover
> + * @uaddr: target user address to start at
> + * @kaddr: virtual address of vmalloc kernel memory
> + * @size: size of map area
> *
> * Returns: 0 for success, -Exxx on failure
> *
> - * This function checks that addr is a valid vmalloc'ed area, and
> - * that it is big enough to cover the vma. Will return failure if
> - * that criteria isn't met.
> + * This function checks that @kaddr is a valid vmalloc'ed area,
> + * and that it is big enough to cover the range starting at
> + * @uaddr in @vma. Will return failure if that criteria isn't
> + * met.
> *
> * Similar to remap_pfn_range() (see mm/memory.c)
> */
> -int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
> - unsigned long pgoff)
> +int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
> + void *kaddr, unsigned long size)
> {
> struct vm_struct *area;
> - unsigned long uaddr = vma->vm_start;
> - unsigned long usize = vma->vm_end - vma->vm_start;
>
> - if ((PAGE_SIZE-1) & (unsigned long)addr)
> + size = PAGE_ALIGN(size);
> +
> + if (((PAGE_SIZE-1) & (unsigned long)uaddr) ||
> + ((PAGE_SIZE-1) & (unsigned long)kaddr))
> return -EINVAL;
>
> - area = find_vm_area(addr);
> + area = find_vm_area(kaddr);
> if (!area)
> return -EINVAL;
>
> if (!(area->flags & VM_USERMAP))
> return -EINVAL;
>
> - if (usize + (pgoff << PAGE_SHIFT) > area->size - PAGE_SIZE)
> + if (kaddr + size > area->addr + area->size)
> return -EINVAL;
>
> - addr += pgoff << PAGE_SHIFT;
> do {
> - struct page *page = vmalloc_to_page(addr);
> + struct page *page = vmalloc_to_page(kaddr);
> int ret;
>
> ret = vm_insert_page(vma, uaddr, page);
> @@ -2191,14 +2193,37 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
> return ret;
>
> uaddr += PAGE_SIZE;
> - addr += PAGE_SIZE;
> - usize -= PAGE_SIZE;
> - } while (usize > 0);
> + kaddr += PAGE_SIZE;
> + size -= PAGE_SIZE;
> + } while (size > 0);
>
> vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
>
> return 0;
> }
> +EXPORT_SYMBOL(remap_vmalloc_range_partial);
> +
> +/**
> + * remap_vmalloc_range - map vmalloc pages to userspace
> + * @vma: vma to cover (map full range of vma)
> + * @addr: vmalloc memory
> + * @pgoff: number of pages into addr before first page to map
> + *
> + * Returns: 0 for success, -Exxx on failure
> + *
> + * This function checks that addr is a valid vmalloc'ed area, and
> + * that it is big enough to cover the vma. Will return failure if
> + * that criteria isn't met.
> + *
> + * Similar to remap_pfn_range() (see mm/memory.c)
> + */
> +int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
> + unsigned long pgoff)
> +{
> + return remap_vmalloc_range_partial(vma, vma->vm_start,
> + addr + (pgoff << PAGE_SHIFT),
> + vma->vm_end - vma->vm_start);
> +}
> EXPORT_SYMBOL(remap_vmalloc_range);
>
> /*
--
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