linux-kernel - Re: [PATCH] Correct alignment of huge page requests.

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Date:	Thu, 01 Mar 2012 21:58:31 -0500
From:	Steven Truelove <steven.truelove@...ronto.ca>
To:	Steven Truelove <steven.truelove@...ronto.ca>
CC:	wli@...omorphy.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] Correct alignment of huge page requests.

Sorry, I just realized I forgot to sign off the patch.  Will resend now.


On 01/03/2012 9:41 PM, Steven Truelove wrote:
> When calling shmget() with SHM_HUGETLB, shmget aligns the request size to PAGE_SIZE, but this is not sufficient.  Modified hugetlb_file_setup() to align requests to the huge page size, and to accept an address argument so that all alignment checks can be performed in hugetlb_file_setup(), rather than in its callers.  Changed newseg and mmap_pgoff to match new prototype and eliminated a now redundant alignment check.
> ---
>   fs/hugetlbfs/inode.c    |   12 ++++++++----
>   include/linux/hugetlb.h |    3 ++-
>   ipc/shm.c               |    2 +-
>   mm/mmap.c               |    6 +++---
>   4 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 1e85a7a..a97b7cc 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -928,7 +928,7 @@ static int can_do_hugetlb_shm(void)
>   	return capable(CAP_IPC_LOCK) || in_group_p(sysctl_hugetlb_shm_group);
>   }
>
> -struct file *hugetlb_file_setup(const char *name, size_t size,
> +struct file *hugetlb_file_setup(const char *name, unsigned long addr, size_t size,
>   				vm_flags_t acctflag,
>   				struct user_struct **user, int creat_flags)
>   {
> @@ -938,6 +938,8 @@ struct file *hugetlb_file_setup(const char *name, size_t size,
>   	struct path path;
>   	struct dentry *root;
>   	struct qstr quick_string;
> +	struct hstate *hstate;
> +	int num_pages;
>
>   	*user = NULL;
>   	if (!hugetlbfs_vfsmount)
> @@ -967,10 +969,12 @@ struct file *hugetlb_file_setup(const char *name, size_t size,
>   	if (!inode)
>   		goto out_dentry;
>
> +	hstate = hstate_inode(inode);
> +	size += addr&  ~huge_page_mask(hstate);
> +	num_pages = ALIGN(size, huge_page_size(hstate))>>
> +			huge_page_shift(hstate);
>   	error = -ENOMEM;
> -	if (hugetlb_reserve_pages(inode, 0,
> -			size>>  huge_page_shift(hstate_inode(inode)), NULL,
> -			acctflag))
> +	if (hugetlb_reserve_pages(inode, 0, num_pages, NULL, acctflag))
>   		goto out_inode;
>
>   	d_instantiate(path.dentry, inode);
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index d9d6c86..4b9e59d 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -164,7 +164,8 @@ static inline struct hugetlbfs_sb_info *HUGETLBFS_SB(struct super_block *sb)
>
>   extern const struct file_operations hugetlbfs_file_operations;
>   extern const struct vm_operations_struct hugetlb_vm_ops;
> -struct file *hugetlb_file_setup(const char *name, size_t size, vm_flags_t acct,
> +struct file *hugetlb_file_setup(const char *name, unsigned long addr,
> +				size_t size, vm_flags_t acct,
>   				struct user_struct **user, int creat_flags);
>   int hugetlb_get_quota(struct address_space *mapping, long delta);
>   void hugetlb_put_quota(struct address_space *mapping, long delta);
> diff --git a/ipc/shm.c b/ipc/shm.c
> index b76be5b..406c5b2 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -482,7 +482,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
>   		/* hugetlb_file_setup applies strict accounting */
>   		if (shmflg&  SHM_NORESERVE)
>   			acctflag = VM_NORESERVE;
> -		file = hugetlb_file_setup(name, size, acctflag,
> +		file = hugetlb_file_setup(name, 0, size, acctflag,
>   					&shp->mlock_user, HUGETLB_SHMFS_INODE);
>   	} else {
>   		/*
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 3f758c7..4bf211a 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1099,9 +1099,9 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
>   		 * A dummy user value is used because we are not locking
>   		 * memory so no accounting is necessary
>   		 */
> -		len = ALIGN(len, huge_page_size(&default_hstate));
> -		file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE,
> -						&user, HUGETLB_ANONHUGE_INODE);
> +		file = hugetlb_file_setup(HUGETLB_ANON_FILE, addr, len,
> +						VM_NORESERVE,&user,
> +						HUGETLB_ANONHUGE_INODE);
>   		if (IS_ERR(file))
>   			return PTR_ERR(file);
>   	}
--
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