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

[Hillf Danton <dhillf@gmail.com>]

On Fri, Mar 2, 2012 at 10:58 AM, Steven Truelove
<steven.truelove@utoronto.ca> 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.
>
> Signed-off-by: Steven Truelove <steven.truelove@utoronto.ca>

Acked-by: Hillf Danton <dhillf@gmail.com>

> ---
>  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);
>        }
> --
> 1.7.3.4
>
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