Hi,
On Tue, Jan 18, 2022 at 09:21:13PM +0800, Chao Peng wrote:
> It maintains a memfile_notifier list in shmem_inode_info structure and
> implements memfile_pfn_ops callbacks defined by memfile_notifier. It
> then exposes them to memfile_notifier via
> shmem_get_memfile_notifier_info.
>
> We use SGP_NOALLOC in shmem_get_lock_pfn since the pages should be
> allocated by userspace for private memory. If there is no pages
> allocated at the offset then error should be returned so KVM knows that
> the memory is not private memory.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> ---
> include/linux/shmem_fs.h | 4 ++
> mm/memfile_notifier.c | 12 +++++-
> mm/shmem.c | 81 ++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 96 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> index 166158b6e917..461633587eaf 100644
> --- a/include/linux/shmem_fs.h
> +++ b/include/linux/shmem_fs.h
> @@ -9,6 +9,7 @@
> #include <linux/percpu_counter.h>
> #include <linux/xattr.h>
> #include <linux/fs_parser.h>
> +#include <linux/memfile_notifier.h>
>
> /* inode in-kernel data */
>
> @@ -24,6 +25,9 @@ struct shmem_inode_info {
> struct shared_policy policy; /* NUMA memory alloc policy */
> struct simple_xattrs xattrs; /* list of xattrs */
> atomic_t stop_eviction; /* hold when working on inode */
> +#ifdef CONFIG_MEMFILE_NOTIFIER
> + struct memfile_notifier_list memfile_notifiers;
> +#endif
> struct inode vfs_inode;
> };
>
> diff --git a/mm/memfile_notifier.c b/mm/memfile_notifier.c
> index 8171d4601a04..b4699cbf629e 100644
> --- a/mm/memfile_notifier.c
> +++ b/mm/memfile_notifier.c
> @@ -41,11 +41,21 @@ void memfile_notifier_fallocate(struct memfile_notifier_list *list,
> srcu_read_unlock(&srcu, id);
> }
>
> +#ifdef CONFIG_SHMEM
> +extern int shmem_get_memfile_notifier_info(struct inode *inode,
> + struct memfile_notifier_list **list,
> + struct memfile_pfn_ops **ops);
> +#endif
> +
> static int memfile_get_notifier_info(struct inode *inode,
> struct memfile_notifier_list **list,
> struct memfile_pfn_ops **ops)
> {
> - return -EOPNOTSUPP;
> + int ret = -EOPNOTSUPP;
> +#ifdef CONFIG_SHMEM
> + ret = shmem_get_memfile_notifier_info(inode, list, ops);
> +#endif
This looks backwards. Can we have some register method for memory backing
store and call it from shmem.c?
> + return ret;
> }
>
> int memfile_register_notifier(struct inode *inode,
--
Sincerely yours,
Mike.
