On Fri, 30 Sep 2022, Jeff Layton wrote:
> From: Jeff Layton <jlayton@xxxxxxxxxx>
>
> The NFS server has a lot of special handling for different types of
> change attribute access, depending on what sort of inode we have. In
> most cases, it's doing a getattr anyway and then fetching that value
> after the fact.
>
> Rather that do that, add a new STATX_VERSION flag that is a kernel-only
> symbol (for now). If requested and getattr can implement it, it can fill
> out this field. For IS_I_VERSION inodes, add a generic implementation in
> vfs_getattr_nosec. Take care to mask STATX_VERSION off in requests from
> userland and in the result mask.
>
> Eventually if we decide to make this available to userland, we can just
> designate a field for it in struct statx, and move the STATX_VERSION
> definition to the uapi header.
Above does not mention STATX_ATTR_VERSION_MONOTONIC, but it appears in
that patch - which is confusing.
But the patch is good, so
Reviewed-by: NeilBrown <neilb@xxxxxxx>
Thanks,
NeilBrown
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/stat.c | 17 +++++++++++++++--
> include/linux/stat.h | 9 +++++++++
> 2 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/stat.c b/fs/stat.c
> index a7930d744483..e7f8cd4b24e1 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -17,6 +17,7 @@
> #include <linux/syscalls.h>
> #include <linux/pagemap.h>
> #include <linux/compat.h>
> +#include <linux/iversion.h>
>
> #include <linux/uaccess.h>
> #include <asm/unistd.h>
> @@ -118,6 +119,11 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
> stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
> STATX_ATTR_DAX);
>
> + if ((request_mask & STATX_VERSION) && IS_I_VERSION(inode)) {
> + stat->result_mask |= STATX_VERSION;
> + stat->version = inode_query_iversion(inode);
> + }
> +
> mnt_userns = mnt_user_ns(path->mnt);
> if (inode->i_op->getattr)
> return inode->i_op->getattr(mnt_userns, path, stat,
> @@ -587,9 +593,11 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
>
> memset(&tmp, 0, sizeof(tmp));
>
> - tmp.stx_mask = stat->result_mask;
> + /* STATX_VERSION is kernel-only for now */
> + tmp.stx_mask = stat->result_mask & ~STATX_VERSION;
> tmp.stx_blksize = stat->blksize;
> - tmp.stx_attributes = stat->attributes;
> + /* STATX_ATTR_VERSION_MONOTONIC is kernel-only for now */
> + tmp.stx_attributes = stat->attributes & ~STATX_ATTR_VERSION_MONOTONIC;
> tmp.stx_nlink = stat->nlink;
> tmp.stx_uid = from_kuid_munged(current_user_ns(), stat->uid);
> tmp.stx_gid = from_kgid_munged(current_user_ns(), stat->gid);
> @@ -628,6 +636,11 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags,
> if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
> return -EINVAL;
>
> + /* STATX_VERSION is kernel-only for now. Ignore requests
> + * from userland.
> + */
> + mask &= ~STATX_VERSION;
> +
> error = vfs_statx(dfd, filename, flags, &stat, mask);
> if (error)
> return error;
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index ff277ced50e9..4e9428d86a3a 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -52,6 +52,15 @@ struct kstat {
> u64 mnt_id;
> u32 dio_mem_align;
> u32 dio_offset_align;
> + u64 version;
> };
>
> +/* These definitions are internal to the kernel for now. Mainly used by nfsd. */
> +
> +/* mask values */
> +#define STATX_VERSION 0x40000000U /* Want/got stx_change_attr */
> +
> +/* file attribute values */
> +#define STATX_ATTR_VERSION_MONOTONIC 0x8000000000000000ULL /* version monotonically increases */
> +
> #endif
> --
> 2.37.3
>
>
