From a1175d6b1bdaf4f74eda47ab18eb44194f9cb796 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Sun, 4 Dec 2016 09:29:46 -0500 Subject: vfs: plumb i_version handling into struct kstat The NFS server has a lot of special handling for different types of change attribute access, depending on the underlying filesystem. 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_CHANGE_COOKIE 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_CHANGE_COOKIE off in requests from userland and in the result mask. Since not all filesystems can give the same guarantees of monotonicity, claim a STATX_ATTR_CHANGE_MONOTONIC flag that filesystems can set to indicate that they offer an i_version value that can never go backward. Eventually if we decide to make the i_version available to userland, we can just designate a field for it in struct statx, and move the STATX_CHANGE_COOKIE definition to the uapi header. Reviewed-by: NeilBrown Reviewed-by: Jan Kara Signed-off-by: Jeff Layton --- include/linux/stat.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/stat.h') diff --git a/include/linux/stat.h b/include/linux/stat.h index ff277ced50e9..52150570d37a 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 change_cookie; }; +/* These definitions are internal to the kernel for now. Mainly used by nfsd. */ + +/* mask values */ +#define STATX_CHANGE_COOKIE 0x40000000U /* Want/got stx_change_attr */ + +/* file attribute values */ +#define STATX_ATTR_CHANGE_MONOTONIC 0x8000000000000000ULL /* version monotonically increases */ + #endif -- cgit v1.2.3