From c374196b2b9f4b803fccd59ed82f0712041e21e1 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 11 Oct 2024 11:00:22 +0200 Subject: fs: name_to_handle_at() support for "explicit connectable" file handles nfsd encodes "connectable" file handles for the subtree_check feature, which can be resolved to an open file with a connected path. So far, userspace nfs server could not make use of this functionality. Introduce a new flag AT_HANDLE_CONNECTABLE to name_to_handle_at(2). When used, the encoded file handle is "explicitly connectable". The "explicitly connectable" file handle sets bits in the high 16bit of the handle_type field, so open_by_handle_at(2) will know that it needs to open a file with a connected path. old kernels will now recognize the handle_type with high bits set, so "explicitly connectable" file handles cannot be decoded by open_by_handle_at(2) on old kernels. The flag AT_HANDLE_CONNECTABLE is not allowed together with either AT_HANDLE_FID or AT_EMPTY_PATH. Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20241011090023.655623-3-amir73il@gmail.com Fixes: 570df4e9c23f ("ceph: snapshot nfs re-export") Acked-by: Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner --- include/uapi/linux/fcntl.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 87e2dec79fea..56ff2100e021 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -153,6 +153,7 @@ object identity and may not be usable with open_by_handle_at(2). */ #define AT_HANDLE_MNT_ID_UNIQUE 0x001 /* Return the u64 unique mount ID. */ +#define AT_HANDLE_CONNECTABLE 0x002 /* Request a connectable file handle */ #if defined(__KERNEL__) #define AT_GETATTR_NOSEC 0x80000000 -- cgit v1.2.3