Re: [PATCH v5 17/17] vfs: expose delegation support to userland
From: Jan Kara <jack@suse.cz>
Date: 2025-11-11 10:48:10
Also in:
linux-cifs, linux-fsdevel, linux-nfs, linux-unionfs, linux-xfs, lkml, netfs
On Wed 05-11-25 11:54:03, Jeff Layton wrote:
Now that support for recallable directory delegations is available, expose this functionality to userland with new F_SETDELEG and F_GETDELEG commands for fcntl(). Note that this also allows userland to request a FL_DELEG type lease on files too. Userland applications that do will get signalled when there are metadata changes in addition to just data changes (which is a limitation of FL_LEASE leases). These commands accept a new "struct delegation" argument that contains a flags field for future expansion. Signed-off-by: Jeff Layton <jlayton@kernel.org>
For new apis CCing linux-api is a good practice ;) ...
quoted hunk ↗ jump to hunk
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 3741ea1b73d8500061567b6590ccf5fb4c6770f0..8123fe70e03cfb1ba9ce1b5e20d61b62e462a7ea 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h@@ -79,6 +79,16 @@ */ #define RWF_WRITE_LIFE_NOT_SET RWH_WRITE_LIFE_NOT_SET +/* Set/Get delegations */ +#define F_GETDELEG (F_LINUX_SPECIFIC_BASE + 15) +#define F_SETDELEG (F_LINUX_SPECIFIC_BASE + 16) + +/* Argument structure for F_GETDELEG and F_SETDELEG */ +struct delegation { + unsigned int d_flags; /* Must be 0 */ + short d_type; /* F_RDLCK, F_WRLCK, F_UNLCK */ +}; +
I think it would make sense for d_type to be unsigned since it's more or less enum. Also struct delegation is going to have a hole in it at the end which is always a concern with uAPI structures (passing around uninitialized stuff). I think it would be good to put an explicit padding there and enforce it is zeroed out. Honza -- Jan Kara [off-list ref] SUSE Labs, CR