afs: Provide mount-time configurable byte-range file locking emulation
Provide byte-range file locking emulation that can be configured at mount
time to one of four modes:
(1) flock=local. Locking is done locally only and no reference is made to
the server.
(2) flock=openafs. Byte-range locking is done locally only; whole-file
locking is done with reference to the server. Whole-file locks cannot
be upgraded unless the client holds an exclusive lock.
(3) flock=strict. Byte-range and whole-file locking both require a
sufficient whole-file lock on the server.
(4) flock=write. As strict, but the client always gets an exclusive
whole-file lock on the server.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 20fd44d..91204e1 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -36,11 +36,24 @@
struct pagevec;
struct afs_call;
+/*
+ * Partial file-locking emulation mode. (The problem being that AFS3 only
+ * allows whole-file locks and no upgrading/downgrading).
+ */
+enum afs_flock_mode {
+ afs_flock_mode_unset,
+ afs_flock_mode_local, /* Local locking only */
+ afs_flock_mode_openafs, /* Don't get server lock for a partial lock */
+ afs_flock_mode_strict, /* Always get a server lock for a partial lock */
+ afs_flock_mode_write, /* Get an exclusive server lock for a partial lock */
+};
+
struct afs_fs_context {
bool force; /* T to force cell type */
bool autocell; /* T if set auto mount operation */
bool dyn_root; /* T if dynamic root */
bool no_cell; /* T if the source is "none" (for dynroot) */
+ enum afs_flock_mode flock_mode; /* Partial file-locking emulation mode */
afs_voltype_t type; /* type of volume requested */
unsigned int volnamesz; /* size of volume name */
const char *volname; /* name of volume to mount */
@@ -221,6 +234,7 @@ struct afs_super_info {
struct net *net_ns; /* Network namespace */
struct afs_cell *cell; /* The cell in which the volume resides */
struct afs_volume *volume; /* volume record */
+ enum afs_flock_mode flock_mode:8; /* File locking emulation mode */
bool dyn_root; /* True if dynamic root */
};
