pnfs: change layout state seqlock to a spinlock
This prepares for future changes, where the layout state needs
to change atomically with several other variables. In particular,
it will need to know if lo->segs is empty, as we test that instead
of manipulating the NFS_LAYOUT_STATEID_SET bit. Moreover, the
layoutstateid is not really a read-mostly structure, as it is
written almost as often as it is read.
The behavior of pnfs_get_layout_stateid is also slightly changed, so that
it no longer changes the stateid. Its name is changed to +pnfs_choose_layoutget_stateid.
Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index c2f1086..1093720 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -44,7 +44,6 @@
enum {
NFS_LAYOUT_RO_FAILED = 0, /* get ro layout failed stop trying */
NFS_LAYOUT_RW_FAILED, /* get rw layout failed stop trying */
- NFS_LAYOUT_STATEID_SET, /* have a valid layout stateid */
};
/* Per-layout driver specific registration structure */
@@ -63,7 +62,6 @@
unsigned long plh_refcount;
struct list_head plh_layouts; /* other client layouts */
struct list_head plh_segs; /* layout segments list */
- seqlock_t plh_seqlock; /* Protects the stateid */
nfs4_stateid plh_stateid;
unsigned long plh_flags;
struct inode *plh_inode;
@@ -143,8 +141,9 @@
void pnfs_destroy_layout(struct nfs_inode *);
void pnfs_destroy_all_layouts(struct nfs_client *);
void put_layout_hdr(struct inode *inode);
-void pnfs_get_layout_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo,
- struct nfs4_state *open_state);
+int pnfs_choose_layoutget_stateid(nfs4_stateid *dst,
+ struct pnfs_layout_hdr *lo,
+ struct nfs4_state *open_state);
static inline int lo_fail_bit(u32 iomode)