pnfs: change lo refcounting to atomic_t

This will be required to allow us to grab reference outside of i_lock.
While we are at it, make put_layout_hdr take the same argument as all the
related functions.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 28 insertions, 24 deletions

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index cd9906415a14..32b66468e5db 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -177,34 +177,38 @@ EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver);
  * pNFS client layout cache
  */
 
+/* Need to hold i_lock if caller does not already hold reference */
 static void
-get_layout_hdr_locked(struct pnfs_layout_hdr *lo)
+get_layout_hdr(struct pnfs_layout_hdr *lo)
 {
-        assert_spin_locked(&lo->plh_inode->i_lock);
-        lo->plh_refcount++;
+        atomic_inc(&lo->plh_refcount);
 }
 
 static void
-put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
+destroy_layout_hdr(struct pnfs_layout_hdr *lo)
 {
-        assert_spin_locked(&lo->plh_inode->i_lock);
-        BUG_ON(lo->plh_refcount == 0);
+        dprintk("%s: freeing layout cache %p\n", __func__, lo);
+        BUG_ON(!list_empty(&lo->plh_layouts));
+        NFS_I(lo->plh_inode)->layout = NULL;
+        kfree(lo);
+}
 
-        lo->plh_refcount--;
-        if (!lo->plh_refcount) {
-                dprintk("%s: freeing layout cache %p\n", __func__, lo);
-                BUG_ON(!list_empty(&lo->plh_layouts));
-                NFS_I(lo->plh_inode)->layout = NULL;
-                kfree(lo);
-        }
+static void
+put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
+{
+        if (atomic_dec_and_test(&lo->plh_refcount))
+                destroy_layout_hdr(lo);
 }
 
 void
-put_layout_hdr(struct inode *inode)
+put_layout_hdr(struct pnfs_layout_hdr *lo)
 {
-        spin_lock(&inode->i_lock);
-        put_layout_hdr_locked(NFS_I(inode)->layout);
-        spin_unlock(&inode->i_lock);
+        struct inode *inode = lo->plh_inode;
+
+        if (atomic_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
+                destroy_layout_hdr(lo);
+                spin_unlock(&inode->i_lock);
+        }
 }
 
 static void
@@ -223,7 +227,7 @@ static void free_lseg(struct pnfs_layout_segment *lseg)
 
         NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
         /* Matched by get_layout_hdr in pnfs_insert_layout */
-        put_layout_hdr(ino);
+        put_layout_hdr(NFS_I(ino)->layout);
 }
 
 /* The use of tmp_list is necessary because pnfs_curr_ld->free_lseg
@@ -490,7 +494,7 @@ pnfs_insert_layout(struct pnfs_layout_hdr *lo,
                         __func__, lseg, lseg->pls_range.iomode,
                         lseg->pls_range.offset, lseg->pls_range.length);
         }
-        get_layout_hdr_locked(lo);
+        get_layout_hdr(lo);
 
         dprintk("%s:Return\n", __func__);
 }
@@ -503,7 +507,7 @@ alloc_init_layout_hdr(struct inode *ino)
         lo = kzalloc(sizeof(struct pnfs_layout_hdr), GFP_KERNEL);
         if (!lo)
                 return NULL;
-        lo->plh_refcount = 1;
+        atomic_set(&lo->plh_refcount, 1);
         INIT_LIST_HEAD(&lo->plh_layouts);
         INIT_LIST_HEAD(&lo->plh_segs);
         lo->plh_inode = ino;
@@ -618,7 +622,7 @@ pnfs_update_layout(struct inode *ino,
                 goto out_unlock;
         atomic_inc(&lo->plh_outstanding);
 
-        get_layout_hdr_locked(lo);
+        get_layout_hdr(lo);
         if (list_empty(&lo->plh_segs)) {
                 /* The lo must be on the clp list if there is any
                  * chance of a CB_LAYOUTRECALL(FILE) coming in.
@@ -641,7 +645,7 @@ pnfs_update_layout(struct inode *ino,
                 spin_unlock(&ino->i_lock);
         }
         atomic_dec(&lo->plh_outstanding);
-        put_layout_hdr(ino);
+        put_layout_hdr(lo);
 out:
         dprintk("%s end, state 0x%lx lseg %p\n", __func__,
                 nfsi->layout->plh_flags, lseg);
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 698380da24cc..8aaab56b794f 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -65,7 +65,7 @@ struct pnfs_layoutdriver_type {
 };
 
 struct pnfs_layout_hdr {
-        unsigned long           plh_refcount;
+        atomic_t                plh_refcount;
         struct list_head        plh_layouts;   /* other client layouts */
         struct list_head        plh_segs;      /* layout segments list */
         nfs4_stateid            plh_stateid;
@@ -147,7 +147,7 @@ void unset_pnfs_layoutdriver(struct nfs_server *);
 int pnfs_layout_process(struct nfs4_layoutget *lgp);
 void pnfs_destroy_layout(struct nfs_inode *);
 void pnfs_destroy_all_layouts(struct nfs_client *);
-void put_layout_hdr(struct inode *inode);
+void put_layout_hdr(struct pnfs_layout_hdr *lo);
 int pnfs_choose_layoutget_stateid(nfs4_stateid *dst,
                                   struct pnfs_layout_hdr *lo,
                                   struct nfs4_state *open_state);