[PATCH 03/10] pnfs-submit: remove list_empty check from put_layout

[Fred Isaman <iisaman@netapp.com>]

The check on list empty before destroying a layout has always bothered me.
Get rid of it by having lsegs take a reference on their backpointer.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
---
 fs/nfs/pnfs.c |   36 +++++++++++++++++++++++++-----------
 1 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 924e6fd..21192b6 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -348,19 +348,27 @@ put_layout(struct pnfs_layout_type *lo)
 	BUG_ON_UNLOCKED_LO(lo);
 	BUG_ON(lo->refcount <= 0);
 
-	if (--lo->refcount == 0 && list_empty(&lo->segs)) {
+	lo->refcount--;
+
+	if (lo->refcount > 1)
+		return;
+
+	/* Make sure is removed from inode list */
+	clp = NFS_SERVER(&nfsi->vfs_inode)->nfs_client;
+	spin_lock(&clp->cl_lock);
+	if (!list_empty(&lo->lo_layouts)) {
+		list_del_init(&lo->lo_layouts);
+		lo->refcount--;
+	}
+	spin_unlock(&clp->cl_lock);
+
+	if (lo->refcount == 0) {
 		struct layoutdriver_io_operations *io_ops =
 			PNFS_LD_IO_OPS(lo);
 
 		dprintk("%s: freeing layout %p\n", __func__, lo->ld_data);
 		io_ops->free_layout(lo->ld_data);
 		lo->ld_data = NULL;
-
-		/* Unlist the layout. */
-		clp = NFS_SERVER(&nfsi->vfs_inode)->nfs_client;
-		spin_lock(&clp->cl_lock);
-		list_del_init(&lo->lo_layouts);
-		spin_unlock(&clp->cl_lock);
 	}
 }
 
@@ -404,6 +412,7 @@ init_lseg(struct pnfs_layout_type *lo, struct pnfs_layout_segment *lseg)
 	kref_init(&lseg->kref);
 	lseg->valid = true;
 	lseg->layout = lo;
+	get_layout(lo);
 }
 
 static void
@@ -413,6 +422,7 @@ destroy_lseg(struct kref *kref)
 		container_of(kref, struct pnfs_layout_segment, kref);
 
 	dprintk("--> %s\n", __func__);
+	put_layout(lseg->layout);
 	PNFS_LD_IO_OPS(lseg->layout)->free_lseg(lseg);
 }
 
@@ -897,9 +907,10 @@ alloc_init_layout(struct inode *ino)
 	void *ld_data;
 	struct pnfs_layout_type *lo;
 	struct layoutdriver_io_operations *io_ops;
+	struct nfs_inode *nfsi = NFS_I(ino);
 
 	io_ops = NFS_SERVER(ino)->pnfs_curr_ld->ld_io_ops;
-	lo = &NFS_I(ino)->layout;
+	lo  = &nfsi->layout;
 	ld_data = io_ops->alloc_layout(ino);
 	if (!ld_data) {
 		printk(KERN_ERR
@@ -908,11 +919,13 @@ alloc_init_layout(struct inode *ino)
 		return NULL;
 	}
 
+	spin_lock(&nfsi->lo_lock);
 	BUG_ON(lo->ld_data != NULL);
 	lo->ld_data = ld_data;
 	memset(&lo->stateid, 0, NFS4_STATEID_SIZE);
 	lo->refcount = 1;
 	lo->roc_iomode = 0;
+	spin_unlock(&nfsi->lo_lock);
 	return lo;
 }
 
@@ -970,8 +983,10 @@ get_lock_alloc_layout(struct inode *ino)
 			spin_lock(&nfsi->lo_lock);
 
 			spin_lock(&clp->cl_lock);
-			if (list_empty(&lo->lo_layouts))
+			if (list_empty(&lo->lo_layouts)) {
 				list_add_tail(&lo->lo_layouts, &clp->cl_layouts);
+				get_layout(lo);
+			}
 			spin_unlock(&clp->cl_lock);
 		} else
 			lo = ERR_PTR(-ENOMEM);
@@ -1259,14 +1274,13 @@ pnfs_layout_process(struct nfs4_pnfs_layoutget *lgp)
 		goto out;
 	}
 
+	spin_lock(&nfsi->lo_lock);
 	init_lseg(lo, lseg);
 	lseg->range = res->lseg;
 	if (lgp->lsegpp) {
 		get_lseg(lseg);
 		*lgp->lsegpp = lseg;
 	}
-
-	spin_lock(&nfsi->lo_lock);
 	pnfs_insert_layout(lo, lseg);
 
 	if (res->return_on_close) {
-- 
1.6.6.1