NFS: Fix a hang in the writeback path
Now that the inode scalability patches have been merged, it is no longer
safe to call igrab() under the inode->i_lock.
Now that we no longer call nfs_clear_request() until the nfs_page is
being freed, we know that we are always holding a reference to the
nfs_open_context, which again holds a reference to the path, and so
the inode cannot be freed until the last nfs_page has been removed
from the radix tree and freed.
We can therefore skip the igrab()/iput() altogether.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 85d7525..af0c627 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -389,11 +389,8 @@
spin_lock(&inode->i_lock);
error = radix_tree_insert(&nfsi->nfs_page_tree, req->wb_index, req);
BUG_ON(error);
- if (!nfsi->npages) {
- igrab(inode);
- if (nfs_have_delegation(inode, FMODE_WRITE))
- nfsi->change_attr++;
- }
+ if (!nfsi->npages && nfs_have_delegation(inode, FMODE_WRITE))
+ nfsi->change_attr++;
set_bit(PG_MAPPED, &req->wb_flags);
SetPagePrivate(req->wb_page);
set_page_private(req->wb_page, (unsigned long)req);
@@ -423,11 +420,7 @@
clear_bit(PG_MAPPED, &req->wb_flags);
radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);
nfsi->npages--;
- if (!nfsi->npages) {
- spin_unlock(&inode->i_lock);
- iput(inode);
- } else
- spin_unlock(&inode->i_lock);
+ spin_unlock(&inode->i_lock);
nfs_release_request(req);
}