[PATCH] NFS: Introduce the use of inode->i_lock to protect fields in nfsi

Down the road we want to eliminate the use of the global kernel lock entirely
from the NFS client.  To do this, we need to protect the fields in the
nfs_inode structure adequately.  Start by serializing updates to the
"cache_validity" field.

Note this change addresses an SMP hang found by njw@osdl.org, where processes
deadlock because nfs_end_data_update and nfs_revalidate_mapping update the
"cache_validity" field without proper serialization.

Test plan:
 Millions of fsx ops on SMP clients.  Run Nick Wilson's breaknfs program on
 large SMP clients.

Signed-off-by: Chuck Lever <cel@netapp.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index deef9567788a..9a6047ff1b25 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -238,8 +238,11 @@ static inline int nfs_caches_unstable(struct inode *inode)
 
 static inline void NFS_CACHEINV(struct inode *inode)
 {
-        if (!nfs_caches_unstable(inode))
+        if (!nfs_caches_unstable(inode)) {
+                spin_lock(&inode->i_lock);
                 NFS_I(inode)->cache_validity |= NFS_INO_INVALID_ATTR | NFS_INO_INVALID_ACCESS;
+                spin_unlock(&inode->i_lock);
+        }
 }
 
 static inline int nfs_server_capable(struct inode *inode, int cap)