[PATCH] NFS: use atomic bitops to manipulate flags in nfsi->flags

Introduce atomic bitops to manipulate the bits in the nfs_inode structure's
"flags" field.

Using bitops means we can use a generic wait_on_bit call instead of an ad hoc
locking scheme in fs/nfs/inode.c, so we can remove the "nfs_i_wait" field from
nfs_inode at the same time.

The other new flags field will continue to use bitmask and logic AND and OR.
This permits several flags to be set at the same time efficiently.  The
following patch adds a spin lock to protect these flags, and this spin lock
will later cover other fields in the nfs_inode structure, amortizing the cost
of using this type of serialization.

Test plan:
 Millions of fsx ops on 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, 43 insertions, 26 deletions

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 622184553516..ee27578277f3 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -739,7 +739,7 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
                         inode->i_fop = &nfs_dir_operations;
                         if (nfs_server_capable(inode, NFS_CAP_READDIRPLUS)
                             && fattr->size <= NFS_LIMIT_READDIRPLUS)
-                                NFS_FLAGS(inode) |= NFS_INO_ADVISE_RDPLUS;
+                                set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_FLAGS(inode));
                 } else if (S_ISLNK(inode->i_mode))
                         inode->i_op = &nfs_symlink_inode_operations;
                 else
@@ -849,26 +849,43 @@ void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr)
         }
 }
 
+static int nfs_wait_schedule(void *word)
+{
+        if (signal_pending(current))
+                return -ERESTARTSYS;
+        schedule();
+        return 0;
+}
+
 /*
  * Wait for the inode to get unlocked.
- * (Used for NFS_INO_LOCKED and NFS_INO_REVALIDATING).
  */
-static int
-nfs_wait_on_inode(struct inode *inode, int flag)
+static int nfs_wait_on_inode(struct inode *inode)
 {
         struct rpc_clnt *clnt = NFS_CLIENT(inode);
         struct nfs_inode *nfsi = NFS_I(inode);
-
+        sigset_t oldmask;
         int error;
-        if (!(NFS_FLAGS(inode) & flag))
-                return 0;
+
         atomic_inc(&inode->i_count);
-        error = nfs_wait_event(clnt, nfsi->nfs_i_wait,
-                                !(NFS_FLAGS(inode) & flag));
+        rpc_clnt_sigmask(clnt, &oldmask);
+        error = wait_on_bit_lock(&nfsi->flags, NFS_INO_REVALIDATING,
+                                        nfs_wait_schedule, TASK_INTERRUPTIBLE);
+        rpc_clnt_sigunmask(clnt, &oldmask);
         iput(inode);
+
         return error;
 }
 
+static void nfs_wake_up_inode(struct inode *inode)
+{
+        struct nfs_inode *nfsi = NFS_I(inode);
+
+        clear_bit(NFS_INO_REVALIDATING, &nfsi->flags);
+        smp_mb__after_clear_bit();
+        wake_up_bit(&nfsi->flags, NFS_INO_REVALIDATING);
+}
+
 int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 {
         struct inode *inode = dentry->d_inode;
@@ -1029,18 +1046,19 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
         if (NFS_STALE(inode))
                 goto out_nowait;
 
-        while (NFS_REVALIDATING(inode)) {
-                status = nfs_wait_on_inode(inode, NFS_INO_REVALIDATING);
-                if (status < 0)
-                        goto out_nowait;
-                if (NFS_ATTRTIMEO(inode) == 0)
-                        continue;
-                if (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ATIME))
-                        continue;
-                status = NFS_STALE(inode) ? -ESTALE : 0;
-                goto out_nowait;
+        status = nfs_wait_on_inode(inode);
+        if (status < 0)
+                goto out;
+        if (NFS_STALE(inode)) {
+                status = -ESTALE;
+                /* Do we trust the cached ESTALE? */
+                if (NFS_ATTRTIMEO(inode) != 0) {
+                        if (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ATIME)) {
+                                /* no */
+                        } else
+                                goto out;
+                }
         }
-        NFS_FLAGS(inode) |= NFS_INO_REVALIDATING;
 
         /* Protect against RPC races by saving the change attribute */
         verifier = nfs_save_change_attribute(inode);
@@ -1052,7 +1070,7 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
                 if (status == -ESTALE) {
                         nfs_zap_caches(inode);
                         if (!S_ISDIR(inode->i_mode))
-                                NFS_FLAGS(inode) |= NFS_INO_STALE;
+                                set_bit(NFS_INO_STALE, &NFS_FLAGS(inode));
                 }
                 goto out;
         }
@@ -1083,9 +1101,9 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
                 inode->i_sb->s_id,
                 (long long)NFS_FILEID(inode));
 
-out:
-        NFS_FLAGS(inode) &= ~NFS_INO_REVALIDATING;
-        wake_up(&nfsi->nfs_i_wait);
+ out:
+        nfs_wake_up_inode(inode);
+
  out_nowait:
         unlock_kernel();
         return status;
@@ -1404,7 +1422,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr, unsign
          */
         nfs_invalidate_inode(inode);
  out_err:
-        NFS_FLAGS(inode) |= NFS_INO_STALE;
+        set_bit(NFS_INO_STALE, &NFS_FLAGS(inode));
         return -ESTALE;
 }
 
@@ -1996,7 +2014,6 @@ static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
                 nfsi->ndirty = 0;
                 nfsi->ncommit = 0;
                 nfsi->npages = 0;
-                init_waitqueue_head(&nfsi->nfs_i_wait);
                 nfs4_init_once(nfsi);
         }
 }