ocfs2: Remove i_generation from inode lock names

OCFS2 puts inode meta data in the "lock value block" provided by the DLM.
Typically, i_generation is encoded in the lock name so that a deleted inode
on and a new one in the same block don't share the same lvb.

Unfortunately, that scheme means that the read in ocfs2_read_locked_inode()
is potentially thrown away as soon as the meta data lock is taken - we
cannot encode the lock name without first knowing i_generation, which
requires a disk read.

This patch encodes i_generation in the inode meta data lvb, and removes the
value from the inode meta data lock name. This way, the read can be covered
by a lock, and at the same time we can distinguish between an up to date and
a stale LVB.

This will help cold-cache stat(2) performance in particular.

Since this patch changes the protocol version, we take the opportunity to do
a minor re-organization of two of the LVB fields.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 36 insertions, 6 deletions

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 6cd84dffbbf4..ecb3cba22814 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -320,6 +320,7 @@ void ocfs2_lock_res_init_once(struct ocfs2_lock_res *res)
 
 void ocfs2_inode_lock_res_init(struct ocfs2_lock_res *res,
                                enum ocfs2_lock_type type,
+                               unsigned int generation,
                                struct inode *inode)
 {
         struct ocfs2_lock_res_ops *ops;
@@ -341,7 +342,7 @@ void ocfs2_inode_lock_res_init(struct ocfs2_lock_res *res,
         };
 
         ocfs2_build_lock_name(type, OCFS2_I(inode)->ip_blkno,
-                              inode->i_generation, res->l_name);
+                              generation, res->l_name);
         ocfs2_lock_res_init_common(OCFS2_SB(inode->i_sb), res, type, ops, inode);
 }
 
@@ -1173,17 +1174,19 @@ static void ocfs2_cluster_unlock(struct ocfs2_super *osb,
 
 int ocfs2_create_new_lock(struct ocfs2_super *osb,
                           struct ocfs2_lock_res *lockres,
-                          int ex)
+                          int ex,
+                          int local)
 {
         int level =  ex ? LKM_EXMODE : LKM_PRMODE;
         unsigned long flags;
+        int lkm_flags = local ? LKM_LOCAL : 0;
 
         spin_lock_irqsave(&lockres->l_lock, flags);
         BUG_ON(lockres->l_flags & OCFS2_LOCK_ATTACHED);
         lockres_or_flags(lockres, OCFS2_LOCK_LOCAL);
         spin_unlock_irqrestore(&lockres->l_lock, flags);
 
-        return ocfs2_lock_create(osb, lockres, level, LKM_LOCAL);
+        return ocfs2_lock_create(osb, lockres, level, lkm_flags);
 }
 
 /* Grants us an EX lock on the data and metadata resources, skipping
@@ -1212,19 +1215,23 @@ int ocfs2_create_new_inode_locks(struct inode *inode)
          * on a resource which has an invalid one -- we'll set it
          * valid when we release the EX. */
 
-        ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_rw_lockres, 1);
+        ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_rw_lockres, 1, 1);
         if (ret) {
                 mlog_errno(ret);
                 goto bail;
         }
 
-        ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_meta_lockres, 1);
+        /*
+         * We don't want to use LKM_LOCAL on a meta data lock as they
+         * don't use a generation in their lock names.
+         */
+        ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_meta_lockres, 1, 0);
         if (ret) {
                 mlog_errno(ret);
                 goto bail;
         }
 
-        ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_data_lockres, 1);
+        ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_data_lockres, 1, 1);
         if (ret) {
                 mlog_errno(ret);
                 goto bail;
@@ -1413,6 +1420,16 @@ static void __ocfs2_stuff_meta_lvb(struct inode *inode)
 
         lvb = (struct ocfs2_meta_lvb *) lockres->l_lksb.lvb;
 
+        /*
+         * Invalidate the LVB of a deleted inode - this way other
+         * nodes are forced to go to disk and discover the new inode
+         * status.
+         */
+        if (oi->ip_flags & OCFS2_INODE_DELETED) {
+                lvb->lvb_version = 0;
+                goto out;
+        }
+
         lvb->lvb_version   = OCFS2_LVB_VERSION;
         lvb->lvb_isize     = cpu_to_be64(i_size_read(inode));
         lvb->lvb_iclusters = cpu_to_be32(oi->ip_clusters);
@@ -1429,6 +1446,7 @@ static void __ocfs2_stuff_meta_lvb(struct inode *inode)
         lvb->lvb_iattr    = cpu_to_be32(oi->ip_attr);
         lvb->lvb_igeneration = cpu_to_be32(inode->i_generation);
 
+out:
         mlog_meta_lvb(0, lockres);
 
         mlog_exit_void();
@@ -1727,6 +1745,18 @@ int ocfs2_meta_lock_full(struct inode *inode,
                 wait_event(osb->recovery_event,
                            ocfs2_node_map_is_empty(osb, &osb->recovery_map));
 
+        /*
+         * We only see this flag if we're being called from
+         * ocfs2_read_locked_inode(). It means we're locking an inode
+         * which hasn't been populated yet, so clear the refresh flag
+         * and let the caller handle it.
+         */
+        if (inode->i_state & I_NEW) {
+                status = 0;
+                ocfs2_complete_lock_res_refresh(lockres, 0);
+                goto bail;
+        }
+
         /* This is fun. The caller may want a bh back, or it may
          * not. ocfs2_meta_lock_update definitely wants one in, but
          * may or may not read one, depending on what's in the