[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, 8 insertions, 11 deletions

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 229a1755842a..deef9567788a 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -112,8 +112,8 @@ struct nfs_inode {
         /*
          * Various flags
          */
-        unsigned int            flags;
-        unsigned long           cache_validity;
+        unsigned long           flags;                  /* atomic bit ops */
+        unsigned long           cache_validity;         /* bit mask */
 
         /*
          * read_cache_jiffies is when we started read-caching this inode,
@@ -175,8 +175,6 @@ struct nfs_inode {
         /* Open contexts for shared mmap writes */
         struct list_head        open_files;
 
-        wait_queue_head_t       nfs_i_wait;
-
 #ifdef CONFIG_NFS_V4
         struct nfs4_cached_acl  *nfs4_acl;
         /* NFSv4 state */
@@ -199,11 +197,11 @@ struct nfs_inode {
 #define NFS_INO_REVAL_PAGECACHE 0x0020          /* must revalidate pagecache */
 
 /*
- * Legal values of flags field
+ * Bit offsets in flags field
  */
-#define NFS_INO_REVALIDATING    0x0001          /* revalidating attrs */
-#define NFS_INO_ADVISE_RDPLUS   0x0002          /* advise readdirplus */
-#define NFS_INO_STALE           0x0004          /* possible stale inode */
+#define NFS_INO_REVALIDATING    (0)             /* revalidating attrs */
+#define NFS_INO_ADVISE_RDPLUS   (1)             /* advise readdirplus */
+#define NFS_INO_STALE           (2)             /* possible stale inode */
 
 static inline struct nfs_inode *NFS_I(struct inode *inode)
 {
@@ -229,8 +227,7 @@ static inline struct nfs_inode *NFS_I(struct inode *inode)
 #define NFS_ATTRTIMEO_UPDATE(inode)     (NFS_I(inode)->attrtimeo_timestamp)
 
 #define NFS_FLAGS(inode)                (NFS_I(inode)->flags)
-#define NFS_REVALIDATING(inode)         (NFS_FLAGS(inode) & NFS_INO_REVALIDATING)
-#define NFS_STALE(inode)                (NFS_FLAGS(inode) & NFS_INO_STALE)
+#define NFS_STALE(inode)                (test_bit(NFS_INO_STALE, &NFS_FLAGS(inode)))
 
 #define NFS_FILEID(inode)               (NFS_I(inode)->fileid)
 
@@ -252,7 +249,7 @@ static inline int nfs_server_capable(struct inode *inode, int cap)
 
 static inline int NFS_USE_READDIRPLUS(struct inode *inode)
 {
-        return NFS_FLAGS(inode) & NFS_INO_ADVISE_RDPLUS;
+        return test_bit(NFS_INO_ADVISE_RDPLUS, &NFS_FLAGS(inode));
 }
 
 /**