[RFC PATCH v3 2/2] tmpfs: refine a file handle for NFS-exporting

["J. R. Okajima" <hooanon05g@gmail.com>]

The inode number in tmpfs is always 32bit.
It is unnecessary to put 64bit into NFS handle, and this commit puts
only 32bit.
While it is also possible to replace ilookup5() by idr_find(), I don't
want to confirm and maintain i_state. So let's keep ilookup5().

Cc: Eric Dumazet <edumazet@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andreas Dilger <adilger@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
---
 mm/shmem.c |   34 ++++++++--------------------------
 1 file changed, 8 insertions(+), 26 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 0023d8d..04b399b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1379,6 +1379,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 		if (ino > 0) {
 			inode->i_ino = ino;
 			mutex_unlock(&sbinfo->idr_lock);
+			__insert_inode_hash(inode, inode->i_ino);
 		} else {
 			mutex_unlock(&sbinfo->idr_lock);
 			iput(inode);	/* shmem_free_inode() will be called */
@@ -2288,8 +2289,7 @@ static struct dentry *shmem_get_parent(struct dentry *child)
 static int shmem_match(struct inode *ino, void *vfh)
 {
 	__u32 *fh = vfh;
-	__u64 inum = fh[2];
-	inum = (inum << 32) | fh[1];
+	__u64 inum = fh[1];
 	return ino->i_ino == inum && fh[0] == ino->i_generation;
 }
 
@@ -2300,14 +2300,11 @@ static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
 	struct dentry *dentry = NULL;
 	u64 inum;
 
-	if (fh_len < 3)
+	if (fh_len < 2)
 		return NULL;
 
-	inum = fid->raw[2];
-	inum = (inum << 32) | fid->raw[1];
-
-	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
-			shmem_match, fid->raw);
+	inum = fid->raw[1];
+	inode = ilookup5(sb, inum, shmem_match, fid->raw);
 	if (inode) {
 		dentry = d_find_alias(inode);
 		iput(inode);
@@ -2319,30 +2316,15 @@ static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
 				struct inode *parent)
 {
-	if (*len < 3) {
-		*len = 3;
+	if (*len < 2) {
+		*len = 2;
 		return FILEID_INVALID;
 	}
 
-	if (inode_unhashed(inode)) {
-		/* Unfortunately insert_inode_hash is not idempotent,
-		 * so as we hash inodes here rather than at creation
-		 * time, we need a lock to ensure we only try
-		 * to do it once
-		 */
-		static DEFINE_SPINLOCK(lock);
-		spin_lock(&lock);
-		if (inode_unhashed(inode))
-			__insert_inode_hash(inode,
-					    inode->i_ino + inode->i_generation);
-		spin_unlock(&lock);
-	}
-
 	fh[0] = inode->i_generation;
 	fh[1] = inode->i_ino;
-	fh[2] = ((__u64)inode->i_ino) >> 32;
 
-	*len = 3;
+	*len = 2;
 	return 1;
 }
 
-- 
1.7.10.4