CIFS: Migrate to shared superblock model

Add cifs_match_super to use in sget to share superblock between mounts
that have the same //server/sharename, credentials and mount options.
It helps us to improve performance on work with future SMB2.1 leases.

Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 46fdd55cf42..360fe2ec2a1 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -630,6 +630,7 @@ cifs_do_mount(struct file_system_type *fs_type,
 	struct super_block *sb;
 	struct cifs_sb_info *cifs_sb;
 	struct smb_vol *volume_info;
+	struct cifs_mnt_data mnt_data;
 	struct dentry *root;
 
 	cFYI(1, "Devname: %s flags: %d ", dev_name, flags);
@@ -646,12 +647,21 @@ cifs_do_mount(struct file_system_type *fs_type,
 
 	cifs_setup_cifs_sb(volume_info, cifs_sb);
 
-	sb = sget(fs_type, NULL, set_anon_super, NULL);
+	mnt_data.vol = volume_info;
+	mnt_data.cifs_sb = cifs_sb;
+	mnt_data.flags = flags;
+
+	sb = sget(fs_type, cifs_match_super, set_anon_super, &mnt_data);
 	if (IS_ERR(sb)) {
 		root = ERR_CAST(sb);
 		goto out_cifs_sb;
 	}
 
+	if (sb->s_fs_info) {
+		cFYI(1, "Use existing superblock");
+		goto out_shared;
+	}
+
 	/*
 	 * Copy mount params for use in submounts. Better to do
 	 * the copy here and deal with the error before cleanup gets
@@ -680,9 +690,16 @@ cifs_do_mount(struct file_system_type *fs_type,
 	root = cifs_get_root(volume_info, sb);
 	if (root == NULL)
 		goto out_super;
+
 	cFYI(1, "dentry root is: %p", root);
 	goto out;
 
+out_shared:
+	root = cifs_get_root(volume_info, sb);
+	if (root)
+		cFYI(1, "dentry root is: %p", root);
+	goto out;
+
 out_super:
 	kfree(cifs_sb->mountdata);
 	deactivate_locked_super(sb);