[v2 4/4] CIFS: Migrate to shared superblock model

[Pavel Shilovsky <piastry-7qunaywFIewox3rIn2DAYQ@public.gmane.org>]

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.

Signed-off-by: Pavel Shilovsky <piastry-7qunaywFIewox3rIn2DAYQ@public.gmane.org>
---
 fs/cifs/cifsfs.c   |   18 ++++++++++-
 fs/cifs/cifsglob.h |    5 +++
 fs/cifs/connect.c  |   90 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 112 insertions(+), 1 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 446b5c2..ba0b7ae 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -644,6 +644,7 @@ 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;
 	char *copied_data = NULL;
 
@@ -661,13 +662,21 @@ 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;
+
+	sb = sget(fs_type, cifs_match_super, set_anon_super, &mnt_data);
 	if (IS_ERR(sb)) {
 		kfree(cifs_sb);
 		root = ERR_CAST(sb);
 		goto out;
 	}
 
+	if (sb->s_fs_info) {
+		cFYI(1, "Use existing superblock");
+		goto out_shared;
+	}
+
 	sb->s_flags = flags;
 
 	/*
@@ -700,6 +709,13 @@ out:
 	cifs_cleanup_volume_info(&volume_info);
 	return root;
 
+out_shared:
+	root = cifs_get_root(volume_info, sb);
+	if (root)
+		cFYI(1, "dentry root is: %p", root);
+	cifs_cleanup_volume_info(&volume_info);
+	return root;
+
 err_out:
 	kfree(cifs_sb);
 	deactivate_locked_super(sb);
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 7ad7d69..55901b0 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -211,6 +211,11 @@ struct smb_vol {
 	struct nls_table *local_nls;
 };
 
+struct cifs_mnt_data {
+	struct cifs_sb_info *cifs_sb;
+	struct smb_vol *vol;
+};
+
 struct TCP_Server_Info {
 	struct list_head tcp_ses_list;
 	struct list_head smb_ses_list;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 1cacfaa..1d39dcf 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2135,6 +2135,96 @@ cifs_put_tlink(struct tcon_link *tlink)
 	return;
 }
 
+static inline struct tcon_link *
+cifs_sb_master_tlink(struct cifs_sb_info *cifs_sb);
+
+static const u32 ACTUAL_MOUNT_FLAGS = CIFS_MOUNT_NO_PERM | CIFS_MOUNT_SET_UID |
+	CIFS_MOUNT_SERVER_INUM | CIFS_MOUNT_DIRECT_IO | CIFS_MOUNT_NO_XATTR |
+	CIFS_MOUNT_MAP_SPECIAL_CHR | CIFS_MOUNT_UNX_EMUL | CIFS_MOUNT_NO_BRL |
+	CIFS_MOUNT_CIFS_ACL | CIFS_MOUNT_OVERR_UID | CIFS_MOUNT_OVERR_GID |
+	CIFS_MOUNT_DYNPERM | CIFS_MOUNT_NOPOSIXBRL | CIFS_MOUNT_NOSSYNC |
+	CIFS_MOUNT_FSCACHE | CIFS_MOUNT_MF_SYMLINKS | CIFS_MOUNT_MULTIUSER |
+	CIFS_MOUNT_STRICT_IO;
+
+static int
+compare_mount_options(struct cifs_sb_info *old, struct cifs_sb_info *new)
+{
+	if ((old->mnt_cifs_flags & ACTUAL_MOUNT_FLAGS) !=
+	    (new->mnt_cifs_flags & ACTUAL_MOUNT_FLAGS))
+		return 0;
+
+	if (old->rsize != new->rsize || old->wsize != new->wsize)
+		return 0;
+
+	if (old->mnt_uid != new->mnt_uid || old->mnt_gid != new->mnt_gid)
+		return 0;
+
+	if (old->mnt_file_mode != new->mnt_file_mode ||
+	    old->mnt_dir_mode != new->mnt_dir_mode)
+		return 0;
+
+	if (strcmp(old->local_nls->charset, new->local_nls->charset))
+		return 0;
+
+	if (old->actimeo != new->actimeo)
+		return 0;
+
+	return 1;
+}
+
+int
+cifs_match_super(struct super_block *sb, void *data)
+{
+	struct cifs_mnt_data *mnt_data = (struct cifs_mnt_data *)data;
+	struct smb_vol *volume_info;
+	struct cifs_sb_info *cifs_sb, *new_cifs_sb;
+	struct TCP_Server_Info *tcp_srv;
+	struct cifsSesInfo *ses;
+	struct cifsTconInfo *tcon;
+	struct tcon_link *tlink;
+	struct sockaddr_storage addr;
+	int rc = 0;
+
+	memset(&addr, 0, sizeof(struct sockaddr_storage));
+
+	spin_lock(&cifs_tcp_ses_lock);
+	cifs_sb = CIFS_SB(sb);
+	tlink = cifs_get_tlink(cifs_sb_master_tlink(cifs_sb));
+	if (IS_ERR(tlink)) {
+		spin_unlock(&cifs_tcp_ses_lock);
+		return rc;
+	}
+	tcon = tlink_tcon(tlink);
+	ses = tcon->ses;
+	tcp_srv = ses->server;
+
+	volume_info = mnt_data->vol;
+	new_cifs_sb = mnt_data->cifs_sb;
+
+	if (!volume_info->UNCip || !volume_info->UNC)
+		goto out;
+
+	rc = cifs_fill_sockaddr((struct sockaddr *)&addr,
+				volume_info->UNCip,
+				strlen(volume_info->UNCip),
+				volume_info->port);
+	if (!rc)
+		goto out;
+
+	if (!match_server(tcp_srv, (struct sockaddr *)&addr, volume_info) ||
+	    !match_session(ses, volume_info) ||
+	    !match_tcon(tcon, volume_info->UNC)) {
+		rc = 0;
+		goto out;
+	}
+
+	rc = compare_mount_options(cifs_sb, new_cifs_sb);
+out:
+	cifs_put_tlink(tlink);
+	spin_unlock(&cifs_tcp_ses_lock);
+	return rc;
+}
+
 int
 get_dfs_path(int xid, struct cifsSesInfo *pSesInfo, const char *old_path,
 	     const struct nls_table *nls_codepage, unsigned int *pnum_referrals,
-- 
1.7.1