Clarify locking of cifs file and tcon structures and make more granular

Remove the global file_list_lock to simplify cifs/smb3 locking and
have spinlocks that more closely match the information they are
protecting.

Add new tcon->open_file_lock and file->file_info_lock spinlocks.
Locks continue to follow a heirachy,
	cifs_socket --> cifs_ses --> cifs_tcon --> cifs_file
where global tcp_ses_lock still protects socket and cifs_ses, while the
the newer locks protect the lower level structure's information
(tcon and cifs_file respectively).

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <steve.french@primarydata.com>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Germano Percossi <germano.percossi@citrix.com>

1 files changed, 15 insertions, 15 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 8f1d8c1e72be..65f78b7a9062 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -833,6 +833,7 @@ struct cifs_tcon {
 	struct list_head tcon_list;
 	int tc_count;
 	struct list_head openFileList;
+	spinlock_t open_file_lock; /* protects list above */
 	struct cifs_ses *ses;	/* pointer to session associated with */
 	char treeName[MAX_TREE_SIZE + 1]; /* UNC name of resource in ASCII */
 	char *nativeFileSystem;
@@ -889,7 +890,7 @@ struct cifs_tcon {
 #endif /* CONFIG_CIFS_STATS2 */
 	__u64    bytes_read;
 	__u64    bytes_written;
-	spinlock_t stat_lock;
+	spinlock_t stat_lock;  /* protects the two fields above */
 #endif /* CONFIG_CIFS_STATS */
 	FILE_SYSTEM_DEVICE_INFO fsDevInfo;
 	FILE_SYSTEM_ATTRIBUTE_INFO fsAttrInfo; /* ok if fs name truncated */
@@ -1040,8 +1041,10 @@ struct cifs_fid_locks {
 };
 
 struct cifsFileInfo {
+	/* following two lists are protected by tcon->open_file_lock */
 	struct list_head tlist;	/* pointer to next fid owned by tcon */
 	struct list_head flist;	/* next fid (file instance) for this inode */
+	/* lock list below protected by cifsi->lock_sem */
 	struct cifs_fid_locks *llist;	/* brlocks held by this fid */
 	kuid_t uid;		/* allows finding which FileInfo structure */
 	__u32 pid;		/* process id who opened file */
@@ -1049,11 +1052,12 @@ struct cifsFileInfo {
 	/* BB add lock scope info here if needed */ ;
 	/* lock scope id (0 if none) */
 	struct dentry *dentry;
-	unsigned int f_flags;
 	struct tcon_link *tlink;
+	unsigned int f_flags;
 	bool invalidHandle:1;	/* file closed via session abend */
 	bool oplock_break_cancelled:1;
-	int count;		/* refcount protected by cifs_file_list_lock */
+	int count;
+	spinlock_t file_info_lock; /* protects four flag/count fields above */
 	struct mutex fh_mutex; /* prevents reopen race after dead ses*/
 	struct cifs_search_info srch_inf;
 	struct work_struct oplock_break; /* work for oplock breaks */
@@ -1120,7 +1124,7 @@ struct cifs_writedata {
 
 /*
  * Take a reference on the file private data. Must be called with
- * cifs_file_list_lock held.
+ * cfile->file_info_lock held.
  */
 static inline void
 cifsFileInfo_get_locked(struct cifsFileInfo *cifs_file)
@@ -1514,8 +1518,10 @@ require use of the stronger protocol */
  *  GlobalMid_Lock protects:
  *	list operations on pending_mid_q and oplockQ
  *      updates to XID counters, multiplex id  and SMB sequence numbers
- *  cifs_file_list_lock protects:
- *	list operations on tcp and SMB session lists and tCon lists
+ *  tcp_ses_lock protects:
+ *	list operations on tcp and SMB session lists
+ *  tcon->open_file_lock protects the list of open files hanging off the tcon
+ *  cfile->file_info_lock protects counters and fields in cifs file struct
  *  f_owner.lock protects certain per file struct operations
  *  mapping->page_lock protects certain per page operations
  *
@@ -1547,18 +1553,12 @@ GLOBAL_EXTERN struct list_head		cifs_tcp_ses_list;
  * tcp session, and the list of tcon's per smb session. It also protects
  * the reference counters for the server, smb session, and tcon. Finally,
  * changes to the tcon->tidStatus should be done while holding this lock.
+ * generally the locks should be taken in order tcp_ses_lock before
+ * tcon->open_file_lock and that before file->file_info_lock since the
+ * structure order is cifs_socket-->cifs_ses-->cifs_tcon-->cifs_file
  */
 GLOBAL_EXTERN spinlock_t		cifs_tcp_ses_lock;
 
-/*
- * This lock protects the cifs_file->llist and cifs_file->flist
- * list operations, and updates to some flags (cifs_file->invalidHandle)
- * It will be moved to either use the tcon->stat_lock or equivalent later.
- * If cifs_tcp_ses_lock and the lock below are both needed to be held, then
- * the cifs_tcp_ses_lock must be grabbed first and released last.
- */
-GLOBAL_EXTERN spinlock_t	cifs_file_list_lock;
-
 #ifdef CONFIG_CIFS_DNOTIFY_EXPERIMENTAL /* unused temporarily */
 /* Outstanding dir notify requests */
 GLOBAL_EXTERN struct list_head GlobalDnotifyReqList;