[PATCH 3.16 118/306] Clarify locking of cifs file and tcon structures and make more granular

[Ben Hutchings <ben@decadent.org.uk>]

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Steve French <smfrench@gmail.com>

commit 3afca265b5f53a0b15b79531c13858049505582d upstream.

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).

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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/cifs/cifsfs.c   |  1 -
 fs/cifs/cifsglob.h | 30 ++++++++++++-------------
 fs/cifs/cifssmb.c  |  4 ++--
 fs/cifs/file.c     | 66 ++++++++++++++++++++++++++++++++----------------------
 fs/cifs/misc.c     | 15 +++++++------
 fs/cifs/readdir.c  |  6 ++---
 fs/cifs/smb2misc.c | 16 ++++++-------
 7 files changed, 75 insertions(+), 63 deletions(-)

--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1193,7 +1193,6 @@ init_cifs(void)
 	GlobalTotalActiveXid = 0;
 	GlobalMaxActiveXid = 0;
 	spin_lock_init(&cifs_tcp_ses_lock);
-	spin_lock_init(&cifs_file_list_lock);
 	spin_lock_init(&GlobalMid_Lock);
 
 	if (cifs_max_pending < 2) {
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -796,6 +796,7 @@ 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;
@@ -852,7 +853,7 @@ 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 */
@@ -999,8 +1000,10 @@ 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 */
@@ -1008,11 +1011,12 @@ 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 */
@@ -1076,7 +1080,7 @@ 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)
@@ -1463,8 +1467,10 @@ 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
  *
@@ -1496,18 +1502,12 @@ GLOBAL_EXTERN struct list_head		cifs_tcp
  * 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;
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -98,13 +98,13 @@ cifs_mark_open_files_invalid(struct cifs
 	struct list_head *tmp1;
 
 	/* list all files open on tree connection and mark them invalid */
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tcon->open_file_lock);
 	list_for_each_safe(tmp, tmp1, &tcon->openFileList) {
 		open_file = list_entry(tmp, struct cifsFileInfo, tlist);
 		open_file->invalidHandle = true;
 		open_file->oplock_break_cancelled = true;
 	}
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tcon->open_file_lock);
 	/*
 	 * BB Add call to invalidate_inodes(sb) for all superblocks mounted
 	 * to this tcon.
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -306,6 +306,7 @@ cifs_new_fileinfo(struct cifs_fid *fid,
 	cfile->tlink = cifs_get_tlink(tlink);
 	INIT_WORK(&cfile->oplock_break, cifs_oplock_break);
 	mutex_init(&cfile->fh_mutex);
+	spin_lock_init(&cfile->file_info_lock);
 
 	cifs_sb_active(inode->i_sb);
 
@@ -318,7 +319,7 @@ cifs_new_fileinfo(struct cifs_fid *fid,
 		oplock = 0;
 	}
 
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tcon->open_file_lock);
 	if (fid->pending_open->oplock != CIFS_OPLOCK_NO_CHANGE && oplock)
 		oplock = fid->pending_open->oplock;
 	list_del(&fid->pending_open->olist);
@@ -327,12 +328,13 @@ cifs_new_fileinfo(struct cifs_fid *fid,
 	server->ops->set_fid(cfile, fid, oplock);
 
 	list_add(&cfile->tlist, &tcon->openFileList);
+
 	/* if readable file instance put first in list*/
 	if (file->f_mode & FMODE_READ)
 		list_add(&cfile->flist, &cinode->openFileList);
 	else
 		list_add_tail(&cfile->flist, &cinode->openFileList);
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tcon->open_file_lock);
 
 	if (fid->purge_cache)
 		cifs_zap_mapping(inode);
@@ -344,16 +346,16 @@ cifs_new_fileinfo(struct cifs_fid *fid,
 struct cifsFileInfo *
 cifsFileInfo_get(struct cifsFileInfo *cifs_file)
 {
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&cifs_file->file_info_lock);
 	cifsFileInfo_get_locked(cifs_file);
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&cifs_file->file_info_lock);
 	return cifs_file;
 }
 
 /*
  * Release a reference on the file private data. This may involve closing
  * the filehandle out on the server. Must be called without holding
- * cifs_file_list_lock.
+ * tcon->open_file_lock and cifs_file->file_info_lock.
  */
 void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 {
@@ -368,11 +370,15 @@ void cifsFileInfo_put(struct cifsFileInf
 	struct cifs_pending_open open;
 	bool oplock_break_cancelled;
 
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tcon->open_file_lock);
+
+	spin_lock(&cifs_file->file_info_lock);
 	if (--cifs_file->count > 0) {
-		spin_unlock(&cifs_file_list_lock);
+		spin_unlock(&cifs_file->file_info_lock);
+		spin_unlock(&tcon->open_file_lock);
 		return;
 	}
+	spin_unlock(&cifs_file->file_info_lock);
 
 	if (server->ops->get_lease_key)
 		server->ops->get_lease_key(inode, &fid);
@@ -396,7 +402,8 @@ void cifsFileInfo_put(struct cifsFileInf
 			set_bit(CIFS_INO_INVALID_MAPPING, &cifsi->flags);
 		cifs_set_oplock_level(cifsi, 0);
 	}
-	spin_unlock(&cifs_file_list_lock);
+
+	spin_unlock(&tcon->open_file_lock);
 
 	oplock_break_cancelled = cancel_work_sync(&cifs_file->oplock_break);
 
@@ -765,10 +772,10 @@ int cifs_closedir(struct inode *inode, s
 	server = tcon->ses->server;
 
 	cifs_dbg(FYI, "Freeing private data in close dir\n");
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&cfile->file_info_lock);
 	if (server->ops->dir_needs_close(cfile)) {
 		cfile->invalidHandle = true;
-		spin_unlock(&cifs_file_list_lock);
+		spin_unlock(&cfile->file_info_lock);
 		if (server->ops->close_dir)
 			rc = server->ops->close_dir(xid, tcon, &cfile->fid);
 		else
@@ -777,7 +784,7 @@ int cifs_closedir(struct inode *inode, s
 		/* not much we can do if it fails anyway, ignore rc */
 		rc = 0;
 	} else
-		spin_unlock(&cifs_file_list_lock);
+		spin_unlock(&cfile->file_info_lock);
 
 	buf = cfile->srch_inf.ntwrk_buf_start;
 	if (buf) {
@@ -1719,12 +1726,13 @@ struct cifsFileInfo *find_readable_file(
 {
 	struct cifsFileInfo *open_file = NULL;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 
 	/* only filter by fsuid on multiuser mounts */
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
 		fsuid_only = false;
 
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tcon->open_file_lock);
 	/* we could simply get the first_list_entry since write-only entries
 	   are always at the end of the list but since the first entry might
 	   have a close pending, we go through the whole list */
@@ -1735,8 +1743,8 @@ struct cifsFileInfo *find_readable_file(
 			if (!open_file->invalidHandle) {
 				/* found a good file */
 				/* lock it so it will not be closed on us */
-				cifsFileInfo_get_locked(open_file);
-				spin_unlock(&cifs_file_list_lock);
+				cifsFileInfo_get(open_file);
+				spin_unlock(&tcon->open_file_lock);
 				return open_file;
 			} /* else might as well continue, and look for
 			     another, or simply have the caller reopen it
@@ -1744,7 +1752,7 @@ struct cifsFileInfo *find_readable_file(
 		} else /* write only file */
 			break; /* write only files are last so must be done */
 	}
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tcon->open_file_lock);
 	return NULL;
 }
 
@@ -1753,6 +1761,7 @@ struct cifsFileInfo *find_writable_file(
 {
 	struct cifsFileInfo *open_file, *inv_file = NULL;
 	struct cifs_sb_info *cifs_sb;
+	struct cifs_tcon *tcon;
 	bool any_available = false;
 	int rc;
 	unsigned int refind = 0;
@@ -1768,15 +1777,16 @@ struct cifsFileInfo *find_writable_file(
 	}
 
 	cifs_sb = CIFS_SB(cifs_inode->vfs_inode.i_sb);
+	tcon = cifs_sb_master_tcon(cifs_sb);
 
 	/* only filter by fsuid on multiuser mounts */
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER))
 		fsuid_only = false;
 
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tcon->open_file_lock);
 refind_writable:
 	if (refind > MAX_REOPEN_ATT) {
-		spin_unlock(&cifs_file_list_lock);
+		spin_unlock(&tcon->open_file_lock);
 		return NULL;
 	}
 	list_for_each_entry(open_file, &cifs_inode->openFileList, flist) {
@@ -1787,8 +1797,8 @@ refind_writable:
 		if (OPEN_FMODE(open_file->f_flags) & FMODE_WRITE) {
 			if (!open_file->invalidHandle) {
 				/* found a good writable file */
-				cifsFileInfo_get_locked(open_file);
-				spin_unlock(&cifs_file_list_lock);
+				cifsFileInfo_get(open_file);
+				spin_unlock(&tcon->open_file_lock);
 				return open_file;
 			} else {
 				if (!inv_file)
@@ -1804,24 +1814,24 @@ refind_writable:
 
 	if (inv_file) {
 		any_available = false;
-		cifsFileInfo_get_locked(inv_file);
+		cifsFileInfo_get(inv_file);
 	}
 
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tcon->open_file_lock);
 
 	if (inv_file) {
 		rc = cifs_reopen_file(inv_file, false);
 		if (!rc)
 			return inv_file;
 		else {
-			spin_lock(&cifs_file_list_lock);
+			spin_lock(&tcon->open_file_lock);
 			list_move_tail(&inv_file->flist,
 					&cifs_inode->openFileList);
-			spin_unlock(&cifs_file_list_lock);
+			spin_unlock(&tcon->open_file_lock);
 			cifsFileInfo_put(inv_file);
-			spin_lock(&cifs_file_list_lock);
 			++refind;
 			inv_file = NULL;
+			spin_lock(&tcon->open_file_lock);
 			goto refind_writable;
 		}
 	}
@@ -3466,15 +3476,17 @@ static int cifs_readpage(struct file *fi
 static int is_inode_writable(struct cifsInodeInfo *cifs_inode)
 {
 	struct cifsFileInfo *open_file;
+	struct cifs_tcon *tcon =
+		cifs_sb_master_tcon(CIFS_SB(cifs_inode->vfs_inode.i_sb));
 
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tcon->open_file_lock);
 	list_for_each_entry(open_file, &cifs_inode->openFileList, flist) {
 		if (OPEN_FMODE(open_file->f_flags) & FMODE_WRITE) {
-			spin_unlock(&cifs_file_list_lock);
+			spin_unlock(&tcon->open_file_lock);
 			return 1;
 		}
 	}
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tcon->open_file_lock);
 	return 0;
 }
 
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -120,6 +120,7 @@ tconInfoAlloc(void)
 		++ret_buf->tc_count;
 		INIT_LIST_HEAD(&ret_buf->openFileList);
 		INIT_LIST_HEAD(&ret_buf->tcon_list);
+		spin_lock_init(&ret_buf->open_file_lock);
 #ifdef CONFIG_CIFS_STATS
 		spin_lock_init(&ret_buf->stat_lock);
 #endif
@@ -456,7 +457,7 @@ is_valid_oplock_break(char *buffer, stru
 				continue;
 
 			cifs_stats_inc(&tcon->stats.cifs_stats.num_oplock_brks);
-			spin_lock(&cifs_file_list_lock);
+			spin_lock(&tcon->open_file_lock);
 			list_for_each(tmp2, &tcon->openFileList) {
 				netfile = list_entry(tmp2, struct cifsFileInfo,
 						     tlist);
@@ -486,11 +487,11 @@ is_valid_oplock_break(char *buffer, stru
 					   &netfile->oplock_break);
 				netfile->oplock_break_cancelled = false;
 
-				spin_unlock(&cifs_file_list_lock);
+				spin_unlock(&tcon->open_file_lock);
 				spin_unlock(&cifs_tcp_ses_lock);
 				return true;
 			}
-			spin_unlock(&cifs_file_list_lock);
+			spin_unlock(&tcon->open_file_lock);
 			spin_unlock(&cifs_tcp_ses_lock);
 			cifs_dbg(FYI, "No matching file for oplock break\n");
 			return true;
@@ -639,9 +640,9 @@ backup_cred(struct cifs_sb_info *cifs_sb
 void
 cifs_del_pending_open(struct cifs_pending_open *open)
 {
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tlink_tcon(open->tlink)->open_file_lock);
 	list_del(&open->olist);
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tlink_tcon(open->tlink)->open_file_lock);
 }
 
 void
@@ -661,7 +662,7 @@ void
 cifs_add_pending_open(struct cifs_fid *fid, struct tcon_link *tlink,
 		      struct cifs_pending_open *open)
 {
-	spin_lock(&cifs_file_list_lock);
+	spin_lock(&tlink_tcon(tlink)->open_file_lock);
 	cifs_add_pending_open_locked(fid, tlink, open);
-	spin_unlock(&cifs_file_list_lock);
+	spin_unlock(&tlink_tcon(open->tlink)->open_file_lock);
 }
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -592,14 +592,14 @@ find_cifs_entry(const unsigned int xid,
 	     is_dir_changed(file)) || (index_to_find < first_entry_in_buffer)) {
 		/* close and restart search */
 		cifs_dbg(FYI, "search backing up - close and restart search\n");
-		spin_lock(&cifs_file_list_lock);
+		spin_lock(&cfile->file_info_lock);
 		if (server->ops->dir_needs_close(cfile)) {
 			cfile->invalidHandle = true;
-			spin_unlock(&cifs_file_list_lock);
+			spin_unlock(&cfile->file_info_lock);
 			if (server->ops->close_dir)
 				server->ops->close_dir(xid, tcon, &cfile->fid);
 		} else
-			spin_unlock(&cifs_file_list_lock);
+			spin_unlock(&cfile->file_info_lock);
 		if (cfile->srch_inf.ntwrk_buf_start) {
 			cifs_dbg(FYI, "freeing SMB ff cache buf on search rewind\n");
 			if (cfile->srch_inf.smallBuf)
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -502,19 +502,19 @@ smb2_is_valid_lease_break(char *buffer)
 		list_for_each(tmp1, &server->smb_ses_list) {
 			ses = list_entry(tmp1, struct cifs_ses, smb_ses_list);
 
-			spin_lock(&cifs_file_list_lock);
 			list_for_each(tmp2, &ses->tcon_list) {
 				tcon = list_entry(tmp2, struct cifs_tcon,
 						  tcon_list);
+				spin_lock(&tcon->open_file_lock);
 				cifs_stats_inc(
 				    &tcon->stats.cifs_stats.num_oplock_brks);
 				if (smb2_tcon_has_lease(tcon, rsp, lw)) {
-					spin_unlock(&cifs_file_list_lock);
+					spin_unlock(&tcon->open_file_lock);
 					spin_unlock(&cifs_tcp_ses_lock);
 					return true;
 				}
+				spin_unlock(&tcon->open_file_lock);
 			}
-			spin_unlock(&cifs_file_list_lock);
 		}
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
@@ -556,7 +556,7 @@ smb2_is_valid_oplock_break(char *buffer,
 			tcon = list_entry(tmp1, struct cifs_tcon, tcon_list);
 
 			cifs_stats_inc(&tcon->stats.cifs_stats.num_oplock_brks);
-			spin_lock(&cifs_file_list_lock);
+			spin_lock(&tcon->open_file_lock);
 			list_for_each(tmp2, &tcon->openFileList) {
 				cfile = list_entry(tmp2, struct cifsFileInfo,
 						     tlist);
@@ -568,7 +568,7 @@ smb2_is_valid_oplock_break(char *buffer,
 
 				cifs_dbg(FYI, "file id match, oplock break\n");
 				cinode = CIFS_I(cfile->dentry->d_inode);
-
+				spin_lock(&cfile->file_info_lock);
 				if (!CIFS_CACHE_WRITE(cinode) &&
 				    rsp->OplockLevel == SMB2_OPLOCK_LEVEL_NONE)
 					cfile->oplock_break_cancelled = true;
@@ -590,14 +590,14 @@ smb2_is_valid_oplock_break(char *buffer,
 					clear_bit(
 					   CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2,
 					   &cinode->flags);
-
+				spin_unlock(&cfile->file_info_lock);
 				queue_work(cifsiod_wq, &cfile->oplock_break);
 
-				spin_unlock(&cifs_file_list_lock);
+				spin_unlock(&tcon->open_file_lock);
 				spin_unlock(&cifs_tcp_ses_lock);
 				return true;
 			}
-			spin_unlock(&cifs_file_list_lock);
+			spin_unlock(&tcon->open_file_lock);
 			spin_unlock(&cifs_tcp_ses_lock);
 			cifs_dbg(FYI, "No matching file for oplock break\n");
 			return true;