cifs: convert GlobalSMBSeslock from a rwlock to regular spinlock

Convert this lock to a regular spinlock

A rwlock_t offers little value here. It's more expensive than a regular
spinlock unless you have a fairly large section of code that runs under
the read lock and can benefit from the concurrency.

Additionally, we need to ensure that the refcounting for files isn't
racy and to do that we need to lock areas that can increment it for
write. That means that the areas that can actually use a read_lock are
very few and relatively infrequently used.

While we're at it, change the name to something easier to type, and fix
a bug in find_writable_file. cifsFileInfo_put can sleep and shouldn't be
called while holding the lock.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index a420c7b08522..bfb59a68e4fd 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -91,13 +91,13 @@ static void mark_open_files_invalid(struct cifsTconInfo *pTcon)
 	struct list_head *tmp1;
 
 /* list all files open on tree connection and mark them invalid */
-	write_lock(&GlobalSMBSeslock);
+	spin_lock(&cifs_file_list_lock);
 	list_for_each_safe(tmp, tmp1, &pTcon->openFileList) {
 		open_file = list_entry(tmp, struct cifsFileInfo, tlist);
 		open_file->invalidHandle = true;
 		open_file->oplock_break_cancelled = true;
 	}
-	write_unlock(&GlobalSMBSeslock);
+	spin_unlock(&cifs_file_list_lock);
 	/* BB Add call to invalidate_inodes(sb) for all superblocks mounted
 	   to this tcon */
 }