cifs: convert cifs_tcp_ses_lock from a rwlock to a spinlock

cifs_tcp_ses_lock is a rwlock with protects the cifs_tcp_ses_list,
server->smb_ses_list and the ses->tcon_list. It also protects a few
ref counters in server, ses and tcon. In most cases the critical section
doesn't seem to be large, in a few cases where it is slightly large, there
seem to be really no benefit from concurrent access. I briefly considered RCU
mechanism but it appears to me that there is no real need.

Replace it with a spinlock and get rid of the last rwlock in the cifs code.

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

1 files changed, 6 insertions, 6 deletions

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index eb1ba493489f..103ab8b605b0 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -148,7 +148,7 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
         seq_printf(m, "Servers:");
 
         i = 0;
-        read_lock(&cifs_tcp_ses_lock);
+        spin_lock(&cifs_tcp_ses_lock);
         list_for_each(tmp1, &cifs_tcp_ses_list) {
                 server = list_entry(tmp1, struct TCP_Server_Info,
                                     tcp_ses_list);
@@ -230,7 +230,7 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
                         spin_unlock(&GlobalMid_Lock);
                 }
         }
-        read_unlock(&cifs_tcp_ses_lock);
+        spin_unlock(&cifs_tcp_ses_lock);
         seq_putc(m, '\n');
 
         /* BB add code to dump additional info such as TCP session info now */
@@ -270,7 +270,7 @@ static ssize_t cifs_stats_proc_write(struct file *file,
                 atomic_set(&totBufAllocCount, 0);
                 atomic_set(&totSmBufAllocCount, 0);
 #endif /* CONFIG_CIFS_STATS2 */
-                read_lock(&cifs_tcp_ses_lock);
+                spin_lock(&cifs_tcp_ses_lock);
                 list_for_each(tmp1, &cifs_tcp_ses_list) {
                         server = list_entry(tmp1, struct TCP_Server_Info,
                                             tcp_ses_list);
@@ -303,7 +303,7 @@ static ssize_t cifs_stats_proc_write(struct file *file,
                                 }
                         }
                 }
-                read_unlock(&cifs_tcp_ses_lock);
+                spin_unlock(&cifs_tcp_ses_lock);
         }
 
         return count;
@@ -343,7 +343,7 @@ static int cifs_stats_proc_show(struct seq_file *m, void *v)
                 GlobalCurrentXid, GlobalMaxActiveXid);
 
         i = 0;
-        read_lock(&cifs_tcp_ses_lock);
+        spin_lock(&cifs_tcp_ses_lock);
         list_for_each(tmp1, &cifs_tcp_ses_list) {
                 server = list_entry(tmp1, struct TCP_Server_Info,
                                     tcp_ses_list);
@@ -397,7 +397,7 @@ static int cifs_stats_proc_show(struct seq_file *m, void *v)
                         }
                 }
         }
-        read_unlock(&cifs_tcp_ses_lock);
+        spin_unlock(&cifs_tcp_ses_lock);
 
         seq_putc(m, '\n');
         return 0;