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>
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index de6073c..a7b492c 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -347,7 +347,7 @@
if (current_fsuid() != treeCon->ses->linux_uid) {
cFYI(1, "Multiuser mode and UID "
"did not match tcon uid");
- read_lock(&cifs_tcp_ses_lock);
+ spin_lock(&cifs_tcp_ses_lock);
list_for_each(temp_item, &treeCon->ses->server->smb_ses_list) {
ses = list_entry(temp_item, struct cifsSesInfo, smb_ses_list);
if (ses->linux_uid == current_fsuid()) {
@@ -361,7 +361,7 @@
}
}
}
- read_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
}
}
}
@@ -551,7 +551,7 @@
return false;
/* look up tcon based on tid & uid */
- read_lock(&cifs_tcp_ses_lock);
+ spin_lock(&cifs_tcp_ses_lock);
list_for_each(tmp, &srv->smb_ses_list) {
ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
list_for_each(tmp1, &ses->tcon_list) {
@@ -573,7 +573,7 @@
*/
if (netfile->closePend) {
spin_unlock(&cifs_file_list_lock);
- read_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
return true;
}
@@ -595,16 +595,16 @@
netfile->oplock_break_cancelled = false;
spin_unlock(&cifs_file_list_lock);
- read_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
return true;
}
spin_unlock(&cifs_file_list_lock);
- read_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
cFYI(1, "No matching file for oplock break");
return true;
}
}
- read_unlock(&cifs_tcp_ses_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
cFYI(1, "Can not process oplock break for non-existent connection");
return true;
}