cifs: don't allow mmap'ed pages to be dirtied while under writeback (try #3)

This is more or less the same patch as before, but with some merge
conflicts fixed up.

If a process has a dirty page mapped into its page tables, then it has
the ability to change it while the client is trying to write the data
out to the server. If that happens after the signature has been
calculated then that signature will then be wrong, and the server will
likely reset the TCP connection.

This patch adds a page_mkwrite handler for CIFS that simply takes the
page lock. Because the page lock is held over the life of writepage and
writepages, this prevents the page from becoming writeable until
the write call has completed.

With this, we can also remove the "sign_zero_copy" module option and
always inline the pages when writing.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 0 insertions, 4 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index e3352a1ac47..5c412b33cd7 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -81,10 +81,6 @@ module_param(echo_retries, ushort, 0644);
 MODULE_PARM_DESC(echo_retries, "Number of echo attempts before giving up and "
                                "reconnecting server. Default: 5. 0 means "
                                "never reconnect.");
-bool sign_zero_copy;  /* globals init to false automatically */
-module_param(sign_zero_copy, bool, 0644);
-MODULE_PARM_DESC(sign_zero_copy, "Don't copy pages on write with signing "
-                                 "enabled. Default: N");
 extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
 extern mempool_t *cifs_mid_poolp;