[CIFS] Add new nostrictsync cifs mount option to avoid slow SMB flush

If this mount option is set, when an application does an
fsync call then the cifs client does not send an SMB Flush
to the server (to force the server to write all dirty data
for this file immediately to disk), although cifs still sends
all dirty (cached) file data to the server and waits for the
server to respond to the write write.  Since SMB Flush can be
very slow, and some servers may be reliable enough (to risk
delaying slightly flushing the data to disk on the server),
turning on this option may be useful to improve performance for
applications that fsync too much, at a small risk of server
crash.  If this mount option is not set, by default cifs will
send an SMB flush request (and wait for a response) on every
fsync call.

Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/cifs/CHANGES b/fs/cifs/CHANGES
index d43e0fe3339..b33c8412e2c 100644
--- a/fs/cifs/CHANGES
+++ b/fs/cifs/CHANGES
@@ -8,7 +8,9 @@ user's smb session.  This fix allows cifs to mount multiple times to the
 same server with different userids without risking invalidating earlier
 established security contexts.  fsync now sends SMB Flush operation
 to better ensure that we wait for server to write all of the data to
-server disk (not just write it over the network).
+server disk (not just write it over the network).  Add new mount
+parameter to allow user to disable sending the (slow) SMB flush on
+fsync if desired (fsync still flushes all cached write data to the server).
 
 Version 1.56
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