SMB3: Add mount parameter to allow user to override max credits
Add mount option "max_credits" to allow setting maximum SMB3
credits to any value from 10 to 64000 (default is 32000).
This can be useful to workaround servers with problems allocating
credits, or to throttle the client to use smaller amount of
simultaneous i/o or to workaround server performance issues.
Also adds a cap, so that even if the server granted us more than
65000 credits due to a server bug, we would not use that many.
Signed-off-by: Steve French <steve.french@primarydata.com>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 7b67179..657369d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -63,7 +63,6 @@
#define TLINK_IDLE_EXPIRE (600 * HZ)
enum {
-
/* Mount options that take no arguments */
Opt_user_xattr, Opt_nouser_xattr,
Opt_forceuid, Opt_noforceuid,
@@ -95,7 +94,7 @@
Opt_cruid, Opt_gid, Opt_file_mode,
Opt_dirmode, Opt_port,
Opt_rsize, Opt_wsize, Opt_actimeo,
- Opt_echo_interval,
+ Opt_echo_interval, Opt_max_credits,
/* Mount options which take string value */
Opt_user, Opt_pass, Opt_ip,
@@ -190,6 +189,7 @@
{ Opt_wsize, "wsize=%s" },
{ Opt_actimeo, "actimeo=%s" },
{ Opt_echo_interval, "echo_interval=%s" },
+ { Opt_max_credits, "max_credits=%s" },
{ Opt_blank_user, "user=" },
{ Opt_blank_user, "username=" },
@@ -1586,6 +1586,15 @@
}
vol->echo_interval = option;
break;
+ case Opt_max_credits:
+ if (get_option_ul(args, &option) || (option < 20) ||
+ (option > 60000)) {
+ cifs_dbg(VFS, "%s: Invalid max_credits value\n",
+ __func__);
+ goto cifs_parse_mount_err;
+ }
+ vol->max_credits = option;
+ break;
/* String Arguments */
@@ -3598,7 +3607,11 @@
bdi_destroy(&cifs_sb->bdi);
goto out;
}
-
+ if ((volume_info->max_credits < 20) ||
+ (volume_info->max_credits > 60000))
+ server->max_credits = SMB2_MAX_CREDITS_AVAILABLE;
+ else
+ server->max_credits = volume_info->max_credits;
/* get a reference to a SMB session */
ses = cifs_get_smb_ses(server, volume_info);
if (IS_ERR(ses)) {