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Groups > linux.kernel > #1509296

[PATCH 4.4 072/112] cifs: Limit the overall credit acquired

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.4 072/112] cifs: Limit the overall credit acquired
Date 2016-10-26 15:00 +0200
Message-ID <swvYe-3Qk-37@gated-at.bofh.it> (permalink)
References <swvER-3Eq-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ross Lagerwall <ross.lagerwall@citrix.com>

commit 7d414f396c91a3382e51cf628c1cf0709ad0188b upstream.

The kernel client requests 2 credits for many operations even though
they only use 1 credit (presumably to build up a buffer of credit).
Some servers seem to give the client as much credit as is requested.  In
this case, the amount of credit the client has continues increasing to
the point where (server->credits * MAX_BUFFER_SIZE) overflows in
smb2_wait_mtu_credits().

Fix this by throttling the credit requests if an set limit is reached.
For async requests where the credit charge may be > 1, request as much
credit as what is charged.
The limit is chosen somewhat arbitrarily. The Windows client
defaults to 128 credits, the Windows server allows clients up to
512 credits (or 8192 for Windows 2016), and the NetApp server
(and at least one other) does not limit clients at all.
Choose a high enough value such that the client shouldn't limit
performance.

This behavior was seen with a NetApp filer (NetApp Release 9.0RC2).

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/cifs/smb2glob.h |   10 ++++++++++
 fs/cifs/smb2pdu.c  |   18 +++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

--- a/fs/cifs/smb2glob.h
+++ b/fs/cifs/smb2glob.h
@@ -61,4 +61,14 @@
 /* Maximum buffer size value we can send with 1 credit */
 #define SMB2_MAX_BUFFER_SIZE 65536
 
+/*
+ * Maximum number of credits to keep available.
+ * This value is chosen somewhat arbitrarily. The Windows client
+ * defaults to 128 credits, the Windows server allows clients up to
+ * 512 credits, and the NetApp server does not limit clients at all.
+ * Choose a high enough value such that the client shouldn't limit
+ * performance.
+ */
+#define SMB2_MAX_CREDITS_AVAILABLE 32000
+
 #endif	/* _SMB2_GLOB_H */
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -103,7 +103,21 @@ smb2_hdr_assemble(struct smb2_hdr *hdr,
 	hdr->ProtocolId[3] = 'B';
 	hdr->StructureSize = cpu_to_le16(64);
 	hdr->Command = smb2_cmd;
-	hdr->CreditRequest = cpu_to_le16(2); /* BB make this dynamic */
+	if (tcon && tcon->ses && tcon->ses->server) {
+		struct TCP_Server_Info *server = tcon->ses->server;
+
+		spin_lock(&server->req_lock);
+		/* Request up to 2 credits but don't go over the limit. */
+		if (server->credits >= SMB2_MAX_CREDITS_AVAILABLE)
+			hdr->CreditRequest = cpu_to_le16(0);
+		else
+			hdr->CreditRequest = cpu_to_le16(
+				min_t(int, SMB2_MAX_CREDITS_AVAILABLE -
+						server->credits, 2));
+		spin_unlock(&server->req_lock);
+	} else {
+		hdr->CreditRequest = cpu_to_le16(2);
+	}
 	hdr->ProcessId = cpu_to_le32((__u16)current->tgid);
 
 	if (!tcon)
@@ -2059,6 +2073,7 @@ smb2_async_readv(struct cifs_readdata *r
 	if (rdata->credits) {
 		buf->CreditCharge = cpu_to_le16(DIV_ROUND_UP(rdata->bytes,
 						SMB2_MAX_BUFFER_SIZE));
+		buf->CreditRequest = buf->CreditCharge;
 		spin_lock(&server->req_lock);
 		server->credits += rdata->credits -
 						le16_to_cpu(buf->CreditCharge);
@@ -2245,6 +2260,7 @@ smb2_async_writev(struct cifs_writedata
 	if (wdata->credits) {
 		req->hdr.CreditCharge = cpu_to_le16(DIV_ROUND_UP(wdata->bytes,
 						    SMB2_MAX_BUFFER_SIZE));
+		req->hdr.CreditRequest = req->hdr.CreditCharge;
 		spin_lock(&server->req_lock);
 		server->credits += wdata->credits -
 					le16_to_cpu(req->hdr.CreditCharge);

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[PATCH 4.4 000/112] 4.4.28-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 14:50 +0200
  [PATCH 4.4 061/112] NFSv4: Dont report revoked delegations as valid in nfs_have_delegation() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 084/112] irqchip/gicv3: Handle loop timeout proper Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 028/112] powerpc/powernv: Use CPU-endian hub diag-data type in pnv_eeh_get_and_dump_hub_diag() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 051/112] ALSA: hda - Fix a failure of micmute led when having multi adcs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 074/112] Clarify locking of cifs file and tcon structures and make more granular Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 027/112] powerpc/powernv: Pass CPU-endian PE number to opal_pci_eeh_freeze_clear() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 071/112] fs/super.c: fix race between freeze_super() and thaw_super() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 077/112] SMB3: GUIDs should be constructed as random but valid uuids Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 019/112] perf intel-pt: Fix snapshot overlap detection decoder errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 024/112] dm mpath: check if paths request_queue is dying in activate_path() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 072/112] cifs: Limit the overall credit acquired Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 070/112] arc: dont leak bits of kernel stack into coredump Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 057/112] Input: i8042 - skip selftest on ASUS laptops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 054/112] lib: move strtobool() to kstrtobool() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 037/112] zfcp: restore: Dont use 0 to indicate invalid LUN in rec trace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 058/112] Input: elantech - force needed quirks on Fujitsu H760 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 055/112] lib: update single-char callers of strtobool() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 060/112] sunrpc: fix write space race causing stalls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 053/112] MIPS: ptrace: Fix regs_return_value for kernel context Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 056/112] lib: add "on"/"off" support to kstrtobool Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:00 +0200
  [PATCH 4.4 010/112] platform: dont return 0 from platform_get_irq[_byname]() on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 047/112] [media] mb86a20s: fix the locking logic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 022/112] dm: mark request_queue dead before destroying the DM device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 021/112] perf intel-pt: Fix MTC timestamp calculation for large MTC periods Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 043/112] scsi: zfcp: spin_lock_irqsave() is not nestable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 017/112] pstore/ram: Use memcpy_toio instead of memcpy Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 041/112] zfcp: fix payload trace length for SAN request&response Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 050/112] [media] cx231xx: fix GPIOs for Pixelview SBTVD hybrid Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 049/112] [media] cx231xx: dont return error on success Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 044/112] fbdev/efifb: Fix 16 color palette entry calculation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 048/112] [media] mb86a20s: fix demod settings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 015/112] pstore/ramoops: fixup driver removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 032/112] ubi: Deal with interrupted erasures in WL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 046/112] ovl: copy_up_xattr(): use strnlen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 036/112] zfcp: retain trace level for SCSI and HBA FSF response records Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 013/112] parisc: Fix kernel memory layout regarding position of __gp Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 011/112] cpufreq: intel_pstate: Fix unsafe HWP MSR access Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 038/112] zfcp: trace on request for open and close of WKA port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 035/112] zfcp: close window with unblocked rport during rport gone Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 034/112] zfcp: fix ELS/GS request&response length for hardware data router Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 042/112] zfcp: trace full payload of all SAN records (req,resp,iels) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 040/112] zfcp: fix D_ID field with actual value on tracing SAN responses Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 045/112] ovl: Fix info leak in ovl_lookup_temp() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  [PATCH 4.4 033/112] zfcp: fix fc_host port_type with NPIV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-10-26 15:10 +0200
  Re: [PATCH 4.4 000/112] 4.4.28-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-10-26 20:50 +0200
  Re: [PATCH 4.4 000/112] 4.4.28-stable review Guenter Roeck <linux@roeck-us.net> - 2016-10-26 23:50 +0200

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