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* [PATCH v2 0/4] SUNRPC: Various RCU fixes
@ 2023-12-04 20:25 Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 1/4] SUNRPC: Clean up unused variable in rpc_xprt_probe_trunked() Anna Schumaker
                   ` (3 more replies)
  0 siblings, 4 replies; 6+ messages in thread
From: Anna Schumaker @ 2023-12-04 20:25 UTC (permalink / raw)
  To: linux-nfs, trond.myklebust; +Cc: anna

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

These are various fixes that I found after turning on CONFIG_LOCKDEP,
CONFIG_PROVE_RCU, and CONFIG_DEBUG_ATOMIC_SLEEP. I didn't hit any issues
when testing against a Linux server, but running against Netapp with pNFS
had several different lockdep & rcu related spews show up in my dmesg
(and that's just from running cthon, not even xfstests). These patches fix
all the issues that I found, and have a couple extra cleanups that I noticed
along the way.

Changes in v2:
* Have rpc_xprt_switch_has_addr() unconditionally take the
  rcu_read_lock(), since we don't need to worry about this deadlocking
  if the lock is already held by the caller.

Thoughts?
Anna


Anna Schumaker (4):
  SUNRPC: Clean up unused variable in rpc_xprt_probe_trunked()
  SUNRPC: Remove unused function rpc_clnt_xprt_switch_put()
  SUNRPC: Create a helper function for accessing the rpc_clnt's
    xprt_switch
  SUNRPC: Fix a suspicious RCU usage warning

 include/linux/sunrpc/clnt.h |  1 -
 net/sunrpc/clnt.c           | 45 +++++++++++++++++--------------------
 net/sunrpc/xprtmultipath.c  | 17 ++++++++++++--
 3 files changed, 36 insertions(+), 27 deletions(-)

-- 
2.43.0


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH v2 1/4] SUNRPC: Clean up unused variable in rpc_xprt_probe_trunked()
  2023-12-04 20:25 [PATCH v2 0/4] SUNRPC: Various RCU fixes Anna Schumaker
@ 2023-12-04 20:25 ` Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 2/4] SUNRPC: Remove unused function rpc_clnt_xprt_switch_put() Anna Schumaker
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 6+ messages in thread
From: Anna Schumaker @ 2023-12-04 20:25 UTC (permalink / raw)
  To: linux-nfs, trond.myklebust; +Cc: anna

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

We don't use the rpc_xprt_switch anywhere in this function, so let's not
take an extra reference to in unnecessarily.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 net/sunrpc/clnt.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index daa9582ec861..4aa838543f79 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -3116,7 +3116,6 @@ static int rpc_xprt_probe_trunked(struct rpc_clnt *clnt,
 				  struct rpc_xprt *xprt,
 				  struct rpc_add_xprt_test *data)
 {
-	struct rpc_xprt_switch *xps;
 	struct rpc_xprt *main_xprt;
 	int status = 0;
 
@@ -3124,7 +3123,6 @@ static int rpc_xprt_probe_trunked(struct rpc_clnt *clnt,
 
 	rcu_read_lock();
 	main_xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
-	xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
 	status = rpc_cmp_addr_port((struct sockaddr *)&xprt->addr,
 				   (struct sockaddr *)&main_xprt->addr);
 	rcu_read_unlock();
@@ -3135,7 +3133,6 @@ static int rpc_xprt_probe_trunked(struct rpc_clnt *clnt,
 	status = rpc_clnt_add_xprt_helper(clnt, xprt, data);
 out:
 	xprt_put(xprt);
-	xprt_switch_put(xps);
 	return status;
 }
 
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH v2 2/4] SUNRPC: Remove unused function rpc_clnt_xprt_switch_put()
  2023-12-04 20:25 [PATCH v2 0/4] SUNRPC: Various RCU fixes Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 1/4] SUNRPC: Clean up unused variable in rpc_xprt_probe_trunked() Anna Schumaker
@ 2023-12-04 20:25 ` Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 3/4] SUNRPC: Create a helper function for accessing the rpc_clnt's xprt_switch Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 4/4] SUNRPC: Fix a suspicious RCU usage warning Anna Schumaker
  3 siblings, 0 replies; 6+ messages in thread
From: Anna Schumaker @ 2023-12-04 20:25 UTC (permalink / raw)
  To: linux-nfs, trond.myklebust; +Cc: anna

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 include/linux/sunrpc/clnt.h | 1 -
 net/sunrpc/clnt.c           | 8 --------
 2 files changed, 9 deletions(-)

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index e9d4377d03c6..5e9d1469c6fa 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -252,7 +252,6 @@ void		rpc_clnt_probe_trunked_xprts(struct rpc_clnt *,
 
 const char *rpc_proc_name(const struct rpc_task *task);
 
-void rpc_clnt_xprt_switch_put(struct rpc_clnt *);
 void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *, struct rpc_xprt *);
 void rpc_clnt_xprt_switch_remove_xprt(struct rpc_clnt *, struct rpc_xprt *);
 bool rpc_clnt_xprt_switch_has_addr(struct rpc_clnt *clnt,
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 4aa838543f79..8df944444e9b 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -3247,14 +3247,6 @@ rpc_set_connect_timeout(struct rpc_clnt *clnt,
 }
 EXPORT_SYMBOL_GPL(rpc_set_connect_timeout);
 
-void rpc_clnt_xprt_switch_put(struct rpc_clnt *clnt)
-{
-	rcu_read_lock();
-	xprt_switch_put(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
-	rcu_read_unlock();
-}
-EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_put);
-
 void rpc_clnt_xprt_set_online(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
 	struct rpc_xprt_switch *xps;
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH v2 3/4] SUNRPC: Create a helper function for accessing the rpc_clnt's xprt_switch
  2023-12-04 20:25 [PATCH v2 0/4] SUNRPC: Various RCU fixes Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 1/4] SUNRPC: Clean up unused variable in rpc_xprt_probe_trunked() Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 2/4] SUNRPC: Remove unused function rpc_clnt_xprt_switch_put() Anna Schumaker
@ 2023-12-04 20:25 ` Anna Schumaker
  2023-12-04 20:25 ` [PATCH v2 4/4] SUNRPC: Fix a suspicious RCU usage warning Anna Schumaker
  3 siblings, 0 replies; 6+ messages in thread
From: Anna Schumaker @ 2023-12-04 20:25 UTC (permalink / raw)
  To: linux-nfs, trond.myklebust; +Cc: anna

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

This function takes the necessary rcu read lock to dereference the
client's rpc_xprt_switch and bump the reference count so it doesn't
disappear underneath us before returning. This does mean that callers
are responsible for calling xprt_switch_put() on the returned object
when they are done with it.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 net/sunrpc/clnt.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 8df944444e9b..0b2c4b5484f5 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -797,15 +797,24 @@ int rpc_switch_client_transport(struct rpc_clnt *clnt,
 }
 EXPORT_SYMBOL_GPL(rpc_switch_client_transport);
 
+static struct rpc_xprt_switch *rpc_clnt_xprt_switch_get(struct rpc_clnt *clnt)
+{
+	struct rpc_xprt_switch *xps;
+
+	rcu_read_lock();
+	xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
+	rcu_read_unlock();
+
+	return xps;
+}
+
 static
 int _rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi,
 			     void func(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps))
 {
 	struct rpc_xprt_switch *xps;
 
-	rcu_read_lock();
-	xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
-	rcu_read_unlock();
+	xps = rpc_clnt_xprt_switch_get(clnt);
 	if (xps == NULL)
 		return -EAGAIN;
 	func(xpi, xps);
@@ -2206,9 +2215,7 @@ call_connect_status(struct rpc_task *task)
 			struct rpc_xprt *saved = task->tk_xprt;
 			struct rpc_xprt_switch *xps;
 
-			rcu_read_lock();
-			xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
-			rcu_read_unlock();
+			xps = rpc_clnt_xprt_switch_get(clnt);
 			if (xps->xps_nxprts > 1) {
 				long value;
 
@@ -3251,22 +3258,23 @@ void rpc_clnt_xprt_set_online(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
 	struct rpc_xprt_switch *xps;
 
-	rcu_read_lock();
-	xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
-	rcu_read_unlock();
+	xps = rpc_clnt_xprt_switch_get(clnt);
 	xprt_set_online_locked(xprt, xps);
+	xprt_switch_put(xps);
 }
 
 void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
+	struct rpc_xprt_switch *xps;
+
 	if (rpc_clnt_xprt_switch_has_addr(clnt,
 		(const struct sockaddr *)&xprt->addr)) {
 		return rpc_clnt_xprt_set_online(clnt, xprt);
 	}
-	rcu_read_lock();
-	rpc_xprt_switch_add_xprt(rcu_dereference(clnt->cl_xpi.xpi_xpswitch),
-				 xprt);
-	rcu_read_unlock();
+
+	xps = rpc_clnt_xprt_switch_get(clnt);
+	rpc_xprt_switch_add_xprt(xps, xprt);
+	xprt_switch_put(xps);
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_add_xprt);
 
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH v2 4/4] SUNRPC: Fix a suspicious RCU usage warning
  2023-12-04 20:25 [PATCH v2 0/4] SUNRPC: Various RCU fixes Anna Schumaker
                   ` (2 preceding siblings ...)
  2023-12-04 20:25 ` [PATCH v2 3/4] SUNRPC: Create a helper function for accessing the rpc_clnt's xprt_switch Anna Schumaker
@ 2023-12-04 20:25 ` Anna Schumaker
  2023-12-05 10:51   ` Jeff Layton
  3 siblings, 1 reply; 6+ messages in thread
From: Anna Schumaker @ 2023-12-04 20:25 UTC (permalink / raw)
  To: linux-nfs, trond.myklebust; +Cc: anna

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

I received the following warning while running cthon against an ontap
server running pNFS:

[   57.202521] =============================
[   57.202522] WARNING: suspicious RCU usage
[   57.202523] 6.7.0-rc3-g2cc14f52aeb7 #41492 Not tainted
[   57.202525] -----------------------------
[   57.202525] net/sunrpc/xprtmultipath.c:349 RCU-list traversed in non-reader section!!
[   57.202527]
               other info that might help us debug this:

[   57.202528]
               rcu_scheduler_active = 2, debug_locks = 1
[   57.202529] no locks held by test5/3567.
[   57.202530]
               stack backtrace:
[   57.202532] CPU: 0 PID: 3567 Comm: test5 Not tainted 6.7.0-rc3-g2cc14f52aeb7 #41492 5b09971b4965c0aceba19f3eea324a4a806e227e
[   57.202534] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 2/2/2022
[   57.202536] Call Trace:
[   57.202537]  <TASK>
[   57.202540]  dump_stack_lvl+0x77/0xb0
[   57.202551]  lockdep_rcu_suspicious+0x154/0x1a0
[   57.202556]  rpc_xprt_switch_has_addr+0x17c/0x190 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
[   57.202596]  rpc_clnt_setup_test_and_add_xprt+0x50/0x180 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
[   57.202621]  ? rpc_clnt_add_xprt+0x254/0x300 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
[   57.202646]  rpc_clnt_add_xprt+0x27a/0x300 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
[   57.202671]  ? __pfx_rpc_clnt_setup_test_and_add_xprt+0x10/0x10 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
[   57.202696]  nfs4_pnfs_ds_connect+0x345/0x760 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
[   57.202728]  ? __pfx_nfs4_test_session_trunk+0x10/0x10 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
[   57.202754]  nfs4_fl_prepare_ds+0x75/0xc0 [nfs_layout_nfsv41_files e3a4187f18ae8a27b630f9feae6831b584a9360a]
[   57.202760]  filelayout_write_pagelist+0x4a/0x200 [nfs_layout_nfsv41_files e3a4187f18ae8a27b630f9feae6831b584a9360a]
[   57.202765]  pnfs_generic_pg_writepages+0xbe/0x230 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
[   57.202788]  __nfs_pageio_add_request+0x3fd/0x520 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202813]  nfs_pageio_add_request+0x18b/0x390 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202831]  nfs_do_writepage+0x116/0x1e0 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202849]  nfs_writepages_callback+0x13/0x30 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202866]  write_cache_pages+0x265/0x450
[   57.202870]  ? __pfx_nfs_writepages_callback+0x10/0x10 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202891]  nfs_writepages+0x141/0x230 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202913]  do_writepages+0xd2/0x230
[   57.202917]  ? filemap_fdatawrite_wbc+0x5c/0x80
[   57.202921]  filemap_fdatawrite_wbc+0x67/0x80
[   57.202924]  filemap_write_and_wait_range+0xd9/0x170
[   57.202930]  nfs_wb_all+0x49/0x180 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
[   57.202947]  nfs4_file_flush+0x72/0xb0 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
[   57.202969]  __se_sys_close+0x46/0xd0
[   57.202972]  do_syscall_64+0x68/0x100
[   57.202975]  ? do_syscall_64+0x77/0x100
[   57.202976]  ? do_syscall_64+0x77/0x100
[   57.202979]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
[   57.202982] RIP: 0033:0x7fe2b12e4a94
[   57.202985] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 18 0e 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 44 c3 0f 1f 00 48 83 ec 18 89 7c 24 0c e8 c3
[   57.202987] RSP: 002b:00007ffe857ddb38 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
[   57.202989] RAX: ffffffffffffffda RBX: 00007ffe857dfd68 RCX: 00007fe2b12e4a94
[   57.202991] RDX: 0000000000002000 RSI: 00007ffe857ddc40 RDI: 0000000000000003
[   57.202992] RBP: 00007ffe857dfc50 R08: 7fffffffffffffff R09: 0000000065650f49
[   57.202993] R10: 00007fe2b11f8300 R11: 0000000000000202 R12: 0000000000000000
[   57.202994] R13: 00007ffe857dfd80 R14: 00007fe2b1445000 R15: 0000000000000000
[   57.202999]  </TASK>

The problem seems to be that two out of three callers aren't taking the
rcu_read_lock() before calling the list_for_each_entry_rcu() function in
rpc_xprt_switch_has_addr(). I fix this by having
rpc_xprt_switch_has_addr() unconditionaly take the rcu_read_lock(),
which is okay to do recursively in the case that the lock has already
been taken by a caller.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
v2: Don't provide a function bypass to skip taking the rcu_read_lock()
---
 net/sunrpc/xprtmultipath.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/xprtmultipath.c b/net/sunrpc/xprtmultipath.c
index 701250b305db..0706575d9392 100644
--- a/net/sunrpc/xprtmultipath.c
+++ b/net/sunrpc/xprtmultipath.c
@@ -336,8 +336,9 @@ struct rpc_xprt *xprt_iter_current_entry_offline(struct rpc_xprt_iter *xpi)
 			xprt_switch_find_current_entry_offline);
 }
 
-bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
-			      const struct sockaddr *sap)
+static
+bool __rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
+				const struct sockaddr *sap)
 {
 	struct list_head *head;
 	struct rpc_xprt *pos;
@@ -356,6 +357,18 @@ bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
 	return false;
 }
 
+bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
+			      const struct sockaddr *sap)
+{
+	bool res;
+
+	rcu_read_lock();
+	res = __rpc_xprt_switch_has_addr(xps, sap);
+	rcu_read_unlock();
+
+	return res;
+}
+
 static
 struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head,
 		const struct rpc_xprt *cur, bool check_active)
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH v2 4/4] SUNRPC: Fix a suspicious RCU usage warning
  2023-12-04 20:25 ` [PATCH v2 4/4] SUNRPC: Fix a suspicious RCU usage warning Anna Schumaker
@ 2023-12-05 10:51   ` Jeff Layton
  0 siblings, 0 replies; 6+ messages in thread
From: Jeff Layton @ 2023-12-05 10:51 UTC (permalink / raw)
  To: Anna Schumaker, linux-nfs, trond.myklebust

On Mon, 2023-12-04 at 15:25 -0500, Anna Schumaker wrote:
> From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> 
> I received the following warning while running cthon against an ontap
> server running pNFS:
> 
> [   57.202521] =============================
> [   57.202522] WARNING: suspicious RCU usage
> [   57.202523] 6.7.0-rc3-g2cc14f52aeb7 #41492 Not tainted
> [   57.202525] -----------------------------
> [   57.202525] net/sunrpc/xprtmultipath.c:349 RCU-list traversed in non-reader section!!
> [   57.202527]
>                other info that might help us debug this:
> 
> [   57.202528]
>                rcu_scheduler_active = 2, debug_locks = 1
> [   57.202529] no locks held by test5/3567.
> [   57.202530]
>                stack backtrace:
> [   57.202532] CPU: 0 PID: 3567 Comm: test5 Not tainted 6.7.0-rc3-g2cc14f52aeb7 #41492 5b09971b4965c0aceba19f3eea324a4a806e227e
> [   57.202534] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 2/2/2022
> [   57.202536] Call Trace:
> [   57.202537]  <TASK>
> [   57.202540]  dump_stack_lvl+0x77/0xb0
> [   57.202551]  lockdep_rcu_suspicious+0x154/0x1a0
> [   57.202556]  rpc_xprt_switch_has_addr+0x17c/0x190 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
> [   57.202596]  rpc_clnt_setup_test_and_add_xprt+0x50/0x180 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
> [   57.202621]  ? rpc_clnt_add_xprt+0x254/0x300 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
> [   57.202646]  rpc_clnt_add_xprt+0x27a/0x300 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
> [   57.202671]  ? __pfx_rpc_clnt_setup_test_and_add_xprt+0x10/0x10 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6]
> [   57.202696]  nfs4_pnfs_ds_connect+0x345/0x760 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
> [   57.202728]  ? __pfx_nfs4_test_session_trunk+0x10/0x10 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
> [   57.202754]  nfs4_fl_prepare_ds+0x75/0xc0 [nfs_layout_nfsv41_files e3a4187f18ae8a27b630f9feae6831b584a9360a]
> [   57.202760]  filelayout_write_pagelist+0x4a/0x200 [nfs_layout_nfsv41_files e3a4187f18ae8a27b630f9feae6831b584a9360a]
> [   57.202765]  pnfs_generic_pg_writepages+0xbe/0x230 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
> [   57.202788]  __nfs_pageio_add_request+0x3fd/0x520 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202813]  nfs_pageio_add_request+0x18b/0x390 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202831]  nfs_do_writepage+0x116/0x1e0 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202849]  nfs_writepages_callback+0x13/0x30 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202866]  write_cache_pages+0x265/0x450
> [   57.202870]  ? __pfx_nfs_writepages_callback+0x10/0x10 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202891]  nfs_writepages+0x141/0x230 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202913]  do_writepages+0xd2/0x230
> [   57.202917]  ? filemap_fdatawrite_wbc+0x5c/0x80
> [   57.202921]  filemap_fdatawrite_wbc+0x67/0x80
> [   57.202924]  filemap_write_and_wait_range+0xd9/0x170
> [   57.202930]  nfs_wb_all+0x49/0x180 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902]
> [   57.202947]  nfs4_file_flush+0x72/0xb0 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9]
> [   57.202969]  __se_sys_close+0x46/0xd0
> [   57.202972]  do_syscall_64+0x68/0x100
> [   57.202975]  ? do_syscall_64+0x77/0x100
> [   57.202976]  ? do_syscall_64+0x77/0x100
> [   57.202979]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
> [   57.202982] RIP: 0033:0x7fe2b12e4a94
> [   57.202985] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 18 0e 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 44 c3 0f 1f 00 48 83 ec 18 89 7c 24 0c e8 c3
> [   57.202987] RSP: 002b:00007ffe857ddb38 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
> [   57.202989] RAX: ffffffffffffffda RBX: 00007ffe857dfd68 RCX: 00007fe2b12e4a94
> [   57.202991] RDX: 0000000000002000 RSI: 00007ffe857ddc40 RDI: 0000000000000003
> [   57.202992] RBP: 00007ffe857dfc50 R08: 7fffffffffffffff R09: 0000000065650f49
> [   57.202993] R10: 00007fe2b11f8300 R11: 0000000000000202 R12: 0000000000000000
> [   57.202994] R13: 00007ffe857dfd80 R14: 00007fe2b1445000 R15: 0000000000000000
> [   57.202999]  </TASK>
> 
> The problem seems to be that two out of three callers aren't taking the
> rcu_read_lock() before calling the list_for_each_entry_rcu() function in
> rpc_xprt_switch_has_addr(). I fix this by having
> rpc_xprt_switch_has_addr() unconditionaly take the rcu_read_lock(),
> which is okay to do recursively in the case that the lock has already
> been taken by a caller.
> 
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> ---
> v2: Don't provide a function bypass to skip taking the rcu_read_lock()
> ---
>  net/sunrpc/xprtmultipath.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/xprtmultipath.c b/net/sunrpc/xprtmultipath.c
> index 701250b305db..0706575d9392 100644
> --- a/net/sunrpc/xprtmultipath.c
> +++ b/net/sunrpc/xprtmultipath.c
> @@ -336,8 +336,9 @@ struct rpc_xprt *xprt_iter_current_entry_offline(struct rpc_xprt_iter *xpi)
>  			xprt_switch_find_current_entry_offline);
>  }
>  
> -bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
> -			      const struct sockaddr *sap)
> +static
> +bool __rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
> +				const struct sockaddr *sap)
>  {
>  	struct list_head *head;
>  	struct rpc_xprt *pos;
> @@ -356,6 +357,18 @@ bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
>  	return false;
>  }
>  
> +bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
> +			      const struct sockaddr *sap)
> +{
> +	bool res;
> +
> +	rcu_read_lock();
> +	res = __rpc_xprt_switch_has_addr(xps, sap);
> +	rcu_read_unlock();
> +
> +	return res;
> +}
> +
>  static
>  struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head,
>  		const struct rpc_xprt *cur, bool check_active)

Reviewed-by: Jeff Layton <jlayton@kernel.org>

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-12-05 10:51 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-12-04 20:25 [PATCH v2 0/4] SUNRPC: Various RCU fixes Anna Schumaker
2023-12-04 20:25 ` [PATCH v2 1/4] SUNRPC: Clean up unused variable in rpc_xprt_probe_trunked() Anna Schumaker
2023-12-04 20:25 ` [PATCH v2 2/4] SUNRPC: Remove unused function rpc_clnt_xprt_switch_put() Anna Schumaker
2023-12-04 20:25 ` [PATCH v2 3/4] SUNRPC: Create a helper function for accessing the rpc_clnt's xprt_switch Anna Schumaker
2023-12-04 20:25 ` [PATCH v2 4/4] SUNRPC: Fix a suspicious RCU usage warning Anna Schumaker
2023-12-05 10:51   ` Jeff Layton

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