[PATCH 0/3] afs: Miscellaneous fixes

[PATCH 0/3] afs: Miscellaneous fixes

[David Howells]

Here are some fixes for AFS:

 (1) Fix a tracepoint that causes one of the tracing subsystem query files
     to crash if the module is loaded[1].

 (2) Fix afs_writepages() to take account of whether the storage rpc
     actually succeeded when updating the cyclic writeback counter[2].

 (3) Fix some error code propagation/handling[3].

The patches can be found here:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-fixes

David

Link: https://lore.kernel.org/r/162430903582.2896199.6098150063997983353.stgit@warthog.procyon.org.uk/ [1]
Link: https://lore.kernel.org/r/20210430155031.3287870-1-trix@redhat.com [2]
Link: https://lore.kernel.org/r/1619691492-83866-1-git-send-email-jiapeng.chong@linux.alibaba.com [3]

---
David Howells (1):
      afs: Fix tracepoint string placement with built-in AFS

Jiapeng Chong (1):
      afs: Remove redundant assignment to ret

Tom Rix (1):
      afs: check function return


 fs/afs/dir.c   | 10 ++++++----
 fs/afs/write.c |  2 +-
 2 files changed, 7 insertions(+), 5 deletions(-)

[PATCH 1/3] afs: Fix tracepoint string placement with built-in AFS

[David Howells]

To quote Alexey[1]:

    I was adding custom tracepoint to the kernel, grabbed full F34 kernel
    .config, disabled modules and booted whole shebang as VM kernel.

    Then did

	perf record -a -e ...

    It crashed:

	general protection fault, probably for non-canonical address 0x435f5346592e4243: 0000 [#1] SMP PTI
	CPU: 1 PID: 842 Comm: cat Not tainted 5.12.6+ #26
	Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
	RIP: 0010:t_show+0x22/0xd0

    Then reproducer was narrowed to

	# cat /sys/kernel/tracing/printk_formats

    Original F34 kernel with modules didn't crash.

    So I started to disable options and after disabling AFS everything
    started working again.

    The root cause is that AFS was placing char arrays content into a
    section full of _pointers_ to strings with predictable consequences.

    Non canonical address 435f5346592e4243 is "CB.YFS_" which came from
    CM_NAME macro.

    Steps to reproduce:

	CONFIG_AFS=y
	CONFIG_TRACING=y

	# cat /sys/kernel/tracing/printk_formats

Fix this by the following means:

 (1) Add enum->string translation tables in the event header with the AFS
     and YFS cache/callback manager operations listed by RPC operation ID.

 (2) Modify the afs_cb_call tracepoint to print the string from the
     translation table rather than using the string at the afs_call name
     pointer.

 (3) Switch translation table depending on the service we're being accessed
     as (AFS or YFS) in the tracepoint print clause.  Will this cause
     problems to userspace utilities?

     Note that the symbolic representation of the YFS service ID isn't
     available to this header, so I've put it in as a number.  I'm not sure
     if this is the best way to do this.

 (4) Remove the name wrangling (CM_NAME) macro and put the names directly
     into the afs_call_type structs in cmservice.c.

Fixes: 8e8d7f13b6d5a9 ("afs: Add some tracepoints")
Reported-by: Alexey Dobriyan (SK hynix) <adobriyan@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/YLAXfvZ+rObEOdc%2F@localhost.localdomain/ [1]
Link: https://lore.kernel.org/r/643721.1623754699@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/162430903582.2896199.6098150063997983353.stgit@warthog.procyon.org.uk/ # v1
---

 fs/afs/cmservice.c         |   25 +++++-----------
 include/trace/events/afs.h |   67 +++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 69 insertions(+), 23 deletions(-)

diff --git a/fs/afs/cmservice.c b/fs/afs/cmservice.c
index d3c6bb22c5f4..a3f5de28be79 100644
--- a/fs/afs/cmservice.c
+++ b/fs/afs/cmservice.c
@@ -29,16 +29,11 @@ static void SRXAFSCB_TellMeAboutYourself(struct work_struct *);
 
 static int afs_deliver_yfs_cb_callback(struct afs_call *);
 
-#define CM_NAME(name) \
-	char afs_SRXCB##name##_name[] __tracepoint_string =	\
-		"CB." #name
-
 /*
  * CB.CallBack operation type
  */
-static CM_NAME(CallBack);
 static const struct afs_call_type afs_SRXCBCallBack = {
-	.name		= afs_SRXCBCallBack_name,
+	.name		= "CB.CallBack",
 	.deliver	= afs_deliver_cb_callback,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_CallBack,
@@ -47,9 +42,8 @@ static const struct afs_call_type afs_SRXCBCallBack = {
 /*
  * CB.InitCallBackState operation type
  */
-static CM_NAME(InitCallBackState);
 static const struct afs_call_type afs_SRXCBInitCallBackState = {
-	.name		= afs_SRXCBInitCallBackState_name,
+	.name		= "CB.InitCallBackState",
 	.deliver	= afs_deliver_cb_init_call_back_state,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_InitCallBackState,
@@ -58,9 +52,8 @@ static const struct afs_call_type afs_SRXCBInitCallBackState = {
 /*
  * CB.InitCallBackState3 operation type
  */
-static CM_NAME(InitCallBackState3);
 static const struct afs_call_type afs_SRXCBInitCallBackState3 = {
-	.name		= afs_SRXCBInitCallBackState3_name,
+	.name		= "CB.InitCallBackState3",
 	.deliver	= afs_deliver_cb_init_call_back_state3,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_InitCallBackState,
@@ -69,9 +62,8 @@ static const struct afs_call_type afs_SRXCBInitCallBackState3 = {
 /*
  * CB.Probe operation type
  */
-static CM_NAME(Probe);
 static const struct afs_call_type afs_SRXCBProbe = {
-	.name		= afs_SRXCBProbe_name,
+	.name		= "CB.Probe",
 	.deliver	= afs_deliver_cb_probe,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_Probe,
@@ -80,9 +72,8 @@ static const struct afs_call_type afs_SRXCBProbe = {
 /*
  * CB.ProbeUuid operation type
  */
-static CM_NAME(ProbeUuid);
 static const struct afs_call_type afs_SRXCBProbeUuid = {
-	.name		= afs_SRXCBProbeUuid_name,
+	.name		= "CB.ProbeUuid",
 	.deliver	= afs_deliver_cb_probe_uuid,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_ProbeUuid,
@@ -91,9 +82,8 @@ static const struct afs_call_type afs_SRXCBProbeUuid = {
 /*
  * CB.TellMeAboutYourself operation type
  */
-static CM_NAME(TellMeAboutYourself);
 static const struct afs_call_type afs_SRXCBTellMeAboutYourself = {
-	.name		= afs_SRXCBTellMeAboutYourself_name,
+	.name		= "CB.TellMeAboutYourself",
 	.deliver	= afs_deliver_cb_tell_me_about_yourself,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_TellMeAboutYourself,
@@ -102,9 +92,8 @@ static const struct afs_call_type afs_SRXCBTellMeAboutYourself = {
 /*
  * YFS CB.CallBack operation type
  */
-static CM_NAME(YFS_CallBack);
 static const struct afs_call_type afs_SRXYFSCB_CallBack = {
-	.name		= afs_SRXCBYFS_CallBack_name,
+	.name		= "YFSCB.CallBack",
 	.deliver	= afs_deliver_yfs_cb_callback,
 	.destructor	= afs_cm_destructor,
 	.work		= SRXAFSCB_CallBack,
diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index 3ccf591b2374..9f73ed2cf061 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -174,6 +174,34 @@ enum afs_vl_operation {
 	afs_VL_GetCapabilities	= 65537,	/* AFS Get VL server capabilities */
 };
 
+enum afs_cm_operation {
+	afs_CB_CallBack			= 204,	/* AFS break callback promises */
+	afs_CB_InitCallBackState	= 205,	/* AFS initialise callback state */
+	afs_CB_Probe			= 206,	/* AFS probe client */
+	afs_CB_GetLock			= 207,	/* AFS get contents of CM lock table */
+	afs_CB_GetCE			= 208,	/* AFS get cache file description */
+	afs_CB_GetXStatsVersion		= 209,	/* AFS get version of extended statistics */
+	afs_CB_GetXStats		= 210,	/* AFS get contents of extended statistics data */
+	afs_CB_InitCallBackState3	= 213,	/* AFS initialise callback state, version 3 */
+	afs_CB_ProbeUuid		= 214,	/* AFS check the client hasn't rebooted */
+};
+
+enum yfs_cm_operation {
+	yfs_CB_Probe			= 206,	/* YFS probe client */
+	yfs_CB_GetLock			= 207,	/* YFS get contents of CM lock table */
+	yfs_CB_XStatsVersion		= 209,	/* YFS get version of extended statistics */
+	yfs_CB_GetXStats		= 210,	/* YFS get contents of extended statistics data */
+	yfs_CB_InitCallBackState3	= 213,	/* YFS initialise callback state, version 3 */
+	yfs_CB_ProbeUuid		= 214,	/* YFS check the client hasn't rebooted */
+	yfs_CB_GetServerPrefs		= 215,
+	yfs_CB_GetCellServDV		= 216,
+	yfs_CB_GetLocalCell		= 217,
+	yfs_CB_GetCacheConfig		= 218,
+	yfs_CB_GetCellByNum		= 65537,
+	yfs_CB_TellMeAboutYourself	= 65538, /* get client capabilities */
+	yfs_CB_CallBack			= 64204,
+};
+
 enum afs_edit_dir_op {
 	afs_edit_dir_create,
 	afs_edit_dir_create_error,
@@ -436,6 +464,32 @@ enum afs_cb_break_reason {
 	EM(afs_YFSVL_GetCellName,		"YFSVL.GetCellName") \
 	E_(afs_VL_GetCapabilities,		"VL.GetCapabilities")
 
+#define afs_cm_operations \
+	EM(afs_CB_CallBack,			"CB.CallBack") \
+	EM(afs_CB_InitCallBackState,		"CB.InitCallBackState") \
+	EM(afs_CB_Probe,			"CB.Probe") \
+	EM(afs_CB_GetLock,			"CB.GetLock") \
+	EM(afs_CB_GetCE,			"CB.GetCE") \
+	EM(afs_CB_GetXStatsVersion,		"CB.GetXStatsVersion") \
+	EM(afs_CB_GetXStats,			"CB.GetXStats") \
+	EM(afs_CB_InitCallBackState3,		"CB.InitCallBackState3") \
+	E_(afs_CB_ProbeUuid,			"CB.ProbeUuid")
+
+#define yfs_cm_operations \
+	EM(yfs_CB_Probe,			"YFSCB.Probe") \
+	EM(yfs_CB_GetLock,			"YFSCB.GetLock") \
+	EM(yfs_CB_XStatsVersion,		"YFSCB.XStatsVersion") \
+	EM(yfs_CB_GetXStats,			"YFSCB.GetXStats") \
+	EM(yfs_CB_InitCallBackState3,		"YFSCB.InitCallBackState3") \
+	EM(yfs_CB_ProbeUuid,			"YFSCB.ProbeUuid") \
+	EM(yfs_CB_GetServerPrefs,		"YFSCB.GetServerPrefs") \
+	EM(yfs_CB_GetCellServDV,		"YFSCB.GetCellServDV") \
+	EM(yfs_CB_GetLocalCell,			"YFSCB.GetLocalCell") \
+	EM(yfs_CB_GetCacheConfig,		"YFSCB.GetCacheConfig") \
+	EM(yfs_CB_GetCellByNum,			"YFSCB.GetCellByNum") \
+	EM(yfs_CB_TellMeAboutYourself,		"YFSCB.TellMeAboutYourself") \
+	E_(yfs_CB_CallBack,			"YFSCB.CallBack")
+
 #define afs_edit_dir_ops				  \
 	EM(afs_edit_dir_create,			"create") \
 	EM(afs_edit_dir_create_error,		"c_fail") \
@@ -569,6 +623,8 @@ afs_server_traces;
 afs_cell_traces;
 afs_fs_operations;
 afs_vl_operations;
+afs_cm_operations;
+yfs_cm_operations;
 afs_edit_dir_ops;
 afs_edit_dir_reasons;
 afs_eproto_causes;
@@ -649,20 +705,21 @@ TRACE_EVENT(afs_cb_call,
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
-		    __field(const char *,		name		)
 		    __field(u32,			op		)
+		    __field(u16,			service_id	)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->call	= call->debug_id;
-		    __entry->name	= call->type->name;
 		    __entry->op		= call->operation_ID;
+		    __entry->service_id	= call->service_id;
 			   ),
 
-	    TP_printk("c=%08x %s o=%u",
+	    TP_printk("c=%08x %s",
 		      __entry->call,
-		      __entry->name,
-		      __entry->op)
+		      __entry->service_id == 2501 ?
+		      __print_symbolic(__entry->op, yfs_cm_operations) :
+		      __print_symbolic(__entry->op, afs_cm_operations))
 	    );
 
 TRACE_EVENT(afs_call,

[PATCH 2/3] afs: check function return

[David Howells]

From: Tom Rix <trix@redhat.com>

Static analysis reports this problem

write.c:773:29: warning: Assigned value is garbage or undefined
  mapping->writeback_index = next;
                           ^ ~~~~
The call to afs_writepages_region() can return without setting
next.  So check the function return before using next.

Fixes: e87b03f5830e ("afs: Prepare for use of THPs")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20210430155031.3287870-1-trix@redhat.com
---

 fs/afs/write.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 3104b62c2082..2794147f82ff 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -777,7 +777,7 @@ int afs_writepages(struct address_space *mapping,
 		mapping->writeback_index = next / PAGE_SIZE;
 	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 		ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
-		if (wbc->nr_to_write > 0)
+		if (wbc->nr_to_write > 0 && ret == 0)
 			mapping->writeback_index = next;
 	} else {
 		ret = afs_writepages_region(mapping, wbc,

[PATCH 3/3] afs: Remove redundant assignment to ret

[David Howells]

From: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

Variable ret is set to -ENOENT and -ENOMEM but this value is never
read as it is overwritten or not used later on, hence it is a
redundant assignment and can be removed.

Cleans up the following clang-analyzer warning:

fs/afs/dir.c:2014:4: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].

fs/afs/dir.c:659:2: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].

[DH made the following modifications:

 - In afs_rename(), -ENOMEM should be placed in op->error instead of ret,
   rather than the assignment being removed entirely.  afs_put_operation()
   will pick it up from there and return it.

 - If afs_sillyrename() fails, its error code should be placed in op->error
   rather than in ret also.
]

Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept")
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/1619691492-83866-1-git-send-email-jiapeng.chong@linux.alibaba.com
---

 fs/afs/dir.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 78719f2f567e..ac829e63c570 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -656,7 +656,6 @@ static int afs_do_lookup_one(struct inode *dir, struct dentry *dentry,
 		return ret;
 	}
 
-	ret = -ENOENT;
 	if (!cookie.found) {
 		_leave(" = -ENOENT [not found]");
 		return -ENOENT;
@@ -2020,17 +2019,20 @@ static int afs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 
 		if (d_count(new_dentry) > 2) {
 			/* copy the target dentry's name */
-			ret = -ENOMEM;
 			op->rename.tmp = d_alloc(new_dentry->d_parent,
 						 &new_dentry->d_name);
-			if (!op->rename.tmp)
+			if (!op->rename.tmp) {
+				op->error = -ENOMEM;
 				goto error;
+			}
 
 			ret = afs_sillyrename(new_dvnode,
 					      AFS_FS_I(d_inode(new_dentry)),
 					      new_dentry, op->key);
-			if (ret)
+			if (ret) {
+				op->error = ret;
 				goto error;
+			}
 
 			op->dentry_2 = op->rename.tmp;
 			op->rename.rehash = NULL;

Re: [PATCH 3/3] afs: Remove redundant assignment to ret

[Marc Dionne]

On Mon, Jul 12, 2021 at 9:57 AM David Howells <dhowells@redhat.com> wrote:
>
> From: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
>
> Variable ret is set to -ENOENT and -ENOMEM but this value is never
> read as it is overwritten or not used later on, hence it is a
> redundant assignment and can be removed.
>
> Cleans up the following clang-analyzer warning:
>
> fs/afs/dir.c:2014:4: warning: Value stored to 'ret' is never read
> [clang-analyzer-deadcode.DeadStores].
>
> fs/afs/dir.c:659:2: warning: Value stored to 'ret' is never read
> [clang-analyzer-deadcode.DeadStores].
>
> [DH made the following modifications:
>
>  - In afs_rename(), -ENOMEM should be placed in op->error instead of ret,
>    rather than the assignment being removed entirely.  afs_put_operation()
>    will pick it up from there and return it.
>
>  - If afs_sillyrename() fails, its error code should be placed in op->error
>    rather than in ret also.
> ]
>
> Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept")
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: linux-afs@lists.infradead.org
> Link: https://lore.kernel.org/r/1619691492-83866-1-git-send-email-jiapeng.chong@linux.alibaba.com
> ---
>
>  fs/afs/dir.c |   10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/fs/afs/dir.c b/fs/afs/dir.c
> index 78719f2f567e..ac829e63c570 100644
> --- a/fs/afs/dir.c
> +++ b/fs/afs/dir.c
> @@ -656,7 +656,6 @@ static int afs_do_lookup_one(struct inode *dir, struct dentry *dentry,
>                 return ret;
>         }
>
> -       ret = -ENOENT;
>         if (!cookie.found) {
>                 _leave(" = -ENOENT [not found]");
>                 return -ENOENT;
> @@ -2020,17 +2019,20 @@ static int afs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>
>                 if (d_count(new_dentry) > 2) {
>                         /* copy the target dentry's name */
> -                       ret = -ENOMEM;
>                         op->rename.tmp = d_alloc(new_dentry->d_parent,
>                                                  &new_dentry->d_name);
> -                       if (!op->rename.tmp)
> +                       if (!op->rename.tmp) {
> +                               op->error = -ENOMEM;
>                                 goto error;
> +                       }
>
>                         ret = afs_sillyrename(new_dvnode,
>                                               AFS_FS_I(d_inode(new_dentry)),
>                                               new_dentry, op->key);
> -                       if (ret)
> +                       if (ret) {
> +                               op->error = ret;
>                                 goto error;
> +                       }
>
>                         op->dentry_2 = op->rename.tmp;
>                         op->rename.rehash = NULL;
>
>
>
> _______________________________________________
> linux-afs mailing list
> http://lists.infradead.org/mailman/listinfo/linux-afs

Reviewed-by: Marc Dionne <marc.dionne@auristor.com>

Marc

Re: [PATCH 2/3] afs: check function return

[Marc Dionne]

On Mon, Jul 12, 2021 at 9:57 AM David Howells <dhowells@redhat.com> wrote:
>
> From: Tom Rix <trix@redhat.com>
>
> Static analysis reports this problem
>
> write.c:773:29: warning: Assigned value is garbage or undefined
>   mapping->writeback_index = next;
>                            ^ ~~~~
> The call to afs_writepages_region() can return without setting
> next.  So check the function return before using next.
>
> Fixes: e87b03f5830e ("afs: Prepare for use of THPs")
> Signed-off-by: Tom Rix <trix@redhat.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Link: https://lore.kernel.org/r/20210430155031.3287870-1-trix@redhat.com
> ---
>
>  fs/afs/write.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/afs/write.c b/fs/afs/write.c
> index 3104b62c2082..2794147f82ff 100644
> --- a/fs/afs/write.c
> +++ b/fs/afs/write.c
> @@ -777,7 +777,7 @@ int afs_writepages(struct address_space *mapping,
>                 mapping->writeback_index = next / PAGE_SIZE;

Isn't there the same issue with the use of next here.

>         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
>                 ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
> -               if (wbc->nr_to_write > 0)
> +               if (wbc->nr_to_write > 0 && ret == 0)
>                         mapping->writeback_index = next;

Unrelated to this patch, but since next is a byte offset, should this
also divide by PAGE_SIZE as above.

>         } else {
>                 ret = afs_writepages_region(mapping, wbc,
>
>

Marc

Re: [PATCH 2/3] afs: check function return

[David Howells]

Marc Dionne <marc.c.dionne@gmail.com> wrote:

> > @@ -777,7 +777,7 @@ int afs_writepages(struct address_space *mapping,
> >                 mapping->writeback_index = next / PAGE_SIZE;
> 
> Isn't there the same issue with the use of next here.

Good point.

> >                         mapping->writeback_index = next;
> 
> Unrelated to this patch, but since next is a byte offset, should this
> also divide by PAGE_SIZE as above.

Also a good point.  I'll whip up a separate patch for that.

David