Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-04 Thread Stanislav Kinsburskiy 


03.09.2017 21:23, Dmitry V. Levin P?P8QP5Q:
> On Sat, Sep 02, 2017 at 02:26:26PM +0300, Stanislav Kinsburskiy wrote:
>> 01.09.2017 21:23, Dmitry V. Levin P?P8QP5Q:
>>> On Fri, Sep 01, 2017 at 05:02:45PM +0300, Stanislav Kinsburskiy wrote:
 01.09.2017 16:53, Dmitry V. Levin P?P8QP5Q:
> On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote:
>> 31.08.2017 20:22, Dmitry V. Levin P?P8QP5Q:
>>> On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
 The structure autofs_v5_packet (except name) is not aligned by 8 
 bytes, which
 lead to different sizes in 32 and 64-bit architectures.
 Let's form 32-bit compatible packet when daemon has 32-bit 
 addressation.

 Signed-off-by: Stanislav Kinsburskiy 
 ---
  fs/autofs4/waitq.c |   11 +--
  1 file changed, 9 insertions(+), 2 deletions(-)

 diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
 index 309ca6b..484cf2e 100644
 --- a/fs/autofs4/waitq.c
 +++ b/fs/autofs4/waitq.c
 @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
 autofs_sb_info *sbi,
{
struct autofs_v5_packet *packet = _pkt.v5_packet;
struct user_namespace *user_ns = 
 sbi->pipe->f_cred->user_ns;
 +  size_t name_offset;
  
 -  pktsz = sizeof(*packet);
 +  if (sbi->is32bit)
 +  name_offset = offsetof(struct autofs_v5_packet, 
 len) +
 +sizeof(packet->len);
 +  else
 +  name_offset = offsetof(struct autofs_v5_packet, 
 name);
>>>
>>> This doesn't help at all because the offset of struct 
>>> autofs_v5_packet.name
>>> does not change.
>>>
 +  pktsz = name_offset + sizeof(packet->name);
>>>
>>> What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
>>> or 4 bytes less, depending on the architecture.
>>
>> Indeed. Thanks!
>>
>>> For example,
>>>
>>> #ifdef CONFIG_COMPAT
>>> if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)
>>
>> Unfortunately I don't get this "alignof" checks.
>> The intention of "is32bit" was to define this compat case completely.
>> Why are they required?
>
> On some 32-bit architectures like arm, u64 is 64-bit aligned, on others
> like x86 it is not.  This alignof check ensures that compat 32-bit
> architectures with 64-bit alignment are not going to be broken
> by the change.

 Thanks for the explanation!
 But looks like the issue is hidden so deep (thanks to O_DIRECT), that 
 becomes unimportant.
>>>
>>> I'm not quite sure how O_DIRECT makes this unimportant.
>>> For example, automount_dispatch_io from systemd tries to read exactly
>>> sizeof(union autofs_v5_packet_union) bytes and fails in case of short read.
>>
>> That's weird. Can you reproduce it?
>> The problem is that kernel always send arch packet (i.e. 300 bytes for x86, 
>> or 304 for x86_64).
> 
> Well, if sending a lengthy packet is not a problem, what is the problem
> you were trying to solve by patching struct autofs_v5_packet?
> 

Well, nothing anymore. I took some time to realize, that this issue doesn't 
hurt anyone.
So I fixed our test instead.

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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-03 Thread Dmitry V. Levin 
On Sat, Sep 02, 2017 at 02:26:26PM +0300, Stanislav Kinsburskiy wrote:
> 01.09.2017 21:23, Dmitry V. Levin P?P8QP5Q:
> > On Fri, Sep 01, 2017 at 05:02:45PM +0300, Stanislav Kinsburskiy wrote:
> >> 01.09.2017 16:53, Dmitry V. Levin P?P8QP5Q:
> >>> On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote:
>  31.08.2017 20:22, Dmitry V. Levin P?P8QP5Q:
> > On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
> >> The structure autofs_v5_packet (except name) is not aligned by 8 
> >> bytes, which
> >> lead to different sizes in 32 and 64-bit architectures.
> >> Let's form 32-bit compatible packet when daemon has 32-bit 
> >> addressation.
> >>
> >> Signed-off-by: Stanislav Kinsburskiy 
> >> ---
> >>  fs/autofs4/waitq.c |   11 +--
> >>  1 file changed, 9 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
> >> index 309ca6b..484cf2e 100644
> >> --- a/fs/autofs4/waitq.c
> >> +++ b/fs/autofs4/waitq.c
> >> @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
> >> autofs_sb_info *sbi,
> >>{
> >>struct autofs_v5_packet *packet = _pkt.v5_packet;
> >>struct user_namespace *user_ns = 
> >> sbi->pipe->f_cred->user_ns;
> >> +  size_t name_offset;
> >>  
> >> -  pktsz = sizeof(*packet);
> >> +  if (sbi->is32bit)
> >> +  name_offset = offsetof(struct autofs_v5_packet, 
> >> len) +
> >> +sizeof(packet->len);
> >> +  else
> >> +  name_offset = offsetof(struct autofs_v5_packet, 
> >> name);
> >
> > This doesn't help at all because the offset of struct 
> > autofs_v5_packet.name
> > does not change.
> >
> >> +  pktsz = name_offset + sizeof(packet->name);
> >
> > What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
> > or 4 bytes less, depending on the architecture.
> 
>  Indeed. Thanks!
> 
> > For example,
> >
> > #ifdef CONFIG_COMPAT
> > if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)
> 
>  Unfortunately I don't get this "alignof" checks.
>  The intention of "is32bit" was to define this compat case completely.
>  Why are they required?
> >>>
> >>> On some 32-bit architectures like arm, u64 is 64-bit aligned, on others
> >>> like x86 it is not.  This alignof check ensures that compat 32-bit
> >>> architectures with 64-bit alignment are not going to be broken
> >>> by the change.
> >>
> >> Thanks for the explanation!
> >> But looks like the issue is hidden so deep (thanks to O_DIRECT), that 
> >> becomes unimportant.
> > 
> > I'm not quite sure how O_DIRECT makes this unimportant.
> > For example, automount_dispatch_io from systemd tries to read exactly
> > sizeof(union autofs_v5_packet_union) bytes and fails in case of short read.
> 
> That's weird. Can you reproduce it?
> The problem is that kernel always send arch packet (i.e. 300 bytes for x86, 
> or 304 for x86_64).

Well, if sending a lengthy packet is not a problem, what is the problem
you were trying to solve by patching struct autofs_v5_packet?


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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-02 Thread Stanislav Kinsburskiy 


01.09.2017 21:23, Dmitry V. Levin P?P8QP5Q:
> On Fri, Sep 01, 2017 at 05:02:45PM +0300, Stanislav Kinsburskiy wrote:
>>
>>
>> 01.09.2017 16:53, Dmitry V. Levin P?P8QP5Q:
>>> On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote:
 31.08.2017 20:22, Dmitry V. Levin P?P8QP5Q:
> On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
>> The structure autofs_v5_packet (except name) is not aligned by 8 bytes, 
>> which
>> lead to different sizes in 32 and 64-bit architectures.
>> Let's form 32-bit compatible packet when daemon has 32-bit addressation.
>>
>> Signed-off-by: Stanislav Kinsburskiy 
>> ---
>>  fs/autofs4/waitq.c |   11 +--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
>> index 309ca6b..484cf2e 100644
>> --- a/fs/autofs4/waitq.c
>> +++ b/fs/autofs4/waitq.c
>> @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
>> autofs_sb_info *sbi,
>>  {
>>  struct autofs_v5_packet *packet = _pkt.v5_packet;
>>  struct user_namespace *user_ns = 
>> sbi->pipe->f_cred->user_ns;
>> +size_t name_offset;
>>  
>> -pktsz = sizeof(*packet);
>> +if (sbi->is32bit)
>> +name_offset = offsetof(struct autofs_v5_packet, 
>> len) +
>> +  sizeof(packet->len);
>> +else
>> +name_offset = offsetof(struct autofs_v5_packet, 
>> name);
>
> This doesn't help at all because the offset of struct 
> autofs_v5_packet.name
> does not change.
>
>> +pktsz = name_offset + sizeof(packet->name);
>
> What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
> or 4 bytes less, depending on the architecture.

 Indeed. Thanks!

> For example,
>
> #ifdef CONFIG_COMPAT
>   if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)

 Unfortunately I don't get this "alignof" checks.
 The intention of "is32bit" was to define this compat case completely.
 Why are they required?
>>>
>>> On some 32-bit architectures like arm, u64 is 64-bit aligned, on others
>>> like x86 it is not.  This alignof check ensures that compat 32-bit
>>> architectures with 64-bit alignment are not going to be broken
>>> by the change.
>>
>> Thanks for the explanation!
>> But looks like the issue is hidden so deep (thanks to O_DIRECT), that 
>> becomes unimportant.
> 
> I'm not quite sure how O_DIRECT makes this unimportant.
> For example, automount_dispatch_io from systemd tries to read exactly
> sizeof(union autofs_v5_packet_union) bytes and fails in case of short read.
> 

That's weird. Can you reproduce it?
The problem is that kernel always send arch packet (i.e. 300 bytes for x86, or 
304 for x86_64).
So, how can systemd get less? It can get more, but only if it'll try to read 
more.
Otherwise, as "man pipe(2)" says:

*  If a read(2) specifies a buffer size that is smaller than the next packet, 
then the requested number of bytes are read, and the excess bytes in the packet 
are discarded.

> 
> 
> 
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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-01 Thread Dmitry V. Levin 
On Fri, Sep 01, 2017 at 05:02:45PM +0300, Stanislav Kinsburskiy wrote:
> 
> 
> 01.09.2017 16:53, Dmitry V. Levin P?P8QP5Q:
> > On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote:
> >> 31.08.2017 20:22, Dmitry V. Levin P?P8QP5Q:
> >>> On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
>  The structure autofs_v5_packet (except name) is not aligned by 8 bytes, 
>  which
>  lead to different sizes in 32 and 64-bit architectures.
>  Let's form 32-bit compatible packet when daemon has 32-bit addressation.
> 
>  Signed-off-by: Stanislav Kinsburskiy 
>  ---
>   fs/autofs4/waitq.c |   11 +--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
>  diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
>  index 309ca6b..484cf2e 100644
>  --- a/fs/autofs4/waitq.c
>  +++ b/fs/autofs4/waitq.c
>  @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
>  autofs_sb_info *sbi,
>   {
>   struct autofs_v5_packet *packet = _pkt.v5_packet;
>   struct user_namespace *user_ns = 
>  sbi->pipe->f_cred->user_ns;
>  +size_t name_offset;
>   
>  -pktsz = sizeof(*packet);
>  +if (sbi->is32bit)
>  +name_offset = offsetof(struct autofs_v5_packet, 
>  len) +
>  +  sizeof(packet->len);
>  +else
>  +name_offset = offsetof(struct autofs_v5_packet, 
>  name);
> >>>
> >>> This doesn't help at all because the offset of struct 
> >>> autofs_v5_packet.name
> >>> does not change.
> >>>
>  +pktsz = name_offset + sizeof(packet->name);
> >>>
> >>> What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
> >>> or 4 bytes less, depending on the architecture.
> >>
> >> Indeed. Thanks!
> >>
> >>> For example,
> >>>
> >>> #ifdef CONFIG_COMPAT
> >>>   if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)
> >>
> >> Unfortunately I don't get this "alignof" checks.
> >> The intention of "is32bit" was to define this compat case completely.
> >> Why are they required?
> > 
> > On some 32-bit architectures like arm, u64 is 64-bit aligned, on others
> > like x86 it is not.  This alignof check ensures that compat 32-bit
> > architectures with 64-bit alignment are not going to be broken
> > by the change.
> 
> Thanks for the explanation!
> But looks like the issue is hidden so deep (thanks to O_DIRECT), that becomes 
> unimportant.

I'm not quite sure how O_DIRECT makes this unimportant.
For example, automount_dispatch_io from systemd tries to read exactly
sizeof(union autofs_v5_packet_union) bytes and fails in case of short read.


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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-01 Thread Stanislav Kinsburskiy 


01.09.2017 16:53, Dmitry V. Levin P?P8QP5Q:
> On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote:
>> 31.08.2017 20:22, Dmitry V. Levin P?P8QP5Q:
>>> On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
 The structure autofs_v5_packet (except name) is not aligned by 8 bytes, 
 which
 lead to different sizes in 32 and 64-bit architectures.
 Let's form 32-bit compatible packet when daemon has 32-bit addressation.

 Signed-off-by: Stanislav Kinsburskiy 
 ---
  fs/autofs4/waitq.c |   11 +--
  1 file changed, 9 insertions(+), 2 deletions(-)

 diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
 index 309ca6b..484cf2e 100644
 --- a/fs/autofs4/waitq.c
 +++ b/fs/autofs4/waitq.c
 @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
 autofs_sb_info *sbi,
{
struct autofs_v5_packet *packet = _pkt.v5_packet;
struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 +  size_t name_offset;
  
 -  pktsz = sizeof(*packet);
 +  if (sbi->is32bit)
 +  name_offset = offsetof(struct autofs_v5_packet, len) +
 +sizeof(packet->len);
 +  else
 +  name_offset = offsetof(struct autofs_v5_packet, name);
>>>
>>> This doesn't help at all because the offset of struct autofs_v5_packet.name
>>> does not change.
>>>
 +  pktsz = name_offset + sizeof(packet->name);
>>>
>>> What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
>>> or 4 bytes less, depending on the architecture.
>>
>> Indeed. Thanks!
>>
>>> For example,
>>>
>>> #ifdef CONFIG_COMPAT
>>> if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)
>>
>> Unfortunately I don't get this "alignof" checks.
>> The intention of "is32bit" was to define this compat case completely.
>> Why are they required?
> 
> On some 32-bit architectures like arm, u64 is 64-bit aligned, on others
> like x86 it is not.  This alignof check ensures that compat 32-bit
> architectures with 64-bit alignment are not going to be broken
> by the change.
> 

Thanks for the explanation!
But looks like the issue is hidden so deep (thanks to O_DIRECT), that becomes 
unimportant.

> 
> 
> 
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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-01 Thread Dmitry V. Levin 
On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote:
> 31.08.2017 20:22, Dmitry V. Levin пишет:
> > On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
> >> The structure autofs_v5_packet (except name) is not aligned by 8 bytes, 
> >> which
> >> lead to different sizes in 32 and 64-bit architectures.
> >> Let's form 32-bit compatible packet when daemon has 32-bit addressation.
> >>
> >> Signed-off-by: Stanislav Kinsburskiy 
> >> ---
> >>  fs/autofs4/waitq.c |   11 +--
> >>  1 file changed, 9 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
> >> index 309ca6b..484cf2e 100644
> >> --- a/fs/autofs4/waitq.c
> >> +++ b/fs/autofs4/waitq.c
> >> @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
> >> autofs_sb_info *sbi,
> >>{
> >>struct autofs_v5_packet *packet = _pkt.v5_packet;
> >>struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
> >> +  size_t name_offset;
> >>  
> >> -  pktsz = sizeof(*packet);
> >> +  if (sbi->is32bit)
> >> +  name_offset = offsetof(struct autofs_v5_packet, len) +
> >> +sizeof(packet->len);
> >> +  else
> >> +  name_offset = offsetof(struct autofs_v5_packet, name);
> > 
> > This doesn't help at all because the offset of struct autofs_v5_packet.name
> > does not change.
> > 
> >> +  pktsz = name_offset + sizeof(packet->name);
> > 
> > What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
> > or 4 bytes less, depending on the architecture.
> 
> Indeed. Thanks!
> 
> > For example,
> > 
> > #ifdef CONFIG_COMPAT
> > if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)
> 
> Unfortunately I don't get this "alignof" checks.
> The intention of "is32bit" was to define this compat case completely.
> Why are they required?

On some 32-bit architectures like arm, u64 is 64-bit aligned, on others
like x86 it is not.  This alignof check ensures that compat 32-bit
architectures with 64-bit alignment are not going to be broken
by the change.


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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-09-01 Thread Stanislav Kinsburskiy 


31.08.2017 20:22, Dmitry V. Levin пишет:
> On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
>> The structure autofs_v5_packet (except name) is not aligned by 8 bytes, which
>> lead to different sizes in 32 and 64-bit architectures.
>> Let's form 32-bit compatible packet when daemon has 32-bit addressation.
>>
>> Signed-off-by: Stanislav Kinsburskiy 
>> ---
>>  fs/autofs4/waitq.c |   11 +--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
>> index 309ca6b..484cf2e 100644
>> --- a/fs/autofs4/waitq.c
>> +++ b/fs/autofs4/waitq.c
>> @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct 
>> autofs_sb_info *sbi,
>>  {
>>  struct autofs_v5_packet *packet = _pkt.v5_packet;
>>  struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
>> +size_t name_offset;
>>  
>> -pktsz = sizeof(*packet);
>> +if (sbi->is32bit)
>> +name_offset = offsetof(struct autofs_v5_packet, len) +
>> +  sizeof(packet->len);
>> +else
>> +name_offset = offsetof(struct autofs_v5_packet, name);
> 
> This doesn't help at all because the offset of struct autofs_v5_packet.name
> does not change.
> 
>> +pktsz = name_offset + sizeof(packet->name);
> 
> What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
> or 4 bytes less, depending on the architecture.

Indeed. Thanks!

> For example,
> 
> #ifdef CONFIG_COMPAT
>   if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)

Unfortunately I don't get this "alignof" checks.
The intention of "is32bit" was to define this compat case completely.
Why are they required?

>   pktsz = offsetofend(struct autofs_v5_packet, name);
>   else
> #endif
>   pktsz = sizeof(*packet);
> 
> 



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Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process

2017-08-31 Thread Dmitry V. Levin 
On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote:
> The structure autofs_v5_packet (except name) is not aligned by 8 bytes, which
> lead to different sizes in 32 and 64-bit architectures.
> Let's form 32-bit compatible packet when daemon has 32-bit addressation.
> 
> Signed-off-by: Stanislav Kinsburskiy 
> ---
>  fs/autofs4/waitq.c |   11 +--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
> index 309ca6b..484cf2e 100644
> --- a/fs/autofs4/waitq.c
> +++ b/fs/autofs4/waitq.c
> @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct autofs_sb_info 
> *sbi,
>   {
>   struct autofs_v5_packet *packet = _pkt.v5_packet;
>   struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
> + size_t name_offset;
>  
> - pktsz = sizeof(*packet);
> + if (sbi->is32bit)
> + name_offset = offsetof(struct autofs_v5_packet, len) +
> +   sizeof(packet->len);
> + else
> + name_offset = offsetof(struct autofs_v5_packet, name);

This doesn't help at all because the offset of struct autofs_v5_packet.name
does not change.

> + pktsz = name_offset + sizeof(packet->name);

What changes is pktsz: it's either sizeof(struct autofs_v5_packet)
or 4 bytes less, depending on the architecture.  For example,

#ifdef CONFIG_COMPAT
if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit)
pktsz = offsetofend(struct autofs_v5_packet, name);
else
#endif
pktsz = sizeof(*packet);


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