[Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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); + + pktsz = name_offset + sizeof(packet->name); packet->wait_queue_token = wq->wait_queue_token; packet->len = wq->name.len; - memcpy(packet->name, wq->name.name, wq->name.len); + memcpy(packet + name_offset, wq->name.name, wq->name.len); packet->name[wq->name.len] = '\0'; packet->dev = wq->dev; packet->ino = wq->ino; ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
[Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
The structure autofs_v5_packet (except name) is not aligned by 8 bytes, which leads to different sizes in 32 and 64-bit architectures. Let's form 32-bit compatible packet when daemon has 32-bit addressation. Suggested-by: Dmitry V. Levin Signed-off-by: Stanislav Kinsburskiy --- fs/autofs4/waitq.c |5 + 1 file changed, 5 insertions(+) diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c index 24a58bf..1f9b7d8 100644 --- a/fs/autofs4/waitq.c +++ b/fs/autofs4/waitq.c @@ -151,6 +151,11 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi, struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet; struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns; +#ifdef CONFIG_COMPAT + if (sbi->is32bit) + pktsz = offsetofend(struct autofs_v5_packet, name); + else +#endif pktsz = sizeof(*packet); packet->wait_queue_token = wq->wait_queue_token; ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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); -- ldv signature.asc Description: PGP signature ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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); > > ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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. -- ldv signature.asc Description: PGP signature ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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. > > > > ___ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel > ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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. -- ldv signature.asc Description: PGP signature ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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. > > > > ___ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel > ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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? -- ldv signature.asc Description: PGP signature ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
Re: [Devel] [RFC PATCH 2/2] autofs: sent 32-bit sized packet for 32-bit process
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_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. ___ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel