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6f52b16c |
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01-Nov-2017 |
Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
License cleanup: add SPDX license identifier to uapi header files with no license
Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.
By default are files without license information under the default
license of the kernel, which is GPLV2. Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:
NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".
otherwise syscall usage would not be possible.
Update the files which contain no license information with an SPDX
license identifier. The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception. SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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e067eba5 |
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22-Feb-2017 |
Andrea Arcangeli <aarcange@redhat.com> |
userfaultfd: document _IOR/_IOW
Patch series "userfaultfd tmpfs/hugetlbfs/non-cooperative", v2
These userfaultfd features are finished and are ready for larger
exposure in -mm and upstream merging.
1) tmpfs non present userfault
2) hugetlbfs non present userfault
3) non cooperative userfault for fork/madvise/mremap
qemu development code is already exercising 2) and container postcopy
live migration needs 3).
1) is not currently used but there's a self test and we know some qemu
user for various reasons uses tmpfs as backing for KVM so it'll need it
too to use postcopy live migration with tmpfs memory.
All review feedback from the previous submit has been handled and the
fixes are included. There's no outstanding issue AFIK.
Upstream code just did a s/fe/vmf/ conversion in the page faults and
this has been converted as well incrementally.
In addition to the previous submits, this also wakes up stuck userfaults
during UFFDIO_UNREGISTER. The non cooperative testcase actually
reproduced this problem by getting stuck instead of quitting clean in
some rare case as it could call UFFDIO_UNREGISTER while some userfault
could be still in flight. The other option would have been to keep
leaving it up to userland to serialize itself and to patch the testcase
instead but the wakeup during unregister I think is preferable.
David also asked the UFFD_FEATURE_MISSING_HUGETLBFS and
UFFD_FEATURE_MISSING_SHMEM feature flags to be added so QEMU can avoid
to probe if the hugetlbfs/shmem missing support is available by calling
UFFDIO_REGISTER. QEMU already checks HUGETLBFS_MAGIC with fstatfs so if
UFFD_FEATURE_MISSING_HUGETLBFS is also set, it knows UFFDIO_REGISTER
will succeed (or if it fails, it's for some other more concerning
reason). There's no reason to worry about adding too many feature
flags. There are 64 available and worst case we've to bump the API if
someday we're really going to run out of them.
The round-trip network latency of hugetlbfs userfaults during postcopy
live migration is still of the order of dozen milliseconds on 10GBit if
at 2MB hugepage granularity so it's working perfectly and it should
provide for higher bandwidth or lower CPU usage (which makes it
interesting to add an option in the future to support THP granularity
too for anonymous memory, UFFDIO_COPY would then have to create THP if
alignment/len allows for it). 1GB hugetlbfs granularity will require
big changes in hugetlbfs to work so it's deferred for later.
This patch (of 42):
This adds proper documentation (inline) to avoid the risk of further
misunderstandings about the semantics of _IOW/_IOR and it also reminds
whoever will bump the UFFDIO_API in the future, to change the two ioctl
to _IOW.
This was found while implementing strace support for those ioctl,
otherwise we could have never found it by just reviewing kernel code and
testing it.
_IOC_READ or _IOC_WRITE alters nothing but the ioctl number itself, so
it's only worth fixing if the UFFDIO_API is bumped someday.
Link: http://lkml.kernel.org/r/20161216144821.5183-2-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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