OpenAFS Master Repository branch, master, updated. openafs-devel-1_9_0-103-g78ef922

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 78ef922612bef5f5fd6904896e84b9d2ea802404
Author: Cheyenne Wills <cwills@sinenomine.net>
Date:   Fri Jan 22 07:57:55 2021 -0700

    Linux 5.11: Test 32bit compat with in_compat_syscall
    
    Linux 5.11 removed the TIF_IA32 thread flag with commit:
      x86: Reclaim TIF_IA32 and TIF_X32 (8d71d2bf6efec)
    
    The flag TIF_IA32 was being used by openafs to determine if the task was
    handling a syscall request from a 32 bit process.  Building against a
    Linux 5.11 kernel results in a build failure as TIF_IA32 is undefined.
    
    The function 'in_compat_syscall' was introduced in Linux 4.6 as
    the preferred method to determine if a syscall needed to handle a
    compatible call (e.g. 32bit application).
    
    To resolve the build problem, use 'in_compat_syscall' if present (Linux
    4.6 and later) to determine if the syscall needs to handle a
    compatibility mode call.
    
    Add autoconf check for in_compat_syscall.
    
    Notes about in_compat_syscall:
    
    In Linux 4.6 'in_compat_syscall' was defined for all architectures with
    a generic return of 'is_compat_task', but allows architecture specific
    overriding implementations (x86 and sparc).
    
    At 4.6 (and later), the function 'is_compat_task' is defined only for
    the following architectures to return:
    
    Arch              Returns
    =======           ==============================
    arm64             test_thread_flag(TIF_32BIT);
    mips              test_thread_flag(TIF_32BIT_ADDR)
    parisc            test_ti_thread_flag(task_thread_info(t), TIF_32BIT)
    powerpc           is_32bit_task()
    s390              test_thread_flag(TIF_31BIT)
    sparc             test_thread_flag(TIF_32BIT)
    
    If the Linux kernel is not built with compat mode, is_compat_task and
    in_compat_syscall is set to always return 0
    
    Linux commit that introduced in_compat_syscall:
      compat: add in_compat_syscall to ask whether we're in a compat syscall
      (5180e3e24fd3e8e7)
    
    Change-Id: I59deebfe5d8cddaf845b15ef69e65a684a961280
    Reviewed-on: https://gerrit.openafs.org/14499
    Reviewed-by: Andrew Deason <adeason@sinenomine.net>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
    Tested-by: BuildBot <buildbot@rampaginggeek.com>

 src/afs/LINUX/osi_machdep.h |    4 +++-
 src/cf/linux-kernel-func.m4 |    6 ++++++
 2 files changed, 9 insertions(+), 1 deletions(-)

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