OpenAFS Master Repository branch, master, updated. openafs-devel-1_9_2-317-g84534b5

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 84534b5cf468f93ff1e83c8148af90b011124815
Author: Cheyenne Wills <cwills@sinenomine.net>
Date:   Thu Aug 28 09:58:11 2025 -0600

    Linux: Use a stable dentry name in d_revalidate
    
    Accessing a stable dentry name (dentry.d_name) directly requires taking
    the d_lock, which can only be held for a short periods of time and
    cannot be easily used in d_revalidate
    
    The Linux 4.13 commit:
        dentry name snapshots (49d31c2f389ac)
    provides a utility function, take_dentry_name_snapshot(), that creates a
    safe copy of the dentry name.
    
    Update the d_revalidate function to obtain a stable dentry name instead
    of making multiple accesses to the dentry name directly in an unsafe
    manner.
    
    Create wrapper functions get_stable_dentry_name() and
    release_stable_dentry_name() for take_dentry_name_snapshot() and
    release_dentry_name_snapshot() to help deal with backward compatibility
    with Linux versions prior to the 49d31c2f389ac commit.
    
    For Linux versions where take_dentry_name_snapshot is available, use the
    take_dentry_sname_snapshot but also return a pointer to the name that
    was obtained (name_snapshot.name).
    
    For Linux versions prior that do not have the take_dentry_name_snapshot
    the wrapper function simply returns a pointer to the dentry's
    d_name.name, so the existing behavior of accessing the d_name remains
    the same.
    
    Add configure checks to determine if take_dentry_name_snapshot exists,
    and if so check the datatype used within the name_snapshot structure
    to see if it is a qstr or not.  (Some distributions backported the
    49d31c2f389ac commit for older Linux kernels, but the name_snapshot
    structure uses a char * instead of a qstr).
    
    Add a compile time check to ensure that Linux provides
    take_dentry_name_snapshot() after 4.13 so errors during 'configure'
    don't cause us to silently use the unsafe code path by mistake.
    
    Note: This commit doesn't address the issues of using an unstable d_name
    for Linux versions that do not provide the take_dentry_name_snapshot().
    For these versions of Linux, there are problems within the Linux code
    base itself surrounding the use of the dentry's name.
    
    Change-Id: Ic99b1e5d7667f6841feea78ccf94db43ede40356
    Reviewed-on: https://gerrit.openafs.org/16528
    Reviewed-by: Andrew Deason <adeason@sinenomine.net>
    Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
    Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
    Tested-by: Benjamin Kaduk <kaduk@mit.edu>

 src/afs/LINUX/osi_vnodeops.c    | 60 +++++++++++++++++++++++++++++++++++++----
 src/cf/linux-kernel-assorted.m4 |  7 ++++-
 src/cf/linux-kernel-func.m4     |  7 +++++
 src/cf/linux-test4.m4           | 14 ++++++++++
 4 files changed, 82 insertions(+), 6 deletions(-)

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