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From c87b1e31f62b827e2f421a57362923d78afc2279 Mon Sep 17 00:00:00 2001
From: Cheyenne Wills <cwills@sinenomine.net>
Date: Tue, 10 Mar 2026 14:24:54 -0600
Subject: [PATCH] Linux: Use set_default_d_op() to set dentry ops
The Linux 6.17 commit:
'new helper: set_default_d_op()' (05fb0e666495c)
replaced the way that the default dentry_operations is set on a
super_block. The s_d_op member was renamed to __s_d_op and a new helper
function set_default_d_op() is now used to set the default
dentry_operations.
The OpenAFS commit 'linux: 2.6.38: New d_op handling' (08bb83d950) added
an autoconf test for using the s_d_op member in the super_block struct.
With the above Linux commit, the test for STRUCT_SUPER_BLOCK_HAS_S_D_OP
fails, and the __s_d_op member in the super_block is not set during
afs_fill_super(), but instead dp->d_op is set during various vfs
operations. Doing so sets the dentry ops for the dentry, but does not
set the flag DCACHE_OP_REVALIDATE on the dentry, and so Linux never
calls our d_revalidate function, causing dentries to not get properly
revalidated.
To fix this, add a new autoconf test for set_default_d_op(), and use
that function when available. Add a comment for the autoconf test for
the super_block member s_d_op to note the change. Add an additional
build time check to ensure that we don't accidentally revert to the
pre-2.6.38 behavior after Linux 2.6.38
In afs_fill_super(), use set_default_d_op() to initialize the
super_block with the afs_dentry_operations.
The dentry->d_op member only needs to be updated when set_default_d_op()
is not available and the super_block does not have the s_d_op member.
Note: This commit fixes a reported problem with stale dentries that was
discovered on a Linux 6.17 system.
Reviewed-on: https://gerrit.openafs.org/16700
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
(cherry picked from commit a99b2ff4c04a9b1a4ba3ab5fac1b37bfd5d43568)
Change-Id: Ic454c52ca88c82a9efa62a486ec05300a95c6cb0
(cherry picked from commit 6d0a2107fcab28fc4ba64d365133d171b75bd3dc)
---
src/afs/LINUX/osi_vfsops.c | 8 ++++++--
src/afs/LINUX/osi_vnodeops.c | 6 +++---
src/cf/linux-kernel-func.m4 | 10 ++++++++++
src/cf/linux-kernel-struct.m4 | 4 ++++
4 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/src/afs/LINUX/osi_vfsops.c b/src/afs/LINUX/osi_vfsops.c
index 18506474ee48..f1e59074760c 100644
--- a/src/afs/LINUX/osi_vfsops.c
+++ b/src/afs/LINUX/osi_vfsops.c
@@ -117,8 +117,12 @@ afs_fill_super(struct super_block *sb, void *data, int silent)
sb->s_magic = AFS_VFSMAGIC;
sb->s_op = &afs_sops; /* Super block (vfs) ops */
-#if defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
+#if defined(HAVE_LINUX_SET_DEFAULT_D_OP)
+ set_default_d_op(sb, &afs_dentry_operations);
+#elif defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
sb->s_d_op = &afs_dentry_operations;
+#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,38)
+# error "Missing method to set the super_block's dentry operations member"
#endif
#if defined(HAVE_LINUX_SUPER_SETUP_BDI)
code = super_setup_bdi(sb);
@@ -221,7 +225,7 @@ afs_root(struct super_block *afsp)
#else
afsp->s_root = d_alloc_root(ip);
#endif
-#if !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
+#if !defined(HAVE_LINUX_SET_DEFAULT_D_OP) && !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
afsp->s_root->d_op = &afs_dentry_operations;
#endif
afs_DestroyAttr(vattr);
diff --git a/src/afs/LINUX/osi_vnodeops.c b/src/afs/LINUX/osi_vnodeops.c
index b525126c20a1..432643fe5583 100644
--- a/src/afs/LINUX/osi_vnodeops.c
+++ b/src/afs/LINUX/osi_vnodeops.c
@@ -1844,7 +1844,7 @@ afs_linux_create(struct inode *dip, struct dentry *dp, int mode)
afs_getattr(vcp, vattr, credp);
afs_fill_inode(ip, vattr);
insert_inode_hash(ip);
-#if !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
+#if !defined(HAVE_LINUX_SET_DEFAULT_D_OP) && !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
dp->d_op = &afs_dentry_operations;
#endif
dp->d_time = parent_vcache_dv(dip, credp);
@@ -1925,7 +1925,7 @@ afs_linux_lookup(struct inode *dip, struct dentry *dp)
afs_DestroyAttr(vattr);
}
-#if !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
+#if !defined(HAVE_LINUX_SET_DEFAULT_D_OP) && !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
dp->d_op = &afs_dentry_operations;
#endif
dp->d_time = parent_vcache_dv(dip, credp);
@@ -2171,7 +2171,7 @@ afs_linux_mkdir(struct inode *dip, struct dentry *dp, int mode)
afs_getattr(tvcp, vattr, credp);
afs_fill_inode(ip, vattr);
-#if !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
+#if !defined(HAVE_LINUX_SET_DEFAULT_D_OP) && !defined(STRUCT_SUPER_BLOCK_HAS_S_D_OP)
dp->d_op = &afs_dentry_operations;
#endif
dp->d_time = parent_vcache_dv(dip, credp);
diff --git a/src/cf/linux-kernel-func.m4 b/src/cf/linux-kernel-func.m4
index 0784262d70b9..6845c9918ad1 100644
--- a/src/cf/linux-kernel-func.m4
+++ b/src/cf/linux-kernel-func.m4
@@ -379,6 +379,16 @@ AC_CHECK_LINUX_FUNC([write_begin_end_kiocb],
[[aops->write_begin(kiocb, mapping, 0, 0, &foliop, fsdata);
aops->write_end(kiocb, mapping, 0, 0, 0, foliop, fsdata);]])
+dnl Linux 6.17 added a helper function set_default_d_op() to set the default
+dnl dentry_operations for a super_block. The super_block member s_d_op is now
+dnl a private member of the super_block.
+AC_CHECK_LINUX_FUNC([set_default_d_op],
+ [#include <linux/kernel.h>
+ #include <linux/dcache.h>],
+ [[static struct super_block sb;
+ static struct dentry_operations d_op;
+ set_default_d_op(&sb, &d_op);]])
+
dnl Consequences - things which get set as a result of the
dnl above tests
AS_IF([test "x$ac_cv_linux_func_d_alloc_anon" = "xno"],
diff --git a/src/cf/linux-kernel-struct.m4 b/src/cf/linux-kernel-struct.m4
index 24841e9f3245..46c23a25fbb8 100644
--- a/src/cf/linux-kernel-struct.m4
+++ b/src/cf/linux-kernel-struct.m4
@@ -44,6 +44,10 @@ AC_CHECK_LINUX_STRUCT([nameidata], [path], [namei.h])
AC_CHECK_LINUX_STRUCT([proc_dir_entry], [owner], [proc_fs.h])
AC_CHECK_LINUX_STRUCT([proc_ops], [proc_compat_ioctl], [proc_fs.h])
AC_CHECK_LINUX_STRUCT([super_block], [s_bdi], [fs.h])
+dnl Linux 2.6.38 added the s_d_op field to hold the default dentry ops.
+dnl Linux 6.17 renamed s_d_op to a private member, requiring users to instead
+dnl call set_default_d_op() to initialize the super_block with the default
+dnl dentry ops.
AC_CHECK_LINUX_STRUCT([super_block], [s_d_op], [fs.h])
AC_CHECK_LINUX_STRUCT([super_operations], [alloc_inode],
[fs.h])
--
2.52.0
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