From 7d7ae8979acff0bde9963bd80c0c9433e986c33e Mon Sep 17 00:00:00 2001 From: Rob Norris Date: Thu, 31 Jul 2025 13:12:43 +1000 Subject: [PATCH] Linux 6.17: d_set_d_op() is no longer available We only have extremely narrow uses, so move it all into a single function that does only what we need, with and without d_set_d_op(). Sponsored-by: https://despairlabs.com/sponsor/ Reviewed-by: Brian Behlendorf Reviewed-by: Tony Hutter Signed-off-by: Rob Norris Closes #17621 --- config/kernel-dentry-operations.m4 | 10 +++- include/os/linux/kernel/linux/dcache_compat.h | 26 --------- module/os/linux/zfs/zpl_ctldir.c | 55 ++++++++++++++++--- 3 files changed, 55 insertions(+), 36 deletions(-) diff --git a/config/kernel-dentry-operations.m4 b/config/kernel-dentry-operations.m4 index aa5a9f2af..9d1bb3a74 100644 --- a/config/kernel-dentry-operations.m4 +++ b/config/kernel-dentry-operations.m4 @@ -24,6 +24,9 @@ dnl # dnl # 2.6.38 API change dnl # Added d_set_d_op() helper function. dnl # +dnl # 6.17 API change +dnl # d_set_d_op() removed. No direct replacement. +dnl # AC_DEFUN([ZFS_AC_KERNEL_SRC_D_SET_D_OP], [ ZFS_LINUX_TEST_SRC([d_set_d_op], [ #include @@ -34,11 +37,12 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_D_SET_D_OP], [ AC_DEFUN([ZFS_AC_KERNEL_D_SET_D_OP], [ AC_MSG_CHECKING([whether d_set_d_op() is available]) - ZFS_LINUX_TEST_RESULT_SYMBOL([d_set_d_op], - [d_set_d_op], [fs/dcache.c], [ + ZFS_LINUX_TEST_RESULT([d_set_d_op], [ AC_MSG_RESULT(yes) + AC_DEFINE(HAVE_D_SET_D_OP, 1, + [Define if d_set_d_op() is available]) ], [ - ZFS_LINUX_TEST_ERROR([d_set_d_op]) + AC_MSG_RESULT(no) ]) ]) diff --git a/include/os/linux/kernel/linux/dcache_compat.h b/include/os/linux/kernel/linux/dcache_compat.h index de533a5fd..72f603c52 100644 --- a/include/os/linux/kernel/linux/dcache_compat.h +++ b/include/os/linux/kernel/linux/dcache_compat.h @@ -59,32 +59,6 @@ } while (0) #endif -/* - * 2.6.30 API change, - * The const keyword was added to the 'struct dentry_operations' in - * the dentry structure. To handle this we define an appropriate - * dentry_operations_t typedef which can be used. - */ -typedef const struct dentry_operations dentry_operations_t; - -/* - * 2.6.38 API addition, - * Added d_clear_d_op() helper function which clears some flags and the - * registered dentry->d_op table. This is required because d_set_d_op() - * issues a warning when the dentry operations table is already set. - * For the .zfs control directory to work properly we must be able to - * override the default operations table and register custom .d_automount - * and .d_revalidate callbacks. - */ -static inline void -d_clear_d_op(struct dentry *dentry) -{ - dentry->d_op = NULL; - dentry->d_flags &= ~( - DCACHE_OP_HASH | DCACHE_OP_COMPARE | - DCACHE_OP_REVALIDATE | DCACHE_OP_DELETE); -} - /* * Walk and invalidate all dentry aliases of an inode * unless it's a mountpoint diff --git a/module/os/linux/zfs/zpl_ctldir.c b/module/os/linux/zfs/zpl_ctldir.c index a7fdb8f28..3e3bec69b 100644 --- a/module/os/linux/zfs/zpl_ctldir.c +++ b/module/os/linux/zfs/zpl_ctldir.c @@ -197,7 +197,7 @@ zpl_snapdir_revalidate(struct dentry *dentry, unsigned int flags) return (!!dentry->d_inode); } -static dentry_operations_t zpl_dops_snapdirs = { +static const struct dentry_operations zpl_dops_snapdirs = { /* * Auto mounting of snapshots is only supported for 2.6.37 and * newer kernels. Prior to this kernel the ops->follow_link() @@ -210,6 +210,51 @@ static dentry_operations_t zpl_dops_snapdirs = { .d_revalidate = zpl_snapdir_revalidate, }; +/* + * For the .zfs control directory to work properly we must be able to override + * the default operations table and register custom .d_automount and + * .d_revalidate callbacks. + */ +static void +set_snapdir_dentry_ops(struct dentry *dentry, unsigned int extraflags) { + static const unsigned int op_flags = + DCACHE_OP_HASH | DCACHE_OP_COMPARE | + DCACHE_OP_REVALIDATE | DCACHE_OP_DELETE | + DCACHE_OP_PRUNE | DCACHE_OP_WEAK_REVALIDATE | DCACHE_OP_REAL; + +#ifdef HAVE_D_SET_D_OP + /* + * d_set_d_op() will set the DCACHE_OP_ flags according to what it + * finds in the passed dentry_operations, so we don't have to. + * + * We clear the flags and the old op table before calling d_set_d_op() + * because issues a warning when the dentry operations table is already + * set. + */ + dentry->d_op = NULL; + dentry->d_flags &= ~op_flags; + d_set_d_op(dentry, &zpl_dops_snapdirs); + dentry->d_flags |= extraflags; +#else + /* + * Since 6.17 there's no exported way to modify dentry ops, so we have + * to reach in and do it ourselves. This should be safe for our very + * narrow use case, which is to create or splice in an entry to give + * access to a snapshot. + * + * We need to set the op flags directly. We hardcode + * DCACHE_OP_REVALIDATE because that's the only operation we have; if + * we ever extend zpl_dops_snapdirs we will need to update the op flags + * to match. + */ + spin_lock(&dentry->d_lock); + dentry->d_op = &zpl_dops_snapdirs; + dentry->d_flags &= ~op_flags; + dentry->d_flags |= DCACHE_OP_REVALIDATE | extraflags; + spin_unlock(&dentry->d_lock); +#endif +} + static struct dentry * zpl_snapdir_lookup(struct inode *dip, struct dentry *dentry, unsigned int flags) @@ -231,10 +276,7 @@ zpl_snapdir_lookup(struct inode *dip, struct dentry *dentry, return (ERR_PTR(error)); ASSERT(error == 0 || ip == NULL); - d_clear_d_op(dentry); - d_set_d_op(dentry, &zpl_dops_snapdirs); - dentry->d_flags |= DCACHE_NEED_AUTOMOUNT; - + set_snapdir_dentry_ops(dentry, DCACHE_NEED_AUTOMOUNT); return (d_splice_alias(ip, dentry)); } @@ -368,8 +410,7 @@ zpl_snapdir_mkdir(struct inode *dip, struct dentry *dentry, umode_t mode) error = -zfsctl_snapdir_mkdir(dip, dname(dentry), vap, &ip, cr, 0); if (error == 0) { - d_clear_d_op(dentry); - d_set_d_op(dentry, &zpl_dops_snapdirs); + set_snapdir_dentry_ops(dentry, 0); d_instantiate(dentry, ip); }