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Linux 4.2 compat: follow_link() / put_link() 

As of Linux 4.2 the kernel has completely retired the nameidata
structure.  One of the few remaining consumers of this interface
were the follow_link() and put_link() callbacks.

This patch adds the required checks to configure to detect the
interface change and updates the functions accordingly.  Migrating
to the simple_follow_link() interface was considered but was decided
against ironically due to the increased complexity.

It also should be noted that the kernel follow_link() and put_link()
interfaces changes several times after 4.1 and but before 4.2.  This
means there is a narrow range of kernel commits which never appear
in an official tag of the Linux kernel which ZoL will not build.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Issue #3596
This commit is contained in:
Brian Behlendorf 2015-07-15 10:54:26 -07:00
parent 7eb333fbdd
commit bd29109f1a
6 changed files with 81 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
config/kernel-create-nameidata.m4
View File

@ -2,7 +2,7 @@ dnl #
dnl # 3.6 API change
dnl #
AC_DEFUN([ZFS_AC_KERNEL_CREATE_NAMEIDATA], [
AC_MSG_CHECKING([whether iops->create() takes struct nameidata])
AC_MSG_CHECKING([whether iops->create() passes nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
@ -22,7 +22,7 @@ AC_DEFUN([ZFS_AC_KERNEL_CREATE_NAMEIDATA], [
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_CREATE_NAMEIDATA, 1,
[iops->create() operation takes nameidata])
[iops->create() passes nameidata])
],[
AC_MSG_RESULT(no)
])

24
config/kernel-follow-link-nameidata.m4 Normal file
View File

@ -0,0 +1,24 @@
dnl #
dnl # 4.2 API change
dnl # This kernel retired the nameidata structure which forced the
dnl # restructuring of the follow_link() prototype and how it is called.
dnl # We check for the new interface rather than detecting the old one.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_FOLLOW_LINK], [
AC_MSG_CHECKING([whether iops->follow_link() passes nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
const char *follow_link(struct dentry *de, void **cookie)
{ return "symlink"; }
static struct inode_operations iops __attribute__ ((unused)) = {
.follow_link = follow_link,
};
],[
],[
AC_MSG_RESULT(no)
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_FOLLOW_LINK_NAMEIDATA, 1,
[iops->follow_link() nameidata])
])
])

4
config/kernel-lookup-nameidata.m4
View File

@ -2,7 +2,7 @@ dnl #
dnl # 3.6 API change
dnl #
AC_DEFUN([ZFS_AC_KERNEL_LOOKUP_NAMEIDATA], [
AC_MSG_CHECKING([whether iops->lookup() takes struct nameidata])
AC_MSG_CHECKING([whether iops->lookup() passes nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
@ -18,7 +18,7 @@ AC_DEFUN([ZFS_AC_KERNEL_LOOKUP_NAMEIDATA], [
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_LOOKUP_NAMEIDATA, 1,
[iops->lookup() operation takes nameidata])
[iops->lookup() passes nameidata])
],[
AC_MSG_RESULT(no)
])

23
config/kernel-put-link-nameidata.m4 Normal file
View File

@ -0,0 +1,23 @@
dnl #
dnl # 4.2 API change
dnl # This kernel retired the nameidata structure which forced the
dnl # restructuring of the put_link() prototype and how it is called.
dnl # We check for the new interface rather than detecting the old one.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_PUT_LINK], [
AC_MSG_CHECKING([whether iops->put_link() passes nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
void put_link(struct inode *ip, void *cookie) { return; }
static struct inode_operations iops __attribute__ ((unused)) = {
.put_link = put_link,
};
],[
],[
AC_MSG_RESULT(no)
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_PUT_LINK_NAMEIDATA, 1,
[iops->put_link() nameidata])
])
])

2
config/kernel.m4
View File

@ -70,6 +70,8 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_MKDIR_UMODE_T
ZFS_AC_KERNEL_LOOKUP_NAMEIDATA
ZFS_AC_KERNEL_CREATE_NAMEIDATA
ZFS_AC_KERNEL_FOLLOW_LINK
ZFS_AC_KERNEL_PUT_LINK
ZFS_AC_KERNEL_TRUNCATE_RANGE
ZFS_AC_KERNEL_AUTOMOUNT
ZFS_AC_KERNEL_ENCODE_FH_WITH_INODE

33
module/zfs/zpl_inode.c
View File

@ -348,8 +348,13 @@ zpl_symlink(struct inode *dir, struct dentry *dentry, const char *name)
return (error);
}
#ifdef HAVE_FOLLOW_LINK_NAMEIDATA
static void *
zpl_follow_link(struct dentry *dentry, struct nameidata *nd)
#else
const char *
zpl_follow_link(struct dentry *dentry, void **symlink_cookie)
#endif
{
cred_t *cr = CRED();
struct inode *ip = dentry->d_inode;
@ -372,17 +377,28 @@ zpl_follow_link(struct dentry *dentry, struct nameidata *nd)
cookie = spl_fstrans_mark();
error = -zfs_readlink(ip, &uio, cr);
spl_fstrans_unmark(cookie);
if (error) {
if (error)
kmem_free(link, MAXPATHLEN);
nd_set_link(nd, ERR_PTR(error));
} else {
nd_set_link(nd, link);
}
crfree(cr);
#ifdef HAVE_FOLLOW_LINK_NAMEIDATA
if (error)
nd_set_link(nd, ERR_PTR(error));
else
nd_set_link(nd, link);
return (NULL);
#else
if (error)
return (ERR_PTR(error));
else
return (*symlink_cookie = link);
#endif
}
#ifdef HAVE_PUT_LINK_NAMEIDATA
static void
zpl_put_link(struct dentry *dentry, struct nameidata *nd, void *ptr)
{
@ -391,6 +407,13 @@ zpl_put_link(struct dentry *dentry, struct nameidata *nd, void *ptr)
if (!IS_ERR(link))
kmem_free(link, MAXPATHLEN);
}
#else
static void
zpl_put_link(struct inode *unused, void *symlink_cookie)
{
kmem_free(symlink_cookie, MAXPATHLEN);
}
#endif
static int
zpl_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)