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Linux 5.5 compat: blkg_tryget()

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Commit https://github.com/torvalds/linux/commit/9e8d42a0f accidentally
converted the static inline function blkg_tryget() to GPL-only for
kernels built with CONFIG_PREEMPT_RCU=y and CONFIG_BLK_CGROUP=y.

Resolve the build issue by providing our own equivalent functionality
when needed which uses rcu_read_lock_sched() internally as before.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #9745
Closes #10072
This commit is contained in:
Brian Behlendorf 2020-02-28 08:58:39 -08:00 committed by Tony Hutter
parent ebc8e360d5
commit 49f065d5a4
3 changed files with 70 additions and 1 deletions
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37
config/kernel-bio-tryget.m4 Normal file
View File

@ -0,0 +1,37 @@
dnl #
dnl # Linux 5.5 API,
dnl #
dnl # The Linux 5.5 kernel updated percpu_ref_tryget() which is inlined by
dnl # blkg_tryget() to use rcu_read_lock() instead of rcu_read_lock_sched().
dnl # As a side effect the function was converted to GPL-only.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKG_TRYGET], [
ZFS_LINUX_TEST_SRC([blkg_tryget], [
#include <linux/blk-cgroup.h>
#include <linux/bio.h>
#include <linux/fs.h>
],[
struct blkcg_gq blkg __attribute__ ((unused));
bool rc __attribute__ ((unused));
rc = blkg_tryget(&blkg);
], [], [$ZFS_META_LICENSE])
])
AC_DEFUN([ZFS_AC_KERNEL_BLKG_TRYGET], [
AC_MSG_CHECKING([whether blkg_tryget() is available])
ZFS_LINUX_TEST_RESULT([blkg_tryget], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BLKG_TRYGET, 1, [blkg_tryget() is available])
AC_MSG_CHECKING([whether blkg_tryget() is GPL-only])
ZFS_LINUX_TEST_RESULT([blkg_tryget_license], [
AC_MSG_RESULT(no)
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BLKG_TRYGET_GPL_ONLY, 1,
[blkg_tryget() GPL-only])
])
],[
AC_MSG_RESULT(no)
])
])

2
config/kernel.m4
View File

@ -78,6 +78,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
ZFS_AC_KERNEL_SRC_BLK_QUEUE_MAX_HW_SECTORS
ZFS_AC_KERNEL_SRC_BLK_QUEUE_MAX_SEGMENTS
ZFS_AC_KERNEL_SRC_BLK_QUEUE_PLUG
ZFS_AC_KERNEL_SRC_BLKG_TRYGET
ZFS_AC_KERNEL_SRC_GET_DISK_AND_MODULE
ZFS_AC_KERNEL_SRC_GET_DISK_RO
ZFS_AC_KERNEL_SRC_GENERIC_READLINK_GLOBAL
@ -186,6 +187,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
ZFS_AC_KERNEL_BIO_BI_STATUS
ZFS_AC_KERNEL_BIO_RW_BARRIER
ZFS_AC_KERNEL_BIO_RW_DISCARD
ZFS_AC_KERNEL_BLKG_TRYGET
ZFS_AC_KERNEL_BLK_QUEUE_BDI
ZFS_AC_KERNEL_BLK_QUEUE_DISCARD
ZFS_AC_KERNEL_BLK_QUEUE_SECURE_ERASE

32
module/zfs/vdev_disk.c
View File

@ -473,6 +473,36 @@ vdev_submit_bio_impl(struct bio *bio)
#ifdef HAVE_BIO_SET_DEV
#if defined(CONFIG_BLK_CGROUP) && defined(HAVE_BIO_SET_DEV_GPL_ONLY)
/*
* The Linux 5.5 kernel updated percpu_ref_tryget() which is inlined by
* blkg_tryget() to use rcu_read_lock() instead of rcu_read_lock_sched().
* As a side effect the function was converted to GPL-only. Define our
* own version when needed which uses rcu_read_lock_sched().
*/
#if defined(HAVE_BLKG_TRYGET_GPL_ONLY)
static inline bool
vdev_blkg_tryget(struct blkcg_gq *blkg)
{
struct percpu_ref *ref = &blkg->refcnt;
unsigned long __percpu *count;
bool rc;
rcu_read_lock_sched();
if (__ref_is_percpu(ref, &count)) {
this_cpu_inc(*count);
rc = true;
} else {
rc = atomic_long_inc_not_zero(&ref->count);
}
rcu_read_unlock_sched();
return (rc);
}
#elif defined(HAVE_BLKG_TRYGET)
#define vdev_blkg_tryget(bg) blkg_tryget(bg)
#endif
/*
* The Linux 5.0 kernel updated the bio_set_dev() macro so it calls the
* GPL-only bio_associate_blkg() symbol thus inadvertently converting
@ -487,7 +517,7 @@ vdev_bio_associate_blkg(struct bio *bio)
ASSERT3P(q, !=, NULL);
ASSERT3P(bio->bi_blkg, ==, NULL);
if (q->root_blkg && blkg_tryget(q->root_blkg))
if (q->root_blkg && vdev_blkg_tryget(q->root_blkg))
bio->bi_blkg = q->root_blkg;
}
#define bio_associate_blkg vdev_bio_associate_blkg