LinuxLists.cc - [PATCH 0/3] vmw_balloon: misc fixes and enhancements

2022-09-13 18:22:48

Subject: [PATCH 0/3] vmw_balloon: misc fixes and enhancements

From: Nadav Amit <[email protected]>

Various relatively minor enhancements. Patches 1-2 address borderline
bugs. There have been no actual bug reports, and the first bug is
theoretical and the second one is a minor performance issue. We
therefore do not ask to backport them, but keep them first since we (or
distributions) might want to backport them later.

Patch 3 is doing some cleanup due to recent changes, with no expected
functional change.

Nadav Amit (3):
vmw_balloon: access reset_required through READ/WRITE_ONCE
vmw_balloon: exit if initalization fails
vmw_balloon: open-code vmballoon_compaction_init()

drivers/misc/vmw_balloon.c | 71 +++++++++++++++++---------------------
1 file changed, 31 insertions(+), 40 deletions(-)

--
2.25.1

2022-09-13 18:22:49

by Nadav Amit

[permalink] [raw]

Subject: [PATCH 3/3] vmw_balloon: open-code vmballoon_compaction_init()

From: Nadav Amit <[email protected]>

Following commit 68f2736a85832 ("mm: Convert all PageMovable users to
movable_operations"), the code of vmballoon_compaction_init() is very
simple and does not worth a separate function.

Instead, open code vmballoon_compaction_init. As migratepage is always
defined, use IS_ENABLED(), which makes the code easier to read. No
functional change is intended.

Signed-off-by: Nadav Amit <[email protected]>
---
drivers/misc/vmw_balloon.c | 26 +++-----------------------
1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 762442b9ece8..46212cd09854 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -1848,28 +1848,6 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
return ret;
}

-/**
- * vmballoon_compaction_init() - initialized compaction for the balloon.
- *
- * @b: pointer to the balloon.
- *
- * If during the initialization a failure occurred, this function does not
- * perform cleanup. The caller must call vmballoon_compaction_deinit() in this
- * case.
- *
- * Return: zero on success or error code on failure.
- */
-static __init void vmballoon_compaction_init(struct vmballoon *b)
-{
- b->b_dev_info.migratepage = vmballoon_migratepage;
-}
-
-#else /* CONFIG_BALLOON_COMPACTION */
-static inline void vmballoon_compaction_init(struct vmballoon *b)
-{
-}
-#endif /* CONFIG_BALLOON_COMPACTION */
-
static int __init vmballoon_init(void)
{
int error;
@@ -1909,7 +1887,9 @@ static int __init vmballoon_init(void)
* balloon_devinfo_init() .
*/
balloon_devinfo_init(&balloon.b_dev_info);
- vmballoon_compaction_init(&balloon);
+
+ if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
+ b->b_dev_info.migratepage = vmballoon_migratepage;

queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);

--
2.25.1

2022-09-13 18:28:04

by Nadav Amit

[permalink] [raw]

Subject: [PATCH 1/3] vmw_balloon: access reset_required through READ/WRITE_ONCE

From: Nadav Amit <[email protected]>

reset_required might be accessed concurrently, at least through debugfs.
While there is no apparent functional risk, avoid any potential race,
even if it is benign.

Use READ_ONCE() and WRITE_ONCE() when accessing reset_required.

Signed-off-by: Nadav Amit <[email protected]>
---
drivers/misc/vmw_balloon.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 61a2be712bf7..7fa91983c567 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -492,7 +492,7 @@ __vmballoon_cmd(struct vmballoon *b, unsigned long cmd, unsigned long arg1,

/* mark reset required accordingly */
if (status == VMW_BALLOON_ERROR_RESET)
- b->reset_required = true;
+ WRITE_ONCE(b->reset_required, true);

return status;
}
@@ -965,7 +965,7 @@ static int64_t vmballoon_change(struct vmballoon *b)
* Otherwise we might get huge positives instead of negatives
*/

- if (b->reset_required)
+ if (READ_ONCE(b->reset_required))
return 0;

/* consider a 2MB slack on deflate, unless the balloon is emptied */
@@ -1446,7 +1446,7 @@ static void vmballoon_reset(struct vmballoon *b)
}

vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_RESET);
- b->reset_required = false;
+ WRITE_ONCE(b->reset_required, false);

error = vmballoon_vmci_init(b);
if (error)
@@ -1473,7 +1473,7 @@ static void vmballoon_work(struct work_struct *work)
struct vmballoon *b = container_of(dwork, struct vmballoon, dwork);
int64_t change = 0;

- if (b->reset_required)
+ if (READ_ONCE(b->reset_required))
vmballoon_reset(b);

down_read(&b->conf_sem);
@@ -1666,7 +1666,7 @@ static int vmballoon_debug_show(struct seq_file *f, void *offset)
VMW_BALLOON_CAPABILITIES);
seq_printf(f, "%-22s: %#16lx\n", "used capabilities", b->capabilities);
seq_printf(f, "%-22s: %16s\n", "is resetting",
- b->reset_required ? "y" : "n");
+ READ_ONCE(b->reset_required) ? "y" : "n");

/* format size info */
seq_printf(f, "%-22s: %16lu\n", "target", READ_ONCE(b->target));
--
2.25.1

2022-09-13 18:41:06

by Nadav Amit

[permalink] [raw]

Subject: [PATCH 2/3] vmw_balloon: exit if initalization fails

From: Nadav Amit <[email protected]>

In certain VMware hypervisor variants the balloon might not be
supported. In such cases initialization would fail, but resources would
keep being unnecessarily wasted. The balloon driver would retry
reinitialization every second for no reason.

Initialize the balloon once during init, before starting the worker. If
initialization fails, put out a message and fail gracefully.

Signed-off-by: Nadav Amit <[email protected]>
---
drivers/misc/vmw_balloon.c | 37 ++++++++++++++++++++++++-------------
1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 7fa91983c567..762442b9ece8 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -1416,7 +1416,7 @@ static void vmballoon_pop(struct vmballoon *b)
* is not empty) and then restarting protocol. This operation normally
* happens when host responds with VMW_BALLOON_ERROR_RESET to a command.
*/
-static void vmballoon_reset(struct vmballoon *b)
+static int vmballoon_reset(struct vmballoon *b)
{
int error;

@@ -1427,11 +1427,13 @@ static void vmballoon_reset(struct vmballoon *b)
/* free all pages, skipping monitor unlock */
vmballoon_pop(b);

- if (vmballoon_send_start(b, VMW_BALLOON_CAPABILITIES))
+ error = vmballoon_send_start(b, VMW_BALLOON_CAPABILITIES);
+ if (error)
goto unlock;

if ((b->capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
- if (vmballoon_init_batching(b)) {
+ error = vmballoon_init_batching(b);
+ if (error) {
/*
* We failed to initialize batching, inform the monitor
* about it by sending a null capability.
@@ -1448,8 +1450,7 @@ static void vmballoon_reset(struct vmballoon *b)
vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_RESET);
WRITE_ONCE(b->reset_required, false);

- error = vmballoon_vmci_init(b);
- if (error)
+ if (vmballoon_vmci_init(b))
pr_err_once("failed to initialize vmci doorbell\n");

if (vmballoon_send_guest_id(b))
@@ -1457,6 +1458,7 @@ static void vmballoon_reset(struct vmballoon *b)

unlock:
up_write(&b->conf_sem);
+ return error;
}

/**
@@ -1879,6 +1881,23 @@ static int __init vmballoon_init(void)
if (x86_hyper_type != X86_HYPER_VMWARE)
return -ENODEV;

+ INIT_LIST_HEAD(&balloon.huge_pages);
+ spin_lock_init(&balloon.comm_lock);
+ init_rwsem(&balloon.conf_sem);
+ balloon.vmci_doorbell = VMCI_INVALID_HANDLE;
+ balloon.batch_page = NULL;
+ balloon.page = NULL;
+ balloon.reset_required = true;
+
+ /*
+ * Reset the balloon to check that it is indeed supported.
+ */
+ error = vmballoon_reset(&balloon);
+ if (error) {
+ pr_err("memory ballooning is disabled");
+ goto fail;
+ }
+
INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);

error = vmballoon_register_shrinker(&balloon);
@@ -1892,14 +1911,6 @@ static int __init vmballoon_init(void)
balloon_devinfo_init(&balloon.b_dev_info);
vmballoon_compaction_init(&balloon);

- INIT_LIST_HEAD(&balloon.huge_pages);
- spin_lock_init(&balloon.comm_lock);
- init_rwsem(&balloon.conf_sem);
- balloon.vmci_doorbell = VMCI_INVALID_HANDLE;
- balloon.batch_page = NULL;
- balloon.page = NULL;
- balloon.reset_required = true;
-
queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);

vmballoon_debugfs_init(&balloon);
--
2.25.1

2022-09-14 10:46:58

by David Hildenbrand

[permalink] [raw]

Subject: Re: [PATCH 3/3] vmw_balloon: open-code vmballoon_compaction_init()

On 13.09.22 11:43, Nadav Amit wrote:
> From: Nadav Amit <[email protected]>
>
> Following commit 68f2736a85832 ("mm: Convert all PageMovable users to
> movable_operations"), the code of vmballoon_compaction_init() is very
> simple and does not worth a separate function.
>
> Instead, open code vmballoon_compaction_init. As migratepage is always
> defined, use IS_ENABLED(), which makes the code easier to read. No
> functional change is intended.
>
> Signed-off-by: Nadav Amit <[email protected]>
> ---

Reviewed-by: David Hildenbrand <[email protected]>

--
Thanks,

David / dhildenb

2022-09-15 00:31:06

by kernel test robot

[permalink] [raw]

Subject: Re: [PATCH 3/3] vmw_balloon: open-code vmballoon_compaction_init()

Hi Nadav,

I love your patch! Yet something
[auto build test ERROR on char-misc/char-m [also build test ERROR on linus/master [If your patch is applied to the And when submitting patch, we suggest # https://01.org/lkp
isc-testing]
v6.0-rc5 next-20220914]
wrong git tree, kindly drop us a note.
to use '--base' as documented in
mat-patch#_base_tree_information]">https://git-scm.com/docs/git-format-patch#_base_tree_information]
-lab-lkp/linux/commits/Nadav-Amit/vmw_balloon-misc-fixes-and-enhancements/20220914-021333">https://github.com/intel-lab-lkp/linux/commits/Nadav-Amit/vmw_balloon-misc-fixes-and-enhancements/20220914-021333
ub/scm/linux/kernel/git/gregkh/char-misc.git">https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git ceecbbddbf549fe0b7ffa3804a6e255b3360030f
href="https://download.01.org/0day-ci/archive/20220915/202209150729.vb9gopf2-lkp@intel.com/config)">https://download.01.org/0day-ci/archive/20220915/[email protected]/config)
href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
sercontent.com/intel/lkp-tests/master/sbin/make.cross">https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
el-lab-lkp/linux/commit/aa1f38765dd703cbeb3450454d0b5b2c7f5a8f8d">https://github.com/intel-lab-lkp/linux/commit/aa1f38765dd703cbeb3450454d0b5b2c7f5a8f8d
href="https://github.com/intel-lab-lkp/linux">https://github.com/intel-lab-lkp/linux
Nadav-Amit/vmw_balloon-misc-fixes-and-enhancements/20220914-021333
0454d0b5b2c7f5a8f8d
cp config build_dir/.config
COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash
following tag where applicable
href="/cdn-cgi/l/email-protection#f4d29880cf989f84b49d9a809198da979b99d29380cf"><[email protected]>
>>):
error: unterminated conditional directive
Dmitry Torokhov 2010-04-23 1730
Nadav Amit 2019-04-25 1731
Nadav Amit 2019-04-25 @1732 #ifdef CONFIG_BALLOON_COMPACTION
Nadav Amit 2019-04-25 1733 /**
Nadav Amit 2019-04-25 1734 * vmballoon_migratepage() - migrates a balloon page.
Nadav Amit 2019-04-25 1735 * @b_dev_info: balloon device information descriptor.
Nadav Amit 2019-04-25 1736 * @newpage: the page to which @page should be migrated.
Nadav Amit 2019-04-25 1737 * @page: a ballooned page that should be migrated.
Nadav Amit 2019-04-25 1738 * @mode: migration mode, ignored.
Nadav Amit 2019-04-25 1739 *
Nadav Amit 2019-04-25 1740 * This function is really open-coded, but that is according to the interface
Nadav Amit 2019-04-25 1741 * that balloon_compaction provides.
Nadav Amit 2019-04-25 1742 *
Nadav Amit 2019-04-25 1743 * Return: zero on success, -EAGAIN when migration cannot be performed
Nadav Amit 2019-04-25 1744 * momentarily, and -EBUSY if migration failed and should be retried
Nadav Amit 2019-04-25 1745 * with that specific page.
Nadav Amit 2019-04-25 1746 */
Nadav Amit 2019-04-25 1747 static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
Nadav Amit 2019-04-25 1748 struct page *newpage, struct page *page,
Nadav Amit 2019-04-25 1749 enum migrate_mode mode)
Nadav Amit 2019-04-25 1750 {
Nadav Amit 2019-04-25 1751 unsigned long status, flags;
Nadav Amit 2019-04-25 1752 struct vmballoon *b;
Nadav Amit 2019-04-25 1753 int ret;
Nadav Amit 2019-04-25 1754
Nadav Amit 2019-04-25 1755 b = container_of(b_dev_info, struct vmballoon, b_dev_info);
Nadav Amit 2019-04-25 1756
Nadav Amit 2019-04-25 1757 /*
Nadav Amit 2019-04-25 1758 * If the semaphore is taken, there is ongoing configuration change
Nadav Amit 2019-04-25 1759 * (i.e., balloon reset), so try again.
Nadav Amit 2019-04-25 1760 */
Nadav Amit 2019-04-25 1761 if (!down_read_trylock(&b->conf_sem))
Nadav Amit 2019-04-25 1762 return -EAGAIN;
Nadav Amit 2019-04-25 1763
Nadav Amit 2019-04-25 1764 spin_lock(&b->comm_lock);
Nadav Amit 2019-04-25 1765 /*
Nadav Amit 2019-04-25 1766 * We must start by deflating and not inflating, as otherwise the
Nadav Amit 2019-04-25 1767 * hypervisor may tell us that it has enough memory and the new page is
Nadav Amit 2019-04-25 1768 * not needed. Since the old page is isolated, we cannot use the list
Nadav Amit 2019-04-25 1769 * interface to unlock it, as the LRU field is used for isolation.
Nadav Amit 2019-04-25 1770 * Instead, we use the native interface directly.
Nadav Amit 2019-04-25 1771 */
Nadav Amit 2019-04-25 1772 vmballoon_add_page(b, 0, page);
Nadav Amit 2019-04-25 1773 status = vmballoon_lock_op(b, 1, VMW_BALLOON_4K_PAGE,
Nadav Amit 2019-04-25 1774 VMW_BALLOON_DEFLATE);
Nadav Amit 2019-04-25 1775
Nadav Amit 2019-04-25 1776 if (status == VMW_BALLOON_SUCCESS)
Nadav Amit 2019-04-25 1777 status = vmballoon_status_page(b, 0, &page);
Nadav Amit 2019-04-25 1778
Nadav Amit 2019-04-25 1779 /*
Nadav Amit 2019-04-25 1780 * If a failure happened, let the migration mechanism know that it
Nadav Amit 2019-04-25 1781 * should not retry.
Nadav Amit 2019-04-25 1782 */
Nadav Amit 2019-04-25 1783 if (status != VMW_BALLOON_SUCCESS) {
Nadav Amit 2019-04-25 1784 spin_unlock(&b->comm_lock);
Nadav Amit 2019-04-25 1785 ret = -EBUSY;
Nadav Amit 2019-04-25 1786 goto out_unlock;
Nadav Amit 2019-04-25 1787 }
Nadav Amit 2019-04-25 1788
Nadav Amit 2019-04-25 1789 /*
Nadav Amit 2019-04-25 1790 * The page is isolated, so it is safe to delete it without holding
Nadav Amit 2019-04-25 1791 * @pages_lock . We keep holding @comm_lock since we will need it in a
Nadav Amit 2019-04-25 1792 * second.
Nadav Amit 2019-04-25 1793 */
Nadav Amit 2019-04-25 1794 balloon_page_delete(page);
Nadav Amit 2019-04-25 1795
Nadav Amit 2019-04-25 1796 put_page(page);
Nadav Amit 2019-04-25 1797
Nadav Amit 2019-04-25 1798 /* Inflate */
Nadav Amit 2019-04-25 1799 vmballoon_add_page(b, 0, newpage);
Nadav Amit 2019-04-25 1800 status = vmballoon_lock_op(b, 1, VMW_BALLOON_4K_PAGE,
Nadav Amit 2019-04-25 1801 VMW_BALLOON_INFLATE);
Nadav Amit 2019-04-25 1802
Nadav Amit 2019-04-25 1803 if (status == VMW_BALLOON_SUCCESS)
Nadav Amit 2019-04-25 1804 status = vmballoon_status_page(b, 0, &newpage);
Nadav Amit 2019-04-25 1805
Nadav Amit 2019-04-25 1806 spin_unlock(&b->comm_lock);
Nadav Amit 2019-04-25 1807
Nadav Amit 2019-04-25 1808 if (status != VMW_BALLOON_SUCCESS) {
Nadav Amit 2019-04-25 1809 /*
Nadav Amit 2019-04-25 1810 * A failure happened. While we can deflate the page we just
Nadav Amit 2019-04-25 1811 * inflated, this deflation can also encounter an error. Instead
Nadav Amit 2019-04-25 1812 * we will decrease the size of the balloon to reflect the
Nadav Amit 2019-04-25 1813 * change and report failure.
Nadav Amit 2019-04-25 1814 */
Nadav Amit 2019-04-25 1815 atomic64_dec(&b->size);
Nadav Amit 2019-04-25 1816 ret = -EBUSY;
Nadav Amit 2019-04-25 1817 } else {
Nadav Amit 2019-04-25 1818 /*
Nadav Amit 2019-04-25 1819 * Success. Take a reference for the page, and we will add it to
Nadav Amit 2019-04-25 1820 * the list after acquiring the lock.
Nadav Amit 2019-04-25 1821 */
Nadav Amit 2019-04-25 1822 get_page(newpage);
Nadav Amit 2019-04-25 1823 ret = MIGRATEPAGE_SUCCESS;
Nadav Amit 2019-04-25 1824 }
Nadav Amit 2019-04-25 1825
Nadav Amit 2019-04-25 1826 /* Update the balloon list under the @pages_lock */
Nadav Amit 2019-04-25 1827 spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
Nadav Amit 2019-04-25 1828
Nadav Amit 2019-04-25 1829 /*
Nadav Amit 2019-04-25 1830 * On inflation success, we already took a reference for the @newpage.
Nadav Amit 2019-04-25 1831 * If we succeed just insert it to the list and update the statistics
Nadav Amit 2019-04-25 1832 * under the lock.
Nadav Amit 2019-04-25 1833 */
Nadav Amit 2019-04-25 1834 if (ret == MIGRATEPAGE_SUCCESS) {
Nadav Amit 2019-04-25 1835 balloon_page_insert(&b->b_dev_info, newpage);
Nadav Amit 2019-04-25 1836 __count_vm_event(BALLOON_MIGRATE);
Nadav Amit 2019-04-25 1837 }
Nadav Amit 2019-04-25 1838
Nadav Amit 2019-04-25 1839 /*
Nadav Amit 2019-04-25 1840 * We deflated successfully, so regardless to the inflation success, we
Nadav Amit 2019-04-25 1841 * need to reduce the number of isolated_pages.
Nadav Amit 2019-04-25 1842 */
Nadav Amit 2019-04-25 1843 b->b_dev_info.isolated_pages--;
Nadav Amit 2019-04-25 1844 spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
Nadav Amit 2019-04-25 1845
Nadav Amit 2019-04-25 1846 out_unlock:
Nadav Amit 2019-04-25 1847 up_read(&b->conf_sem);
Nadav Amit 2019-04-25 1848 return ret;
Nadav Amit 2019-04-25 1849 }
Nadav Amit 2019-04-25 1850
/>

2022-09-15 03:33:20

by Nadav Amit

[permalink] [raw]

Subject: Re: [PATCH 3/3] vmw_balloon: open-code vmballoon_compaction_init()

On Sep 14, 2022, at 5:05 PM, kernel test robot <[email protected]> wrote:

> ⚠ External Email
>
> Hi Nadav,
>
> I love your patch! Yet something to improve:

Ugh. Last minute change and my build was done without VMW_BALLOON.

Sorry. Will send v2.

Regards,
Nadav

2022-09-16 09:16:53

by kernel test robot

[permalink] [raw]

Subject: Re: [PATCH 3/3] vmw_balloon: open-code vmballoon_compaction_init()

Hi Nadav,

I love your patch! Yet something to improve:

[auto build test ERROR on char-misc/char-misc-testing]
[also build test ERROR on linus/master v6.0-rc5 next-20220915]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/Nadav-Amit/vmw_balloon-misc-fixes-and-enhancements/20220914-021333
base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git ceecbbddbf549fe0b7ffa3804a6e255b3360030f
config: x86_64-randconfig-a014 (https://download.01.org/0day-ci/archive/20220916/[email protected]/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/aa1f38765dd703cbeb3450454d0b5b2c7f5a8f8d
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Nadav-Amit/vmw_balloon-misc-fixes-and-enhancements/20220914-021333
git checkout aa1f38765dd703cbeb3450454d0b5b2c7f5a8f8d
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <[email protected]>

All errors (new ones prefixed by >>):

>> drivers/misc/vmw_balloon.c:1892:3: error: use of undeclared identifier 'b'
b->b_dev_info.migratepage = vmballoon_migratepage;
^
drivers/misc/vmw_balloon.c:1732:2: error: unterminated conditional directive
#ifdef CONFIG_BALLOON_COMPACTION
^
2 errors generated.

vim +/b +1892 drivers/misc/vmw_balloon.c

1850
1851 static int __init vmballoon_init(void)
1852 {
1853 int error;
1854
1855 /*
1856 * Check if we are running on VMware's hypervisor and bail out
1857 * if we are not.
1858 */
1859 if (x86_hyper_type != X86_HYPER_VMWARE)
1860 return -ENODEV;
1861
1862 INIT_LIST_HEAD(&balloon.huge_pages);
1863 spin_lock_init(&balloon.comm_lock);
1864 init_rwsem(&balloon.conf_sem);
1865 balloon.vmci_doorbell = VMCI_INVALID_HANDLE;
1866 balloon.batch_page = NULL;
1867 balloon.page = NULL;
1868 balloon.reset_required = true;
1869
1870 /*
1871 * Reset the balloon to check that it is indeed supported.
1872 */
1873 error = vmballoon_reset(&balloon);
1874 if (error) {
1875 pr_err("memory ballooning is disabled");
1876 goto fail;
1877 }
1878
1879 INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);
1880
1881 error = vmballoon_register_shrinker(&balloon);
1882 if (error)
1883 goto fail;
1884
1885 /*
1886 * Initialization of compaction must be done after the call to
1887 * balloon_devinfo_init() .
1888 */
1889 balloon_devinfo_init(&balloon.b_dev_info);
1890
1891 if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
> 1892 b->b_dev_info.migratepage = vmballoon_migratepage;
1893
1894 queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);
1895
1896 vmballoon_debugfs_init(&balloon);
1897
1898 return 0;
1899 fail:
1900 vmballoon_unregister_shrinker(&balloon);
1901 return error;
1902 }
1903

--
0-DAY CI Kernel Test Service
https://01.org/lkp