/*
 * f2fs shrinker support
 *   the basic infra was copied from fs/ubifs/shrinker.c
 *
 * Copyright (c) 2015 Motorola Mobility
 * Copyright (c) 2015 Jaegeuk Kim <jaegeuk@kernel.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/fs.h>
#include <linux/f2fs_fs.h>

#include "f2fs.h"
#include "node.h"

static LIST_HEAD(f2fs_list);
static DEFINE_SPINLOCK(f2fs_list_lock);
static unsigned int shrinker_run_no;

static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi)
{
	long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;

	return count > 0 ? count : 0;
}

static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
{
	long count = NM_I(sbi)->nid_cnt[FREE_NID_LIST] - MAX_FREE_NIDS;

	return count > 0 ? count : 0;
}

static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
{
	return atomic_read(&sbi->total_zombie_tree) +
				atomic_read(&sbi->total_ext_node);
}

unsigned long f2fs_shrink_count(struct shrinker *shrink,
				struct shrink_control *sc)
{
	struct f2fs_sb_info *sbi;
	struct list_head *p;
	unsigned long count = 0;

	spin_lock(&f2fs_list_lock);
	p = f2fs_list.next;
	while (p != &f2fs_list) {
		sbi = list_entry(p, struct f2fs_sb_info, s_list);

		/* stop f2fs_put_super */
		if (!mutex_trylock(&sbi->umount_mutex)) {
			p = p->next;
			continue;
		}
		spin_unlock(&f2fs_list_lock);

		/* count extent cache entries */
		count += __count_extent_cache(sbi);

		/* shrink clean nat cache entries */
		count += __count_nat_entries(sbi);

		/* count free nids cache entries */
		count += __count_free_nids(sbi);

		spin_lock(&f2fs_list_lock);
		p = p->next;
		mutex_unlock(&sbi->umount_mutex);
	}
	spin_unlock(&f2fs_list_lock);
	return count;
}

unsigned long f2fs_shrink_scan(struct shrinker *shrink,
				struct shrink_control *sc)
{
	unsigned long nr = sc->nr_to_scan;
	struct f2fs_sb_info *sbi;
	struct list_head *p;
	unsigned int run_no;
	unsigned long freed = 0;

	spin_lock(&f2fs_list_lock);
	do {
		run_no = ++shrinker_run_no;
	} while (run_no == 0);
	p = f2fs_list.next;
	while (p != &f2fs_list) {
		sbi = list_entry(p, struct f2fs_sb_info, s_list);

		if (sbi->shrinker_run_no == run_no)
			break;

		/* stop f2fs_put_super */
		if (!mutex_trylock(&sbi->umount_mutex)) {
			p = p->next;
			continue;
		}
		spin_unlock(&f2fs_list_lock);

		sbi->shrinker_run_no = run_no;

		/* shrink extent cache entries */
		freed += f2fs_shrink_extent_tree(sbi, nr >> 1);

		/* shrink clean nat cache entries */
		if (freed < nr)
			freed += try_to_free_nats(sbi, nr - freed);

		/* shrink free nids cache entries */
		if (freed < nr)
			freed += try_to_free_nids(sbi, nr - freed);

		spin_lock(&f2fs_list_lock);
		p = p->next;
		list_move_tail(&sbi->s_list, &f2fs_list);
		mutex_unlock(&sbi->umount_mutex);
		if (freed >= nr)
			break;
	}
	spin_unlock(&f2fs_list_lock);
	return freed;
}

void f2fs_join_shrinker(struct f2fs_sb_info *sbi)
{
	spin_lock(&f2fs_list_lock);
	list_add_tail(&sbi->s_list, &f2fs_list);
	spin_unlock(&f2fs_list_lock);
}

void f2fs_leave_shrinker(struct f2fs_sb_info *sbi)
{
	f2fs_shrink_extent_tree(sbi, __count_extent_cache(sbi));

	spin_lock(&f2fs_list_lock);
	list_del(&sbi->s_list);
	spin_unlock(&f2fs_list_lock);
}
ntext' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/net/gue.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/include/net/gue.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/include/net/gue.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>include/net/gue.h</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/net/gue.h?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/include/net/gue.h?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'include/net/gue.h')</div><table summary='diffstat' class='diffstat'>