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Revert "mm/z3fold.c: fix race between migration and destruction"

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With the original commit applied, z3fold_zpool_destroy() may get blocked
on wait_event() for indefinite time.  Revert this commit for the time
being to get rid of this problem since the issue the original commit
addresses is less severe.

Link: http://lkml.kernel.org/r/20190910123142.7a9c8d2de4d0acbc0977c602@gmail.com
Fixes: d776aaa989 ("mm/z3fold.c: fix race between migration and destruction")
Reported-by: Agustín Dall'Alba <agustin@dallalba.com.ar>
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vitaly Wool 2019-09-23 15:32:56 -07:00 committed by Linus Torvalds
parent 07bfa4415a
commit 6e73fd25e2
1 changed files with 0 additions and 90 deletions
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90
mm/z3fold.c
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@ -41,7 +41,6 @@
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/zpool.h>
#include <linux/magic.h>
@ -146,8 +145,6 @@ struct z3fold_header {
* @release_wq: workqueue for safe page release
* @work: work_struct for safe page release
* @inode: inode for z3fold pseudo filesystem
* @destroying: bool to stop migration once we start destruction
* @isolated: int to count the number of pages currently in isolation
*
* This structure is allocated at pool creation time and maintains metadata
* pertaining to a particular z3fold pool.
@ -166,11 +163,8 @@ struct z3fold_pool {
const struct zpool_ops *zpool_ops;
struct workqueue_struct *compact_wq;
struct workqueue_struct *release_wq;
struct wait_queue_head isolate_wait;
struct work_struct work;
struct inode *inode;
bool destroying;
int isolated;
};
/*
@ -775,7 +769,6 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
goto out_c;
spin_lock_init(&pool->lock);
spin_lock_init(&pool->stale_lock);
init_waitqueue_head(&pool->isolate_wait);
pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
if (!pool->unbuddied)
goto out_pool;
@ -815,15 +808,6 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
return NULL;
}
static bool pool_isolated_are_drained(struct z3fold_pool *pool)
{
bool ret;
spin_lock(&pool->lock);
ret = pool->isolated == 0;
spin_unlock(&pool->lock);
return ret;
}
/**
* z3fold_destroy_pool() - destroys an existing z3fold pool
* @pool: the z3fold pool to be destroyed
@ -833,22 +817,6 @@ static bool pool_isolated_are_drained(struct z3fold_pool *pool)
static void z3fold_destroy_pool(struct z3fold_pool *pool)
{
kmem_cache_destroy(pool->c_handle);
/*
* We set pool-> destroying under lock to ensure that
* z3fold_page_isolate() sees any changes to destroying. This way we
* avoid the need for any memory barriers.
*/
spin_lock(&pool->lock);
pool->destroying = true;
spin_unlock(&pool->lock);
/*
* We need to ensure that no pages are being migrated while we destroy
* these workqueues, as migration can queue work on either of the
* workqueues.
*/
wait_event(pool->isolate_wait, !pool_isolated_are_drained(pool));
/*
* We need to destroy pool->compact_wq before pool->release_wq,
@ -1339,28 +1307,6 @@ static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
return atomic64_read(&pool->pages_nr);
}
/*
* z3fold_dec_isolated() expects to be called while pool->lock is held.
*/
static void z3fold_dec_isolated(struct z3fold_pool *pool)
{
assert_spin_locked(&pool->lock);
VM_BUG_ON(pool->isolated <= 0);
pool->isolated--;
/*
* If we have no more isolated pages, we have to see if
* z3fold_destroy_pool() is waiting for a signal.
*/
if (pool->isolated == 0 && waitqueue_active(&pool->isolate_wait))
wake_up_all(&pool->isolate_wait);
}
static void z3fold_inc_isolated(struct z3fold_pool *pool)
{
pool->isolated++;
}
static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
{
struct z3fold_header *zhdr;
@ -1387,34 +1333,6 @@ static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
spin_lock(&pool->lock);
if (!list_empty(&page->lru))
list_del(&page->lru);
/*
* We need to check for destruction while holding pool->lock, as
* otherwise destruction could see 0 isolated pages, and
* proceed.
*/
if (unlikely(pool->destroying)) {
spin_unlock(&pool->lock);
/*
* If this page isn't stale, somebody else holds a
* reference to it. Let't drop our refcount so that they
* can call the release logic.
*/
if (unlikely(kref_put(&zhdr->refcount,
release_z3fold_page_locked))) {
/*
* If we get here we have kref problems, so we
* should freak out.
*/
WARN(1, "Z3fold is experiencing kref problems\n");
z3fold_page_unlock(zhdr);
return false;
}
z3fold_page_unlock(zhdr);
return false;
}
z3fold_inc_isolated(pool);
spin_unlock(&pool->lock);
z3fold_page_unlock(zhdr);
return true;
@ -1483,10 +1401,6 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
spin_lock(&pool->lock);
z3fold_dec_isolated(pool);
spin_unlock(&pool->lock);
page_mapcount_reset(page);
put_page(page);
return 0;
@ -1506,14 +1420,10 @@ static void z3fold_page_putback(struct page *page)
INIT_LIST_HEAD(&page->lru);
if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
atomic64_dec(&pool->pages_nr);
spin_lock(&pool->lock);
z3fold_dec_isolated(pool);
spin_unlock(&pool->lock);
return;
}
spin_lock(&pool->lock);
list_add(&page->lru, &pool->lru);
z3fold_dec_isolated(pool);
spin_unlock(&pool->lock);
z3fold_page_unlock(zhdr);
}