Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
new file mode 100644
index 0000000..d92b3e7
--- /dev/null
+++ b/fs/erofs/utils.c
@@ -0,0 +1,333 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2018 HUAWEI, Inc.
+ * http://www.huawei.com/
+ * Created by Gao Xiang <gaoxiang25@huawei.com>
+ */
+#include "internal.h"
+#include <linux/pagevec.h>
+
+struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp, bool nofail)
+{
+ struct page *page;
+
+ if (!list_empty(pool)) {
+ page = lru_to_page(pool);
+ DBG_BUGON(page_ref_count(page) != 1);
+ list_del(&page->lru);
+ } else {
+ page = alloc_pages(gfp | (nofail ? __GFP_NOFAIL : 0), 0);
+ }
+ return page;
+}
+
+#if (EROFS_PCPUBUF_NR_PAGES > 0)
+static struct {
+ u8 data[PAGE_SIZE * EROFS_PCPUBUF_NR_PAGES];
+} ____cacheline_aligned_in_smp erofs_pcpubuf[NR_CPUS];
+
+void *erofs_get_pcpubuf(unsigned int pagenr)
+{
+ preempt_disable();
+ return &erofs_pcpubuf[smp_processor_id()].data[pagenr * PAGE_SIZE];
+}
+#endif
+
+#ifdef CONFIG_EROFS_FS_ZIP
+/* global shrink count (for all mounted EROFS instances) */
+static atomic_long_t erofs_global_shrink_cnt;
+
+#define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount)
+#define __erofs_workgroup_put(grp) atomic_dec(&(grp)->refcount)
+
+static int erofs_workgroup_get(struct erofs_workgroup *grp)
+{
+ int o;
+
+repeat:
+ o = erofs_wait_on_workgroup_freezed(grp);
+ if (o <= 0)
+ return -1;
+
+ if (atomic_cmpxchg(&grp->refcount, o, o + 1) != o)
+ goto repeat;
+
+ /* decrease refcount paired by erofs_workgroup_put */
+ if (o == 1)
+ atomic_long_dec(&erofs_global_shrink_cnt);
+ return 0;
+}
+
+struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
+ pgoff_t index, bool *tag)
+{
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+ struct erofs_workgroup *grp;
+
+repeat:
+ rcu_read_lock();
+ grp = radix_tree_lookup(&sbi->workstn_tree, index);
+ if (grp) {
+ *tag = xa_pointer_tag(grp);
+ grp = xa_untag_pointer(grp);
+
+ if (erofs_workgroup_get(grp)) {
+ /* prefer to relax rcu read side */
+ rcu_read_unlock();
+ goto repeat;
+ }
+
+ DBG_BUGON(index != grp->index);
+ }
+ rcu_read_unlock();
+ return grp;
+}
+
+int erofs_register_workgroup(struct super_block *sb,
+ struct erofs_workgroup *grp,
+ bool tag)
+{
+ struct erofs_sb_info *sbi;
+ int err;
+
+ /* grp shouldn't be broken or used before */
+ if (atomic_read(&grp->refcount) != 1) {
+ DBG_BUGON(1);
+ return -EINVAL;
+ }
+
+ err = radix_tree_preload(GFP_NOFS);
+ if (err)
+ return err;
+
+ sbi = EROFS_SB(sb);
+ xa_lock(&sbi->workstn_tree);
+
+ grp = xa_tag_pointer(grp, tag);
+
+ /*
+ * Bump up reference count before making this workgroup
+ * visible to other users in order to avoid potential UAF
+ * without serialized by workstn_lock.
+ */
+ __erofs_workgroup_get(grp);
+
+ err = radix_tree_insert(&sbi->workstn_tree, grp->index, grp);
+ if (err)
+ /*
+ * it's safe to decrease since the workgroup isn't visible
+ * and refcount >= 2 (cannot be freezed).
+ */
+ __erofs_workgroup_put(grp);
+
+ xa_unlock(&sbi->workstn_tree);
+ radix_tree_preload_end();
+ return err;
+}
+
+static void __erofs_workgroup_free(struct erofs_workgroup *grp)
+{
+ atomic_long_dec(&erofs_global_shrink_cnt);
+ erofs_workgroup_free_rcu(grp);
+}
+
+int erofs_workgroup_put(struct erofs_workgroup *grp)
+{
+ int count = atomic_dec_return(&grp->refcount);
+
+ if (count == 1)
+ atomic_long_inc(&erofs_global_shrink_cnt);
+ else if (!count)
+ __erofs_workgroup_free(grp);
+ return count;
+}
+
+static void erofs_workgroup_unfreeze_final(struct erofs_workgroup *grp)
+{
+ erofs_workgroup_unfreeze(grp, 0);
+ __erofs_workgroup_free(grp);
+}
+
+static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
+ struct erofs_workgroup *grp,
+ bool cleanup)
+{
+ /*
+ * If managed cache is on, refcount of workgroups
+ * themselves could be < 0 (freezed). In other words,
+ * there is no guarantee that all refcounts > 0.
+ */
+ if (!erofs_workgroup_try_to_freeze(grp, 1))
+ return false;
+
+ /*
+ * Note that all cached pages should be unattached
+ * before deleted from the radix tree. Otherwise some
+ * cached pages could be still attached to the orphan
+ * old workgroup when the new one is available in the tree.
+ */
+ if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
+ erofs_workgroup_unfreeze(grp, 1);
+ return false;
+ }
+
+ /*
+ * It's impossible to fail after the workgroup is freezed,
+ * however in order to avoid some race conditions, add a
+ * DBG_BUGON to observe this in advance.
+ */
+ DBG_BUGON(xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,
+ grp->index)) != grp);
+
+ /*
+ * If managed cache is on, last refcount should indicate
+ * the related workstation.
+ */
+ erofs_workgroup_unfreeze_final(grp);
+ return true;
+}
+
+static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
+ unsigned long nr_shrink,
+ bool cleanup)
+{
+ pgoff_t first_index = 0;
+ void *batch[PAGEVEC_SIZE];
+ unsigned int freed = 0;
+
+ int i, found;
+repeat:
+ xa_lock(&sbi->workstn_tree);
+
+ found = radix_tree_gang_lookup(&sbi->workstn_tree,
+ batch, first_index, PAGEVEC_SIZE);
+
+ for (i = 0; i < found; ++i) {
+ struct erofs_workgroup *grp = xa_untag_pointer(batch[i]);
+
+ first_index = grp->index + 1;
+
+ /* try to shrink each valid workgroup */
+ if (!erofs_try_to_release_workgroup(sbi, grp, cleanup))
+ continue;
+
+ ++freed;
+ if (!--nr_shrink)
+ break;
+ }
+ xa_unlock(&sbi->workstn_tree);
+
+ if (i && nr_shrink)
+ goto repeat;
+ return freed;
+}
+
+/* protected by 'erofs_sb_list_lock' */
+static unsigned int shrinker_run_no;
+
+/* protects the mounted 'erofs_sb_list' */
+static DEFINE_SPINLOCK(erofs_sb_list_lock);
+static LIST_HEAD(erofs_sb_list);
+
+void erofs_shrinker_register(struct super_block *sb)
+{
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+ mutex_init(&sbi->umount_mutex);
+
+ spin_lock(&erofs_sb_list_lock);
+ list_add(&sbi->list, &erofs_sb_list);
+ spin_unlock(&erofs_sb_list_lock);
+}
+
+void erofs_shrinker_unregister(struct super_block *sb)
+{
+ struct erofs_sb_info *const sbi = EROFS_SB(sb);
+
+ mutex_lock(&sbi->umount_mutex);
+ erofs_shrink_workstation(sbi, ~0UL, true);
+
+ spin_lock(&erofs_sb_list_lock);
+ list_del(&sbi->list);
+ spin_unlock(&erofs_sb_list_lock);
+ mutex_unlock(&sbi->umount_mutex);
+}
+
+static unsigned long erofs_shrink_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ return atomic_long_read(&erofs_global_shrink_cnt);
+}
+
+static unsigned long erofs_shrink_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct erofs_sb_info *sbi;
+ struct list_head *p;
+
+ unsigned long nr = sc->nr_to_scan;
+ unsigned int run_no;
+ unsigned long freed = 0;
+
+ spin_lock(&erofs_sb_list_lock);
+ do {
+ run_no = ++shrinker_run_no;
+ } while (run_no == 0);
+
+ /* Iterate over all mounted superblocks and try to shrink them */
+ p = erofs_sb_list.next;
+ while (p != &erofs_sb_list) {
+ sbi = list_entry(p, struct erofs_sb_info, list);
+
+ /*
+ * We move the ones we do to the end of the list, so we stop
+ * when we see one we have already done.
+ */
+ if (sbi->shrinker_run_no == run_no)
+ break;
+
+ if (!mutex_trylock(&sbi->umount_mutex)) {
+ p = p->next;
+ continue;
+ }
+
+ spin_unlock(&erofs_sb_list_lock);
+ sbi->shrinker_run_no = run_no;
+
+ freed += erofs_shrink_workstation(sbi, nr, false);
+
+ spin_lock(&erofs_sb_list_lock);
+ /* Get the next list element before we move this one */
+ p = p->next;
+
+ /*
+ * Move this one to the end of the list to provide some
+ * fairness.
+ */
+ list_move_tail(&sbi->list, &erofs_sb_list);
+ mutex_unlock(&sbi->umount_mutex);
+
+ if (freed >= nr)
+ break;
+ }
+ spin_unlock(&erofs_sb_list_lock);
+ return freed;
+}
+
+static struct shrinker erofs_shrinker_info = {
+ .scan_objects = erofs_shrink_scan,
+ .count_objects = erofs_shrink_count,
+ .seeks = DEFAULT_SEEKS,
+};
+
+int __init erofs_init_shrinker(void)
+{
+ return register_shrinker(&erofs_shrinker_info);
+}
+
+void erofs_exit_shrinker(void)
+{
+ unregister_shrinker(&erofs_shrinker_info);
+}
+#endif /* !CONFIG_EROFS_FS_ZIP */
+