erofs: move erofs out of staging

EROFS filesystem has been merged into linux-staging for a year.

EROFS is designed to be a better solution of saving extra storage
space with guaranteed end-to-end performance for read-only files
with the help of reduced metadata, fixed-sized output compression
and decompression inplace technologies.

In the past year, EROFS was greatly improved by many people as
a staging driver, self-tested, betaed by a large number of our
internal users, successfully applied to almost all in-service
HUAWEI smartphones as the part of EMUI 9.1 and proven to be stable
enough to be moved out of staging.

EROFS is a self-contained filesystem driver. Although there are
still some TODOs to be more generic, we have a dedicated team
actively keeping on working on EROFS in order to make it better
with the evolution of Linux kernel as the other in-kernel filesystems.

As Pavel suggested, it's better to do as one commit since git
can do moves and all histories will be saved in this way.

Let's promote it from staging and enhance it more actively as
a "real" part of kernel for more wider scenarios!

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Pavel Machek <pavel@denx.de>
Cc: David Sterba <dsterba@suse.cz>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Darrick J . Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Richard Weinberger <richard@nod.at>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Miao Xie <miaoxie@huawei.com>
Cc: Li Guifu <bluce.liguifu@huawei.com>
Cc: Fang Wei <fangwei1@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190822213659.5501-1-hsiangkao@aol.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 333 insertions, 0 deletions

diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
new file mode 100644
index 000000000000..1dd041aa0f5a
--- /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 (unlikely(o <= 0))
+                return -1;
+
+        if (unlikely(atomic_cmpxchg(&grp->refcount, o, o + 1) != o))
+                goto repeat;
+
+        /* decrease refcount paired by erofs_workgroup_put */
+        if (unlikely(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 (unlikely(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 (unlikely(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 (unlikely(!--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 */
+