[PATCH 24/25] staging: erofs: introduce cached decompression

Gao Xiang
2018-07-26T12:29:17Z

This patch adds an optional choice which can be
enabled by users in order to cache both incomplete
ends of compressed clusters as a complement to
the in-place decompression in order to boost random
read, but it costs more memory than the in-place
decompression only.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
drivers/staging/erofs/Kconfig | 38 ++++++
drivers/staging/erofs/internal.h | 26 ++++
drivers/staging/erofs/super.c | 73 ++++++++++
drivers/staging/erofs/unzip_vle.c | 274 ++++++++++++++++++++++++++++++++++++++
drivers/staging/erofs/utils.c | 17 ++-
5 files changed, 427 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/erofs/Kconfig b/drivers/staging/erofs/Kconfig
index b55ce1c..663b755 100644
--- a/drivers/staging/erofs/Kconfig
+++ b/drivers/staging/erofs/Kconfig
@@ -101,3 +101,41 @@ config EROFS_FS_CLUSTER_PAGE_LIMIT
than 2. Otherwise, the image cannot be mounted
correctly on this kernel.

+choice
+ prompt "EROFS VLE Data Decompression mode"
+ depends on EROFS_FS_ZIP
+ default EROFS_FS_ZIP_CACHE_BIPOLAR
+ help
+ EROFS supports three options for VLE decompression.
+ "In-place Decompression Only" consumes the minimum memory
+ with lowest random read.
+
+ "Bipolar Cached Decompression" consumes the maximum memory
+ with highest random read.
+
+ If unsure, select "Bipolar Cached Decompression"
+
+config EROFS_FS_ZIP_NO_CACHE
+ bool "In-place Decompression Only"
+ help
+ Read compressed data into page cache and do in-place
+ decompression directly.
+
+config EROFS_FS_ZIP_CACHE_UNIPOLAR
+ bool "Unipolar Cached Decompression"
+ help
+ For each request, it caches the last compressed page
+ for further reading.
+ It still decompresses in place for the rest compressed pages.
+
+config EROFS_FS_ZIP_CACHE_BIPOLAR
+ bool "Bipolar Cached Decompression"
+ help
+ For each request, it caches the both end compressed pages
+ for further reading.
+ It still decompresses in place for the rest compressed pages.
+
+ Recommended for performance priority.
+
+endchoice
+
diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
index 3adec7d..669f93a 100644
--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -58,6 +58,18 @@ struct erofs_fault_info {
};
#endif

+#ifdef CONFIG_EROFS_FS_ZIP_CACHE_BIPOLAR
+#define EROFS_FS_ZIP_CACHE_LVL (2)
+#elif defined(EROFS_FS_ZIP_CACHE_UNIPOLAR)
+#define EROFS_FS_ZIP_CACHE_LVL (1)
+#else
+#define EROFS_FS_ZIP_CACHE_LVL (0)
+#endif
+
+#if (!defined(EROFS_FS_HAS_MANAGED_CACHE) && (EROFS_FS_ZIP_CACHE_LVL > 0))
+#define EROFS_FS_HAS_MANAGED_CACHE
+#endif
+
/* EROFS_SUPER_MAGIC_V1 to represent the whole file system */
#define EROFS_SUPER_MAGIC EROFS_SUPER_MAGIC_V1

@@ -82,6 +94,11 @@ struct erofs_sb_info {

/* the dedicated workstation for compression */
struct radix_tree_root workstn_tree;
+
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ struct inode *managed_cache;
+#endif
+
#endif

u32 build_time_nsec;
@@ -240,6 +257,15 @@ static inline void erofs_workstation_cleanup_all(struct super_block *sb)
erofs_shrink_workstation(EROFS_SB(sb), ~0UL, true);
}

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+#define EROFS_UNALLOCATED_CACHED_PAGE ((void *)0x5F0EF00D)
+
+extern int try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
+ struct erofs_workgroup *egrp);
+extern int try_to_free_cached_page(struct address_space *mapping,
+ struct page *page);
+#endif
+
#endif

/* we strictly follow PAGE_SIZE and no buffer head yet */
diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
index 2bd433a..97da5c8 100644
--- a/drivers/staging/erofs/super.c
+++ b/drivers/staging/erofs/super.c
@@ -256,6 +256,63 @@ static int parse_options(struct super_block *sb, char *options)
return 0;
}

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+
+static const struct address_space_operations managed_cache_aops;
+
+static int managed_cache_releasepage(struct page *page, gfp_t gfp_mask)
+{
+ int ret = 1; /* 0 - busy */
+ struct address_space *const mapping = page->mapping;
+
+ BUG_ON(!PageLocked(page));
+ BUG_ON(mapping->a_ops != &managed_cache_aops);
+
+ if (PagePrivate(page))
+ ret = try_to_free_cached_page(mapping, page);
+
+ return ret;
+}
+
+static void managed_cache_invalidatepage(struct page *page,
+ unsigned int offset, unsigned int length)
+{
+ const unsigned int stop = length + offset;
+
+ BUG_ON(!PageLocked(page));
+
+ /* Check for overflow */
+ BUG_ON(stop > PAGE_SIZE || stop < length);
+
+ if (offset == 0 && stop == PAGE_SIZE)
+ while (!managed_cache_releasepage(page, GFP_NOFS))
+ cond_resched();
+}
+
+static const struct address_space_operations managed_cache_aops = {
+ .releasepage = managed_cache_releasepage,
+ .invalidatepage = managed_cache_invalidatepage,
+};
+
+static struct inode *erofs_init_managed_cache(struct super_block *sb)
+{
+ struct inode *inode = new_inode(sb);
+
+ if (unlikely(inode == NULL))
+ return ERR_PTR(-ENOMEM);
+
+ set_nlink(inode, 1);
+ inode->i_size = OFFSET_MAX;
+
+ inode->i_mapping->a_ops = &managed_cache_aops;
+ mapping_set_gfp_mask(inode->i_mapping,
+ GFP_NOFS | __GFP_HIGHMEM |
+ __GFP_MOVABLE | __GFP_NOFAIL);
+ return inode;
+}
+
+#endif
+
static int erofs_read_super(struct super_block *sb,
const char *dev_name, void *data, int silent)
{
@@ -307,6 +364,14 @@ static int erofs_read_super(struct super_block *sb,
INIT_RADIX_TREE(&sbi->workstn_tree, GFP_ATOMIC);
#endif

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ sbi->managed_cache = erofs_init_managed_cache(sb);
+ if (IS_ERR(sbi->managed_cache)) {
+ err = PTR_ERR(sbi->managed_cache);
+ goto err_init_managed_cache;
+ }
+#endif
+
/* get the root inode */
inode = erofs_iget(sb, ROOT_NID(sbi), true);
if (IS_ERR(inode)) {
@@ -361,6 +426,10 @@ static int erofs_read_super(struct super_block *sb,
if (sb->s_root == NULL)
iput(inode);
err_iget:
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ iput(sbi->managed_cache);
+err_init_managed_cache:
+#endif
err_parseopt:
err_sbread:
sb->s_fs_info = NULL;
@@ -386,6 +455,10 @@ static void erofs_put_super(struct super_block *sb)
infoln("unmounted for %s", sbi->dev_name);
__putname(sbi->dev_name);

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ iput(sbi->managed_cache);
+#endif
+
mutex_lock(&sbi->umount_mutex);

#ifdef CONFIG_EROFS_FS_ZIP
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index f0ead60..7671fe8 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -95,6 +95,111 @@ struct z_erofs_vle_work_builder {
#define VLE_WORK_BUILDER_INIT() \
{ .work = NULL, .role = Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED }

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+
+static bool grab_managed_cache_pages(struct address_space *mapping,
+ erofs_blk_t start,
+ struct page **compressed_pages,
+ int clusterblks,
+ bool reserve_allocation)
+{
+ bool noio = true;
+ unsigned int i;
+
+ /* TODO: optimize by introducing find_get_pages_range */
+ for (i = 0; i < clusterblks; ++i) {
+ struct page *page, *found;
+
+ if (READ_ONCE(compressed_pages[i]) != NULL)
+ continue;
+
+ page = found = find_get_page(mapping, start + i);
+ if (found == NULL) {
+ noio = false;
+ if (!reserve_allocation)
+ continue;
+ page = EROFS_UNALLOCATED_CACHED_PAGE;
+ }
+
+ if (NULL == cmpxchg(compressed_pages + i, NULL, page))
+ continue;
+
+ if (found != NULL)
+ put_page(found);
+ }
+ return noio;
+}
+
+/* called by erofs_shrinker to get rid of all compressed_pages */
+int try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
+ struct erofs_workgroup *egrp)
+{
+ struct z_erofs_vle_workgroup *const grp =
+ container_of(egrp, struct z_erofs_vle_workgroup, obj);
+ struct address_space *const mapping = sbi->managed_cache->i_mapping;
+ const int clusterpages = erofs_clusterpages(sbi);
+ int i;
+
+ /*
+ * refcount of workgroup is now freezed as 1,
+ * therefore no need to worry about available decompression users.
+ */
+ for (i = 0; i < clusterpages; ++i) {
+ struct page *page = grp->compressed_pages[i];
+
+ if (page == NULL || page->mapping != mapping)
+ continue;
+
+ /* block other users from reclaiming or migrating the page */
+ if (!trylock_page(page))
+ return -EBUSY;
+
+ /* barrier is implied in the following 'unlock_page' */
+ WRITE_ONCE(grp->compressed_pages[i], NULL);
+
+ set_page_private(page, 0);
+ ClearPagePrivate(page);
+
+ unlock_page(page);
+ put_page(page);
+ }
+ return 0;
+}
+
+int try_to_free_cached_page(struct address_space *mapping, struct page *page)
+{
+ struct erofs_sb_info *const sbi = EROFS_SB(mapping->host->i_sb);
+ const unsigned int clusterpages = erofs_clusterpages(sbi);
+
+ struct z_erofs_vle_workgroup *grp;
+ int ret = 0; /* 0 - busy */
+
+ /* prevent the workgroup from being freed */
+ rcu_read_lock();
+ grp = (void *)page_private(page);
+
+ if (erofs_workgroup_try_to_freeze(&grp->obj, 1)) {
+ unsigned int i;
+
+ for (i = 0; i < clusterpages; ++i) {
+ if (grp->compressed_pages[i] == page) {
+ WRITE_ONCE(grp->compressed_pages[i], NULL);
+ ret = 1;
+ break;
+ }
+ }
+ erofs_workgroup_unfreeze(&grp->obj, 1);
+ }
+ rcu_read_unlock();
+
+ if (ret) {
+ ClearPagePrivate(page);
+ put_page(page);
+ }
+ return ret;
+}
+#endif
+
/* page_type must be Z_EROFS_PAGE_TYPE_EXCLUSIVE */
static inline bool try_to_reuse_as_compressed_page(
struct z_erofs_vle_work_builder *b,
@@ -463,6 +568,9 @@ struct z_erofs_vle_frontend {
z_erofs_vle_owned_workgrp_t owned_head;

bool initial;
+#if (EROFS_FS_ZIP_CACHE_LVL >= 2)
+ erofs_off_t cachedzone_la;
+#endif
};

#define VLE_FRONTEND_INIT(__i) { \
@@ -489,6 +597,12 @@ static int z_erofs_do_read_page(struct z_erofs_vle_frontend *fe,
bool tight = builder_is_followed(builder);
struct z_erofs_vle_work *work = builder->work;

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ struct address_space *const mngda = sbi->managed_cache->i_mapping;
+ struct z_erofs_vle_workgroup *grp;
+ bool noio_outoforder;
+#endif
+
enum z_erofs_page_type page_type;
unsigned cur, end, spiltted, index;
int err;
@@ -529,6 +643,21 @@ static int z_erofs_do_read_page(struct z_erofs_vle_frontend *fe,
if (unlikely(err))
goto err_out;

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ grp = fe->builder.grp;
+
+ /* let's do out-of-order decompression for noio */
+ noio_outoforder = grab_managed_cache_pages(mngda,
+ erofs_blknr(map->m_pa),
+ grp->compressed_pages, erofs_blknr(map->m_plen),
+ /* compressed page caching selection strategy */
+ fe->initial | (EROFS_FS_ZIP_CACHE_LVL >= 2 ?
+ map->m_la < fe->cachedzone_la : 0));
+
+ if (noio_outoforder && builder_is_followed(builder))
+ builder->role = Z_EROFS_VLE_WORK_PRIMARY;
+#endif
+
tight &= builder_is_followed(builder);
work = builder->work;
hitted:
@@ -607,15 +736,39 @@ static inline void z_erofs_vle_read_endio(struct bio *bio)
const blk_status_t err = bio->bi_status;
unsigned i;
struct bio_vec *bvec;
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ struct address_space *mngda = NULL;
+#endif

bio_for_each_segment_all(bvec, bio, i) {
struct page *page = bvec->bv_page;
+ bool cachemngd = false;

DBG_BUGON(PageUptodate(page));
BUG_ON(page->mapping == NULL);

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ if (unlikely(mngda == NULL && !z_erofs_is_stagingpage(page))) {
+ struct inode *const inode = page->mapping->host;
+ struct super_block *const sb = inode->i_sb;
+
+ mngda = EROFS_SB(sb)->managed_cache->i_mapping;
+ }
+
+ /*
+ * If mngda has not gotten, it equals NULL,
+ * however, page->mapping never be NULL if working properly.
+ */
+ cachemngd = (page->mapping == mngda);
+#endif
+
if (unlikely(err))
SetPageError(page);
+ else if (cachemngd)
+ SetPageUptodate(page);
+
+ if (cachemngd)
+ unlock_page(page);
}

z_erofs_vle_unzip_kickoff(bio->bi_private, -1);
@@ -630,6 +783,9 @@ static int z_erofs_vle_unzip(struct super_block *sb,
struct list_head *page_pool)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ struct address_space *const mngda = sbi->managed_cache->i_mapping;
+#endif
const unsigned clusterpages = erofs_clusterpages(sbi);

struct z_erofs_pagevec_ctor ctor;
@@ -727,6 +883,13 @@ static int z_erofs_vle_unzip(struct super_block *sb,

if (z_erofs_is_stagingpage(page))
continue;
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ else if (page->mapping == mngda) {
+ BUG_ON(PageLocked(page));
+ BUG_ON(!PageUptodate(page));
+ continue;
+ }
+#endif

/* only non-head page could be reused as a compressed page */
pagenr = z_erofs_onlinepage_index(page);
@@ -804,6 +967,10 @@ static int z_erofs_vle_unzip(struct super_block *sb,
for (i = 0; i < clusterpages; ++i) {
page = compressed_pages[i];

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ if (page->mapping == mngda)
+ continue;
+#endif
/* recycle all individual staging pages */
(void)z_erofs_gather_if_stagingpage(page_pool, page);

@@ -898,7 +1065,31 @@ static void z_erofs_vle_unzip_wq(struct work_struct *work)
return io;
}

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+/* true - unlocked (noio), false - locked (need submit io) */
+static inline bool recover_managed_page(struct z_erofs_vle_workgroup *grp,
+ struct page *page)
+{
+ wait_on_page_locked(page);
+ if (PagePrivate(page) && PageUptodate(page))
+ return true;
+
+ lock_page(page);
+ if (unlikely(!PagePrivate(page))) {
+ set_page_private(page, (unsigned long)grp);
+ SetPagePrivate(page);
+ }
+ if (unlikely(PageUptodate(page))) {
+ unlock_page(page);
+ return true;
+ }
+ return false;
+}
+
+#define __FSIO_1 1
+#else
#define __FSIO_1 0
+#endif

static bool z_erofs_vle_submit_all(struct super_block *sb,
z_erofs_vle_owned_workgrp_t owned_head,
@@ -909,6 +1100,10 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,
struct erofs_sb_info *const sbi = EROFS_SB(sb);
const unsigned clusterpages = erofs_clusterpages(sbi);
const gfp_t gfp = GFP_NOFS;
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ struct address_space *const mngda = sbi->managed_cache->i_mapping;
+ struct z_erofs_vle_workgroup *lstgrp_noio = NULL, *lstgrp_io = NULL;
+#endif
struct z_erofs_vle_unzip_io *ios[1 + __FSIO_1];
struct bio *bio;
tagptr1_t bi_private;
@@ -924,6 +1119,10 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,
* force_fg == 1, (io, fg_io[0]) no io, (io, fg_io[1]) need submit io
* force_fg == 0, (io, fg_io[0]) no io; (io[1], bg_io) need submit io
*/
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ ios[0] = prepare_io_handler(sb, fg_io + 0, false);
+#endif
+
if (force_fg) {
ios[__FSIO_1] = prepare_io_handler(sb, fg_io + __FSIO_1, false);
bi_private = tagptr_fold(tagptr1_t, ios[__FSIO_1], 0);
@@ -944,6 +1143,10 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,
struct page **compressed_pages, *oldpage, *page;
pgoff_t first_index;
unsigned i = 0;
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ unsigned int noio = 0;
+ bool cachemngd;
+#endif
int err;

/* no possible 'owned_head' equals the following */
@@ -964,15 +1167,40 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,
/* fulfill all compressed pages */
oldpage = page = READ_ONCE(compressed_pages[i]);

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ cachemngd = false;
+
+ if (page == EROFS_UNALLOCATED_CACHED_PAGE) {
+ cachemngd = true;
+ goto do_allocpage;
+ } else if (page != NULL) {
+ if (page->mapping != mngda)
+ BUG_ON(PageUptodate(page));
+ else if (recover_managed_page(grp, page)) {
+ /* page is uptodate, skip io submission */
+ force_submit = true;
+ ++noio;
+ goto skippage;
+ }
+ } else {
+do_allocpage:
+#else
if (page != NULL)
BUG_ON(PageUptodate(page));
else {
+#endif
page = __stagingpage_alloc(pagepool, gfp);

if (oldpage != cmpxchg(compressed_pages + i,
oldpage, page)) {
list_add(&page->lru, pagepool);
goto repeat;
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ } else if (cachemngd && !add_to_page_cache_lru(page,
+ mngda, first_index + i, gfp)) {
+ set_page_private(page, (unsigned long)grp);
+ SetPagePrivate(page);
+#endif
}
}

@@ -996,14 +1224,51 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,

force_submit = false;
last_index = first_index + i;
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+skippage:
+#endif
if (++i < clusterpages)
goto repeat;
+
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ if (noio < clusterpages) {
+ lstgrp_io = grp;
+ } else {
+ z_erofs_vle_owned_workgrp_t iogrp_next =
+ owned_head == Z_EROFS_VLE_WORKGRP_TAIL ?
+ Z_EROFS_VLE_WORKGRP_TAIL_CLOSED :
+ owned_head;
+
+ if (lstgrp_io == NULL)
+ ios[1]->head = iogrp_next;
+ else
+ WRITE_ONCE(lstgrp_io->next, iogrp_next);
+
+ if (lstgrp_noio == NULL)
+ ios[0]->head = grp;
+ else
+ WRITE_ONCE(lstgrp_noio->next, grp);
+
+ lstgrp_noio = grp;
+ }
+#endif
} while (owned_head != Z_EROFS_VLE_WORKGRP_TAIL);

if (bio != NULL)
__submit_bio(bio, REQ_OP_READ, 0);

+#ifndef EROFS_FS_HAS_MANAGED_CACHE
BUG_ON(!nr_bios);
+#else
+ if (lstgrp_noio != NULL)
+ WRITE_ONCE(lstgrp_noio->next, Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
+
+ if (!force_fg && !nr_bios) {
+ kvfree(container_of(ios[1],
+ struct z_erofs_vle_unzip_io_sb, io));
+ return true;
+ }
+#endif

z_erofs_vle_unzip_kickoff(tagptr_cast_ptr(bi_private), nr_bios);
return true;
@@ -1019,6 +1284,9 @@ static void z_erofs_submit_and_unzip(struct z_erofs_vle_frontend *f,
if (!z_erofs_vle_submit_all(sb, f->owned_head, pagepool, io, force_fg))
return;

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ z_erofs_vle_unzip_all(sb, &io[0], pagepool);
+#endif
if (!force_fg)
return;

@@ -1038,6 +1306,9 @@ static int z_erofs_vle_normalaccess_readpage(struct file *file,
int err;
LIST_HEAD(pagepool);

+#if (EROFS_FS_ZIP_CACHE_LVL >= 2)
+ f.cachedzone_la = page->index << PAGE_SHIFT;
+#endif
err = z_erofs_do_read_page(&f, page, &pagepool);
(void)z_erofs_vle_work_iter_end(&f.builder);

@@ -1068,6 +1339,9 @@ static inline int __z_erofs_vle_normalaccess_readpages(
struct page *head = NULL;
LIST_HEAD(pagepool);

+#if (EROFS_FS_ZIP_CACHE_LVL >= 2)
+ f.cachedzone_la = lru_to_page(pages)->index << PAGE_SHIFT;
+#endif
for (; nr_pages; --nr_pages) {
struct page *page = lru_to_page(pages);

diff --git a/drivers/staging/erofs/utils.c b/drivers/staging/erofs/utils.c
index 6530035..ee70bb9 100644
--- a/drivers/staging/erofs/utils.c
+++ b/drivers/staging/erofs/utils.c
@@ -143,13 +143,28 @@ unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
if (cleanup)
BUG_ON(cnt != 1);

+#ifndef EROFS_FS_HAS_MANAGED_CACHE
else if (cnt > 1)
+#else
+ if (!erofs_workgroup_try_to_freeze(grp, 1))
+#endif
continue;

if (radix_tree_delete(&sbi->workstn_tree,
- grp->index) != grp)
+ grp->index) != grp) {
+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+skip:
+ erofs_workgroup_unfreeze(grp, 1);
+#endif
continue;
+ }

+#ifdef EROFS_FS_HAS_MANAGED_CACHE
+ if (try_to_free_all_cached_pages(sbi, grp))
+ goto skip;
+
+ erofs_workgroup_unfreeze(grp, 1);
+#endif
/* (rarely) grabbed again when freeing */
erofs_workgroup_put(grp);

--
1.9.1