Changes since RFC:
1. Fix the macro CONFIG_EROFS_FS_ONDEMAND misuse in
erofs_fc_parse_param().
2. Move the code in domain.c to fscache.c
3. Remove the definition of anon_inode_fs_type and just use erofs
filesystem type to init pseudo mnt.
4. Use mutex lock for erofs_domain_list.
5. Unregister the cookies before kill_sb() to avoid inode busy when
umount erofs.
6. Remove useless declaration of domain_get/put in internal.h
[Kernel Patchset]
===============
Git tree:
https://github.com/userzj/linux.git zhujia/shared-domain-v1
Git web:
https://github.com/userzj/linux/tree/zhujia/shared-domain-v1
[Background]
============
In ondemand read mode, we use individual volume to present an erofs
mountpoint, cookies to present bootstrap and data blobs.
In which case, since cookies can't be shared between fscache volumes,
even if the data blobs between different mountpoints are exactly same,
they can't be shared.
[Introduction]
==============
Here we introduce erofs shared domain to resolve above mentioned case.
Several erofs filesystems can belong to one domain, and data blobs can
be shared among these erofs filesystems of same domain.
[Usage]
Users could specify 'domain_id' mount option to create or join into a
domain which reuses the same cookies(blobs).
[Design]
========
1. Use pseudo mnt to manage domain's lifecycle.
2. Use a linked list to maintain & traverse domains.
3. Use pseudo sb to create anonymous inode for recording cookie's info
and manage cookies lifecycle.
[Flow Path]
===========
1. User specify a new 'domain_id' in mount option.
1.1 Traverse domain list, compare domain_id with existing domain.[Miss]
1.2 Create a new domain(volume), add it to domain list.
1.3 Traverse pseudo sb's inode list, compare cookie name with
existing cookies.[Miss]
1.4 Alloc new anonymous inodes and cookies.
2. User specify an existing 'domain_id' in mount option and the data
blob is existed in domain.
2.1 Traverse domain list, compare domain_id with existing domain.[Hit]
2.2 Reuse the domain and increase its refcnt.
2.3 Traverse pseudo sb's inode list, compare cookie name with
existing cookies.[Hit]
2.4 Reuse the cookie and increase its refcnt.
[Test]
======
Git web:
https://github.com/userzj/demand-read-cachefilesd/tree/shared-domain
More test cases will be added to:
https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git/log/?h=experimental-tests-fscache
RFC: https://lore.kernel.org/all/YxAlO%[email protected]/
Jia Zhu (5):
erofs: add 'domain_id' mount option for on-demand read sementics
erofs: introduce fscache-based domain
erofs: add 'domain_id' prefix when register sysfs
erofs: remove duplicated unregister_cookie
erofs: support fscache based shared domain
fs/erofs/fscache.c | 169 +++++++++++++++++++++++++++++++++++++++++++-
fs/erofs/internal.h | 33 ++++++++-
fs/erofs/super.c | 94 ++++++++++++++++++------
fs/erofs/sysfs.c | 11 ++-
4 files changed, 281 insertions(+), 26 deletions(-)
--
2.20.1
Introduce 'domain_id' mount option to enable shared domain sementics.
In which case, the related cookie is shared if two mountpoints in the
same domain have the same data blob. Users could specify the name of
domain by this mount option.
Signed-off-by: Jia Zhu <[email protected]>
---
fs/erofs/internal.h | 1 +
fs/erofs/super.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+)
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index cfee49d33b95..fe435d077f1a 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -76,6 +76,7 @@ struct erofs_mount_opts {
#endif
unsigned int mount_opt;
char *fsid;
+ char *domain_id;
};
struct erofs_dev_context {
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 3173debeaa5a..d01109069c6b 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -440,6 +440,7 @@ enum {
Opt_dax_enum,
Opt_device,
Opt_fsid,
+ Opt_domain_id,
Opt_err
};
@@ -465,6 +466,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[] = {
fsparam_enum("dax", Opt_dax_enum, erofs_dax_param_enums),
fsparam_string("device", Opt_device),
fsparam_string("fsid", Opt_fsid),
+ fsparam_string("domain_id", Opt_domain_id),
{}
};
@@ -568,6 +570,16 @@ static int erofs_fc_parse_param(struct fs_context *fc,
return -ENOMEM;
#else
errorfc(fc, "fsid option not supported");
+#endif
+ break;
+ case Opt_domain_id:
+#ifdef CONFIG_EROFS_FS_ONDEMAND
+ kfree(ctx->opt.domain_id);
+ ctx->opt.domain_id = kstrdup(param->string, GFP_KERNEL);
+ if (!ctx->opt.domain_id)
+ return -ENOMEM;
+#else
+ errorfc(fc, "domain_id option not supported");
#endif
break;
default:
@@ -695,6 +707,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
sb->s_fs_info = sbi;
sbi->opt = ctx->opt;
ctx->opt.fsid = NULL;
+ ctx->opt.domain_id = NULL;
sbi->devs = ctx->devs;
ctx->devs = NULL;
@@ -838,6 +851,7 @@ static void erofs_fc_free(struct fs_context *fc)
erofs_free_dev_context(ctx->devs);
kfree(ctx->opt.fsid);
+ kfree(ctx->opt.domain_id);
kfree(ctx);
}
@@ -892,6 +906,7 @@ static void erofs_kill_sb(struct super_block *sb)
erofs_fscache_unregister_cookie(&sbi->s_fscache);
erofs_fscache_unregister_fs(sb);
kfree(sbi->opt.fsid);
+ kfree(sbi->opt.domain_id);
kfree(sbi);
sb->s_fs_info = NULL;
}
@@ -1044,6 +1059,8 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
#ifdef CONFIG_EROFS_FS_ONDEMAND
if (opt->fsid)
seq_printf(seq, ",fsid=%s", opt->fsid);
+ if (opt->domain_id)
+ seq_printf(seq, ",domain_id=%s", opt->domain_id);
#endif
return 0;
}
--
2.20.1
Several erofs filesystems can belong to one domain, and data blobs can
be shared among these erofs filesystems of same domain.
Users could specify domain_id mount option to create or join into a domain.
Signed-off-by: Jia Zhu <[email protected]>
---
fs/erofs/fscache.c | 67 +++++++++++++++++++++++++++++++++++++++++++++
fs/erofs/internal.h | 13 +++++++++
fs/erofs/super.c | 10 +++++--
3 files changed, 88 insertions(+), 2 deletions(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index bf6c9ecabec1..07e5d71e412b 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -569,6 +569,8 @@ void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
if (!ctx)
return;
+ if (ctx->domain && !refcount_dec_and_test(&ctx->ref))
+ return;
fscache_unuse_cookie(ctx->cookie, NULL, NULL);
fscache_relinquish_cookie(ctx->cookie, false);
@@ -576,7 +578,12 @@ void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
iput(ctx->inode);
ctx->inode = NULL;
+ iput(ctx->anon_inode);
+ ctx->anon_inode = NULL;
+ erofs_fscache_domain_put(ctx->domain);
+ kfree(ctx->name);
+ ctx->name = NULL;
kfree(ctx);
*fscache = NULL;
}
@@ -616,3 +623,63 @@ void erofs_fscache_unregister_fs(struct super_block *sb)
sbi->volume = NULL;
sbi->domain = NULL;
}
+
+static int erofs_fscache_domain_init_cookie(struct super_block *sb,
+ struct erofs_fscache **fscache, char *name, bool need_inode)
+{
+ int ret;
+ struct inode *inode;
+ struct erofs_fscache *ctx;
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+ struct erofs_domain *domain = sbi->domain;
+
+ ret = erofs_fscache_register_cookie(sb, &ctx, name, need_inode);
+ if (ret)
+ return ret;
+
+ ctx->name = kstrdup(name, GFP_KERNEL);
+ if (!ctx->name)
+ return -ENOMEM;
+
+ inode = new_inode(domain->mnt->mnt_sb);
+ if (!inode) {
+ kfree(ctx->name);
+ return -ENOMEM;
+ }
+
+ ctx->domain = domain;
+ ctx->anon_inode = inode;
+ inode->i_private = ctx;
+ refcount_set(&ctx->ref, 1);
+ erofs_fscache_domain_get(domain);
+ *fscache = ctx;
+ return 0;
+}
+
+int erofs_domain_register_cookie(struct super_block *sb,
+ struct erofs_fscache **fscache, char *name, bool need_inode)
+{
+ int err;
+ struct inode *inode;
+ struct erofs_fscache *ctx;
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+ struct erofs_domain *domain = sbi->domain;
+ struct super_block *psb = domain->mnt->mnt_sb;
+
+ mutex_lock(&domain->mutex);
+ list_for_each_entry(inode, &psb->s_inodes, i_sb_list) {
+ ctx = inode->i_private;
+ if (!ctx)
+ continue;
+ if (!strcmp(ctx->name, name)) {
+ *fscache = ctx;
+ refcount_inc(&ctx->ref);
+ mutex_unlock(&domain->mutex);
+ return 0;
+ }
+ }
+ err = erofs_fscache_domain_init_cookie(sb, fscache, name, need_inode);
+ mutex_unlock(&domain->mutex);
+
+ return err;
+}
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 7240a2acaa5c..25e5031ca878 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -109,8 +109,12 @@ struct erofs_domain {
};
struct erofs_fscache {
+ refcount_t ref;
struct fscache_cookie *cookie;
struct inode *inode;
+ struct inode *anon_inode;
+ struct erofs_domain *domain;
+ char *name;
};
struct erofs_sb_info {
@@ -626,6 +630,9 @@ int erofs_fscache_register_domain(struct super_block *sb);
int erofs_fscache_register_cookie(struct super_block *sb,
struct erofs_fscache **fscache,
char *name, bool need_inode);
+int erofs_domain_register_cookie(struct super_block *sb,
+ struct erofs_fscache **fscache,
+ char *name, bool need_inode);
void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache);
extern const struct address_space_operations erofs_fscache_access_aops;
@@ -647,6 +654,12 @@ static inline int erofs_fscache_register_cookie(struct super_block *sb,
{
return -EOPNOTSUPP;
}
+static inline int erofs_domain_register_cookie(struct super_block *sb,
+ struct erofs_fscache **fscache,
+ char *name, bool need_inode)
+{
+ return -EOPNOTSUPP;
+}
static inline void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
{
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 667a78f0ee70..11c5ba84567c 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -245,8 +245,12 @@ static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
}
if (erofs_is_fscache_mode(sb)) {
- ret = erofs_fscache_register_cookie(sb, &dif->fscache,
- dif->path, false);
+ if (sbi->opt.domain_id)
+ ret = erofs_domain_register_cookie(sb, &dif->fscache, dif->path,
+ false);
+ else
+ ret = erofs_fscache_register_cookie(sb, &dif->fscache, dif->path,
+ false);
if (ret)
return ret;
} else {
@@ -726,6 +730,8 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
err = erofs_fscache_register_domain(sb);
if (err)
return err;
+ err = erofs_domain_register_cookie(sb, &sbi->s_fscache,
+ sbi->opt.fsid, true);
} else {
err = erofs_fscache_register_fs(sb);
if (err)
--
2.20.1
A new fscache-based shared domain mode is going to be introduced for
erofs. In which case, same data blobs in same domain will be shared
and reused to reduce on-disk space usage.
As the first step, we use pseudo mnt to manage and maintain domain's
lifecycle.
The implementation of sharing blobs will be introduced in subsequent
patches.
Signed-off-by: Jia Zhu <[email protected]>
---
fs/erofs/fscache.c | 103 +++++++++++++++++++++++++++++++++++++++++++-
fs/erofs/internal.h | 19 +++++++-
fs/erofs/super.c | 52 ++++++++++++++++------
3 files changed, 159 insertions(+), 15 deletions(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 8e01d89c3319..3238813ed520 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -1,10 +1,17 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2022, Alibaba Cloud
+ * Copyright (C) 2022, Bytedance Inc. All rights reserved.
*/
+#include <linux/pseudo_fs.h>
+#include <linux/fs_context.h>
+#include <linux/magic.h>
#include <linux/fscache.h>
#include "internal.h"
+static DEFINE_MUTEX(erofs_domain_list_lock);
+static LIST_HEAD(erofs_domain_list);
+
static struct netfs_io_request *erofs_fscache_alloc_request(struct address_space *mapping,
loff_t start, size_t len)
{
@@ -417,6 +424,92 @@ const struct address_space_operations erofs_fscache_access_aops = {
.readahead = erofs_fscache_readahead,
};
+static void erofs_fscache_domain_get(struct erofs_domain *domain)
+{
+ if (!domain)
+ return;
+ refcount_inc(&domain->ref);
+}
+
+static void erofs_fscache_domain_put(struct erofs_domain *domain)
+{
+ if (!domain)
+ return;
+ if (refcount_dec_and_test(&domain->ref)) {
+ fscache_relinquish_volume(domain->volume, NULL, false);
+ mutex_lock(&erofs_domain_list_lock);
+ list_del(&domain->list);
+ mutex_unlock(&erofs_domain_list_lock);
+ kern_unmount(domain->mnt);
+ kfree(domain->domain_id);
+ kfree(domain);
+ }
+}
+
+static int erofs_fscache_init_domain(struct super_block *sb)
+{
+ int err;
+ struct erofs_domain *domain;
+ struct vfsmount *pseudo_mnt;
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+ domain = kzalloc(sizeof(struct erofs_domain), GFP_KERNEL);
+ if (!domain)
+ return -ENOMEM;
+
+ domain->domain_id = kstrdup(sbi->opt.domain_id, GFP_KERNEL);
+ if (!domain->domain_id) {
+ kfree(domain);
+ return -ENOMEM;
+ }
+ sbi->domain = domain;
+ pseudo_mnt = kern_mount(&erofs_fs_type);
+ if (IS_ERR(pseudo_mnt)) {
+ err = PTR_ERR(pseudo_mnt);
+ goto out;
+ }
+ err = erofs_fscache_register_fs(sb);
+ if (err) {
+ kern_unmount(pseudo_mnt);
+ goto out;
+ }
+
+ domain->mnt = pseudo_mnt;
+ domain->volume = sbi->volume;
+ refcount_set(&domain->ref, 1);
+ mutex_init(&domain->mutex);
+ pseudo_mnt->mnt_sb->s_fs_info = domain;
+ list_add(&domain->list, &erofs_domain_list);
+ return 0;
+out:
+ kfree(domain->domain_id);
+ kfree(domain);
+ sbi->domain = NULL;
+ return err;
+}
+
+int erofs_fscache_register_domain(struct super_block *sb)
+{
+ int err;
+ struct erofs_domain *domain;
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+ mutex_lock(&erofs_domain_list_lock);
+ list_for_each_entry(domain, &erofs_domain_list, list) {
+ if (!strcmp(domain->domain_id, sbi->opt.domain_id)) {
+ erofs_fscache_domain_get(domain);
+ sbi->domain = domain;
+ sbi->volume = domain->volume;
+ mutex_unlock(&erofs_domain_list_lock);
+ return 0;
+ }
+ }
+ err = erofs_fscache_init_domain(sb);
+ mutex_unlock(&erofs_domain_list_lock);
+
+ return err;
+}
+
int erofs_fscache_register_cookie(struct super_block *sb,
struct erofs_fscache **fscache,
char *name, bool need_inode)
@@ -495,7 +588,8 @@ int erofs_fscache_register_fs(struct super_block *sb)
char *name;
int ret = 0;
- name = kasprintf(GFP_KERNEL, "erofs,%s", sbi->opt.fsid);
+ name = kasprintf(GFP_KERNEL, "erofs,%s",
+ sbi->domain ? sbi->domain->domain_id : sbi->opt.fsid);
if (!name)
return -ENOMEM;
@@ -515,6 +609,11 @@ void erofs_fscache_unregister_fs(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
- fscache_relinquish_volume(sbi->volume, NULL, false);
+ if (sbi->domain)
+ erofs_fscache_domain_put(sbi->domain);
+ else
+ fscache_relinquish_volume(sbi->volume, NULL, false);
+
sbi->volume = NULL;
+ sbi->domain = NULL;
}
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index fe435d077f1a..7240a2acaa5c 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -99,6 +99,15 @@ struct erofs_sb_lz4_info {
u16 max_pclusterblks;
};
+struct erofs_domain {
+ refcount_t ref;
+ struct mutex mutex;
+ struct vfsmount *mnt;
+ struct list_head list;
+ struct fscache_volume *volume;
+ char *domain_id;
+};
+
struct erofs_fscache {
struct fscache_cookie *cookie;
struct inode *inode;
@@ -158,6 +167,7 @@ struct erofs_sb_info {
/* fscache support */
struct fscache_volume *volume;
struct erofs_fscache *s_fscache;
+ struct erofs_domain *domain;
};
#define EROFS_SB(sb) ((struct erofs_sb_info *)(sb)->s_fs_info)
@@ -394,6 +404,7 @@ struct page *erofs_grab_cache_page_nowait(struct address_space *mapping,
}
extern const struct super_operations erofs_sops;
+extern struct file_system_type erofs_fs_type;
extern const struct address_space_operations erofs_raw_access_aops;
extern const struct address_space_operations z_erofs_aops;
@@ -610,6 +621,7 @@ static inline int z_erofs_load_lzma_config(struct super_block *sb,
#ifdef CONFIG_EROFS_FS_ONDEMAND
int erofs_fscache_register_fs(struct super_block *sb);
void erofs_fscache_unregister_fs(struct super_block *sb);
+int erofs_fscache_register_domain(struct super_block *sb);
int erofs_fscache_register_cookie(struct super_block *sb,
struct erofs_fscache **fscache,
@@ -620,10 +632,15 @@ extern const struct address_space_operations erofs_fscache_access_aops;
#else
static inline int erofs_fscache_register_fs(struct super_block *sb)
{
- return 0;
+ return -EOPNOTSUPP;
}
static inline void erofs_fscache_unregister_fs(struct super_block *sb) {}
+static inline int erofs_fscache_register_domain(const struct super_block *sb)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int erofs_fscache_register_cookie(struct super_block *sb,
struct erofs_fscache **fscache,
char *name, bool need_inode)
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index d01109069c6b..a3ff87e45f2c 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -688,6 +688,13 @@ static const struct export_operations erofs_export_ops = {
.get_parent = erofs_get_parent,
};
+static int erofs_fc_fill_pseudo_super(struct super_block *sb, struct fs_context *fc)
+{
+ static const struct tree_descr empty_descr = {""};
+
+ return simple_fill_super(sb, EROFS_SUPER_MAGIC, &empty_descr);
+}
+
static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct inode *inode;
@@ -715,12 +722,17 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
sb->s_blocksize = EROFS_BLKSIZ;
sb->s_blocksize_bits = LOG_BLOCK_SIZE;
- err = erofs_fscache_register_fs(sb);
- if (err)
- return err;
-
- err = erofs_fscache_register_cookie(sb, &sbi->s_fscache,
- sbi->opt.fsid, true);
+ if (sbi->opt.domain_id) {
+ err = erofs_fscache_register_domain(sb);
+ if (err)
+ return err;
+ } else {
+ err = erofs_fscache_register_fs(sb);
+ if (err)
+ return err;
+ err = erofs_fscache_register_cookie(sb, &sbi->s_fscache,
+ sbi->opt.fsid, true);
+ }
if (err)
return err;
@@ -798,8 +810,12 @@ static int erofs_fc_get_tree(struct fs_context *fc)
{
struct erofs_fs_context *ctx = fc->fs_private;
- if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->opt.fsid)
- return get_tree_nodev(fc, erofs_fc_fill_super);
+ if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND)) {
+ if (!ctx && fc->sb_flags & SB_KERNMOUNT)
+ return get_tree_nodev(fc, erofs_fc_fill_pseudo_super);
+ if (ctx->opt.fsid)
+ return get_tree_nodev(fc, erofs_fc_fill_super);
+ }
return get_tree_bdev(fc, erofs_fc_fill_super);
}
@@ -849,6 +865,9 @@ static void erofs_fc_free(struct fs_context *fc)
{
struct erofs_fs_context *ctx = fc->fs_private;
+ if (!ctx)
+ return;
+
erofs_free_dev_context(ctx->devs);
kfree(ctx->opt.fsid);
kfree(ctx->opt.domain_id);
@@ -864,8 +883,12 @@ static const struct fs_context_operations erofs_context_ops = {
static int erofs_init_fs_context(struct fs_context *fc)
{
- struct erofs_fs_context *ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ struct erofs_fs_context *ctx;
+ if (fc->sb_flags & SB_KERNMOUNT)
+ goto out;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
ctx->devs = kzalloc(sizeof(struct erofs_dev_context), GFP_KERNEL);
@@ -878,6 +901,7 @@ static int erofs_init_fs_context(struct fs_context *fc)
idr_init(&ctx->devs->tree);
init_rwsem(&ctx->devs->rwsem);
erofs_default_options(ctx);
+out:
fc->ops = &erofs_context_ops;
return 0;
}
@@ -892,6 +916,10 @@ static void erofs_kill_sb(struct super_block *sb)
WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
+ if (sb->s_flags & SB_KERNMOUNT) {
+ kill_litter_super(sb);
+ return;
+ }
if (erofs_is_fscache_mode(sb))
generic_shutdown_super(sb);
else
@@ -916,8 +944,8 @@ static void erofs_put_super(struct super_block *sb)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
- DBG_BUGON(!sbi);
-
+ if (!sbi)
+ return;
erofs_unregister_sysfs(sb);
erofs_shrinker_unregister(sb);
#ifdef CONFIG_EROFS_FS_ZIP
@@ -927,7 +955,7 @@ static void erofs_put_super(struct super_block *sb)
erofs_fscache_unregister_cookie(&sbi->s_fscache);
}
-static struct file_system_type erofs_fs_type = {
+struct file_system_type erofs_fs_type = {
.owner = THIS_MODULE,
.name = "erofs",
.init_fs_context = erofs_init_fs_context,
--
2.20.1