Re: [External] Re: [PATCH V3 4/6] erofs: introduce fscache-based domain
From: Jia Zhu
Date: Thu Sep 15 2022 - 04:01:18 EST
在 2022/9/14 21:21, Gao Xiang 写道:
On Wed, Sep 14, 2022 at 06:50:39PM +0800, Jia Zhu wrote:
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 <zhujia.zj@xxxxxxxxxxxxx>
---
fs/erofs/fscache.c | 134 ++++++++++++++++++++++++++++++++++++++------
fs/erofs/internal.h | 9 +++
2 files changed, 127 insertions(+), 16 deletions(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 4159cf781924..b2100dc67cde 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -1,10 +1,14 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2022, Alibaba Cloud
+ * Copyright (C) 2022, Bytedance Inc. All rights reserved.
*/
#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 +421,106 @@ const struct address_space_operations erofs_fscache_access_aops = {
.readahead = erofs_fscache_readahead,
};
+static
+struct erofs_domain *erofs_fscache_domain_get(struct erofs_domain *domain)
+{
+ refcount_inc(&domain->ref);
+ return domain;
+}
We can just open-code that.
Thanks, I'll revise it.
+
+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);
+ kfree(domain->domain_id);
+ kfree(domain);
+ }
+}
+
+static int erofs_fscache_register_volume(struct super_block *sb)
+{
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+ char *domain_id = sbi->opt.domain_id;
+ struct fscache_volume *volume;
+ char *name;
+ int ret = 0;
+
+ if (domain_id)
+ name = kasprintf(GFP_KERNEL, "erofs,%s", domain_id);
+ else
+ name = kasprintf(GFP_KERNEL, "erofs,%s", sbi->opt.fsid);
I think we could just use
name = kasprintf(GFP_KERNEL, "erofs,%s",
domain_id ? domain_id : sbi->opt.fsid);
here.
Thanks.
+ if (!name)
+ return -ENOMEM;
+
+ volume = fscache_acquire_volume(name, NULL, NULL, 0);
+ if (IS_ERR_OR_NULL(volume)) {
+ erofs_err(sb, "failed to register volume for %s", name);
+ ret = volume ? PTR_ERR(volume) : -EOPNOTSUPP;
+ volume = NULL;
+ }
+
+ sbi->volume = volume;
+ kfree(name);
+ return ret;
+}
+
+static int erofs_fscache_init_domain(struct super_block *sb)
+{
+ int err;
+ struct erofs_domain *domain;
+ 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;
+ err = erofs_fscache_register_volume(sb);
+ if (err)
+ goto out;
+
+ domain->volume = sbi->volume;
+ refcount_set(&domain->ref, 1);
+ mutex_init(&domain->mutex);
+ list_add(&domain->list, &erofs_domain_list);
+ return 0;
+out:
+ kfree(domain->domain_id);
+ kfree(domain);
+ sbi->domain = NULL;
+ return err;
+}
+
+static 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)) {
+ sbi->domain = erofs_fscache_domain_get(domain);
+ sbi->volume = domain->volume;
+ mutex_unlock(&erofs_domain_list_lock);
+ return 0;
+ }
+ }
+ err = erofs_fscache_init_domain(sb);
why introduce erofs_fscache_init_domain?
To make error handling path simpler, avoid lots of 'goto' and 'unlock'
+ mutex_unlock(&erofs_domain_list_lock);
+ return err;
+}
+
struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
char *name, bool need_inode)
{
@@ -486,24 +590,16 @@ void erofs_fscache_unregister_cookie(struct erofs_fscache *ctx)
int erofs_fscache_register_fs(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
- struct fscache_volume *volume;
struct erofs_fscache *fscache;
- char *name;
- int ret = 0;
+ int ret;
- name = kasprintf(GFP_KERNEL, "erofs,%s", sbi->opt.fsid);
- if (!name)
- return -ENOMEM;
+ if (sbi->opt.domain_id)
+ ret = erofs_fscache_register_domain(sb);
+ else
+ ret = erofs_fscache_register_volume(sb);
- volume = fscache_acquire_volume(name, NULL, NULL, 0);
- if (IS_ERR_OR_NULL(volume)) {
- erofs_err(sb, "failed to register volume for %s", name);
- ret = volume ? PTR_ERR(volume) : -EOPNOTSUPP;
- volume = NULL;
- }
-
- sbi->volume = volume;
- kfree(name);
+ if (ret)
+ return ret;
fscache = erofs_fscache_register_cookie(sb, sbi->opt.fsid, true);
if (IS_ERR(fscache))
@@ -518,7 +614,13 @@ void erofs_fscache_unregister_fs(struct super_block *sb)
struct erofs_sb_info *sbi = EROFS_SB(sb);
erofs_fscache_unregister_cookie(sbi->s_fscache);
- fscache_relinquish_volume(sbi->volume, NULL, false);
sbi->s_fscache = NULL;
+
+ if (sbi->domain)
+ erofs_fscache_domain_put(sbi->domain);
+ else
+ fscache_relinquish_volume(sbi->volume, NULL, false);
+
How about using one helper and pass in sb directly instead?
Thanks for your suggestion, I'll revise it in next version.
Thanks,
Gao Xiang