erofs: introduce fscache-based domain

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.

The implementation of sharing blobs will be introduced in subsequent
patches.

Signed-off-by: Jia Zhu <zhujia.zj@bytedance.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220918043456.147-4-zhujia.zj@bytedance.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 1eb63987e815cfc5de3cfacb92665ea4d48b104c..8a1be6077ca450af148cc922f665007d1b2febe9 100644 (file)
--- 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)
 {
@@ -421,6 +425,99 @@ const struct address_space_operations erofs_fscache_access_aops = {
        .readahead = erofs_fscache_readahead,
 };
 
+static void erofs_fscache_domain_put(struct erofs_domain *domain)
+{
+       if (!domain)
+               return;
+       mutex_lock(&erofs_domain_list_lock);
+       if (refcount_dec_and_test(&domain->ref)) {
+               list_del(&domain->list);
+               mutex_unlock(&erofs_domain_list_lock);
+               fscache_relinquish_volume(domain->volume, NULL, false);
+               kfree(domain->domain_id);
+               kfree(domain);
+               return;
+       }
+       mutex_unlock(&erofs_domain_list_lock);
+}
+
+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;
+
+       name = kasprintf(GFP_KERNEL, "erofs,%s",
+                        domain_id ? domain_id : sbi->opt.fsid);
+       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;
+       }
+
+       err = erofs_fscache_register_volume(sb);
+       if (err)
+               goto out;
+
+       domain->volume = sbi->volume;
+       refcount_set(&domain->ref, 1);
+       list_add(&domain->list, &erofs_domain_list);
+       sbi->domain = domain;
+       return 0;
+out:
+       kfree(domain->domain_id);
+       kfree(domain);
+       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 = domain;
+                       sbi->volume = domain->volume;
+                       refcount_inc(&domain->ref);
+                       mutex_unlock(&erofs_domain_list_lock);
+                       return 0;
+               }
+       }
+       err = erofs_fscache_init_domain(sb);
+       mutex_unlock(&erofs_domain_list_lock);
+       return err;
+}
+
 struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
                                                     char *name, bool need_inode)
 {
@@ -484,27 +581,19 @@ void erofs_fscache_unregister_cookie(struct erofs_fscache *ctx)
 
 int erofs_fscache_register_fs(struct super_block *sb)
 {
+       int ret;
        struct erofs_sb_info *sbi = EROFS_SB(sb);
-       struct fscache_volume *volume;
        struct erofs_fscache *fscache;
-       char *name;
-
-       name = kasprintf(GFP_KERNEL, "erofs,%s", sbi->opt.fsid);
-       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);
-               kfree(name);
-               return volume ? PTR_ERR(volume) : -EOPNOTSUPP;
-       }
-
-       sbi->volume = volume;
-       kfree(name);
+       if (sbi->opt.domain_id)
+               ret = erofs_fscache_register_domain(sb);
+       else
+               ret = erofs_fscache_register_volume(sb);
+       if (ret)
+               return ret;
 
+       /* acquired domain/volume will be relinquished in kill_sb() on error */
        fscache = erofs_fscache_register_cookie(sb, sbi->opt.fsid, true);
-       /* acquired volume will be relinquished in kill_sb() */
        if (IS_ERR(fscache))
                return PTR_ERR(fscache);
 
@@ -517,7 +606,13 @@ 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);
+
+       if (sbi->domain)
+               erofs_fscache_domain_put(sbi->domain);
+       else
+               fscache_relinquish_volume(sbi->volume, NULL, false);
+
        sbi->s_fscache = NULL;
        sbi->volume = NULL;
+       sbi->domain = NULL;
 }

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 39fb124ce6705938be7bd0323fdaf80a8621df3e..93fc4ad61cfb01ba8f8858b039f60f3a1a4ae990 100644 (file)
--- 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 {
@@ -98,6 +99,13 @@ struct erofs_sb_lz4_info {
        u16 max_pclusterblks;
 };
 
+struct erofs_domain {
+       refcount_t ref;
+       struct list_head list;
+       struct fscache_volume *volume;
+       char *domain_id;
+};
+
 struct erofs_fscache {
        struct fscache_cookie *cookie;
        struct inode *inode;
@@ -157,6 +165,7 @@ 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)