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SubjectRe: [External] Re: [PATCH V2 2/5] erofs: introduce fscache-based domain
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在 2022/9/9 16:42, JeffleXu 写道:
>
>
> On 9/2/22 6:53 PM, 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@bytedance.com>
>> ---
>> fs/erofs/fscache.c | 95 ++++++++++++++++++++++++++++++++++++++++++++-
>> fs/erofs/internal.h | 18 ++++++++-
>> fs/erofs/super.c | 51 ++++++++++++++++++------
>> 3 files changed, 149 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
>> index 8e01d89c3319..439dd3cc096a 100644
>> --- a/fs/erofs/fscache.c
>> +++ b/fs/erofs/fscache.c
>> @@ -1,10 +1,15 @@
>> // 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 vfsmount *erofs_pseudo_mnt;
>> +
>> static struct netfs_io_request *erofs_fscache_alloc_request(struct address_space *mapping,
>> loff_t start, size_t len)
>> {
>> @@ -417,6 +422,87 @@ 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);
>> +}
>
Hi Jingbo,
Thanks for your careful review.
> It seems that the input @domain can not be NULL, and thus the NULL check
> is not needed.
>
I will remove it in next version.
> Besides how about:
>
> struct erofs_domain *domain erofs_fscache_domain_get(struct erofs_domain
> *domain)
> {
> refcount_inc(&domain->ref);
> return domain;
> }
>
Thanks for the suggestion, I will apply 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_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;
>> + if (!erofs_pseudo_mnt) {
>> + erofs_pseudo_mnt = kern_mount(&erofs_fs_type);
>> + if (IS_ERR(erofs_pseudo_mnt)) {
>> + err = PTR_ERR(erofs_pseudo_mnt);
>> + goto out;
>> + }
>> + }
>> + err = erofs_fscache_register_fs(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;
>> +}
>> +
>> +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->domain = erofs_fscache_domain_get(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 +581,8 @@ 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);
>
> Do we also need to encode the cookie name in the "<domain_id>,<fsid>"
> format? This will affect the path of the cache files.
>
I think even though the cookies have the same name, they belong to
different volumes(path). Cookies do not affect each other.
Are there other benefits to doing so?
>> if (!name)
>> return -ENOMEM;
>>
>> @@ -515,6 +602,10 @@ 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..2790c93ffb83 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -99,6 +99,14 @@ struct erofs_sb_lz4_info {
>> u16 max_pclusterblks;
>> };
>>
>> +struct erofs_domain {
>> + refcount_t ref;
>> + struct mutex mutex;
>> + struct list_head list;
>> + struct fscache_volume *volume;
>> + char *domain_id;
>> +};
>> +
>> struct erofs_fscache {
>> struct fscache_cookie *cookie;
>> struct inode *inode;
>> @@ -158,6 +166,7 @@ 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 +403,7 @@ 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 +620,7 @@ 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 +631,15 @@ 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..69de1731f454 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);
>
> We'd better keep only one entry to the fscache related codes. How about
> moving erofs_fscache_register_cookie(), i.e. registering cookie for
> bootstrap, into erofs_fscache_register_fs()? Similarly, check the
> domain_id and call erofs_fscache_register_domain() inside
> erofs_fscache_register_fs().
>
> Similarly, check domain_id and call erofs_domain_register_cookie()
> inside erofs_fscache_register_cookie().
>
Thanks, that looks great, I will revise it in next version.
>
>
>> + }
>> 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 +865,8 @@ 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 +882,12 @@ 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 +900,7 @@ 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 +915,10 @@ 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 +943,8 @@ 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 +954,7 @@ 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,
>

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