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@xxxxxxxxxxxxx>
> ---
> 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);
> +}
It seems that the input @domain can not be NULL, and thus the NULL check
is not needed.
Besides how about:
struct erofs_domain *domain erofs_fscache_domain_get(struct erofs_domain
*domain)
{
refcount_inc(&domain->ref);
return domain;
}
> +
> +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.
> 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().
> + }
> 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,
--
Thanks,
Jingbo
