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Date: Thu, 9 Feb 2023 10:43:28 +0800
From: Jia Zhu <zhujia.zj@...edance.com>
To: Jingbo Xu <jefflexu@...ux.alibaba.com>, xiang@...nel.org,
chao@...nel.org, linux-erofs@...ts.ozlabs.org, houtao1@...wei.com
Cc: huyue2@...lpad.com, linux-kernel@...r.kernel.org,
zhujia.zj@...edance.com
Subject: Re: [PATCH 4/4] erofs: simplify the name collision checking in share
domain mode
在 2023/2/8 15:17, Jingbo Xu 写道:
> When share domain is enabled, data blobs can be shared among filesystem
> instances in the same domain for data deduplication, while bootstrap
> blobs are always dedicated to the corresponding filesystem instance, and
> have no need to be shared.
>
> In the initial implementation of share domain (commit 7d41963759fe
> ("erofs: Support sharing cookies in the same domain")), bootstrap blobs
> are also in the share domain, and thus can be referenced by the
> following filesystem instances. In this case, mounting twice with the
> same fsid and domain_id will trigger warning in sysfs. Commit
> 27f2a2dcc626 ("erofs: check the uniqueness of fsid in shared domain in
> advance") fixes this by introducing the name collision checking.
>
> This patch attempts to fix the above issue in another simpler way.
> Since the bootstrap blobs have no need to be shared, move them out of
> the share domain, so that one bootstrap blob can not be referenced by
> other filesystem instances. Attempt to mount twice with the same fsid
> and domain_id will fail with info of duplicate cookies, which is
> consistent with the behavior in non-share-domain mode.
>
> Signed-off-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@...edance.com>
> ---
> fs/erofs/fscache.c | 36 ++++++++----------------------------
> fs/erofs/internal.h | 4 ++--
> fs/erofs/super.c | 2 +-
> 3 files changed, 11 insertions(+), 31 deletions(-)
>
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 8353a5fe8c71..8da6e05e9d23 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -505,25 +505,18 @@ struct erofs_fscache *erofs_fscache_domain_init_cookie(struct super_block *sb,
>
> static
> struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
> - char *name,
> - unsigned int flags)
> + char *name)
> {
> struct erofs_fscache *ctx;
> struct erofs_domain *domain = EROFS_SB(sb)->domain;
>
> mutex_lock(&erofs_domain_cookies_lock);
> list_for_each_entry(ctx, &erofs_domain_cookies_list, node) {
> - if (ctx->domain != domain || strcmp(ctx->name, name))
> - continue;
> - if (!(flags & EROFS_REG_COOKIE_NEED_NOEXIST)) {
> + if (ctx->domain == domain && !strcmp(ctx->name, name)) {
> refcount_inc(&ctx->ref);
> - } else {
> - erofs_err(sb, "%s already exists in domain %s", name,
> - domain->domain_id);
> - ctx = ERR_PTR(-EEXIST);
> + mutex_unlock(&erofs_domain_cookies_lock);
> + return ctx;
> }
> - mutex_unlock(&erofs_domain_cookies_lock);
> - return ctx;
> }
> ctx = erofs_fscache_domain_init_cookie(sb, name);
> mutex_unlock(&erofs_domain_cookies_lock);
> @@ -531,11 +524,10 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
> }
>
> struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
> - char *name,
> - unsigned int flags)
> + char *name)
> {
> if (EROFS_SB(sb)->domain_id)
> - return erofs_domain_register_cookie(sb, name, flags);
> + return erofs_domain_register_cookie(sb, name);
> return erofs_fscache_acquire_cookie(sb, sb, name);
> }
>
> @@ -564,7 +556,6 @@ int erofs_fscache_register_fs(struct super_block *sb)
> int ret;
> struct erofs_sb_info *sbi = EROFS_SB(sb);
> struct erofs_fscache *fscache;
> - unsigned int flags = 0;
>
> if (sbi->domain_id)
> ret = erofs_fscache_register_domain(sb);
> @@ -573,19 +564,8 @@ int erofs_fscache_register_fs(struct super_block *sb)
> if (ret)
> return ret;
>
> - /*
> - * When shared domain is enabled, using NEED_NOEXIST to guarantee
> - * the primary data blob (aka fsid) is unique in the shared domain.
> - *
> - * For non-shared-domain case, fscache_acquire_volume() invoked by
> - * erofs_fscache_register_volume() has already guaranteed
> - * the uniqueness of primary data blob.
> - *
> - * Acquired domain/volume will be relinquished in kill_sb() on error.
> - */
> - if (sbi->domain_id)
> - flags |= EROFS_REG_COOKIE_NEED_NOEXIST;
> - fscache = erofs_fscache_register_cookie(sb, sbi->fsid, flags);
> + /* acquired domain/volume will be relinquished in kill_sb() on error */
> + fscache = erofs_fscache_acquire_cookie(sb, sb, sbi->fsid);
> if (IS_ERR(fscache))
> return PTR_ERR(fscache);
>
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 125e4aa8d295..fded736bc3d5 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -570,7 +570,7 @@ int erofs_fscache_register_fs(struct super_block *sb);
> void erofs_fscache_unregister_fs(struct super_block *sb);
>
> struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
> - char *name, unsigned int flags);
> + char *name);
> void erofs_fscache_unregister_cookie(struct erofs_fscache *fscache);
> #else
> static inline int erofs_fscache_register_fs(struct super_block *sb)
> @@ -581,7 +581,7 @@ static inline void erofs_fscache_unregister_fs(struct super_block *sb) {}
>
> static inline
> struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
> - char *name, unsigned int flags)
> + char *name)
> {
> return ERR_PTR(-EOPNOTSUPP);
> }
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 19b1ae79cec4..8706ca34f26a 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -244,7 +244,7 @@ static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
> }
>
> if (erofs_is_fscache_mode(sb)) {
> - fscache = erofs_fscache_register_cookie(sb, dif->path, 0);
> + fscache = erofs_fscache_register_cookie(sb, dif->path);
> if (IS_ERR(fscache))
> return PTR_ERR(fscache);
> dif->fscache = fscache;
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