erofs: add 'fsid' mount option

Introduce 'fsid' mount option to enable on-demand read sementics, in
which case, erofs will be mounted from data blobs. Users could specify
the name of primary data blob by this mount option.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220425122143.56815-22-jefflexu@linux.alibaba.com
Acked-by: Chao Yu <chao@kernel.org>
Tested-by: Zichen Tian <tianzichen@kuaishou.com>
Tested-by: Jia Zhu <zhujia.zj@bytedance.com>
Tested-by: Yan Song <yansong.ys@antgroup.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 0467084403665c9170bc06e73c54058e7bf6f600..d0d33fd368e66fe1a70b36668af05435e1cd84f5 100644 (file)
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -372,6 +372,8 @@ static int erofs_read_superblock(struct super_block *sb)
 
        if (erofs_sb_has_ztailpacking(sbi))
                erofs_info(sb, "EXPERIMENTAL compressed inline data feature in use. Use at your own risk!");
+       if (erofs_is_fscache_mode(sb))
+               erofs_info(sb, "EXPERIMENTAL fscache-based on-demand read feature in use. Use at your own risk!");
 out:
        erofs_put_metabuf(&buf);
        return ret;
@@ -400,6 +402,7 @@ enum {
        Opt_dax,
        Opt_dax_enum,
        Opt_device,
+       Opt_fsid,
        Opt_err
 };
 
@@ -424,6 +427,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[] = {
        fsparam_flag("dax",             Opt_dax),
        fsparam_enum("dax",             Opt_dax_enum, erofs_dax_param_enums),
        fsparam_string("device",        Opt_device),
+       fsparam_string("fsid",          Opt_fsid),
        {}
 };
 
@@ -519,6 +523,16 @@ static int erofs_fc_parse_param(struct fs_context *fc,
                }
                ++ctx->devs->extra_devices;
                break;
+       case Opt_fsid:
+#ifdef CONFIG_EROFS_FS_ONDEMAND
+               kfree(ctx->opt.fsid);
+               ctx->opt.fsid = kstrdup(param->string, GFP_KERNEL);
+               if (!ctx->opt.fsid)
+                       return -ENOMEM;
+#else
+               errorfc(fc, "fsid option not supported");
+#endif
+               break;
        default:
                return -ENOPARAM;
        }
@@ -643,6 +657,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 
        sb->s_fs_info = sbi;
        sbi->opt = ctx->opt;
+       ctx->opt.fsid = NULL;
        sbi->devs = ctx->devs;
        ctx->devs = NULL;
 
@@ -730,6 +745,11 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 
 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);
+
        return get_tree_bdev(fc, erofs_fc_fill_super);
 }
 
@@ -779,6 +799,7 @@ static void erofs_fc_free(struct fs_context *fc)
        struct erofs_fs_context *ctx = fc->fs_private;
 
        erofs_free_dev_context(ctx->devs);
+       kfree(ctx->opt.fsid);
        kfree(ctx);
 }
 
@@ -819,7 +840,10 @@ static void erofs_kill_sb(struct super_block *sb)
 
        WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
 
-       kill_block_super(sb);
+       if (erofs_is_fscache_mode(sb))
+               generic_shutdown_super(sb);
+       else
+               kill_block_super(sb);
 
        sbi = EROFS_SB(sb);
        if (!sbi)
@@ -829,6 +853,7 @@ static void erofs_kill_sb(struct super_block *sb)
        fs_put_dax(sbi->dax_dev);
        erofs_fscache_unregister_cookie(&sbi->s_fscache);
        erofs_fscache_unregister_fs(sb);
+       kfree(sbi->opt.fsid);
        kfree(sbi);
        sb->s_fs_info = NULL;
 }
@@ -978,6 +1003,10 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
                seq_puts(seq, ",dax=always");
        if (test_opt(opt, DAX_NEVER))
                seq_puts(seq, ",dax=never");
+#ifdef CONFIG_EROFS_FS_ONDEMAND
+       if (opt->fsid)
+               seq_printf(seq, ",fsid=%s", opt->fsid);
+#endif
        return 0;
 }
 

diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index f3babf1e6608320aa542e563cc12b26cd690e294..c1383e508bbecf50b877ac1a4b529f0c4807e146 100644 (file)
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -205,8 +205,8 @@ int erofs_register_sysfs(struct super_block *sb)
 
        sbi->s_kobj.kset = &erofs_root;
        init_completion(&sbi->s_kobj_unregister);
-       err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL,
-                                  "%s", sb->s_id);
+       err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL, "%s",
+                       erofs_is_fscache_mode(sb) ? sbi->opt.fsid : sb->s_id);
        if (err)
                goto put_sb_kobj;
        return 0;