[Linux-cachefs] [PATCH v8 20/20] erofs: add 'fsid' mount option

[Jeffle Xu]

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 <jeffl...@linux.alibaba.com>
---
 fs/erofs/super.c | 48 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index a5e4de60a0d8..292b4a70ce19 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -398,6 +398,7 @@ enum {
        Opt_dax,
        Opt_dax_enum,
        Opt_device,
+       Opt_fsid,
        Opt_err
 };
 
@@ -422,6 +423,7 @@ 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),
        {}
 };
 
@@ -517,6 +519,16 @@ 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;
        }
@@ -597,9 +609,14 @@ static int erofs_fc_fill_super(struct super_block *sb, 
struct fs_context *fc)
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_op = &erofs_sops;
 
-       if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
-               erofs_err(sb, "failed to set erofs blksize");
-               return -EINVAL;
+       if (erofs_is_fscache_mode(sb)) {
+               sb->s_blocksize = EROFS_BLKSIZ;
+               sb->s_blocksize_bits = LOG_BLOCK_SIZE;
+       } else {
+               if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
+                       erofs_err(sb, "failed to set erofs blksize");
+                       return -EINVAL;
+               }
        }
 
        sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
@@ -608,7 +625,7 @@ static int erofs_fc_fill_super(struct super_block *sb, 
struct fs_context *fc)
 
        sb->s_fs_info = sbi;
        sbi->opt = ctx->opt;
-       sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->dax_part_off);
+       ctx->opt.fsid = NULL;
        sbi->devs = ctx->devs;
        ctx->devs = NULL;
 
@@ -625,6 +642,8 @@ static int erofs_fc_fill_super(struct super_block *sb, 
struct fs_context *fc)
                err = super_setup_bdi(sb);
                if (err)
                        return err;
+       } else {
+               sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, 
&sbi->dax_part_off);
        }
 
        err = erofs_read_superblock(sb);
@@ -684,6 +703,11 @@ 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);
 }
 
@@ -733,6 +757,7 @@ 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);
 }
 
@@ -773,7 +798,10 @@ 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)
@@ -783,6 +811,7 @@ 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;
 }
@@ -884,7 +913,10 @@ static int erofs_statfs(struct dentry *dentry, struct 
kstatfs *buf)
 {
        struct super_block *sb = dentry->d_sb;
        struct erofs_sb_info *sbi = EROFS_SB(sb);
-       u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
+       u64 id = 0;
+
+       if (!erofs_is_fscache_mode(sb))
+               id = huge_encode_dev(sb->s_bdev->bd_dev);
 
        buf->f_type = sb->s_magic;
        buf->f_bsize = EROFS_BLKSIZ;
@@ -929,6 +961,10 @@ 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;
 }
 
-- 
2.27.0

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