erofs: initialize decompression early

 - Rename erofs_init_managed_cache() to z_erofs_init_super();
 - Move the initialization of managed_pslots into z_erofs_init_super() too;
 - Move z_erofs_init_super() and packed inode preparation upwards, before
   the root inode initialization.

Therefore, the root directory can also be compressible.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Acked-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20250317054840.3483000-1-hsiangkao@linux.alibaba.com

fs/erofs/internal.h

@@ -436,6 +436,7 @@ int __init erofs_init_shrinker(void);
 void erofs_exit_shrinker(void);
 int __init z_erofs_init_subsystem(void);
 void z_erofs_exit_subsystem(void);
+int z_erofs_init_super(struct super_block *sb);
 unsigned long z_erofs_shrink_scan(struct erofs_sb_info *sbi,
 				  unsigned long nr_shrink);
 int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map,
@@ -445,7 +446,6 @@ void z_erofs_put_gbuf(void *ptr);
 int z_erofs_gbuf_growsize(unsigned int nrpages);
 int __init z_erofs_gbuf_init(void);
 void z_erofs_gbuf_exit(void);
-int erofs_init_managed_cache(struct super_block *sb);
 int z_erofs_parse_cfgs(struct super_block *sb, struct erofs_super_block *dsb);
 #else
 static inline void erofs_shrinker_register(struct super_block *sb) {}
@@ -454,7 +454,7 @@ static inline int erofs_init_shrinker(void) { return 0; }
 static inline void erofs_exit_shrinker(void) {}
 static inline int z_erofs_init_subsystem(void) { return 0; }
 static inline void z_erofs_exit_subsystem(void) {}
-static inline int erofs_init_managed_cache(struct super_block *sb) { return 0; }
+static inline int z_erofs_init_super(struct super_block *sb) { return 0; }
 #endif	/* !CONFIG_EROFS_FS_ZIP */
 
 #ifdef CONFIG_EROFS_FS_BACKED_BY_FILE

fs/erofs/super.c

@@ -636,9 +636,16 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 	else
 		sb->s_flags &= ~SB_POSIXACL;
 
-#ifdef CONFIG_EROFS_FS_ZIP
-	xa_init(&sbi->managed_pslots);
-#endif
+	err = z_erofs_init_super(sb);
+	if (err)
+		return err;
+
+	if (erofs_sb_has_fragments(sbi) && sbi->packed_nid) {
+		inode = erofs_iget(sb, sbi->packed_nid);
+		if (IS_ERR(inode))
+			return PTR_ERR(inode);
+		sbi->packed_inode = inode;
+	}
 
 	inode = erofs_iget(sb, sbi->root_nid);
 	if (IS_ERR(inode))
@@ -650,24 +657,11 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 		iput(inode);
 		return -EINVAL;
 	}
-
 	sb->s_root = d_make_root(inode);
 	if (!sb->s_root)
 		return -ENOMEM;
 
 	erofs_shrinker_register(sb);
-	if (erofs_sb_has_fragments(sbi) && sbi->packed_nid) {
-		sbi->packed_inode = erofs_iget(sb, sbi->packed_nid);
-		if (IS_ERR(sbi->packed_inode)) {
-			err = PTR_ERR(sbi->packed_inode);
-			sbi->packed_inode = NULL;
-			return err;
-		}
-	}
-	err = erofs_init_managed_cache(sb);
-	if (err)
-		return err;
-
 	err = erofs_xattr_prefixes_init(sb);
 	if (err)
 		return err;
@@ -803,6 +797,16 @@ static int erofs_init_fs_context(struct fs_context *fc)
 	return 0;
 }
 
+static void erofs_drop_internal_inodes(struct erofs_sb_info *sbi)
+{
+	iput(sbi->packed_inode);
+	sbi->packed_inode = NULL;
+#ifdef CONFIG_EROFS_FS_ZIP
+	iput(sbi->managed_cache);
+	sbi->managed_cache = NULL;
+#endif
+}
+
 static void erofs_kill_sb(struct super_block *sb)
 {
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
@@ -812,6 +816,7 @@ static void erofs_kill_sb(struct super_block *sb)
 		kill_anon_super(sb);
 	else
 		kill_block_super(sb);
+	erofs_drop_internal_inodes(sbi);
 	fs_put_dax(sbi->dif0.dax_dev, NULL);
 	erofs_fscache_unregister_fs(sb);
 	erofs_sb_free(sbi);
@@ -822,17 +827,10 @@ static void erofs_put_super(struct super_block *sb)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(sb);
 
-	DBG_BUGON(!sbi);
-
 	erofs_unregister_sysfs(sb);
 	erofs_shrinker_unregister(sb);
 	erofs_xattr_prefixes_cleanup(sb);
-#ifdef CONFIG_EROFS_FS_ZIP
-	iput(sbi->managed_cache);
-	sbi->managed_cache = NULL;
-#endif
-	iput(sbi->packed_inode);
-	sbi->packed_inode = NULL;
+	erofs_drop_internal_inodes(sbi);
 	erofs_free_dev_context(sbi->devs);
 	sbi->devs = NULL;
 	erofs_fscache_unregister_fs(sb);

fs/erofs/zdata.c

@@ -644,18 +644,18 @@ static const struct address_space_operations z_erofs_cache_aops = {
 	.invalidate_folio = z_erofs_cache_invalidate_folio,
 };
 
-int erofs_init_managed_cache(struct super_block *sb)
+int z_erofs_init_super(struct super_block *sb)
 {
 	struct inode *const inode = new_inode(sb);
 
 	if (!inode)
 		return -ENOMEM;
-
 	set_nlink(inode, 1);
 	inode->i_size = OFFSET_MAX;
 	inode->i_mapping->a_ops = &z_erofs_cache_aops;
 	mapping_set_gfp_mask(inode->i_mapping, GFP_KERNEL);
 	EROFS_SB(sb)->managed_cache = inode;
+	xa_init(&EROFS_SB(sb)->managed_pslots);
 	return 0;
 }