[PATCH] erofs: set SB_NODEV sb_flags when mounting with fsid

[Baokun Li]

When erofs_kill_sb() is called in block dev based mode, s_bdev may not have
been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will
be mistaken for fscache mode, and then attempt to free an anon_dev that has
never been allocated, triggering the following warning:

============================================
ida_free called for id=0 which is not allocated.
WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
Modules linked in:
CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
RIP: 0010:ida_free+0x134/0x140
Call Trace:
 <TASK>
 erofs_kill_sb+0x81/0x90
 deactivate_locked_super+0x35/0x80
 get_tree_bdev+0x136/0x1e0
 vfs_get_tree+0x2c/0xf0
 do_new_mount+0x190/0x2f0
 [...]
============================================

To avoid this problem, add SB_NODEV to fc->sb_flags after successfully
parsing the fsid, and then the superblock inherits this flag when it is
allocated, so that the sb_flags can be used to distinguish whether it is
in block dev based mode when calling erofs_kill_sb().

Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
---
 fs/erofs/super.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index b21bd8f78dc1..7539ce7d64bc 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -520,6 +520,7 @@ static int erofs_fc_parse_param(struct fs_context *fc,
 		ctx->fsid = kstrdup(param->string, GFP_KERNEL);
 		if (!ctx->fsid)
 			return -ENOMEM;
+		fc->sb_flags |= SB_NODEV;
 		break;
 	case Opt_domain_id:
 		kfree(ctx->domain_id);
@@ -706,9 +707,7 @@ 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->fsid)
+	if (fc->sb_flags & SB_NODEV)
 		return get_tree_nodev(fc, erofs_fc_fill_super);
 
 	return get_tree_bdev(fc, erofs_fc_fill_super);
@@ -801,7 +800,7 @@ static void erofs_kill_sb(struct super_block *sb)
 {
 	struct erofs_sb_info *sbi;
 
-	if (erofs_is_fscache_mode(sb))
+	if (sb->s_flags & SB_NODEV)
 		kill_anon_super(sb);
 	else
 		kill_block_super(sb);
-- 
2.31.1