On 2024/4/15 21:38, Christian Brauner wrote:
On Mon, Apr 15, 2024 at 08:17:46PM +0800, Baokun Li wrote:
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 <libaok...@huawei.com>
---
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;
Hm, I wouldn't do it this way. That's an abuse of that flag imho.
Record the information in the erofs_fs_context if you need to.
The stack diagram that triggers the problem is as follows, the call to
erofs_kill_sb() fails before fill_super() has been executed, and we can
only use super_block to determine whether it is currently in nodev
fscahe mode or block device based mode. So if it is recorded in
erofs_fs_context (aka fc->fs_private), we can't access the recorded data
unless we pass fc into erofs_kill_sb() as well.
do_new_mount
fs_context_for_mount
alloc_fs_context
erofs_init_fs_context
// Mount options have not been parsed yet,
// it is not clear if there is an fsid
parse_monolithic_mount_data
generic_parse_monolithic
erofs_fc_parse_param
case Opt_fsid:
// fc->sb_flags |= SB_NODEV;
vfs_get_tree
erofs_fc_get_tree
get_tree_bdev
s = sget_dev(fc, dev)
s = alloc_super()
s->s_flags = fc->sb_flags;
setup_bdev_super
// return error
sb->s_bdev = bdev // s_bdev is NULL
deactivate_locked_super
erofs_kill_sb
// Block device based mode is considered fscahe mode for nodev
erofs_is_fscache_mode(sb)
IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && !sb->s_bdev
kill_anon_super(sb)
free_anon_bdev(dev)
ida_free(&unnamed_dev_ida, MINOR(dev))
((int)id < 0)
WARN(1, "ida_free called for id=%d which is not
allocated.\n", id);
Thanks!
--
With Best Regards,
Baokun Li
