In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix potential deadlock in gc_merge path of f2fs_balance_fs()

When we mount device w/ gc_merge mount option, we may suffer below
potential deadlock:

Kworker GC trehad Truncator
- f2fs_write_cache_pages
- f2fs_write_single_data_page
- f2fs_do_write_data_page
- folio_start_writeback --- set writeback flag on folio
- f2fs_outplace_write_data
: cached folio in internal bio cache
- f2fs_balance_fs
- wake_up(gc_thread)
: wake up gc thread to run foreground GC
- finish_wait(fggc_wq)
: wait on the waitqueue --- wait on GC thread to finish the work
- truncate_inode_pages_range
- __filemap_get_folio(, FGP_LOCK) --- lock folio
- truncate_inode_partial_folio
- folio_wait_writeback --- wait on writeback being cleared
- do_garbage_collect
- move_data_page
- f2fs_get_lock_data_folio
- lock on folio --- blocked on folio's lock

In order to avoid such deadlock, let's call below functions to commit
cached bios in GC_MERGE path of f2fs_balance_fs() as the same as we did
in NOGC_MERGE path.
- f2fs_submit_merged_write(sbi, DATA);
- f2fs_submit_all_merged_ipu_writes(sbi);