In the Linux kernel, the following vulnerability has been resolved: f2fs: fix potential deadlock...

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);