On Thu, 04 May 2023 14:47:23 +0200, Jan Kara wrote:
Ext4 has a filesystem wide lock protecting ext4_writepages() calls to avoid races with switching of journalled data flag or inode format. This lock can however cause a deadlock like:
CPU0 CPU1
ext4_writepages() percpu_down_read(sbi->s_writepages_rwsem); ext4_change_inode_journal_flag() percpu_down_write(sbi->s_writepages_rwsem); - blocks, all readers block from now on ext4_do_writepages() ext4_init_io_end() kmem_cache_zalloc(io_end_cachep, GFP_KERNEL) fs_reclaim frees dentry... dentry_unlink_inode() iput() - last ref => iput_final() - inode dirty => write_inode_now()... ext4_writepages() tries to acquire sbi->s_writepages_rwsem and blocks forever
[...]
Applied, thanks!
[1/1] ext4: Avoid deadlock in fs reclaim with page writeback commit: 568e5b263e8bf81ffb575686f980bd18fdb7428f
Best regards,