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,
--
Theodore Ts'o <tytso@xxxxxxx>
