Re: [PATCH v11 2/5] ext4: introduce ext4_put_ea_inode() for safe deferred iput

[Jan Kara]

On Mon 29-06-26 19:08:45, Yun Zhou wrote:
> Calling iput() on EA inodes while holding xattr_sem or a jbd2 handle
> can trigger write_inode_now() -> ext4_writepages() -> s_writepages_rwsem,
> creating a lock ordering issue during mount (!SB_ACTIVE).
> 
> Add ext4_put_ea_inode() which uses iput_if_not_last() as a fast path.
> If this is not the last reference, it is dropped immediately.  If this
> is the last reference, the inode is linked onto a per-sb lock-free llist
> via i_ea_iput_node (embedded in ext4_inode_info, sharing space with the
> unused xattr_sem of EA inodes via a union) and a delayed worker
> (1 jiffie) performs the final iput() in a clean context.  This avoids
> per-iput memory allocation.
> 
> Flush points are placed before quota shutdown (ext4_put_super and
> failed_mount9) and before freeing structures that eviction depends on
> (failed_mount_wq and failed_mount3a).  Initialization is placed before
> journal loading since fast commit replay may trigger evictions that call
> ext4_put_ea_inode().
> 
> Also moves init_rwsem(xattr_sem) from init_once to ext4_alloc_inode to
> handle slab object reuse after the union field has been overwritten.
> 
> Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
> Suggested-by: Jan Kara <jack@xxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR