On 12/18/18 9:56 PM, Yang Shi wrote: > > > On 12/18/18 4:16 PM, Tim Chen wrote: >> On 12/18/18 3:43 PM, Yang Shi wrote: >>> >>> On 12/18/18 11:29 AM, Tim Chen wrote: >>>> On 12/17/18 10:52 PM, Yang Shi wrote: >>>> >>>>> diff --git a/mm/swap_state.c b/mm/swap_state.c >>>>> index fd2f21e..7cc3c29 100644 >>>>> --- a/mm/swap_state.c >>>>> +++ b/mm/swap_state.c >>>>> @@ -538,11 +538,15 @@ struct page *swap_cluster_readahead(swp_entry_t >>>>> entry, gfp_t gfp_mask, >>>>> bool do_poll = true, page_allocated; >>>>> struct vm_area_struct *vma = vmf->vma; >>>>> unsigned long addr = vmf->address; >>>>> + struct inode *inode = si->swap_file->f_mapping->host; >>>>> mask = swapin_nr_pages(offset) - 1; >>>>> if (!mask) >>>>> goto skip; >>>>> >>>> Shmem will also be using this function and I don't think the >>>> inode_read_congested >>>> logic is relevant for that case. >>> IMHO, shmem is also relevant. As long as it is trying to readahead from >>> swap, it should check if the underlying device is busy or not regardless of >>> shmem or anon page. >>> >> I don't think your dereference inode = si->swap_file->f_mapping->host >> is always safe. You should do it only when (si->flags & SWP_FS) is true. > > Do you mean it is not safe for swap partition?
The f_mapping may not be instantiated. It is only done for SWP_FS. Tim
