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. Tim
