Merge "mm: fix the race between swapin_readahead and SWP_SYNCHRONOUS_IO path" (aaa96242) · Commits · e / devices / android_kernel_oneplus_sm7250

mm/memory.c

+16 −5

Original line number	Diff line number	Diff line
		@@ -3078,6 +3078,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
		struct page page = NULL, swapcache;
		struct mem_cgroup *memcg;
		swp_entry_t entry;
		struct swap_info_struct *si;
		bool skip_swapcache = false;
		pte_t pte;
		int locked;
		int exclusive = 0;
		@@ -3119,15 +3121,24 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)


		delayacct_set_flag(DELAYACCT_PF_SWAPIN);

		/*
		* lookup_swap_cache below can fail and before the SWP_SYNCHRONOUS_IO
		* check is made, another process can populate the swapcache, delete
		* the swap entry and decrement the swap count. So decide on taking
		* the SWP_SYNCHRONOUS_IO path before the lookup. In the event of the
		* race described, the victim process will find a swap_count > 1
		* and can then take the readahead path instead of SWP_SYNCHRONOUS_IO.
		*/
		si = swp_swap_info(entry);
		if (si->flags & SWP_SYNCHRONOUS_IO && __swap_count(si, entry) == 1)
		skip_swapcache = true;

		page = lookup_swap_cache(entry, vma, vmf->address);
		swapcache = page;

		if (!page) {
		struct swap_info_struct *si = swp_swap_info(entry);

		if (si->flags & SWP_SYNCHRONOUS_IO &&
		__swap_count(si, entry) == 1) {
		/* skip swapcache */
		if (skip_swapcache) {
		page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
		vmf->address);
		if (page) {