Commit 46a774d3 authored by Huang Ying's avatar Huang Ying Committed by Andrew Morton
Browse files

swap, __read_swap_cache_async(): enlarge get/put_swap_device protection range 

This makes the function a little easier to be understood because we don't
need to consider swapoff.  And this makes it possible to remove
get/put_swap_device() calling in some functions called by
__read_swap_cache_async().

Link: https://lkml.kernel.org/r/20230529061355.125791-3-ying.huang@intel.com


Signed-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarChris Li (Google) <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f9f956b5

mm/swap_state.c

+21 −10
Original line number Diff line number Diff line
@@ -417,9 +417,13 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
{

	struct swap_info_struct *si;

	struct folio *folio;

	struct page *page;

	void *shadow = NULL;



	*new_page_allocated = false;

	si = get_swap_device(entry);

	if (!si)

		return NULL;



	for (;;) {

		int err;
@@ -428,14 +432,12 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
		 * called after swap_cache_get_folio() failed, re-calling

		 * that would confuse statistics.

		 */

		si = get_swap_device(entry);

		if (!si)

			return NULL;

		folio = filemap_get_folio(swap_address_space(entry),

						swp_offset(entry));

		put_swap_device(si);

		if (!IS_ERR(folio))

			return folio_file_page(folio, swp_offset(entry));

		if (!IS_ERR(folio)) {

			page = folio_file_page(folio, swp_offset(entry));

			goto got_page;

		}



		/*

		 * Just skip read ahead for unused swap slot.
@@ -446,7 +448,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
		 * else swap_off will be aborted if we return NULL.

		 */

		if (!__swp_swapcount(entry) && swap_slot_cache_enabled)

			return NULL;

			goto fail_put_swap;



		/*

		 * Get a new page to read into from swap.  Allocate it now,
@@ -455,7 +457,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
		 */

		folio = vma_alloc_folio(gfp_mask, 0, vma, addr, false);

		if (!folio)

			return NULL;

                        goto fail_put_swap;



		/*

		 * Swap entry may have been freed since our caller observed it.
@@ -466,7 +468,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 


		folio_put(folio);

		if (err != -EEXIST)

			return NULL;

			goto fail_put_swap;



		/*

		 * We might race against __delete_from_swap_cache(), and
@@ -500,12 +502,17 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
	/* Caller will initiate read into locked folio */

	folio_add_lru(folio);

	*new_page_allocated = true;

	return &folio->page;

	page = &folio->page;

got_page:

	put_swap_device(si);

	return page;



fail_unlock:

	put_swap_folio(folio, entry);

	folio_unlock(folio);

	folio_put(folio);

fail_put_swap:

	put_swap_device(si);

	return NULL;

}
@@ -514,6 +521,10 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
 * and reading the disk if it is not already cached.

 * A failure return means that either the page allocation failed or that

 * the swap entry is no longer in use.

 *

 * get/put_swap_device() aren't needed to call this function, because

 * __read_swap_cache_async() call them and swap_readpage() holds the

 * swap cache folio lock.

 */

struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,

				   struct vm_area_struct *vma,