The patch titled
Subject: swap, __read_swap_cache_async(): enlarge get/put_swap_device protection range
has been added to the -mm mm-unstable branch. Its filename is
swap-__read_swap_cache_async-enlarge-get-put_swap_device-protection-range.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/swap-__read_swap_cache_async-enlarge-get-put_swap_device-protection-range.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: swap, __read_swap_cache_async(): enlarge get/put_swap_device protection range
Date: Mon, 29 May 2023 14:13:52 +0800
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@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap_state.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
--- a/mm/swap_state.c~swap-__read_swap_cache_async-enlarge-get-put_swap_device-protection-range
+++ a/mm/swap_state.c
@@ -417,9 +417,13 @@ struct page *__read_swap_cache_async(swp
{
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
* 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
* 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
*/
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
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
/* 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 @@ fail_unlock:
* 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,
_
Patches currently in -mm which might be from ying.huang@xxxxxxxxx are
migrate_pages_batch-simplify-retrying-and-failure-counting-of-large-folios.patch
swap-remove-get-put_swap_device-in-__swap_count.patch
swap-__read_swap_cache_async-enlarge-get-put_swap_device-protection-range.patch
swap-remove-__swp_swapcount.patch
swap-remove-get-put_swap_device-in-__swap_duplicate.patch
swap-comments-get_swap_device-with-usage-rule.patch
