[PATCH] swap: cleanup get/_put_swap_device()

From: Huang Ying
Date: Fri Jul 23 2021 - 03:56:26 EST

---
mm/madvise.c | 10 ++++++++++
mm/memory.c | 12 +++++++++++-
mm/swap_state.c | 11 -----------
mm/swapfile.c | 36 ++++++------------------------------
mm/zswap.c | 5 +++++
5 files changed, 32 insertions(+), 42 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 012129fbfaf8..5e38e888645d 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -199,6 +199,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
swp_entry_t entry;
struct page *page;
spinlock_t *ptl;
+ struct swap_info_struct *si;

orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
pte = *(orig_pte + ((index - start) / PAGE_SIZE));
@@ -209,11 +210,15 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
entry = pte_to_swp_entry(pte);
if (unlikely(non_swap_entry(entry)))
continue;
+ si = get_swap_device(entry);
+ if (!si)
+ continue;

page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
vma, index, false);
if (page)
put_page(page);
+ put_swap_device(si);
}

return 0;
@@ -234,6 +239,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
rcu_read_lock();
xas_for_each(&xas, page, end_index) {
swp_entry_t swap;
+ struct swap_info_struct *si;

if (!xa_is_value(page))
continue;
@@ -241,10 +247,14 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
rcu_read_unlock();

swap = radix_to_swp_entry(page);
+ si = get_swap_device(swap);
+ if (!si)
+ continue;
page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
NULL, 0, false);
if (page)
put_page(page);
+ put_swap_device(si);

rcu_read_lock();
}
diff --git a/mm/memory.c b/mm/memory.c
index 39e7a1495c3c..b150d1d577cd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1096,8 +1096,18 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
cond_resched();

if (ret == -EIO) {
+ int err;
+ struct swap_info_struct *si;
+
VM_WARN_ON_ONCE(!entry.val);
- if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) {
+ si = get_swap_device(entry);
+ if (!si) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ err = add_swap_count_continuation(entry, GFP_KERNEL);
+ put_swap_device(si);
+ if (err < 0) {
ret = -ENOMEM;
goto out;
}
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 1a29b4f98208..7a800f6783fc 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -335,14 +335,8 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
unsigned long addr)
{
struct page *page;
- struct swap_info_struct *si;

- si = get_swap_device(entry);
- if (!si)
- return NULL;
page = find_get_page(swap_address_space(entry), swp_offset(entry));
- put_swap_device(si);
-
INC_CACHE_INFO(find_total);
if (page) {
bool vma_ra = swap_use_vma_readahead();
@@ -418,7 +412,6 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
struct vm_area_struct *vma, unsigned long addr,
bool *new_page_allocated)
{
- struct swap_info_struct *si;
struct page *page;
void *shadow = NULL;

@@ -431,12 +424,8 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* called after lookup_swap_cache() failed, re-calling
* that would confuse statistics.
*/
- si = get_swap_device(entry);
- if (!si)
- return NULL;
page = find_get_page(swap_address_space(entry),
swp_offset(entry));
- put_swap_device(si);
if (page)
return page;

diff --git a/mm/swapfile.c b/mm/swapfile.c
index e3dcaeecc50f..d7cd7fe2eaf9 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1472,14 +1472,9 @@ int __swap_count(swp_entry_t entry)
{
struct swap_info_struct *si;
pgoff_t offset = swp_offset(entry);
- int count = 0;

- si = get_swap_device(entry);
- if (si) {
- count = swap_count(si->swap_map[offset]);
- put_swap_device(si);
- }
- return count;
+ si = swp_swap_info(entry);
+ return swap_count(si->swap_map[offset]);
}

static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
@@ -1501,15 +1496,10 @@ static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
*/
int __swp_swapcount(swp_entry_t entry)
{
- int count = 0;
struct swap_info_struct *si;

- si = get_swap_device(entry);
- if (si) {
- count = swap_swapcount(si, entry);
- put_swap_device(si);
- }
- return count;
+ si = swp_swap_info(entry);
+ return swap_swapcount(si, entry);
}

/*
@@ -3430,10 +3420,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
unsigned char has_cache;
int err;

- p = get_swap_device(entry);
- if (!p)
- return -EINVAL;
-
+ p = swp_swap_info(entry);
offset = swp_offset(entry);
ci = lock_cluster_or_swap_info(p, offset);

@@ -3479,8 +3466,6 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)

unlock_out:
unlock_cluster_or_swap_info(p, ci);
- if (p)
- put_swap_device(p);
return err;
}

@@ -3581,14 +3566,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
*/
page = alloc_page(gfp_mask | __GFP_HIGHMEM);

- si = get_swap_device(entry);
- if (!si) {
- /*
- * An acceptable race has occurred since the failing
- * __swap_duplicate(): the swap device may be swapoff
- */
- goto outer;
- }
+ si = swp_swap_info(entry);
spin_lock(&si->lock);

offset = swp_offset(entry);
@@ -3660,8 +3638,6 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
out:
unlock_cluster(ci);
spin_unlock(&si->lock);
- put_swap_device(si);
-outer:
if (page)
__free_page(page);
return ret;
diff --git a/mm/zswap.c b/mm/zswap.c
index 7944e3e57e78..f707a73e35aa 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -902,9 +902,14 @@ static int zswap_get_swap_cache_page(swp_entry_t entry,
struct page **retpage)
{
bool page_was_allocated;
+ struct swap_info_struct *si;

+ si = get_swap_device(entry);
+ if (!si)
+ return ZSWAP_SWAPCACHE_FAIL;
*retpage = __read_swap_cache_async(entry, GFP_KERNEL,
NULL, 0, &page_was_allocated);
+ put_swap_device(si);
if (page_was_allocated)
return ZSWAP_SWAPCACHE_NEW;
if (!*retpage)
--
2.30.2