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mm/swapfile.c: use __try_to_reclaim_swap() in free_swap_and_cache() 

The code path to reclaim the swap entry in free_swap_and_cache() is
almost same as that of __try_to_reclaim_swap().  The largest
difference is just coding style.  So the support to the additional
requirement of free_swap_and_cache() is added into
__try_to_reclaim_swap().  free_swap_and_cache() is changed to call
__try_to_reclaim_swap(), and delete the duplicated code.  This will
improve code readability and reduce the potential bugs.

There are 2 functionality differences between __try_to_reclaim_swap()
and swap entry reclaim code of free_swap_and_cache().

- free_swap_and_cache() only reclaims the swap entry if the page is
  unmapped or swap is getting full.  The support has been added into
  __try_to_reclaim_swap().

- try_to_free_swap() (called by __try_to_reclaim_swap()) checks
  pm_suspended_storage(), while free_swap_and_cache() not.  I think
  this is OK.  Because the page and the swap entry can be reclaimed
  later eventually.

Link: http://lkml.kernel.org/r/20180827075535.17406-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Huang Ying 2018-10-26 15:03:46 -07:00 committed by Linus Torvalds
parent 154221c3e5
commit bcd49e8671
1 changed files with 25 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
mm/swapfile.c
View File

@ -103,26 +103,39 @@ static inline unsigned char swap_count(unsigned char ent)
return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */
}
/* Reclaim the swap entry anyway if possible */
#define TTRS_ANYWAY 0x1
/*
* Reclaim the swap entry if there are no more mappings of the
* corresponding page
*/
#define TTRS_UNMAPPED 0x2
/* Reclaim the swap entry if swap is getting full*/
#define TTRS_FULL 0x4
/* returns 1 if swap entry is freed */
static int
__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset)
static int __try_to_reclaim_swap(struct swap_info_struct *si,
unsigned long offset, unsigned long flags)
{
swp_entry_t entry = swp_entry(si->type, offset);
struct page *page;
int ret = 0;
page = find_get_page(swap_address_space(entry), swp_offset(entry));
page = find_get_page(swap_address_space(entry), offset);
if (!page)
return 0;
/*
* This function is called from scan_swap_map() and it's called
* by vmscan.c at reclaiming pages. So, we hold a lock on a page, here.
* We have to use trylock for avoiding deadlock. This is a special
* When this function is called from scan_swap_map_slots() and it's
* called by vmscan.c at reclaiming pages. So, we hold a lock on a page,
* here. We have to use trylock for avoiding deadlock. This is a special
* case and you should use try_to_free_swap() with explicit lock_page()
* in usual operations.
*/
if (trylock_page(page)) {
ret = try_to_free_swap(page);
if ((flags & TTRS_ANYWAY) ||
((flags & TTRS_UNMAPPED) && !page_mapped(page)) ||
((flags & TTRS_FULL) && mem_cgroup_swap_full(page)))
ret = try_to_free_swap(page);
unlock_page(page);
}
put_page(page);
@ -780,7 +793,7 @@ checks:
int swap_was_freed;
unlock_cluster(ci);
spin_unlock(&si->lock);
swap_was_freed = __try_to_reclaim_swap(si, offset);
swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY);
spin_lock(&si->lock);
/* entry was freed successfully, try to use this again */
if (swap_was_freed)
@ -1612,7 +1625,6 @@ int try_to_free_swap(struct page *page)
int free_swap_and_cache(swp_entry_t entry)
{
struct swap_info_struct *p;
struct page *page = NULL;
unsigned char count;
if (non_swap_entry(entry))
@ -1622,31 +1634,12 @@ int free_swap_and_cache(swp_entry_t entry)
if (p) {
count = __swap_entry_free(p, entry, 1);
if (count == SWAP_HAS_CACHE &&
!swap_page_trans_huge_swapped(p, entry)) {
page = find_get_page(swap_address_space(entry),
swp_offset(entry));
if (page && !trylock_page(page)) {
put_page(page);
page = NULL;
}
} else if (!count)
!swap_page_trans_huge_swapped(p, entry))
__try_to_reclaim_swap(p, swp_offset(entry),
TTRS_UNMAPPED | TTRS_FULL);
else if (!count)
free_swap_slot(entry);
}
if (page) {
/*
* Not mapped elsewhere, or swap space full? Free it!
* Also recheck PageSwapCache now page is locked (above).
*/
if (PageSwapCache(page) && !PageWriteback(page) &&
(!page_mapped(page) || mem_cgroup_swap_full(page)) &&
!swap_page_trans_huge_swapped(p, entry)) {
page = compound_head(page);
delete_from_swap_cache(page);
SetPageDirty(page);
}
unlock_page(page);
put_page(page);
}
return p != NULL;
}