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Subject[PATCH -mm 08/21] mm, THP, swap: Support to read a huge swap cluster for swapin a THP
Date
From: Huang Ying <ying.huang@intel.com>

To swapin a THP as a whole, we need to read a huge swap cluster from
the swap device. This patch revised the __read_swap_cache_async() and
its callee to support this. If __read_swap_cache_async() find the
swap cluster of the specified swap entry is huge, it will try to
allocate a THP, add it into the swap cache. So later the contents of
the huge swap cluster can be read into the THP.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.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>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
---
include/linux/huge_mm.h | 38 ++++++++++++++++++++++++
include/linux/swap.h | 4 +--
mm/huge_memory.c | 26 ----------------
mm/swap_state.c | 66 +++++++++++++++++++++++++++++------------
mm/swapfile.c | 11 ++++---
5 files changed, 94 insertions(+), 51 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 0d0cfddbf4b7..0dbfbe34b01a 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -250,6 +250,39 @@ static inline bool thp_migration_supported(void)
return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION);
}

+/*
+ * always: directly stall for all thp allocations
+ * defer: wake kswapd and fail if not immediately available
+ * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
+ * fail if not immediately available
+ * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
+ * available
+ * never: never stall for any thp allocation
+ */
+static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
+{
+ bool vma_madvised;
+
+ if (!vma)
+ return GFP_TRANSHUGE_LIGHT;
+ vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
+ &transparent_hugepage_flags))
+ return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
+ &transparent_hugepage_flags))
+ return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
+ &transparent_hugepage_flags))
+ return GFP_TRANSHUGE_LIGHT |
+ (vma_madvised ? __GFP_DIRECT_RECLAIM :
+ __GFP_KSWAPD_RECLAIM);
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
+ &transparent_hugepage_flags))
+ return GFP_TRANSHUGE_LIGHT |
+ (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
+ return GFP_TRANSHUGE_LIGHT;
+}
#else /* CONFIG_TRANSPARENT_HUGEPAGE */
#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -362,6 +395,11 @@ static inline bool thp_migration_supported(void)
{
return false;
}
+
+static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
+{
+ return 0;
+}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

#endif /* _LINUX_HUGE_MM_H */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 42e962b9ad3c..c42e7edcf141 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -462,7 +462,7 @@ extern sector_t map_swap_page(struct page *, struct block_device **);
extern sector_t swapdev_block(int, pgoff_t);
extern int page_swapcount(struct page *);
extern int __swap_count(swp_entry_t entry);
-extern int __swp_swapcount(swp_entry_t entry);
+extern int __swp_swapcount(swp_entry_t entry, bool *huge_cluster);
extern int swp_swapcount(swp_entry_t entry);
extern struct swap_info_struct *page_swap_info(struct page *);
extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
@@ -589,7 +589,7 @@ static inline int __swap_count(swp_entry_t entry)
return 0;
}

-static inline int __swp_swapcount(swp_entry_t entry)
+static inline int __swp_swapcount(swp_entry_t entry, bool *huge_cluster)
{
return 0;
}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a2124f0a0454..a40e27447cac 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -623,32 +623,6 @@ static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,

}

-/*
- * always: directly stall for all thp allocations
- * defer: wake kswapd and fail if not immediately available
- * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
- * fail if not immediately available
- * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
- * available
- * never: never stall for any thp allocation
- */
-static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
-{
- const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
-
- if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
- return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
- if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
- return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
- if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
- return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
- __GFP_KSWAPD_RECLAIM);
- if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
- return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
- 0);
- return GFP_TRANSHUGE_LIGHT;
-}
-
/* Caller must hold page table lock. */
static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
diff --git a/mm/swap_state.c b/mm/swap_state.c
index fe079756bb18..53e807a24ec5 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -389,6 +389,9 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
struct page *found_page = NULL, *new_page = NULL;
struct swap_info_struct *si;
int err;
+ bool huge_cluster = false;
+ swp_entry_t hentry;
+
*new_page_allocated = false;

do {
@@ -414,14 +417,32 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* as SWAP_HAS_CACHE. That's done in later part of code or
* else swap_off will be aborted if we return NULL.
*/
- if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
+ if (!__swp_swapcount(entry, &huge_cluster) &&
+ swap_slot_cache_enabled)
break;

/*
* Get a new page to read into from swap.
*/
- if (!new_page) {
- new_page = alloc_page_vma(gfp_mask, vma, addr);
+ if (!new_page ||
+ (thp_swap_supported() &&
+ !!PageTransCompound(new_page) != huge_cluster)) {
+ if (new_page)
+ put_page(new_page);
+ if (thp_swap_supported() && huge_cluster) {
+ gfp_t gfp = alloc_hugepage_direct_gfpmask(vma);
+
+ new_page = alloc_hugepage_vma(gfp, vma,
+ addr, HPAGE_PMD_ORDER);
+ if (new_page)
+ prep_transhuge_page(new_page);
+ hentry = swp_entry(swp_type(entry),
+ round_down(swp_offset(entry),
+ HPAGE_PMD_NR));
+ } else {
+ new_page = alloc_page_vma(gfp_mask, vma, addr);
+ hentry = entry;
+ }
if (!new_page)
break; /* Out of memory */
}
@@ -429,33 +450,37 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
/*
* call radix_tree_preload() while we can wait.
*/
- err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
+ err = radix_tree_maybe_preload_order(gfp_mask & GFP_KERNEL,
+ compound_order(new_page));
if (err)
break;

/*
* Swap entry may have been freed since our caller observed it.
*/
- err = swapcache_prepare(entry);
- if (err == -EEXIST) {
- radix_tree_preload_end();
- /*
- * We might race against get_swap_page() and stumble
- * across a SWAP_HAS_CACHE swap_map entry whose page
- * has not been brought into the swapcache yet.
- */
- cond_resched();
- continue;
- }
- if (err) { /* swp entry is obsolete ? */
+ err = swapcache_prepare(hentry, huge_cluster);
+ if (err) {
radix_tree_preload_end();
- break;
+ if (err == -EEXIST) {
+ /*
+ * We might race against get_swap_page() and
+ * stumble across a SWAP_HAS_CACHE swap_map
+ * entry whose page has not been brought into
+ * the swapcache yet.
+ */
+ cond_resched();
+ continue;
+ } else if (err == -ENOTDIR) {
+ /* huge swap cluster is split under us */
+ continue;
+ } else /* swp entry is obsolete ? */
+ break;
}

/* May fail (-ENOMEM) if radix-tree node allocation failed. */
__SetPageLocked(new_page);
__SetPageSwapBacked(new_page);
- err = __add_to_swap_cache(new_page, entry);
+ err = __add_to_swap_cache(new_page, hentry);
if (likely(!err)) {
radix_tree_preload_end();
/*
@@ -463,6 +488,9 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
*/
lru_cache_add_anon(new_page);
*new_page_allocated = true;
+ if (thp_swap_supported() && huge_cluster)
+ new_page += swp_offset(entry) &
+ (HPAGE_PMD_NR - 1);
return new_page;
}
radix_tree_preload_end();
@@ -471,7 +499,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
* clear SWAP_HAS_CACHE flag.
*/
- put_swap_page(new_page, entry);
+ put_swap_page(new_page, hentry);
} while (err != -ENOMEM);

if (new_page)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index cad3f416cb0a..3bac299a1b25 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1501,7 +1501,8 @@ int __swap_count(swp_entry_t entry)
return count;
}

-static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
+static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry,
+ bool *huge_cluster)
{
int count = 0;
pgoff_t offset = swp_offset(entry);
@@ -1509,6 +1510,8 @@ static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)

ci = lock_cluster_or_swap_info(si, offset);
count = swap_count(si->swap_map[offset]);
+ if (huge_cluster && ci)
+ *huge_cluster = cluster_is_huge(ci);
unlock_cluster_or_swap_info(si, ci);
return count;
}
@@ -1518,14 +1521,14 @@ static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
* This does not give an exact answer when swap count is continued,
* but does include the high COUNT_CONTINUED flag to allow for that.
*/
-int __swp_swapcount(swp_entry_t entry)
+int __swp_swapcount(swp_entry_t entry, bool *huge_cluster)
{
int count = 0;
struct swap_info_struct *si;

si = get_swap_device(entry);
if (si) {
- count = swap_swapcount(si, entry);
+ count = swap_swapcount(si, entry, huge_cluster);
put_swap_device(si);
}
return count;
@@ -1685,7 +1688,7 @@ static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
return map_swapcount;
}
#else
-#define swap_page_trans_huge_swapped(si, entry) swap_swapcount(si, entry)
+#define swap_page_trans_huge_swapped(si, entry) swap_swapcount(si, entry, NULL)
#define page_swapped(page) (page_swapcount(page) != 0)

static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
--
2.17.0
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