[PATCH -V6 08/21] swap: Support to read a huge swap cluster for swapin a THP

Huang Ying
2018-10-10T07:27:24Z

To swapin a THP in one piece, we need to read a huge swap cluster from
the swap device. This patch revised the __read_swap_cache_async() and
its callers and callees 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@kernel.org>
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>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
---
include/linux/huge_mm.h | 8 +++++++
include/linux/swap.h | 4 ++--
mm/huge_memory.c | 3 ++-
mm/swap_state.c | 59 ++++++++++++++++++++++++++++++++++++++++---------
mm/swapfile.c | 9 +++++---
5 files changed, 66 insertions(+), 17 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 0f3e1739986f..a0e7f4f9c12b 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -250,6 +250,8 @@ static inline bool thp_migration_supported(void)
return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION);
}

+gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma,
+ unsigned long addr);
#else /* CONFIG_TRANSPARENT_HUGEPAGE */
#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -363,6 +365,12 @@ static inline bool thp_migration_supported(void)
{
return false;
}
+
+static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ return 0;
+}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

#endif /* _LINUX_HUGE_MM_H */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 60fd5189fde9..f2daf3fbdd4b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -457,7 +457,7 @@ 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, int *entry_size);
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);
@@ -585,7 +585,7 @@ 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, int *entry_size)
{
return 0;
}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 92e0cdb99c5a..a025494dd828 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -629,7 +629,8 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
* available
* never: never stall for any thp allocation
*/
-static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma, unsigned long addr)
+gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma,
+ unsigned long addr)
{
const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
gfp_t this_node = 0;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index bca34fc7a5e5..784ad6388da0 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -361,7 +361,9 @@ 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;
+ int err, entry_size = 1;
+ swp_entry_t hentry;
+
*new_page_allocated = false;

do {
@@ -387,14 +389,42 @@ 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, &entry_size) &&
+ 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 ||
+ (IS_ENABLED(CONFIG_THP_SWAP) &&
+ hpage_nr_pages(new_page) != entry_size)) {
+ if (new_page)
+ put_page(new_page);
+ if (IS_ENABLED(CONFIG_THP_SWAP) &&
+ entry_size == HPAGE_PMD_NR) {
+ gfp_t gfp;
+
+ gfp = alloc_hugepage_direct_gfpmask(vma, addr);
+ /*
+ * Make sure huge page allocation flags are
+ * compatible with that of normal page
+ */
+ VM_WARN_ONCE(gfp_mask & ~(gfp | __GFP_RECLAIM),
+ "ignoring gfp_mask bits: %x",
+ gfp_mask & ~(gfp | __GFP_RECLAIM));
+ new_page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER,
+ vma, addr,
+ numa_node_id());
+ 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 */
}
@@ -402,7 +432,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
/*
* Swap entry may have been freed since our caller observed it.
*/
- err = swapcache_prepare(entry, 1);
+ err = swapcache_prepare(hentry, entry_size);
if (err == -EEXIST) {
/*
* We might race against get_swap_page() and stumble
@@ -411,6 +441,9 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
*/
cond_resched();
continue;
+ } else if (err == -ENOTDIR) {
+ /* huge swap cluster has been split under us */
+ continue;
} else if (err) { /* swp entry is obsolete ? */
break;
}
@@ -424,6 +457,9 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
SetPageWorkingset(new_page);
lru_cache_add_anon(new_page);
*new_page_allocated = true;
+ if (IS_ENABLED(CONFIG_THP_SWAP))
+ new_page += swp_offset(entry) &
+ (entry_size - 1);
return new_page;
}
__ClearPageLocked(new_page);
@@ -431,7 +467,7 @@ 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)
@@ -453,7 +489,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
vma, addr, &page_was_allocated);

if (page_was_allocated)
- swap_readpage(retpage, do_poll);
+ swap_readpage(compound_head(retpage), do_poll);

return retpage;
}
@@ -572,8 +608,9 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
if (!page)
continue;
if (page_allocated) {
- swap_readpage(page, false);
- if (offset != entry_offset) {
+ swap_readpage(compound_head(page), false);
+ if (offset != entry_offset &&
+ !PageTransCompound(page)) {
SetPageReadahead(page);
count_vm_event(SWAP_RA);
}
@@ -734,8 +771,8 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
if (!page)
continue;
if (page_allocated) {
- swap_readpage(page, false);
- if (i != ra_info.offset) {
+ swap_readpage(compound_head(page), false);
+ if (i != ra_info.offset && !PageTransCompound(page)) {
SetPageReadahead(page);
count_vm_event(SWAP_RA);
}
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2020bd494419..2ca013df35e1 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1542,7 +1542,8 @@ 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,
+ int *entry_size)
{
int count = 0;
pgoff_t offset = swp_offset(entry);
@@ -1550,6 +1551,8 @@ 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 (entry_size)
+ *entry_size = ci && cluster_is_huge(ci) ? SWAPFILE_CLUSTER : 1;
unlock_cluster_or_swap_info(si, ci);
return count;
}
@@ -1559,14 +1562,14 @@ 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, int *entry_size)
{
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, entry_size);
put_swap_device(si);
}
return count;
--
2.16.4