[PATCHv4 24/25] shmem: add huge pages support

From: Kirill A. Shutemov
Date: Fri Mar 11 2016 - 18:02:53 EST

Here's basic implementation of huge pages support for shmem/tmpfs.

It's all pretty streight-forward:

- shmem_getpage() allcoates huge page if it can and try to inserd into
radix tree with shmem_add_to_page_cache();

- shmem_add_to_page_cache() puts the page onto radix-tree if there's
space for it;

- shmem_undo_range() removes huge pages, if it fully within range.
Partial truncate of huge pages zero out this part of THP.

This have visible effect on fallocate(FALLOC_FL_PUNCH_HOLE)
behaviour. As we don't really create hole in this case,
lseek(SEEK_HOLE) may have inconsistent results depending what
pages happened to be allocated.

- no need to change shmem_fault: core-mm will map an compound page as
huge if VMA is suitable;

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
include/linux/huge_mm.h | 2 +
mm/memory.c | 5 +-
mm/mempolicy.c | 2 +-
mm/page-writeback.c | 1 +
mm/shmem.c | 355 +++++++++++++++++++++++++++++++++++++-----------
mm/swap.c | 2 +
6 files changed, 282 insertions(+), 85 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index d40eab8c9d00..2696a61d1bdc 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -160,6 +160,8 @@ struct page *get_huge_zero_page(void);

#define transparent_hugepage_enabled(__vma) 0

+static inline void prep_transhuge_page(struct page *page) {}
+
#define transparent_hugepage_flags 0UL
static inline int
split_huge_page_to_list(struct page *page, struct list_head *list)
diff --git a/mm/memory.c b/mm/memory.c
index c0a2510b9e15..939499dbdff5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1090,7 +1090,7 @@ again:
* unmap shared but keep private pages.
*/
if (details->check_mapping &&
- details->check_mapping != page->mapping)
+ details->check_mapping != page_rmapping(page))
continue;
}
ptent = ptep_get_and_clear_full(mm, addr, pte,
@@ -1181,7 +1181,8 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
if (next - addr != HPAGE_PMD_SIZE) {
- VM_BUG_ON_VMA(!rwsem_is_locked(&tlb->mm->mmap_sem), vma);
+ VM_BUG_ON_VMA(vma_is_anonymous(vma) &&
+ !rwsem_is_locked(&tlb->mm->mmap_sem), vma);
split_huge_pmd(vma, pmd, addr);
} else if (zap_huge_pmd(tlb, vma, pmd, addr))
goto next;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 76a0e6e56e05..5d1d9dd9a379 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -534,7 +534,7 @@ retry:
nid = page_to_nid(page);
if (node_isset(nid, *qp->nmask) == !!(flags & MPOL_MF_INVERT))
continue;
- if (PageTransCompound(page) && PageAnon(page)) {
+ if (PageTransCompound(page)) {
get_page(page);
pte_unmap_unlock(pte, ptl);
lock_page(page);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 11ff8f758631..2c8d5386665d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2554,6 +2554,7 @@ int set_page_dirty(struct page *page)
{
struct address_space *mapping = page_mapping(page);

+ page = compound_head(page);
if (likely(mapping)) {
int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
/*
diff --git a/mm/shmem.c b/mm/shmem.c
index e7c2a69ff410..c31216806721 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -173,10 +173,13 @@ static inline int shmem_reacct_size(unsigned long flags,
* shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
* so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
*/
-static inline int shmem_acct_block(unsigned long flags)
+static inline int shmem_acct_block(unsigned long flags, long pages)
{
- return (flags & VM_NORESERVE) ?
- security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
+ if (!(flags & VM_NORESERVE))
+ return 0;
+
+ return security_vm_enough_memory_mm(current->mm,
+ pages * VM_ACCT(PAGE_CACHE_SIZE));
}

static inline void shmem_unacct_blocks(unsigned long flags, long pages)
@@ -376,30 +379,55 @@ static int shmem_add_to_page_cache(struct page *page,
struct address_space *mapping,
pgoff_t index, void *expected)
{
- int error;
+ int error, nr = hpage_nr_pages(page);

+ VM_BUG_ON_PAGE(PageTail(page), page);
+ VM_BUG_ON_PAGE(index != round_down(index, nr), page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
+ VM_BUG_ON(expected && PageTransHuge(page));

- page_cache_get(page);
+ atomic_add(nr, &page->_count);
page->mapping = mapping;
page->index = index;

spin_lock_irq(&mapping->tree_lock);
- if (!expected)
+ if (PageTransHuge(page)) {
+ void __rcu **results;
+ pgoff_t idx;
+ int i;
+
+ error = 0;
+ if (radix_tree_gang_lookup_slot(&mapping->page_tree,
+ &results, &idx, index, 1) &&
+ idx < index + HPAGE_PMD_NR) {
+ error = -EEXIST;
+ }
+
+ if (!error) {
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ error = radix_tree_insert(&mapping->page_tree,
+ index + i, page + i);
+ VM_BUG_ON(error);
+ }
+ count_vm_event(THP_FILE_ALLOC);
+ }
+ } else if (!expected) {
error = radix_tree_insert(&mapping->page_tree, index, page);
- else
+ } else {
error = shmem_radix_tree_replace(mapping, index, expected,
page);
+ }
+
if (!error) {
- mapping->nrpages++;
- __inc_zone_page_state(page, NR_FILE_PAGES);
- __inc_zone_page_state(page, NR_SHMEM);
+ mapping->nrpages += nr;
+ __mod_zone_page_state(page_zone(page), NR_FILE_PAGES, nr);
+ __mod_zone_page_state(page_zone(page), NR_SHMEM, nr);
spin_unlock_irq(&mapping->tree_lock);
} else {
page->mapping = NULL;
spin_unlock_irq(&mapping->tree_lock);
- page_cache_release(page);
+ atomic_sub(nr, &page->_count);
}
return error;
}
@@ -412,6 +440,8 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
struct address_space *mapping = page->mapping;
int error;

+ VM_BUG_ON_PAGE(PageCompound(page), page);
+
spin_lock_irq(&mapping->tree_lock);
error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
page->mapping = NULL;
@@ -596,10 +626,33 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
continue;
}

+ VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page);
+
if (!trylock_page(page))
continue;
+
+ if (PageTransTail(page)) {
+ /* Middle of THP: zero out the page */
+ clear_highpage(page);
+ unlock_page(page);
+ continue;
+ } else if (PageTransHuge(page)) {
+ if (index == round_down(end, HPAGE_PMD_NR)) {
+ /*
+ * Range ends in the middle of THP:
+ * zero out the page
+ */
+ clear_highpage(page);
+ unlock_page(page);
+ continue;
+ }
+ index += HPAGE_PMD_NR - 1;
+ i += HPAGE_PMD_NR - 1;
+ }
+
if (!unfalloc || !PageUptodate(page)) {
- if (page->mapping == mapping) {
+ VM_BUG_ON_PAGE(PageTail(page), page);
+ if (page_mapping(page) == mapping) {
VM_BUG_ON_PAGE(PageWriteback(page), page);
truncate_inode_page(mapping, page);
}
@@ -675,8 +728,36 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
}

lock_page(page);
+
+ if (PageTransTail(page)) {
+ /* Middle of THP: zero out the page */
+ clear_highpage(page);
+ unlock_page(page);
+ /*
+ * Partial thp truncate due 'start' in middle
+ * of THP: don't need to look on these pages
+ * again on !pvec.nr restart.
+ */
+ if (index != round_down(end, HPAGE_PMD_NR))
+ start++;
+ continue;
+ } else if (PageTransHuge(page)) {
+ if (index == round_down(end, HPAGE_PMD_NR)) {
+ /*
+ * Range ends in the middle of THP:
+ * zero out the page
+ */
+ clear_highpage(page);
+ unlock_page(page);
+ continue;
+ }
+ index += HPAGE_PMD_NR - 1;
+ i += HPAGE_PMD_NR - 1;
+ }
+
if (!unfalloc || !PageUptodate(page)) {
- if (page->mapping == mapping) {
+ VM_BUG_ON_PAGE(PageTail(page), page);
+ if (page_mapping(page) == mapping) {
VM_BUG_ON_PAGE(PageWriteback(page), page);
truncate_inode_page(mapping, page);
} else {
@@ -935,6 +1016,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
swp_entry_t swap;
pgoff_t index;

+ VM_BUG_ON_PAGE(PageCompound(page), page);
BUG_ON(!PageLocked(page));
mapping = page->mapping;
index = page->index;
@@ -1034,8 +1116,8 @@ redirty:
return 0;
}

-#ifdef CONFIG_NUMA
#ifdef CONFIG_TMPFS
+#ifdef CONFIG_NUMA
static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
{
char buffer[64];
@@ -1059,68 +1141,129 @@ static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
}
return mpol;
}
+
+#else
+
+static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
+{
+}
+#endif /* CONFIG_NUMA */
#endif /* CONFIG_TMPFS */

+static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
+ struct shmem_inode_info *info, pgoff_t index)
+{
+ /* Create a pseudo vma that just contains the policy */
+ vma->vm_start = 0;
+ /* Bias interleave by inode number to distribute better across nodes */
+ vma->vm_pgoff = index + info->vfs_inode.i_ino;
+ vma->vm_ops = NULL;
+
+#ifdef CONFIG_NUMA
+ vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+#endif /* CONFIG_NUMA */
+}
+
+static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
+{
+#ifdef CONFIG_NUMA
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(vma->vm_policy);
+#endif
+}
+
static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
struct vm_area_struct pvma;
struct page *page;

- /* Create a pseudo vma that just contains the policy */
- pvma.vm_start = 0;
- /* Bias interleave by inode number to distribute better across nodes */
- pvma.vm_pgoff = index + info->vfs_inode.i_ino;
- pvma.vm_ops = NULL;
- pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
-
+ shmem_pseudo_vma_init(&pvma, info, index);
page = swapin_readahead(swap, gfp, &pvma, 0);
-
- /* Drop reference taken by mpol_shared_policy_lookup() */
- mpol_cond_put(pvma.vm_policy);
+ shmem_pseudo_vma_destroy(&pvma);

return page;
}

-static struct page *shmem_alloc_page(gfp_t gfp,
- struct shmem_inode_info *info, pgoff_t index)
+static struct page *shmem_alloc_hugepage(gfp_t gfp,
+ struct shmem_inode_info *info, pgoff_t index)
{
struct vm_area_struct pvma;
+ struct inode *inode = &info->vfs_inode;
+ struct address_space *mapping = inode->i_mapping;
+ pgoff_t idx, hindex = round_down(index, HPAGE_PMD_NR);
+ void __rcu **results;
struct page *page;

- /* Create a pseudo vma that just contains the policy */
- pvma.vm_start = 0;
- /* Bias interleave by inode number to distribute better across nodes */
- pvma.vm_pgoff = index + info->vfs_inode.i_ino;
- pvma.vm_ops = NULL;
- pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
-
- page = alloc_page_vma(gfp, &pvma, 0);
+ if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+ return NULL;

- /* Drop reference taken by mpol_shared_policy_lookup() */
- mpol_cond_put(pvma.vm_policy);
+ rcu_read_lock();
+ if (radix_tree_gang_lookup_slot(&mapping->page_tree, &results, &idx,
+ hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
+ rcu_read_unlock();
+ return NULL;
+ }
+ rcu_read_unlock();

+ shmem_pseudo_vma_init(&pvma, info, hindex);
+ page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
+ HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
+ shmem_pseudo_vma_destroy(&pvma);
+ if (page)
+ prep_transhuge_page(page);
return page;
}
-#else /* !CONFIG_NUMA */
-#ifdef CONFIG_TMPFS
-static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
-{
-}
-#endif /* CONFIG_TMPFS */

-static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
+static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
- return swapin_readahead(swap, gfp, NULL, 0);
+ struct vm_area_struct pvma;
+ struct page *page;
+
+ shmem_pseudo_vma_init(&pvma, info, index);
+ page = alloc_page_vma(gfp, &pvma, 0);
+ shmem_pseudo_vma_destroy(&pvma);
+
+ return page;
}

-static inline struct page *shmem_alloc_page(gfp_t gfp,
- struct shmem_inode_info *info, pgoff_t index)
+static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
+ struct shmem_inode_info *info, struct shmem_sb_info *sbinfo,
+ pgoff_t index, bool huge)
{
- return alloc_page(gfp);
+ struct page *page;
+ int nr;
+ int err = -ENOSPC;
+
+ if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
+ huge = false;
+ nr = huge ? HPAGE_PMD_NR : 1;
+
+ if (shmem_acct_block(info->flags, nr))
+ goto failed;
+ if (sbinfo->max_blocks) {
+ if (percpu_counter_compare(&sbinfo->used_blocks,
+ sbinfo->max_blocks + nr) > 0)
+ goto unacct;
+ percpu_counter_add(&sbinfo->used_blocks, nr);
+ }
+
+ if (huge)
+ page = shmem_alloc_hugepage(gfp, info, index);
+ else
+ page = shmem_alloc_page(gfp, info, index);
+ if (page)
+ return page;
+
+ err = -ENOMEM;
+ if (sbinfo->max_blocks)
+ percpu_counter_add(&sbinfo->used_blocks, -nr);
+unacct:
+ shmem_unacct_blocks(info->flags, nr);
+failed:
+ return ERR_PTR(err);
}
-#endif /* CONFIG_NUMA */

#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
@@ -1228,6 +1371,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
struct mem_cgroup *memcg;
struct page *page;
swp_entry_t swap;
+ pgoff_t hindex = index;
int error;
int once = 0;
int alloced = 0;
@@ -1344,50 +1488,75 @@ repeat:
swap_free(swap);

} else {
- if (shmem_acct_block(info->flags)) {
- error = -ENOSPC;
- goto failed;
- }
- if (sbinfo->max_blocks) {
- if (percpu_counter_compare(&sbinfo->used_blocks,
- sbinfo->max_blocks) >= 0) {
- error = -ENOSPC;
- goto unacct;
- }
- percpu_counter_inc(&sbinfo->used_blocks);
+ /* shmem_symlink() */
+ if (mapping->a_ops != &shmem_aops)
+ goto alloc_nohuge;
+ if (shmem_huge == SHMEM_HUGE_DENY)
+ goto alloc_nohuge;
+ if (shmem_huge == SHMEM_HUGE_FORCE)
+ goto alloc_huge;
+ switch (sbinfo->huge) {
+ loff_t i_size;
+ pgoff_t off;
+ case SHMEM_HUGE_NEVER:
+ goto alloc_nohuge;
+ case SHMEM_HUGE_WITHIN_SIZE:
+ off = round_up(index, HPAGE_PMD_NR);
+ i_size = round_up(i_size_read(inode), PAGE_CACHE_SIZE);
+ if (i_size >> PAGE_CACHE_SHIFT >= off)
+ goto alloc_huge;
+ /* fallthrough */
+ case SHMEM_HUGE_ADVISE:
+ /* TODO: wire up fadvise()/madvise() */
+ goto alloc_nohuge;
}

- page = shmem_alloc_page(gfp, info, index);
- if (!page) {
- error = -ENOMEM;
- goto decused;
+alloc_huge:
+ page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
+ index, true);
+ if (IS_ERR(page)) {
+alloc_nohuge: page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
+ index, false);
+ }
+ if (IS_ERR(page)) {
+ error = PTR_ERR(page);
+ page = NULL;
+ goto failed;
}

+ if (PageTransHuge(page))
+ hindex = round_down(index, HPAGE_PMD_NR);
+ else
+ hindex = index;
+
__SetPageSwapBacked(page);
__SetPageLocked(page);
if (sgp == SGP_WRITE)
__SetPageReferenced(page);

error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg,
- false);
+ PageTransHuge(page));
if (error)
- goto decused;
- error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
+ goto unacct;
+ error = radix_tree_maybe_preload_order(gfp & GFP_RECLAIM_MASK,
+ compound_order(page));
if (!error) {
- error = shmem_add_to_page_cache(page, mapping, index,
+ error = shmem_add_to_page_cache(page, mapping, hindex,
NULL);
radix_tree_preload_end();
}
if (error) {
- mem_cgroup_cancel_charge(page, memcg, false);
- goto decused;
+ mem_cgroup_cancel_charge(page, memcg,
+ PageTransHuge(page));
+ goto unacct;
}
- mem_cgroup_commit_charge(page, memcg, false, false);
+ mem_cgroup_commit_charge(page, memcg, false,
+ PageTransHuge(page));
lru_cache_add_anon(page);

spin_lock(&info->lock);
- info->alloced++;
- inode->i_blocks += BLOCKS_PER_PAGE;
+ info->alloced += 1 << compound_order(page);
+ inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
shmem_recalc_inode(inode);
spin_unlock(&info->lock);
alloced = true;
@@ -1403,10 +1572,15 @@ clear:
* but SGP_FALLOC on a page fallocated earlier must initialize
* it now, lest undo on failure cancel our earlier guarantee.
*/
- if (sgp != SGP_WRITE) {
- clear_highpage(page);
- flush_dcache_page(page);
- SetPageUptodate(page);
+ if (sgp != SGP_WRITE && !PageUptodate(page)) {
+ struct page *head = compound_head(page);
+ int i;
+
+ for (i = 0; i < (1 << compound_order(head)); i++) {
+ clear_highpage(head + i);
+ flush_dcache_page(head + i);
+ }
+ SetPageUptodate(head);
}
if (sgp == SGP_DIRTY)
set_page_dirty(page);
@@ -1425,17 +1599,23 @@ clear:
error = -EINVAL;
goto unlock;
}
- *pagep = page;
+ *pagep = page + index - hindex;
return 0;

/*
* Error recovery.
*/
-decused:
- if (sbinfo->max_blocks)
- percpu_counter_add(&sbinfo->used_blocks, -1);
unacct:
- shmem_unacct_blocks(info->flags, 1);
+ if (sbinfo->max_blocks)
+ percpu_counter_add(&sbinfo->used_blocks,
+ 1 << compound_order(page));
+ shmem_unacct_blocks(info->flags, 1 << compound_order(page));
+
+ if (PageTransHuge(page)) {
+ unlock_page(page);
+ page_cache_release(page);
+ goto alloc_nohuge;
+ }
failed:
if (swap.val && !shmem_confirm_swap(mapping, index, swap))
error = -EEXIST;
@@ -1776,12 +1956,23 @@ shmem_write_end(struct file *file, struct address_space *mapping,
i_size_write(inode, pos + copied);

if (!PageUptodate(page)) {
+ struct page *head = compound_head(page);
+ if (PageTransCompound(page)) {
+ int i;
+
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ if (head + i == page)
+ continue;
+ clear_highpage(head + i);
+ flush_dcache_page(head + i);
+ }
+ }
if (copied < PAGE_CACHE_SIZE) {
unsigned from = pos & (PAGE_CACHE_SIZE - 1);
zero_user_segments(page, 0, from,
from + copied, PAGE_CACHE_SIZE);
}
- SetPageUptodate(page);
+ SetPageUptodate(head);
}
set_page_dirty(page);
unlock_page(page);
diff --git a/mm/swap.c b/mm/swap.c
index 09fe5e97714a..5ee5118f45d4 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -291,6 +291,7 @@ static bool need_activate_page_drain(int cpu)

void activate_page(struct page *page)
{
+ page = compound_head(page);
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);

@@ -315,6 +316,7 @@ void activate_page(struct page *page)
{
struct zone *zone = page_zone(page);

+ page = compound_head(page);
spin_lock_irq(&zone->lru_lock);
__activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
spin_unlock_irq(&zone->lru_lock);
--
2.7.0