[PATCH v2 0/8] Misc MM patches

[PATCH v2 0/8] Misc MM patches

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

These are all things that I noticed while working on the THP patches, but
all stand alone as useful MM cleanups.  Andrew, please consider applying.

There's two extra patches in here compared to v1; I separated out the
patch renaming the arguments to find_subpage() from the patch converting
it to use hpage_nr_pages(), and I added a patch to check PageTail()
in hpage_nr_pages() for the !THP case.

Patch 5 (Remove CONFIG_TRANSPARENT_HUGE_PAGECACHE) adds the missing hunk
that Alex Duyck pointed out.

Patch 8 (pagecache_get_page documentation) also renames the 'offset'
parameter to 'index'.

Original series here:
https://lore.kernel.org/linux-mm/20200303041125.19358-1-willy@infradead.org/

Matthew Wilcox (Oracle) (8):
  mm: Use vm_fault error code directly
  mm: Rename arguments to find_subpage
  mm: Check PageTail in hpage_nr_pages even when !THP
  mm: Optimise find_subpage for !THP
  mm: Remove CONFIG_TRANSPARENT_HUGE_PAGECACHE
  mm: Use VM_BUG_ON_PAGE in clear_page_dirty_for_io
  mm: Unexport find_get_entry
  mm: Rewrite pagecache_get_page documentation

 include/linux/huge_mm.h  |  6 ++++-
 include/linux/pagemap.h  | 15 +++++++-----
 include/linux/shmem_fs.h | 10 +-------
 mm/Kconfig               |  6 +----
 mm/filemap.c             | 52 +++++++++++++++++++---------------------
 mm/huge_memory.c         |  2 +-
 mm/khugepaged.c          | 12 ++++------
 mm/memory.c              |  5 ++--
 mm/page-writeback.c      |  2 +-
 mm/rmap.c                |  2 +-
 mm/shmem.c               | 36 ++++++++++++++--------------
 11 files changed, 67 insertions(+), 81 deletions(-)

-- 
2.25.1

[PATCH v2 1/8] mm: Use vm_fault error code directly

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Use VM_FAULT_OOM instead of indirecting through vmf_error(-ENOMEM).

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 mm/filemap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 1784478270e1..1beb7716276b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2491,7 +2491,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 		if (!page) {
 			if (fpin)
 				goto out_retry;
-			return vmf_error(-ENOMEM);
+			return VM_FAULT_OOM;
 		}
 	}
 
-- 
2.25.1

[PATCH v2 2/8] mm: Rename arguments to find_subpage

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

This isn't just a random struct page, it's known to be a head page,
and calling it head makes the function better self-documenting.
The pgoff_t is less confusing if it's named index instead of offset.
Also add a couple of comments to explain why we're doing various things.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/pagemap.h | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index b4ea3a5d00e5..68db0ed8535d 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -333,14 +333,19 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
 			mapping_gfp_mask(mapping));
 }
 
-static inline struct page *find_subpage(struct page *page, pgoff_t offset)
+/*
+ * Given the page we found in the page cache, return the page corresponding
+ * to this index in the file
+ */
+static inline struct page *find_subpage(struct page *head, pgoff_t index)
 {
-	if (PageHuge(page))
-		return page;
+	/* HugeTLBfs wants the head page regardless */
+	if (PageHuge(head))
+		return head;
 
-	VM_BUG_ON_PAGE(PageTail(page), page);
+	VM_BUG_ON_PAGE(PageTail(head), head);
 
-	return page + (offset & (compound_nr(page) - 1));
+	return head + (index & (compound_nr(head) - 1));
 }
 
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
-- 
2.25.1

[PATCH v2 3/8] mm: Check PageTail in hpage_nr_pages even when !THP

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

It's even more important to check that we don't have a tail page when
calling hpage_nr_pages() when THP are disabled.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/huge_mm.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 5aca3d1bdb32..a155a7929b34 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -289,7 +289,11 @@ static inline struct list_head *page_deferred_list(struct page *page)
 #define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
 #define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
-#define hpage_nr_pages(x) 1
+static inline int hpage_nr_pages(struct page *page)
+{
+	VM_BUG_ON_PAGE(PageTail(page), page);
+	return 1;
+}
 
 static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
 {
-- 
2.25.1

[PATCH v2 4/8] mm: Optimise find_subpage for !THP

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

If THP is disabled, find_subpage() can become a no-op by using
hpage_nr_pages() instead of compound_nr().  hpage_nr_pages() embeds
a check for PageTail, so we can drop the check here.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/pagemap.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 68db0ed8535d..fcb4887e65e8 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -343,9 +343,7 @@ static inline struct page *find_subpage(struct page *head, pgoff_t index)
 	if (PageHuge(head))
 		return head;
 
-	VM_BUG_ON_PAGE(PageTail(head), head);
-
-	return head + (index & (compound_nr(head) - 1));
+	return head + (index & (hpage_nr_pages(head) - 1));
 }
 
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
-- 
2.25.1

[PATCH v2 5/8] mm: Remove CONFIG_TRANSPARENT_HUGE_PAGECACHE

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Commit e496cf3d7821 ("thp: introduce CONFIG_TRANSPARENT_HUGE_PAGECACHE")
notes that it should be reverted when the PowerPC problem was fixed.
The commit fixing the PowerPC problem (953c66c2b22a) did not revert
the commit; instead setting CONFIG_TRANSPARENT_HUGE_PAGECACHE to the
same as CONFIG_TRANSPARENT_HUGEPAGE.  Checking with Kirill and Aneesh,
this was an oversight, so remove the Kconfig symbol and undo the work
of commit e496cf3d7821.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 include/linux/shmem_fs.h | 10 +---------
 mm/Kconfig               |  6 +-----
 mm/huge_memory.c         |  2 +-
 mm/khugepaged.c          | 12 ++++--------
 mm/memory.c              |  5 ++---
 mm/rmap.c                |  2 +-
 mm/shmem.c               | 36 ++++++++++++++++++------------------
 7 files changed, 28 insertions(+), 45 deletions(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index d56fefef8905..7a35a6901221 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -78,6 +78,7 @@ extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
 extern int shmem_unuse(unsigned int type, bool frontswap,
 		       unsigned long *fs_pages_to_unuse);
 
+extern bool shmem_huge_enabled(struct vm_area_struct *vma);
 extern unsigned long shmem_swap_usage(struct vm_area_struct *vma);
 extern unsigned long shmem_partial_swap_usage(struct address_space *mapping,
 						pgoff_t start, pgoff_t end);
@@ -114,15 +115,6 @@ static inline bool shmem_file(struct file *file)
 extern bool shmem_charge(struct inode *inode, long pages);
 extern void shmem_uncharge(struct inode *inode, long pages);
 
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
-extern bool shmem_huge_enabled(struct vm_area_struct *vma);
-#else
-static inline bool shmem_huge_enabled(struct vm_area_struct *vma)
-{
-	return false;
-}
-#endif
-
 #ifdef CONFIG_SHMEM
 extern int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
 				  struct vm_area_struct *dst_vma,
diff --git a/mm/Kconfig b/mm/Kconfig
index ab80933be65f..211a70e8d5cf 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -420,10 +420,6 @@ config THP_SWAP
 
 	  For selection by architectures with reasonable THP sizes.
 
-config	TRANSPARENT_HUGE_PAGECACHE
-	def_bool y
-	depends on TRANSPARENT_HUGEPAGE
-
 #
 # UP and nommu archs use km based percpu allocator
 #
@@ -714,7 +710,7 @@ config GUP_GET_PTE_LOW_HIGH
 
 config READ_ONLY_THP_FOR_FS
 	bool "Read-only THP for filesystems (EXPERIMENTAL)"
-	depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM
+	depends on TRANSPARENT_HUGEPAGE && SHMEM
 
 	help
 	  Allow khugepaged to put read-only file-backed pages in THP.
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b08b199f9a11..e88cce651705 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -326,7 +326,7 @@ static struct attribute *hugepage_attr[] = {
 	&defrag_attr.attr,
 	&use_zero_page_attr.attr,
 	&hpage_pmd_size_attr.attr,
-#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
+#ifdef CONFIG_SHMEM
 	&shmem_enabled_attr.attr,
 #endif
 #ifdef CONFIG_DEBUG_VM
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b679908743cb..cc80b0f2c5f8 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -416,8 +416,6 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
 	    (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
 	     vma->vm_file &&
 	     (vm_flags & VM_DENYWRITE))) {
-		if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
-			return false;
 		return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
 				HPAGE_PMD_NR);
 	}
@@ -1260,7 +1258,7 @@ static void collect_mm_slot(struct mm_slot *mm_slot)
 	}
 }
 
-#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
+#ifdef CONFIG_SHMEM
 /*
  * Notify khugepaged that given addr of the mm is pte-mapped THP. Then
  * khugepaged should try to collapse the page table.
@@ -1975,6 +1973,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
 		if (khugepaged_scan.address < hstart)
 			khugepaged_scan.address = hstart;
 		VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
+		if (shmem_file(vma->vm_file) && !shmem_huge_enabled(vma))
+			goto skip;
 
 		while (khugepaged_scan.address < hend) {
 			int ret;
@@ -1986,14 +1986,10 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
 				  khugepaged_scan.address + HPAGE_PMD_SIZE >
 				  hend);
 			if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
-				struct file *file;
+				struct file *file = get_file(vma->vm_file);
 				pgoff_t pgoff = linear_page_index(vma,
 						khugepaged_scan.address);
 
-				if (shmem_file(vma->vm_file)
-				    && !shmem_huge_enabled(vma))
-					goto skip;
-				file = get_file(vma->vm_file);
 				up_read(&mm->mmap_sem);
 				ret = 1;
 				khugepaged_scan_file(mm, file, pgoff, hpage);
diff --git a/mm/memory.c b/mm/memory.c
index 0bccc622e482..6ab0b03ea9bd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3354,7 +3354,7 @@ static vm_fault_t pte_alloc_one_map(struct vm_fault *vmf)
 	return 0;
 }
 
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static void deposit_prealloc_pte(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
@@ -3456,8 +3456,7 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
 	pte_t entry;
 	vm_fault_t ret;
 
-	if (pmd_none(*vmf->pmd) && PageTransCompound(page) &&
-			IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
+	if (pmd_none(*vmf->pmd) && PageTransCompound(page)) {
 		/* THP on COW? */
 		VM_BUG_ON_PAGE(memcg, page);
 
diff --git a/mm/rmap.c b/mm/rmap.c
index b3e381919835..af48024c6baf 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -940,7 +940,7 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
 			set_pte_at(vma->vm_mm, address, pte, entry);
 			ret = 1;
 		} else {
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 			pmd_t *pmd = pvmw.pmd;
 			pmd_t entry;
 
diff --git a/mm/shmem.c b/mm/shmem.c
index c8f7540ef048..056cec644c17 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -410,7 +410,7 @@ static bool shmem_confirm_swap(struct address_space *mapping,
 #define SHMEM_HUGE_DENY		(-1)
 #define SHMEM_HUGE_FORCE	(-2)
 
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /* ifdef here to avoid bloating shmem.o when not necessary */
 
 static int shmem_huge __read_mostly;
@@ -580,7 +580,7 @@ static long shmem_unused_huge_count(struct super_block *sb,
 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 	return READ_ONCE(sbinfo->shrinklist_len);
 }
-#else /* !CONFIG_TRANSPARENT_HUGE_PAGECACHE */
+#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
 
 #define shmem_huge SHMEM_HUGE_DENY
 
@@ -589,11 +589,11 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 {
 	return 0;
 }
-#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
 {
-	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
 	    (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
 	    shmem_huge != SHMEM_HUGE_DENY)
 		return true;
@@ -1059,7 +1059,7 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
 			 * Part of the huge page can be beyond i_size: subject
 			 * to shrink under memory pressure.
 			 */
-			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
+			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 				spin_lock(&sbinfo->shrinklist_lock);
 				/*
 				 * _careful to defend against unlocked access to
@@ -1472,7 +1472,7 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 	pgoff_t hindex;
 	struct page *page;
 
-	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
 		return NULL;
 
 	hindex = round_down(index, HPAGE_PMD_NR);
@@ -1511,7 +1511,7 @@ static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
 	int nr;
 	int err = -ENOSPC;
 
-	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
 		huge = false;
 	nr = huge ? HPAGE_PMD_NR : 1;
 
@@ -2089,7 +2089,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
 	get_area = current->mm->get_unmapped_area;
 	addr = get_area(file, uaddr, len, pgoff, flags);
 
-	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
 		return addr;
 	if (IS_ERR_VALUE(addr))
 		return addr;
@@ -2228,7 +2228,7 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 
 	file_accessed(file);
 	vma->vm_ops = &shmem_vm_ops;
-	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
 			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
 			(vma->vm_end & HPAGE_PMD_MASK)) {
 		khugepaged_enter(vma, vma->vm_flags);
@@ -3457,7 +3457,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_huge:
 		ctx->huge = result.uint_32;
 		if (ctx->huge != SHMEM_HUGE_NEVER &&
-		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+		    !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
 		      has_transparent_hugepage()))
 			goto unsupported_parameter;
 		ctx->seen |= SHMEM_SEEN_HUGE;
@@ -3603,7 +3603,7 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
 		seq_printf(seq, ",gid=%u",
 				from_kgid_munged(&init_user_ns, sbinfo->gid));
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
 	if (sbinfo->huge)
 		seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
@@ -3848,7 +3848,7 @@ static const struct super_operations shmem_ops = {
 	.evict_inode	= shmem_evict_inode,
 	.drop_inode	= generic_delete_inode,
 	.put_super	= shmem_put_super,
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	.nr_cached_objects	= shmem_unused_huge_count,
 	.free_cached_objects	= shmem_unused_huge_scan,
 #endif
@@ -3910,7 +3910,7 @@ int __init shmem_init(void)
 		goto out1;
 	}
 
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
 	else
@@ -3926,7 +3926,7 @@ int __init shmem_init(void)
 	return error;
 }
 
-#if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && defined(CONFIG_SYSFS)
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
 static ssize_t shmem_enabled_show(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
@@ -3978,9 +3978,9 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
 
 struct kobj_attribute shmem_enabled_attr =
 	__ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
-#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
 
-#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 bool shmem_huge_enabled(struct vm_area_struct *vma)
 {
 	struct inode *inode = file_inode(vma->vm_file);
@@ -4015,7 +4015,7 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
 			return false;
 	}
 }
-#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 #else /* !CONFIG_SHMEM */
 
@@ -4184,7 +4184,7 @@ int shmem_zero_setup(struct vm_area_struct *vma)
 	vma->vm_file = file;
 	vma->vm_ops = &shmem_vm_ops;
 
-	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
 			((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
 			(vma->vm_end & HPAGE_PMD_MASK)) {
 		khugepaged_enter(vma, vma->vm_flags);
-- 
2.25.1

[PATCH v2 6/8] mm: Use VM_BUG_ON_PAGE in clear_page_dirty_for_io

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Dumping the page information in this circumstance helps for debugging.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/page-writeback.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2caf780a42e7..9173c25cf8e6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2655,7 +2655,7 @@ int clear_page_dirty_for_io(struct page *page)
 	struct address_space *mapping = page_mapping(page);
 	int ret = 0;
 
-	BUG_ON(!PageLocked(page));
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
 
 	if (mapping && mapping_cap_account_dirty(mapping)) {
 		struct inode *inode = mapping->host;
-- 
2.25.1

[PATCH v2 7/8] mm: Unexport find_get_entry

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

No in-tree users (proc, madvise, memcg, mincore) can be built as a module.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/filemap.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 1beb7716276b..83ce9ce0bee1 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1536,7 +1536,6 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
 
 	return page;
 }
-EXPORT_SYMBOL(find_get_entry);
 
 /**
  * find_lock_entry - locate, pin and lock a page cache entry
-- 
2.25.1

[PATCH v2 8/8] mm: Rewrite pagecache_get_page documentation

[Matthew Wilcox]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

 - These were never called PCG flags; they've been called FGP flags since
   their introduction in 2014.
 - The FGP_FOR_MMAP flag was misleadingly documented as if it was an
   alternative to FGP_CREAT instead of an option to it.
 - Rename the 'offset' parameter to 'index'.
 - Capitalisation, formatting, rewording.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/filemap.c | 49 +++++++++++++++++++++++--------------------------
 1 file changed, 23 insertions(+), 26 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 83ce9ce0bee1..666c5a3a82ae 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1574,42 +1574,39 @@ struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
 EXPORT_SYMBOL(find_lock_entry);
 
 /**
- * pagecache_get_page - find and get a page reference
- * @mapping: the address_space to search
- * @offset: the page index
- * @fgp_flags: PCG flags
- * @gfp_mask: gfp mask to use for the page cache data page allocation
- *
- * Looks up the page cache slot at @mapping & @offset.
+ * pagecache_get_page - Find and get a reference to a page.
+ * @mapping: The address_space to search.
+ * @index: The page index.
+ * @fgp_flags: %FGP flags modify how the page is returned.
+ * @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified.
  *
- * PCG flags modify how the page is returned.
+ * Looks up the page cache entry at @mapping & @index.
  *
- * @fgp_flags can be:
+ * @fgp_flags can be zero or more of these flags:
  *
- * - FGP_ACCESSED: the page will be marked accessed
- * - FGP_LOCK: Page is return locked
- * - FGP_CREAT: If page is not present then a new page is allocated using
- *   @gfp_mask and added to the page cache and the VM's LRU
- *   list. The page is returned locked and with an increased
- *   refcount.
- * - FGP_FOR_MMAP: Similar to FGP_CREAT, only we want to allow the caller to do
- *   its own locking dance if the page is already in cache, or unlock the page
- *   before returning if we had to add the page to pagecache.
+ * * %FGP_ACCESSED - The page will be marked accessed.
+ * * %FGP_LOCK - The page is returned locked.
+ * * %FGP_CREAT - If no page is present then a new page is allocated using
+ *   @gfp_mask and added to the page cache and the VM's LRU list.
+ *   The page is returned locked and with an increased refcount.
+ * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
+ *   page is already in cache.  If the page was allocated, unlock it before
+ *   returning so the caller can do the same dance.
  *
- * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
- * if the GFP flags specified for FGP_CREAT are atomic.
+ * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
+ * if the %GFP flags specified for %FGP_CREAT are atomic.
  *
  * If there is a page cache page, it is returned with an increased refcount.
  *
- * Return: the found page or %NULL otherwise.
+ * Return: The found page or %NULL otherwise.
  */
-struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
-	int fgp_flags, gfp_t gfp_mask)
+struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
+		int fgp_flags, gfp_t gfp_mask)
 {
 	struct page *page;
 
 repeat:
-	page = find_get_entry(mapping, offset);
+	page = find_get_entry(mapping, index);
 	if (xa_is_value(page))
 		page = NULL;
 	if (!page)
@@ -1631,7 +1628,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
 			put_page(page);
 			goto repeat;
 		}
-		VM_BUG_ON_PAGE(page->index != offset, page);
+		VM_BUG_ON_PAGE(page->index != index, page);
 	}
 
 	if (fgp_flags & FGP_ACCESSED)
@@ -1656,7 +1653,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
 		if (fgp_flags & FGP_ACCESSED)
 			__SetPageReferenced(page);
 
-		err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
+		err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
 		if (unlikely(err)) {
 			put_page(page);
 			page = NULL;
-- 
2.25.1

Re: [PATCH v2 2/8] mm: Rename arguments to find_subpage

[Christoph Hellwig]

On Wed, Mar 18, 2020 at 07:02:47AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> This isn't just a random struct page, it's known to be a head page,
> and calling it head makes the function better self-documenting.
> The pgoff_t is less confusing if it's named index instead of offset.
> Also add a couple of comments to explain why we're doing various things.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 3/8] mm: Check PageTail in hpage_nr_pages even when !THP

[Christoph Hellwig]

On Wed, Mar 18, 2020 at 07:02:48AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> It's even more important to check that we don't have a tail page when
> calling hpage_nr_pages() when THP are disabled.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 4/8] mm: Optimise find_subpage for !THP

[Christoph Hellwig]

On Wed, Mar 18, 2020 at 07:02:49AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> If THP is disabled, find_subpage() can become a no-op by using
> hpage_nr_pages() instead of compound_nr().  hpage_nr_pages() embeds
> a check for PageTail, so we can drop the check here.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 8/8] mm: Rewrite pagecache_get_page documentation

[Christoph Hellwig]

On Wed, Mar 18, 2020 at 07:02:53AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
>  - These were never called PCG flags; they've been called FGP flags since
>    their introduction in 2014.
>  - The FGP_FOR_MMAP flag was misleadingly documented as if it was an
>    alternative to FGP_CREAT instead of an option to it.
>  - Rename the 'offset' parameter to 'index'.
>  - Capitalisation, formatting, rewording.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 2/8] mm: Rename arguments to find_subpage

[Kirill A. Shutemov]

On Wed, Mar 18, 2020 at 07:02:47AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> This isn't just a random struct page, it's known to be a head page,
> and calling it head makes the function better self-documenting.
> The pgoff_t is less confusing if it's named index instead of offset.
> Also add a couple of comments to explain why we're doing various things.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov

Re: [PATCH v2 3/8] mm: Check PageTail in hpage_nr_pages even when !THP

[Kirill A. Shutemov]

On Wed, Mar 18, 2020 at 07:02:48AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> It's even more important to check that we don't have a tail page when
> calling hpage_nr_pages() when THP are disabled.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov

Re: [PATCH v2 5/8] mm: Remove CONFIG_TRANSPARENT_HUGE_PAGECACHE

[Kirill A. Shutemov]

On Wed, Mar 18, 2020 at 07:02:50AM -0700, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> Commit e496cf3d7821 ("thp: introduce CONFIG_TRANSPARENT_HUGE_PAGECACHE")
> notes that it should be reverted when the PowerPC problem was fixed.
> The commit fixing the PowerPC problem (953c66c2b22a) did not revert
> the commit; instead setting CONFIG_TRANSPARENT_HUGE_PAGECACHE to the
> same as CONFIG_TRANSPARENT_HUGEPAGE.  Checking with Kirill and Aneesh,
> this was an oversight, so remove the Kconfig symbol and undo the work
> of commit e496cf3d7821.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov

Re: [PATCH v2 2/8] mm: Rename arguments to find_subpage

[Pankaj Gupta]

> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>
> This isn't just a random struct page, it's known to be a head page,
> and calling it head makes the function better self-documenting.
> The pgoff_t is less confusing if it's named index instead of offset.
> Also add a couple of comments to explain why we're doing various things.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/pagemap.h | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index b4ea3a5d00e5..68db0ed8535d 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -333,14 +333,19 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
>                         mapping_gfp_mask(mapping));
>  }
>
> -static inline struct page *find_subpage(struct page *page, pgoff_t offset)
> +/*
> + * Given the page we found in the page cache, return the page corresponding
> + * to this index in the file
> + */
> +static inline struct page *find_subpage(struct page *head, pgoff_t index)
>  {
> -       if (PageHuge(page))
> -               return page;
> +       /* HugeTLBfs wants the head page regardless */
> +       if (PageHuge(head))
> +               return head;
>
> -       VM_BUG_ON_PAGE(PageTail(page), page);
> +       VM_BUG_ON_PAGE(PageTail(head), head);
>
> -       return page + (offset & (compound_nr(page) - 1));
> +       return head + (index & (compound_nr(head) - 1));
>  }
>
>  struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
> --
> 2.25.1

Makes function much easier to understand. Thanks!
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>

>
>