fs/aio: Add support to aio ring pages migration

As the aio job will pin the ring pages, that will lead to mem migrated failed. In order to fix this problem we use an anon inode to manage the aio ring pages, and setup the migratepage callback in the anon inode's address space, so that when mem migrating the aio ring pages will be moved to other mem node safely.

Signed-off-by Gu Zheng <[email protected]>

Signed-off-by Benjamin LaHaise <[email protected]>

---
 fs/aio.c                |  120 ++++++++++++++++++++++++++++++++++++++++++----
 include/linux/migrate.h |    3 +
 mm/migrate.c            |    2 +-
 3 files changed, 113 insertions(+), 12 deletions(-)

fs/aio.c +36 -2

index 9b5ca11..d10f956 100644
@@ -35,6 +35,9 @@
 #include <linux/eventfd.h>
 #include <linux/blkdev.h>
 #include <linux/compat.h>
+#include <linux/anon_inodes.h>
+#include <linux/migrate.h>
+#include <linux/ramfs.h>
 
 #include <asm/kmap_types.h>
 #include <asm/uaccess.h>

@@ -110,6 +113,7 @@ struct kioctx {
 	} ____cacheline_aligned_in_smp;
 
 	struct page		*internal_pages[AIO_RING_PAGES];
+	struct file		*aio_ring_file;
 };
 
 /*------ sysctl variables----*/

@@ -138,15 +142,78 @@ __initcall(aio_setup);
 
 static void aio_free_ring(struct kioctx *ctx)
 {
-	long i;
+	int i;
+	struct file *aio_ring_file = ctx->aio_ring_file;
 
-	for (i = 0; i < ctx->nr_pages; i++)
+	for (i = 0; i < ctx->nr_pages; i++) {
+		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
+				page_count(ctx->ring_pages[i]));
 		put_page(ctx->ring_pages[i]);
+	}
 
 	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages)
 		kfree(ctx->ring_pages);
+
+	if (aio_ring_file) {
+		truncate_setsize(aio_ring_file->f_inode, 0);
+		pr_debug("pid(%d) i_nlink=%u d_count=%d d_unhashed=%d i_count=%d\n",
+			current->pid, aio_ring_file->f_inode->i_nlink,
+			aio_ring_file->f_path.dentry->d_count,
+			d_unhashed(aio_ring_file->f_path.dentry),
+			atomic_read(&aio_ring_file->f_inode->i_count));
+		fput(aio_ring_file);
+		ctx->aio_ring_file = NULL;
+	}
+}
+
+static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	vma->vm_ops = &generic_file_vm_ops;
+	return 0;
+}
+
+static const struct file_operations aio_ring_fops = {
+	.mmap = aio_ring_mmap,
+};
+
+static int aio_set_page_dirty(struct page *page)
+{
+	return 0;
 }

fs/aio.c +25 -0

+	BUG_ON(PageWriteback(old));
+	put_page(old);
+
+	rc = migrate_page_move_mapping(mapping, new, old, NULL, mode);
+	if (rc != MIGRATEPAGE_SUCCESS) {
+		get_page(old);
+		return rc;
+	}
+
+	get_page(new);
+
+	spin_lock_irqsave(&ctx->completion_lock, flags);
+	migrate_page_copy(new, old);
+	ctx->ring_pages[idx] = new;
+	spin_unlock_irqrestore(&ctx->completion_lock, flags);
+
+	return rc;
+}
+
+static const struct address_space_operations aio_ctx_aops = {
+	.set_page_dirty = aio_set_page_dirty,
+	.migratepage	= aio_migratepage,
+};
+
 static int aio_setup_ring(struct kioctx *ctx)
 {
 	struct aio_ring *ring;

@@ -154,20 +221,45 @@ static int aio_setup_ring(struct kioctx *ctx)
 	struct mm_struct *mm = current->mm;
 	unsigned long size, populate;
 	int nr_pages;
+	int i;

fs/aio.c +36 -8

 	if (nr_pages < 0)
 		return -EINVAL;
 
-	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);
+	file = anon_inode_getfile_private("[aio]", &aio_ring_fops, ctx, O_RDWR);
+	if (IS_ERR(file)) {
+		ctx->aio_ring_file = NULL;
+		return -EAGAIN;
+	}
+
+	file->f_inode->i_mapping->a_ops = &aio_ctx_aops;
+	file->f_inode->i_mapping->private_data = ctx;
+	file->f_inode->i_size = PAGE_SIZE * (loff_t)nr_pages;
+
+	for (i = 0; i < nr_pages; i++) {
+		struct page *page;
+		page = find_or_create_page(file->f_inode->i_mapping,
+					   i, GFP_HIGHUSER | __GFP_ZERO);
+		if (!page)
+			break;
+		pr_debug("pid(%d) page[%d]->count=%d\n",
+			 current->pid, i, page_count(page));
+		SetPageUptodate(page);
+		SetPageDirty(page);
+		unlock_page(page);
+	}
+	ctx->aio_ring_file = file;
+	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
+			/ sizeof(struct io_event);
 
-	ctx->nr_events = 0;
 	ctx->ring_pages = ctx->internal_pages;
 	if (nr_pages > AIO_RING_PAGES) {
 		ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),

@@ -178,28 +270,31 @@ static int aio_setup_ring(struct kioctx *ctx)
 
 	ctx->mmap_size = nr_pages * PAGE_SIZE;
 	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
+
 	down_write(&mm->mmap_sem);
-	ctx->mmap_base = do_mmap_pgoff(NULL, 0, ctx->mmap_size,
-				       PROT_READ|PROT_WRITE,
-				       MAP_ANONYMOUS|MAP_PRIVATE, 0, &populate);
+	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
+				       PROT_READ | PROT_WRITE,
+				       MAP_SHARED | MAP_POPULATE, 0, &populate);
 	if (IS_ERR((void *)ctx->mmap_base)) {
 		up_write(&mm->mmap_sem);
 		ctx->mmap_size = 0;
 		aio_free_ring(ctx);
 		return -EAGAIN;
 	}
+	up_write(&mm->mmap_sem);
+
+	mm_populate(ctx->mmap_base, populate);
 
 	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
 	ctx->nr_pages = get_user_pages(current, mm, ctx->mmap_base, nr_pages,
 				       1, 0, ctx->ring_pages, NULL);
-	up_write(&mm->mmap_sem);
+	for (i = 0; i < ctx->nr_pages; i++)
+		put_page(ctx->ring_pages[i]);
 
 	if (unlikely(ctx->nr_pages != nr_pages)) {
 		aio_free_ring(ctx);
 		return -EAGAIN;
 	}
-	if (populate)
-		mm_populate(ctx->mmap_base, populate);
 
 	ctx->user_id = ctx->mmap_base;
 	ctx->nr_events = nr_events; /* trusted copy */

@@ -399,6 +494,8 @@ out_cleanup:
 	err = -EAGAIN;
 	aio_free_ring(ctx);
 out_freectx:
+	if (ctx->aio_ring_file)
+		fput(ctx->aio_ring_file);
 	kmem_cache_free(kioctx_cachep, ctx);
 	pr_debug("error allocating ioctx %d\n", err);
 	return ERR_PTR(err);

include/linux/migrate.h +3 -0

index a405d3dc..c407d88 100644
@@ -55,6 +55,9 @@ extern int migrate_vmas(struct mm_struct *mm,
 extern void migrate_page_copy(struct page *newpage, struct page *page);
 extern int migrate_huge_page_move_mapping(struct address_space *mapping,
 				  struct page *newpage, struct page *page);
+extern int migrate_page_move_mapping(struct address_space *mapping,
+		struct page *newpage, struct page *page,
+		struct buffer_head *head, enum migrate_mode mode);
 #else
 
 static inline void putback_lru_pages(struct list_head *l) {}

mm/migrate.c +1 -1

index 6f0c244..1da0092 100644
@@ -307,7 +307,7 @@ static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
  * 2 for pages with a mapping
  * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
  */
-static int migrate_page_move_mapping(struct address_space *mapping,
+int migrate_page_move_mapping(struct address_space *mapping,
 		struct page *newpage, struct page *page,
 		struct buffer_head *head, enum migrate_mode mode)
 {

Signature · 1 line

1.7.7

Quoted 4 lines · Gu Zheng

As the aio job will pin the ring pages, that will lead to mem migrated failed. In order to fix this problem we use an anon inode to manage the aio ring pages, and setup the migratepage callback in the anon inode's address space, so that when mem migrating the aio ring pages will be moved to other mem node safely.

There are a few minor issues that needed to be fixed -- see below. I've made these changes and added them to git://git.kvack.org/~bcrl/aio-next.git , and will ask for that tree to be included in linux-next.

mm folks: can someone familiar with page migration / hot plug memory please review the migration changes?

Quoted 3 lines

Signed-off-by Gu Zheng <[email protected]>

Signed-off-by Benjamin LaHaise <[email protected]>

Again, I had not provided my Signed-off-by on this patch previously, so don't add it for me.

Quoted 73 lines

---
 fs/aio.c                |  120 ++++++++++++++++++++++++++++++++++++++++++----
 include/linux/migrate.h |    3 +
 mm/migrate.c            |    2 +-
 3 files changed, 113 insertions(+), 12 deletions(-)

fs/aio.c +36 -2

index 9b5ca11..d10f956 100644
@@ -35,6 +35,9 @@
 #include <linux/eventfd.h>
 #include <linux/blkdev.h>
 #include <linux/compat.h>
+#include <linux/anon_inodes.h>
+#include <linux/migrate.h>
+#include <linux/ramfs.h>
 
 #include <asm/kmap_types.h>
 #include <asm/uaccess.h>

@@ -110,6 +113,7 @@ struct kioctx {
 	} ____cacheline_aligned_in_smp;
 
 	struct page		*internal_pages[AIO_RING_PAGES];
+	struct file		*aio_ring_file;
 };
 
 /*------ sysctl variables----*/

@@ -138,15 +142,78 @@ __initcall(aio_setup);
 
 static void aio_free_ring(struct kioctx *ctx)
 {
-	long i;
+	int i;
+	struct file *aio_ring_file = ctx->aio_ring_file;
 
-	for (i = 0; i < ctx->nr_pages; i++)
+	for (i = 0; i < ctx->nr_pages; i++) {
+		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
+				page_count(ctx->ring_pages[i]));
 		put_page(ctx->ring_pages[i]);
+	}
 
 	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages)
 		kfree(ctx->ring_pages);
+
+	if (aio_ring_file) {
+		truncate_setsize(aio_ring_file->f_inode, 0);
+		pr_debug("pid(%d) i_nlink=%u d_count=%d d_unhashed=%d i_count=%d\n",
+			current->pid, aio_ring_file->f_inode->i_nlink,
+			aio_ring_file->f_path.dentry->d_count,
+			d_unhashed(aio_ring_file->f_path.dentry),
+			atomic_read(&aio_ring_file->f_inode->i_count));
+		fput(aio_ring_file);
+		ctx->aio_ring_file = NULL;
+	}
+}
+
+static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	vma->vm_ops = &generic_file_vm_ops;
+	return 0;
+}
+
+static const struct file_operations aio_ring_fops = {
+	.mmap = aio_ring_mmap,
+};
+
+static int aio_set_page_dirty(struct page *page)
+{
+	return 0;
 }

fs/aio.c __initcall(aio_setup); · line 192

Quoted 10 lines

fs/aio.c +9 -0

 
+static int aio_migratepage(struct address_space *mapping, struct page *new,
+			struct page *old, enum migrate_mode mode)
+{
+	struct kioctx *ctx = mapping->private_data;
+	unsigned long flags;
+	unsigned idx = old->index;
+	int rc;
+
+	/*Writeback must be complete*/

Missing spaces before/after beginning and end of comment.

Quoted 32 lines

fs/aio.c +25 -0

+	BUG_ON(PageWriteback(old));
+	put_page(old);
+
+	rc = migrate_page_move_mapping(mapping, new, old, NULL, mode);
+	if (rc != MIGRATEPAGE_SUCCESS) {
+		get_page(old);
+		return rc;
+	}
+
+	get_page(new);
+
+	spin_lock_irqsave(&ctx->completion_lock, flags);
+	migrate_page_copy(new, old);
+	ctx->ring_pages[idx] = new;
+	spin_unlock_irqrestore(&ctx->completion_lock, flags);
+
+	return rc;
+}
+
+static const struct address_space_operations aio_ctx_aops = {
+	.set_page_dirty = aio_set_page_dirty,
+	.migratepage	= aio_migratepage,
+};
+
 static int aio_setup_ring(struct kioctx *ctx)
 {
 	struct aio_ring *ring;

@@ -154,20 +221,45 @@ static int aio_setup_ring(struct kioctx *ctx)
 	struct mm_struct *mm = current->mm;
 	unsigned long size, populate;
 	int nr_pages;
+	int i;

fs/aio.c static int aio_setup_ring(struct kioctx *ctx) · line 233

Quoted 10 lines

fs/aio.c +2 -1

+	struct file *file;
 
 	/* Compensate for the ring buffer's head/tail overlap entry */
 	nr_events += 2;	/* 1 is required, 2 for good luck */
 
 	size = sizeof(struct aio_ring);
 	size += sizeof(struct io_event) * nr_events;
-	nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT;
 
+	nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT;

Hrm, this should probably be replaced by PFN_UP(size) rather than the old open coding of same.

Quoted 82 lines

fs/aio.c +36 -8

 	if (nr_pages < 0)
 		return -EINVAL;
 
-	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);
+	file = anon_inode_getfile_private("[aio]", &aio_ring_fops, ctx, O_RDWR);
+	if (IS_ERR(file)) {
+		ctx->aio_ring_file = NULL;
+		return -EAGAIN;
+	}
+
+	file->f_inode->i_mapping->a_ops = &aio_ctx_aops;
+	file->f_inode->i_mapping->private_data = ctx;
+	file->f_inode->i_size = PAGE_SIZE * (loff_t)nr_pages;
+
+	for (i = 0; i < nr_pages; i++) {
+		struct page *page;
+		page = find_or_create_page(file->f_inode->i_mapping,
+					   i, GFP_HIGHUSER | __GFP_ZERO);
+		if (!page)
+			break;
+		pr_debug("pid(%d) page[%d]->count=%d\n",
+			 current->pid, i, page_count(page));
+		SetPageUptodate(page);
+		SetPageDirty(page);
+		unlock_page(page);
+	}
+	ctx->aio_ring_file = file;
+	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
+			/ sizeof(struct io_event);
 
-	ctx->nr_events = 0;
 	ctx->ring_pages = ctx->internal_pages;
 	if (nr_pages > AIO_RING_PAGES) {
 		ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),

@@ -178,28 +270,31 @@ static int aio_setup_ring(struct kioctx *ctx)
 
 	ctx->mmap_size = nr_pages * PAGE_SIZE;
 	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
+
 	down_write(&mm->mmap_sem);
-	ctx->mmap_base = do_mmap_pgoff(NULL, 0, ctx->mmap_size,
-				       PROT_READ|PROT_WRITE,
-				       MAP_ANONYMOUS|MAP_PRIVATE, 0, &populate);
+	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
+				       PROT_READ | PROT_WRITE,
+				       MAP_SHARED | MAP_POPULATE, 0, &populate);
 	if (IS_ERR((void *)ctx->mmap_base)) {
 		up_write(&mm->mmap_sem);
 		ctx->mmap_size = 0;
 		aio_free_ring(ctx);
 		return -EAGAIN;
 	}
+	up_write(&mm->mmap_sem);
+
+	mm_populate(ctx->mmap_base, populate);
 
 	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
 	ctx->nr_pages = get_user_pages(current, mm, ctx->mmap_base, nr_pages,
 				       1, 0, ctx->ring_pages, NULL);
-	up_write(&mm->mmap_sem);
+	for (i = 0; i < ctx->nr_pages; i++)
+		put_page(ctx->ring_pages[i]);
 
 	if (unlikely(ctx->nr_pages != nr_pages)) {
 		aio_free_ring(ctx);
 		return -EAGAIN;
 	}
-	if (populate)
-		mm_populate(ctx->mmap_base, populate);
 
 	ctx->user_id = ctx->mmap_base;
 	ctx->nr_events = nr_events; /* trusted copy */

@@ -399,6 +494,8 @@ out_cleanup:
 	err = -EAGAIN;
 	aio_free_ring(ctx);
 out_freectx:
+	if (ctx->aio_ring_file)
+		fput(ctx->aio_ring_file);
 	kmem_cache_free(kioctx_cachep, ctx);
 	pr_debug("error allocating ioctx %d\n", err);
 	return ERR_PTR(err);

fs/aio.c SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp) · line 955

Quoted 7 lines

fs/aio.c +1 -0

@@ -852,6 +949,7 @@ SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
 	ioctx = ioctx_alloc(nr_events);
 	ret = PTR_ERR(ioctx);
 	if (!IS_ERR(ioctx)) {
+		ctx = ioctx->user_id;
 		ret = put_user(ioctx->user_id, ctxp);
 		if (ret)
 			kill_ioctx(ioctx);

This hunk doesn't do anything and needs to be removed. That should cover things.

-ben

Quoted 22 lines

include/linux/migrate.h +3 -0

index a405d3dc..c407d88 100644
@@ -55,6 +55,9 @@ extern int migrate_vmas(struct mm_struct *mm,
 extern void migrate_page_copy(struct page *newpage, struct page *page);
 extern int migrate_huge_page_move_mapping(struct address_space *mapping,
 				  struct page *newpage, struct page *page);
+extern int migrate_page_move_mapping(struct address_space *mapping,
+		struct page *newpage, struct page *page,
+		struct buffer_head *head, enum migrate_mode mode);
 #else
 
 static inline void putback_lru_pages(struct list_head *l) {}

mm/migrate.c +0 -0

index 6f0c244..1da0092 100644
@@ -307,7 +307,7 @@ static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
  * 2 for pages with a mapping
  * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
  */

Quoted 8 lines

mm/migrate.c +1 -1

-static int migrate_page_move_mapping(struct address_space *mapping,
+int migrate_page_move_mapping(struct address_space *mapping,
 		struct page *newpage, struct page *page,
 		struct buffer_head *head, enum migrate_mode mode)
 {

Signature · 1 line

1.7.7

As the aio job will pin the ring pages, that will lead to mem migrated failed. In order to fix this problem we use an anon inode to manage the aio ring pages, and setup the migratepage callback in the anon inode's address space, so that when mem migrating the aio ring pages will be moved to other mem node safely.

v1->v2:
Fix build failed issue if CONFIG_MIGRATION disabled. Fix some minor issues under Benjamin's comments.

From 0c45355fc7c48c82db151bf0e7ca305d513e639e Mon Sep 17 00:00:00 2001

Quoted 8 lines · Gu Zheng

As the aio job will pin the ring pages, that will lead to mem migrated failed. In order to fix this problem we use an anon inode to manage the aio ring pages, and setup the migratepage callback in the anon inode's address space, so that when mem migrating the aio ring pages will be moved to other mem node safely.

v1->v2:
Fix build failed issue if CONFIG_MIGRATION disabled. Fix some minor issues under Benjamin's comments.

I don't know what you did with this patch, but it doesn't apply to any of the trees I can find, and interdiff isn't able to compare it against your original patch. Since the first version of the patch was already applied it is generally more appropriate to provide an incremental fix. I've added the following to my tree (git://git.kvack.org/~bcrl/aio-next.git/)
to fix the build issue. I've tested this with CONFIG_MIGRATION enabled and disabled on x86.

-ben