Re: [PATCH v7 04/14] mm/shmem: Support memfile_notifier

On 7/6/2022 10:20 AM, Chao Peng wrote:

From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com

Implement shmem as a memfile_notifier backing store. Essentially it interacts with the memfile_notifier feature flags for userspace access/page migration/page reclaiming and implements the necessary memfile_backing_store callbacks.

Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Chao Peng chao.p.peng@linux.intel.com

---

include/linux/shmem_fs.h | 2 + mm/shmem.c | 109 ++++++++++++++++++++++++++++++++++++++- 2 files changed, 110 insertions(+), 1 deletion(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index a68f982f22d1..6031c0b08d26 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -9,6 +9,7 @@ #include <linux/percpu_counter.h> #include <linux/xattr.h> #include <linux/fs_parser.h> +#include <linux/memfile_notifier.h> /* inode in-kernel data */ @@ -25,6 +26,7 @@ struct shmem_inode_info { struct simple_xattrs xattrs; /* list of xattrs */ atomic_t stop_eviction; /* hold when working on inode */ struct timespec64 i_crtime; /* file creation time */

• struct memfile_node memfile_node; /* memfile node */ struct inode vfs_inode; };

diff --git a/mm/shmem.c b/mm/shmem.c index 6c8aef15a17d..627e315c3b4d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -905,6 +905,17 @@ static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index) return page ? page_folio(page) : NULL; } +static void notify_invalidate(struct inode *inode, struct folio *folio,

• 		   pgoff_t start, pgoff_t end)
  

+{

• struct shmem_inode_info *info = SHMEM_I(inode);
• start = max(start, folio->index);
• end = min(end, folio->index + folio_nr_pages(folio));
• memfile_notifier_invalidate(&info->memfile_node, start, end);

+}

• /*
  • Remove range of pages and swap entries from page cache, and free them.
  • If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.

@@ -948,6 +959,8 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, } index += folio_nr_pages(folio) - 1;

• 	notify_invalidate(inode, folio, start, end);
  

• if (!unfalloc || !folio_test_uptodate(folio))
  	truncate_inode_folio(mapping, folio);
  folio_unlock(folio);
  

@@ -1021,6 +1034,9 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, index--; break; }

• 		notify_invalidate(inode, folio, start, end);
  

• 	VM_BUG_ON_FOLIO(folio_test_writeback(folio),
  			folio);
  	truncate_inode_folio(mapping, folio);
  

@@ -1092,6 +1108,13 @@ static int shmem_setattr(struct user_namespace *mnt_userns, (newsize > oldsize && (info->seals & F_SEAL_GROW))) return -EPERM;

• if (info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE) {
  

• 	if (oldsize)
  

• 		return -EPERM;
  

• 	if (!PAGE_ALIGNED(newsize))
  

• 		return -EINVAL;
  

• }
  

• if (newsize != oldsize) { error = shmem_reacct_size(SHMEM_I(inode)->flags, oldsize, newsize);

@@ -1336,6 +1359,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) goto redirty; if (!total_swap_pages) goto redirty;

• if (info->memfile_node.flags & MEMFILE_F_UNRECLAIMABLE)

• goto redirty;
  

/* * Our capabilities prevent regular writeback or sync from ever calling @@ -2271,6 +2296,9 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) if (ret) return ret;

• if (info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE)

• return -EPERM;
  

• /* arm64 - allow memory tagging on RAM-based files */ vma->vm_flags |= VM_MTE_ALLOWED;

@@ -2306,6 +2334,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode info->i_crtime = inode->i_mtime; INIT_LIST_HEAD(&info->shrinklist); INIT_LIST_HEAD(&info->swaplist);

• memfile_node_init(&info->memfile_node);
  

  simple_xattrs_init(&info->xattrs); cache_no_acl(inode); mapping_set_large_folios(inode->i_mapping);

@@ -2477,6 +2506,8 @@ shmem_write_begin(struct file *file, struct address_space *mapping, if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size) return -EPERM; }

• if (unlikely(info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE))

• return -EPERM;
  

if (unlikely(info->seals & F_SEAL_AUTO_ALLOCATE)) sgp = SGP_NOALLOC; @@ -2556,6 +2587,13 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) end_index = i_size >> PAGE_SHIFT; if (index > end_index) break;

• if (SHMEM_I(inode)->memfile_node.flags &
  

• 		MEMFILE_F_USER_INACCESSIBLE) {
  

• 	error = -EPERM;
  

• 	break;
  

• }
  

• if (index == end_index) { nr = i_size & ~PAGE_MASK; if (nr <= offset)

@@ -2697,6 +2735,12 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, goto out; }

• if ((info->memfile_node.flags & MEMFILE_F_USER_INACCESSIBLE) &&
  

•     (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len))) {
  

• 	error = -EINVAL;
  

• 	goto out;
  

• }
  

• shmem_falloc.waitq = &shmem_falloc_waitq; shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT; shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;

@@ -3806,6 +3850,20 @@ static int shmem_error_remove_page(struct address_space *mapping, return 0; } +#ifdef CONFIG_MIGRATION +static int shmem_migrate_page(struct address_space *mapping,

• 	      struct page *newpage, struct page *page,
  

• 	      enum migrate_mode mode)
  

+{

• struct inode *inode = mapping->host;
• struct shmem_inode_info *info = SHMEM_I(inode);
• if (info->memfile_node.flags & MEMFILE_F_UNMOVABLE)

• return -EOPNOTSUPP;
  

• return migrate_page(mapping, newpage, page, mode);

Wondering how well page migrate would work for private pages on shmem memfd based backend?

+} +#endif

• const struct address_space_operations shmem_aops = { .writepage = shmem_writepage, .dirty_folio = noop_dirty_folio,

@@ -3814,7 +3872,7 @@ const struct address_space_operations shmem_aops = { .write_end = shmem_write_end, #endif #ifdef CONFIG_MIGRATION

• .migratepage = migrate_page,

• .migratepage = shmem_migrate_page, #endif .error_remove_page = shmem_error_remove_page, };

@@ -3931,6 +3989,51 @@ static struct file_system_type shmem_fs_type = { .fs_flags = FS_USERNS_MOUNT, }; +#ifdef CONFIG_MEMFILE_NOTIFIER +static struct memfile_node *shmem_lookup_memfile_node(struct file *file) +{

• struct inode *inode = file_inode(file);
• if (!shmem_mapping(inode->i_mapping))

• return NULL;
  

• return &SHMEM_I(inode)->memfile_node;

+}

+static int shmem_get_pfn(struct file *file, pgoff_t offset, pfn_t *pfn,

• 	 int *order)
  

+{

• struct page *page;
• int ret;
• ret = shmem_getpage(file_inode(file), offset, &page, SGP_WRITE);
• if (ret)

• return ret;
  

• unlock_page(page);
• *pfn = page_to_pfn_t(page);
• *order = thp_order(compound_head(page));
• return 0;

+}

+static void shmem_put_pfn(pfn_t pfn) +{

• struct page *page = pfn_t_to_page(pfn);
• if (!page)

• return;
  

• put_page(page);

+}

+static struct memfile_backing_store shmem_backing_store = {

• .lookup_memfile_node = shmem_lookup_memfile_node,
• .get_pfn = shmem_get_pfn,
• .put_pfn = shmem_put_pfn,

+}; +#endif /* CONFIG_MEMFILE_NOTIFIER */

• void __init shmem_init(void) { int error;

@@ -3956,6 +4059,10 @@ void __init shmem_init(void) else shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */ #endif

+#ifdef CONFIG_MEMFILE_NOTIFIER

• memfile_register_backing_store(&shmem_backing_store);

+#endif return; out1: