On Thu, Mar 10, 2022 at 6:10 AM Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > > It maintains a memfile_notifier list in shmem_inode_info structure and > implements memfile_pfn_ops callbacks defined by memfile_notifier. It > then exposes them to memfile_notifier via > shmem_get_memfile_notifier_info. > > We use SGP_NOALLOC in shmem_get_lock_pfn since the pages should be > allocated by userspace for private memory. If there is no pages > allocated at the offset then error should be returned so KVM knows that > the memory is not private memory. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > --- > include/linux/shmem_fs.h | 4 +++ > mm/shmem.c | 76 ++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 80 insertions(+) > > diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h > index 2dde843f28ef..7bb16f2d2825 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 */ > > @@ -28,6 +29,9 @@ struct shmem_inode_info { > struct simple_xattrs xattrs; /* list of xattrs */ > atomic_t stop_eviction; /* hold when working on inode */ > unsigned int xflags; /* shmem extended flags */ > +#ifdef CONFIG_MEMFILE_NOTIFIER > + struct memfile_notifier_list memfile_notifiers; > +#endif > struct inode vfs_inode; > }; > > diff --git a/mm/shmem.c b/mm/shmem.c > index 9b31a7056009..7b43e274c9a2 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -903,6 +903,28 @@ static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index) > return page ? page_folio(page) : NULL; > } > > +static void notify_fallocate(struct inode *inode, pgoff_t start, pgoff_t end) > +{ > +#ifdef CONFIG_MEMFILE_NOTIFIER > + struct shmem_inode_info *info = SHMEM_I(inode); > + > + memfile_notifier_fallocate(&info->memfile_notifiers, start, end); > +#endif > +} > + > +static void notify_invalidate_page(struct inode *inode, struct folio *folio, > + pgoff_t start, pgoff_t end) > +{ > +#ifdef CONFIG_MEMFILE_NOTIFIER > + 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_notifiers, start, end); > +#endif > +} > + > /* > * Remove range of pages and swap entries from page cache, and free them. > * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate. > @@ -946,6 +968,8 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, > } > index += folio_nr_pages(folio) - 1; > > + notify_invalidate_page(inode, folio, start, end); > + > if (!unfalloc || !folio_test_uptodate(folio)) > truncate_inode_folio(mapping, folio); > folio_unlock(folio); > @@ -1019,6 +1043,9 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, > index--; > break; > } > + > + notify_invalidate_page(inode, folio, start, end); > + Should this be done in batches or done once for all of range [start, end)? > VM_BUG_ON_FOLIO(folio_test_writeback(folio), > folio); > truncate_inode_folio(mapping, folio); > @@ -2279,6 +2306,9 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode > info->flags = flags & VM_NORESERVE; > INIT_LIST_HEAD(&info->shrinklist); > INIT_LIST_HEAD(&info->swaplist); > +#ifdef CONFIG_MEMFILE_NOTIFIER > + memfile_notifier_list_init(&info->memfile_notifiers); > +#endif > simple_xattrs_init(&info->xattrs); > cache_no_acl(inode); > mapping_set_large_folios(inode->i_mapping); > @@ -2802,6 +2832,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, > if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size) > i_size_write(inode, offset + len); > inode->i_ctime = current_time(inode); > + notify_fallocate(inode, start, end); > undone: > spin_lock(&inode->i_lock); > inode->i_private = NULL; > @@ -3909,6 +3940,47 @@ static struct file_system_type shmem_fs_type = { > .fs_flags = FS_USERNS_MOUNT, > }; > > +#ifdef CONFIG_MEMFILE_NOTIFIER > +static long shmem_get_lock_pfn(struct inode *inode, pgoff_t offset, int *order) > +{ > + struct page *page; > + int ret; > + > + ret = shmem_getpage(inode, offset, &page, SGP_NOALLOC); > + if (ret) > + return ret; > + > + *order = thp_order(compound_head(page)); > + > + return page_to_pfn(page); > +} > + > +static void shmem_put_unlock_pfn(unsigned long pfn) > +{ > + struct page *page = pfn_to_page(pfn); > + > + VM_BUG_ON_PAGE(!PageLocked(page), page); > + > + set_page_dirty(page); > + unlock_page(page); > + put_page(page); > +} > + > +static struct memfile_notifier_list* shmem_get_notifier_list(struct inode *inode) > +{ > + if (!shmem_mapping(inode->i_mapping)) > + return NULL; > + > + return &SHMEM_I(inode)->memfile_notifiers; > +} > + > +static struct memfile_backing_store shmem_backing_store = { > + .pfn_ops.get_lock_pfn = shmem_get_lock_pfn, > + .pfn_ops.put_unlock_pfn = shmem_put_unlock_pfn, > + .get_notifier_list = shmem_get_notifier_list, > +}; > +#endif /* CONFIG_MEMFILE_NOTIFIER */ > + > int __init shmem_init(void) > { > int error; > @@ -3934,6 +4006,10 @@ int __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 0; > > out1: > -- > 2.17.1 >