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mm/shmem: Support memfile_notifier
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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>
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@kiryl @yamahata
kiryl authored and yamahata committed May 26, 2022
1 parent 07b4263 commit a46fd36
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Showing 2 changed files with 121 additions and 1 deletion.
2 changes: 2 additions & 0 deletions include/linux/shmem_fs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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 */

Expand All @@ -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;
};

Expand Down
120 changes: 119 additions & 1 deletion mm/shmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -905,6 +905,24 @@ static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
return page ? page_folio(page) : NULL;
}

static void notify_populate(struct inode *inode, pgoff_t start, pgoff_t end)
{
struct shmem_inode_info *info = SHMEM_I(inode);

memfile_notifier_populate(&info->memfile_node, start, end);
}

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.
Expand Down Expand Up @@ -948,6 +966,8 @@ 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);
Expand Down Expand Up @@ -1021,6 +1041,9 @@ 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);
Expand Down Expand Up @@ -1092,6 +1115,13 @@ 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);
Expand Down Expand Up @@ -1340,6 +1370,8 @@ 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
Expand Down Expand Up @@ -2234,6 +2266,9 @@ 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;

Expand Down Expand Up @@ -2274,6 +2309,7 @@ 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);
Expand Down Expand Up @@ -2442,6 +2478,8 @@ 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;

ret = shmem_getpage(inode, index, pagep, SGP_WRITE);

Expand Down Expand Up @@ -2517,6 +2555,13 @@ 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)
Expand Down Expand Up @@ -2658,6 +2703,12 @@ 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;
Expand Down Expand Up @@ -2777,6 +2828,7 @@ 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_populate(inode, start, end);
undone:
spin_lock(&inode->i_lock);
inode->i_private = NULL;
Expand Down Expand Up @@ -3763,6 +3815,20 @@ 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 -ENOTSUPP;
return migrate_page(mapping, newpage, page, mode);
}
#endif

const struct address_space_operations shmem_aops = {
.writepage = shmem_writepage,
.dirty_folio = noop_dirty_folio,
Expand All @@ -3771,7 +3837,7 @@ 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,
};
Expand Down Expand Up @@ -3888,6 +3954,54 @@ 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_lock_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_NOALLOC);
if (ret)
return ret;

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

static void shmem_put_unlock_pfn(pfn_t pfn)
{
struct page *page = pfn_t_to_page(pfn);

if (!page)
return;

VM_BUG_ON_PAGE(!PageLocked(page), page);

set_page_dirty(page);
unlock_page(page);
put_page(page);
}

static struct memfile_backing_store shmem_backing_store = {
.lookup_memfile_node = shmem_lookup_memfile_node,
.get_lock_pfn = shmem_get_lock_pfn,
.put_unlock_pfn = shmem_put_unlock_pfn,
};
#endif /* CONFIG_MEMFILE_NOTIFIER */

int __init shmem_init(void)
{
int error;
Expand All @@ -3913,6 +4027,10 @@ 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:
Expand Down

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