Re: [PATCH 1/2] f2fs: fix to add refcount once page is tagged PG_private

From: Jaegeuk Kim
Date: Tue Mar 05 2019 - 22:52:24 EST

On 03/05, Chao Yu wrote:
> As Gao Xiang reported in bugzilla:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=202749
>
> f2fs may skip pageout() due to incorrect page reference count.
>
> The problem here is that MM defined the rule [1] very clearly that
> once page was set with PG_private flag, we should increment the
> refcount in that page, also main flows like pageout(), migrate_page()
> will assume there is one additional page reference count if
> page_has_private() returns true.
>
> But currently, f2fs won't add/del refcount when changing PG_private
> flag. Anyway, f2fs should follow MM's rule to make MM's related flows
> running as expected.
>
> [1] https://lore.kernel.org/lkml/2b19b3c4-2bc4-15fa-15cc-27a13e5c7af1@xxxxxxx/
>
> Reported-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> ---
> fs/f2fs/checkpoint.c | 11 +++++++++--
> fs/f2fs/data.c | 32 ++++++++++++++++++++------------
> fs/f2fs/dir.c | 6 +++++-
> fs/f2fs/node.c | 6 +++++-
> fs/f2fs/segment.c | 23 +++++++++++++++++------
> 5 files changed, 56 insertions(+), 22 deletions(-)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index c65a1e8e1e95..4e0e93af5ce0 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -406,7 +406,11 @@ static int f2fs_set_meta_page_dirty(struct page *page)
> if (!PageDirty(page)) {
> __set_page_dirty_nobuffers(page);
> inc_page_count(F2FS_P_SB(page), F2FS_DIRTY_META);
> - SetPagePrivate(page);
> +
> + if (!PagePrivate(page)) {
> + get_page(page);
> + SetPagePrivate(page);

Can we add generic functions?

f2fs_set_page_private(page)
{
if (PagePrivate(page))
return;

SetPagePrivate(page);
get_page(page);
}

f2fs_clear_page_private(page)
{
if (!PagePrivate(page))
return;

set_page_private(page, 0);
ClearPagePrivate(page);
f2fs_put_page(page, 0);
}

>
> + }
> f2fs_trace_pid(page);
> return 1;
> }
> @@ -957,7 +961,10 @@ void f2fs_update_dirty_page(struct inode *inode, struct page *page)
> inode_inc_dirty_pages(inode);
> spin_unlock(&sbi->inode_lock[type]);
>
> - SetPagePrivate(page);
> + if (!PagePrivate(page)) {
> + get_page(page);
> + SetPagePrivate(page);
> + }
> f2fs_trace_pid(page);
> }
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 3f3becd46362..46924d4f69d0 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2715,8 +2715,11 @@ void f2fs_invalidate_page(struct page *page, unsigned int offset,
> if (IS_ATOMIC_WRITTEN_PAGE(page))
> return f2fs_drop_inmem_page(inode, page);
>
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> + if (PagePrivate(page)) {
> + set_page_private(page, 0);
> + ClearPagePrivate(page);
> + f2fs_put_page(page, 0);
> + }
> }
>
> int f2fs_release_page(struct page *page, gfp_t wait)
> @@ -2730,8 +2733,11 @@ int f2fs_release_page(struct page *page, gfp_t wait)
> return 0;
>
> clear_cold_data(page);
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> + if (PagePrivate(page)) {
> + set_page_private(page, 0);
> + ClearPagePrivate(page);
> + f2fs_put_page(page, 0);
> + }
> return 1;
> }
>
> @@ -2799,12 +2805,8 @@ int f2fs_migrate_page(struct address_space *mapping,
> return -EAGAIN;
> }
>
> - /*
> - * A reference is expected if PagePrivate set when move mapping,
> - * however F2FS breaks this for maintaining dirty page counts when
> - * truncating pages. So here adjusting the 'extra_count' make it work.
> - */
> - extra_count = (atomic_written ? 1 : 0) - page_has_private(page);
> + /* one extra reference was held for atomic_write page */
> + extra_count = atomic_written ? 1 : 0;
> rc = migrate_page_move_mapping(mapping, newpage,
> page, mode, extra_count);
> if (rc != MIGRATEPAGE_SUCCESS) {
> @@ -2825,9 +2827,15 @@ int f2fs_migrate_page(struct address_space *mapping,
> get_page(newpage);
> }
>
> - if (PagePrivate(page))
> + if (PagePrivate(page)) {
> + get_page(newpage);
> SetPagePrivate(newpage);
> - set_page_private(newpage, page_private(page));
> + set_page_private(newpage, page_private(page));
> +
> + set_page_private(page, 0);
> + ClearPagePrivate(page);
> + f2fs_put_page(page, 0);
> + }
>
> if (mode != MIGRATE_SYNC_NO_COPY)
> migrate_page_copy(newpage, page);
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index 103f3686a045..fbbafb04a431 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -728,7 +728,11 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
> !f2fs_truncate_hole(dir, page->index, page->index + 1)) {
> f2fs_clear_page_cache_dirty_tag(page);
> clear_page_dirty_for_io(page);
> - ClearPagePrivate(page);
> + if (PagePrivate(page)) {
> + set_page_private(page, 0);
> + ClearPagePrivate(page);
> + f2fs_put_page(page, 0);
> + }
> ClearPageUptodate(page);
> clear_cold_data(page);
> inode_dec_dirty_pages(dir);
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index f6ff84e29749..ce97a9885105 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1961,7 +1961,11 @@ static int f2fs_set_node_page_dirty(struct page *page)
> if (!PageDirty(page)) {
> __set_page_dirty_nobuffers(page);
> inc_page_count(F2FS_P_SB(page), F2FS_DIRTY_NODES);
> - SetPagePrivate(page);
> +
> + if (!PagePrivate(page)) {
> + get_page(page);
> + SetPagePrivate(page);
> + }
> f2fs_trace_pid(page);
> return 1;
> }
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index e730c334abba..2d77dd133a4e 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -191,8 +191,11 @@ void f2fs_register_inmem_page(struct inode *inode, struct page *page)
>
> f2fs_trace_pid(page);
>
> - set_page_private(page, (unsigned long)ATOMIC_WRITTEN_PAGE);
> - SetPagePrivate(page);
> + if (!PagePrivate(page)) {
> + get_page(page);
> + SetPagePrivate(page);
> + set_page_private(page, (unsigned long)ATOMIC_WRITTEN_PAGE);
> + }
>
> new = f2fs_kmem_cache_alloc(inmem_entry_slab, GFP_NOFS);
>
> @@ -280,8 +283,11 @@ static int __revoke_inmem_pages(struct inode *inode,
> ClearPageUptodate(page);
> clear_cold_data(page);
> }
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> + if (PagePrivate(page)) {
> + set_page_private(page, 0);
> + ClearPagePrivate(page);
> + f2fs_put_page(page, 0);
> + }
> f2fs_put_page(page, 1);
>
> list_del(&cur->list);
> @@ -370,8 +376,13 @@ void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
> kmem_cache_free(inmem_entry_slab, cur);
>
> ClearPageUptodate(page);
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> +
> + if (PagePrivate(page)) {
> + set_page_private(page, 0);
> + ClearPagePrivate(page);
> + f2fs_put_page(page, 0);
> + }
> +
> f2fs_put_page(page, 0);
>
> trace_f2fs_commit_inmem_page(page, INMEM_INVALIDATE);
> --
> 2.18.0.rc1