Re: [PATCH 08/15] ubifs: Convert ubifs_write_begin() to use a folio

Zhihao Cheng
2024-01-23T04:28:11Z

在 2024/1/21 7:08, Matthew Wilcox (Oracle) 写道:
> Save eight calls to compound_head() by using the new folio API.
> Remove a few assumptions that would break with large folios.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> fs/ubifs/file.c | 36 +++++++++++++++++-------------------
> 1 file changed, 17 insertions(+), 19 deletions(-)
>

Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>

> diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> index 6302ce65e0b3..ef262499f228 100644
> --- a/fs/ubifs/file.c
> +++ b/fs/ubifs/file.c
> @@ -428,7 +428,7 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
> pgoff_t index = pos >> PAGE_SHIFT;
> int err, appending = !!(pos + len > inode->i_size);
> int skipped_read = 0;
> - struct page *page;
> + struct folio *folio;
>
> ubifs_assert(c, ubifs_inode(inode)->ui_size == inode->i_size);
> ubifs_assert(c, !c->ro_media && !c->ro_mount);
> @@ -437,13 +437,14 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
> return -EROFS;
>
> /* Try out the fast-path part first */
> - page = grab_cache_page_write_begin(mapping, index);
> - if (unlikely(!page))
> - return -ENOMEM;
> + folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
> + mapping_gfp_mask(mapping));
> + if (IS_ERR(folio))
> + return PTR_ERR(folio);
>
> - if (!PageUptodate(page)) {
> + if (!folio_test_uptodate(folio)) {
> /* The page is not loaded from the flash */
> - if (!(pos & ~PAGE_MASK) && len == PAGE_SIZE) {
> + if (pos == folio_pos(folio) && len >= folio_size(folio)) {
> /*
> * We change whole page so no need to load it. But we
> * do not know whether this page exists on the media or
> @@ -453,29 +454,27 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
> * media. Thus, we are setting the @PG_checked flag
> * here.
> */
> - SetPageChecked(page);
> + folio_set_checked(folio);
> skipped_read = 1;
> } else {
> - err = do_readpage(page);
> + err = do_readpage(&folio->page);
> if (err) {
> - unlock_page(page);
> - put_page(page);
> + folio_unlock(folio);
> + folio_put(folio);
> return err;
> }
> }
> }
>
> - err = allocate_budget(c, page, ui, appending);
> + err = allocate_budget(c, &folio->page, ui, appending);
> if (unlikely(err)) {
> ubifs_assert(c, err == -ENOSPC);
> /*
> * If we skipped reading the page because we were going to
> * write all of it, then it is not up to date.
> */
> - if (skipped_read) {
> - ClearPageChecked(page);
> - ClearPageUptodate(page);
> - }
> + if (skipped_read)
> + folio_clear_checked(folio);
> /*
> * Budgeting failed which means it would have to force
> * write-back but didn't, because we set the @fast flag in the
> @@ -487,8 +486,8 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
> ubifs_assert(c, mutex_is_locked(&ui->ui_mutex));
> mutex_unlock(&ui->ui_mutex);
> }
> - unlock_page(page);
> - put_page(page);
> + folio_unlock(folio);
> + folio_put(folio);
>
> return write_begin_slow(mapping, pos, len, pagep);
> }
> @@ -499,9 +498,8 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
> * with @ui->ui_mutex locked if we are appending pages, and unlocked
> * otherwise. This is an optimization (slightly hacky though).
> */
> - *pagep = page;
> + *pagep = &folio->page;
> return 0;
> -
> }
>
> /**