Commit 6c2ae0d5 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

buffer: Rewrite nobh_truncate_page() to use folios 



 - Calculate iblock directly instead of using a while loop
 - Move has_buffers to the end to remove a backwards jump
 - Use __filemap_get_folio() instead of grab_cache_page(), which
   removes a spurious FGP_ACCESSED flag.
 - Eliminate length and pos variables
 - Use folio APIs where they exist

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 2ebdd1df

fs/buffer.c

+27 −37
Original line number Diff line number Diff line
@@ -2791,44 +2791,28 @@ int nobh_truncate_page(struct address_space *mapping, 
			loff_t from, get_block_t *get_block)

{

	pgoff_t index = from >> PAGE_SHIFT;

	unsigned offset = from & (PAGE_SIZE-1);

	unsigned blocksize;

	sector_t iblock;

	unsigned length, pos;

	struct inode *inode = mapping->host;

	struct page *page;

	unsigned blocksize = i_blocksize(inode);

	struct folio *folio;

	struct buffer_head map_bh;

	size_t offset;

	sector_t iblock;

	int err;



	blocksize = i_blocksize(inode);

	length = offset & (blocksize - 1);



	/* Block boundary? Nothing to do */

	if (!length)

	if (!(from & (blocksize - 1)))

		return 0;



	length = blocksize - length;

	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);



	page = grab_cache_page(mapping, index);

	folio = __filemap_get_folio(mapping, index, FGP_LOCK | FGP_CREAT,

			mapping_gfp_mask(mapping));

	err = -ENOMEM;

	if (!page)

	if (!folio)

		goto out;



	if (page_has_buffers(page)) {

has_buffers:

		unlock_page(page);

		put_page(page);

		return block_truncate_page(mapping, from, get_block);

	}



	/* Find the buffer that contains "offset" */

	pos = blocksize;

	while (offset >= pos) {

		iblock++;

		pos += blocksize;

	}

	if (folio_buffers(folio))

		goto has_buffers;



	iblock = from >> inode->i_blkbits;

	map_bh.b_size = blocksize;

	map_bh.b_state = 0;

	err = get_block(inode, iblock, &map_bh, 0);
@@ -2839,29 +2823,35 @@ int nobh_truncate_page(struct address_space *mapping, 
		goto unlock;



	/* Ok, it's mapped. Make sure it's up-to-date */

	if (!PageUptodate(page)) {

		err = mapping->a_ops->readpage(NULL, page);

	if (!folio_test_uptodate(folio)) {

		err = mapping->a_ops->readpage(NULL, &folio->page);

		if (err) {

			put_page(page);

			folio_put(folio);

			goto out;

		}

		lock_page(page);

		if (!PageUptodate(page)) {

		folio_lock(folio);

		if (!folio_test_uptodate(folio)) {

			err = -EIO;

			goto unlock;

		}

		if (page_has_buffers(page))

		if (folio_buffers(folio))

			goto has_buffers;

	}

	zero_user(page, offset, length);

	set_page_dirty(page);

	offset = offset_in_folio(folio, from);

	folio_zero_segment(folio, offset, round_up(offset, blocksize));

	folio_mark_dirty(folio);

	err = 0;



unlock:

	unlock_page(page);

	put_page(page);

	folio_unlock(folio);

	folio_put(folio);

out:

	return err;



has_buffers:

	folio_unlock(folio);

	folio_put(folio);

	return block_truncate_page(mapping, from, get_block);

}

EXPORT_SYMBOL(nobh_truncate_page);