Commit 4d934a5e authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Theodore Ts'o
Browse files

ext4: Convert ext4_write_begin() to use a folio 



Remove a lot of calls to compound_head().

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20230324180129.1220691-17-willy@infradead.org


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 6b90d413

fs/ext4/inode.c

+27 −26
Original line number Diff line number Diff line
@@ -1139,7 +1139,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping, 
	int ret, needed_blocks;

	handle_t *handle;

	int retries = 0;

	struct page *page;

	struct folio *folio;

	pgoff_t index;

	unsigned from, to;
@@ -1166,68 +1166,69 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping, 
	}



	/*

	 * grab_cache_page_write_begin() can take a long time if the

	 * system is thrashing due to memory pressure, or if the page

	 * __filemap_get_folio() can take a long time if the

	 * system is thrashing due to memory pressure, or if the folio

	 * is being written back.  So grab it first before we start

	 * the transaction handle.  This also allows us to allocate

	 * the page (if needed) without using GFP_NOFS.

	 * the folio (if needed) without using GFP_NOFS.

	 */

retry_grab:

	page = grab_cache_page_write_begin(mapping, index);

	if (!page)

	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,

					mapping_gfp_mask(mapping));

	if (!folio)

		return -ENOMEM;

	/*

	 * The same as page allocation, we prealloc buffer heads before

	 * starting the handle.

	 */

	if (!page_has_buffers(page))

		create_empty_buffers(page, inode->i_sb->s_blocksize, 0);

	if (!folio_buffers(folio))

		create_empty_buffers(&folio->page, inode->i_sb->s_blocksize, 0);



	unlock_page(page);

	folio_unlock(folio);



retry_journal:

	handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE, needed_blocks);

	if (IS_ERR(handle)) {

		put_page(page);

		folio_put(folio);

		return PTR_ERR(handle);

	}



	lock_page(page);

	if (page->mapping != mapping) {

		/* The page got truncated from under us */

		unlock_page(page);

		put_page(page);

	folio_lock(folio);

	if (folio->mapping != mapping) {

		/* The folio got truncated from under us */

		folio_unlock(folio);

		folio_put(folio);

		ext4_journal_stop(handle);

		goto retry_grab;

	}

	/* In case writeback began while the page was unlocked */

	wait_for_stable_page(page);

	/* In case writeback began while the folio was unlocked */

	folio_wait_stable(folio);



#ifdef CONFIG_FS_ENCRYPTION

	if (ext4_should_dioread_nolock(inode))

		ret = ext4_block_write_begin(page, pos, len,

		ret = ext4_block_write_begin(&folio->page, pos, len,

					     ext4_get_block_unwritten);

	else

		ret = ext4_block_write_begin(page, pos, len,

		ret = ext4_block_write_begin(&folio->page, pos, len,

					     ext4_get_block);

#else

	if (ext4_should_dioread_nolock(inode))

		ret = __block_write_begin(page, pos, len,

		ret = __block_write_begin(&folio->page, pos, len,

					  ext4_get_block_unwritten);

	else

		ret = __block_write_begin(page, pos, len, ext4_get_block);

		ret = __block_write_begin(&folio->page, pos, len, ext4_get_block);

#endif

	if (!ret && ext4_should_journal_data(inode)) {

		ret = ext4_walk_page_buffers(handle, inode,

					     page_buffers(page), from, to, NULL,

					     do_journal_get_write_access);

					     folio_buffers(folio), from, to,

					     NULL, do_journal_get_write_access);

	}



	if (ret) {

		bool extended = (pos + len > inode->i_size) &&

				!ext4_verity_in_progress(inode);



		unlock_page(page);

		folio_unlock(folio);

		/*

		 * __block_write_begin may have instantiated a few blocks

		 * outside i_size.  Trim these off again. Don't need
@@ -1255,10 +1256,10 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping, 
		if (ret == -ENOSPC &&

		    ext4_should_retry_alloc(inode->i_sb, &retries))

			goto retry_journal;

		put_page(page);

		folio_put(folio);

		return ret;

	}

	*pagep = page;

	*pagep = &folio->page;

	return ret;

}