Commit de0039f6 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

ext4: add support for writepages calls that cannot map blocks 



Add support for calls to ext4_writepages() than cannot map blocks. These
will be issued from jbd2 transaction commit code.

Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221207112722.22220-5-jack@suse.cz


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 5c27088b

fs/ext4/inode.c

+48 −14
Original line number Diff line number Diff line
@@ -1564,6 +1564,7 @@ struct mpage_da_data { 
	struct ext4_map_blocks map;

	struct ext4_io_submit io_submit;	/* IO submission data */

	unsigned int do_map:1;

	unsigned int can_map:1;	/* Can writepages call map blocks? */

	unsigned int scanned_until_end:1;

};
@@ -2556,18 +2557,33 @@ static int ext4_da_writepages_trans_blocks(struct inode *inode) 
				MAX_WRITEPAGES_EXTENT_LEN + bpp - 1, bpp);

}



/* Return true if the page needs to be written as part of transaction commit */

static bool ext4_page_nomap_can_writeout(struct page *page)

{

	struct buffer_head *bh, *head;



	bh = head = page_buffers(page);

	do {

		if (buffer_dirty(bh) && buffer_mapped(bh) && !buffer_delay(bh))

			return true;

	} while ((bh = bh->b_this_page) != head);

	return false;

}



/*

 * mpage_prepare_extent_to_map - find & lock contiguous range of dirty pages

 * 				 and underlying extent to map

 * 				 needing mapping, submit mapped pages

 *

 * @mpd - where to look for pages

 *

 * Walk dirty pages in the mapping. If they are fully mapped, submit them for

 * IO immediately. When we find a page which isn't mapped we start accumulating

 * extent of buffers underlying these pages that needs mapping (formed by

 * either delayed or unwritten buffers). We also lock the pages containing

 * these buffers. The extent found is returned in @mpd structure (starting at

 * mpd->lblk with length mpd->len blocks).

 * IO immediately. If we cannot map blocks, we submit just already mapped

 * buffers in the page for IO and keep page dirty. When we can map blocks and

 * we find a page which isn't mapped we start accumulating extent of buffers

 * underlying these pages that needs mapping (formed by either delayed or

 * unwritten buffers). We also lock the pages containing these buffers. The

 * extent found is returned in @mpd structure (starting at mpd->lblk with

 * length mpd->len blocks).

 *

 * Note that this function can attach bios to one io_end structure which are

 * neither logically nor physically contiguous. Although it may seem as an
@@ -2658,14 +2674,30 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd) 
			if (mpd->map.m_len == 0)

				mpd->first_page = page->index;

			mpd->next_page = page->index + 1;

			/*

			 * Writeout for transaction commit where we cannot

			 * modify metadata is simple. Just submit the page.

			 */

			if (!mpd->can_map) {

				if (ext4_page_nomap_can_writeout(page)) {

					err = mpage_submit_page(mpd, page);

					if (err < 0)

						goto out;

				} else {

					unlock_page(page);

					mpd->first_page++;

				}

			} else {

				/* Add all dirty buffers to mpd */

				lblk = ((ext4_lblk_t)page->index) <<

					(PAGE_SHIFT - blkbits);

				head = page_buffers(page);

			err = mpage_process_page_bufs(mpd, head, head, lblk);

				err = mpage_process_page_bufs(mpd, head, head,

							      lblk);

				if (err <= 0)

					goto out;

				err = 0;

			}

			left--;

		}

		pagevec_release(&pvec);
@@ -2785,6 +2817,7 @@ static int ext4_writepages(struct address_space *mapping, 
	 */

	mpd.do_map = 0;

	mpd.scanned_until_end = 0;

	mpd.can_map = 1;

	mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);

	if (!mpd.io_submit.io_end) {

		ret = -ENOMEM;
@@ -2808,6 +2841,7 @@ static int ext4_writepages(struct address_space *mapping, 
			break;

		}



		WARN_ON_ONCE(!mpd->can_map);

		/*

		 * We have two constraints: We find one extent to map and we

		 * must always write out whole page (makes a difference when