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ext4: add support for writepages calls that cannot map blocks

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

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221207112722.22220-5-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara 2022-12-07 12:27:08 +01:00 committed by Theodore Ts'o
parent 5c27088b3b
commit de0039f69c
1 changed files with 48 additions and 14 deletions
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62
fs/ext4/inode.c
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@ -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;
/* 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);
if (err <= 0)
goto out;
err = 0;
/*
* 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);
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