[PATCH 5/9] ext4: Add support for writepages calls that cannot map blocks

Jan Kara
2022-11-30T16:36:22Z

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

Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/ext4/inode.c | 47 +++++++++++++++++++++++++++++++++++++++--------
1 file changed, 39 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 43eb175d0c1c..1cde20eb6500 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1557,6 +1557,7 @@ 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;
};

@@ -2549,6 +2550,19 @@ 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
@@ -2651,14 +2665,30 @@ 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);
@@ -2778,6 +2808,7 @@ 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;
--
2.35.3