ext4: correct the reserved credits for extent conversion

commit 95ad8ee upstream.

Now, we reserve journal credits for converting extents in only one page
to written state when the I/O operation is complete. This is
insufficient when large folio is enabled.

Fix this by reserving credits for converting up to one extent per block in
the largest 2MB folio, this calculation should only involve extents index
and leaf blocks, so it should not estimate too many credits.

Fixes: 7ac6730 ("ext4: enable large folio for regular file")
Signed-off-by: Zhang Yi <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Baokun Li <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: zhangyi089

fs/ext4/inode.c

@@ -2850,12 +2850,12 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
 	mpd->journalled_more_data = 0;
 
 	if (ext4_should_dioread_nolock(inode)) {
+		int bpf = ext4_journal_blocks_per_folio(inode);
 		/*
 		 * We may need to convert up to one extent per block in
-		 * the page and we may dirty the inode.
+		 * the folio and we may dirty the inode.
 		 */
-		rsv_blocks = 1 + ext4_chunk_trans_blocks(inode,
-						PAGE_SIZE >> inode->i_blkbits);
+		rsv_blocks = 1 + ext4_ext_index_trans_blocks(inode, bpf);
 	}
 
 	if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)