From bbbf150f3f85619569ac19dc6458cca7c492e715 Mon Sep 17 00:00:00 2001 From: Zhang Yi Date: Mon, 7 Jul 2025 22:08:11 +0800 Subject: [PATCH] ext4: reserved credits for one extent during the folio writeback After ext4 supports large folios, reserving journal credits for one maximum-ordered folio based on the worst case cenario during the writeback process can easily exceed the maximum transaction credits. Additionally, reserving journal credits for one page is also no longer appropriate. Currently, the folio writeback process can either extend the journal credits or initiate a new transaction if the currently reserved journal credits are insufficient. Therefore, it can be modified to reserve credits for only one extent at the outset. In most cases involving continuous mapping, these credits are generally adequate, and we may only need to perform some basic credit expansion. However, in extreme cases where the block size and folio size differ significantly, or when the folios are sufficiently discontinuous, it may be necessary to restart a new transaction and resubmit the folios. Suggested-by: Jan Kara Signed-off-by: Zhang Yi Reviewed-by: Jan Kara Link: https://patch.msgid.link/20250707140814.542883-9-yi.zhang@huaweicloud.com Signed-off-by: Theodore Ts'o --- fs/ext4/inode.c | 25 ++++++++----------------- 1 file changed, 8 insertions(+), 17 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 1d158e1de3a1..5230af879814 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2545,21 +2545,6 @@ update_disksize: return err; } -/* - * Calculate the total number of credits to reserve for one writepages - * iteration. This is called from ext4_writepages(). We map an extent of - * up to MAX_WRITEPAGES_EXTENT_LEN blocks and then we go on and finish mapping - * the last partial page. So in total we can map MAX_WRITEPAGES_EXTENT_LEN + - * bpp - 1 blocks in bpp different extents. - */ -static int ext4_da_writepages_trans_blocks(struct inode *inode) -{ - int bpp = ext4_journal_blocks_per_folio(inode); - - return ext4_meta_trans_blocks(inode, - MAX_WRITEPAGES_EXTENT_LEN + bpp - 1, bpp); -} - static int ext4_journal_folio_buffers(handle_t *handle, struct folio *folio, size_t len) { @@ -2916,8 +2901,14 @@ retry: * not supported by delalloc. */ BUG_ON(ext4_should_journal_data(inode)); - needed_blocks = ext4_da_writepages_trans_blocks(inode); - + /* + * Calculate the number of credits needed to reserve for one + * extent of up to MAX_WRITEPAGES_EXTENT_LEN blocks. It will + * attempt to extend the transaction or start a new iteration + * if the reserved credits are insufficient. + */ + needed_blocks = ext4_chunk_trans_blocks(inode, + MAX_WRITEPAGES_EXTENT_LEN); /* start a new transaction */ handle = ext4_journal_start_with_reserve(inode, EXT4_HT_WRITE_PAGE, needed_blocks, rsv_blocks); -- 2.25.1