On Tue 01-07-25 21:06:33, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
>
> 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 <jack@xxxxxxx>
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> 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 3230734a3014..ceaede80d791 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2546,21 +2546,6 @@ static int mpage_map_and_submit_extent(handle_t *handle,
> 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)
> {
> @@ -2917,8 +2902,14 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
> * 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);
> --
> 2.46.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
