On Tue 01-07-25 21:06:30, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@xxxxxxxxxx>
>
> After large folios are supported on ext4, writing back a sufficiently
> large and discontinuous folio may consume a significant number of
> journal credits, placing considerable strain on the journal. For
> example, in a 20GB filesystem with 1K block size and 1MB journal size,
> writing back a 2MB folio could require thousands of credits in the
> worst-case scenario (when each block is discontinuous and distributed
> across different block groups), potentially exceeding the journal size.
> This issue can also occur in ext4_write_begin() and ext4_page_mkwrite()
> when delalloc is not enabled.
>
> Fix this by ensuring that there are sufficient journal credits before
> allocating an extent in mpage_map_one_extent() and
> ext4_block_write_begin(). If there are not enough credits, return
> -EAGAIN, exit the current mapping loop, restart a new handle and a new
> transaction, and allocating blocks on this folio again in the next
> iteration.
>
> Suggested-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Very nice. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
One small comment below:
> +/*
> + * Make sure that the current journal transaction has enough credits to map
> + * one extent. Return -EAGAIN if it cannot extend the current running
> + * transaction.
> + */
> +static inline int ext4_journal_ensure_extent_credits(handle_t *handle,
> + struct inode *inode)
> +{
> + int credits;
> + int ret;
> +
> + if (!handle)
Shouldn't this rather be ext4_handle_valid(handle) to catch nojournal mode
properly?
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
