Re: [PATCH v2 3/6] iomap: advance the ifs allocation if we have more than one blocks per folio

[yangerkun <yangerkun@huawei.com>]

在 2024/8/12 20:11, Zhang Yi 写道:
> From: Zhang Yi <yi.zhang@huawei.com>
> 
> Now we allocate ifs if i_blocks_per_folio is larger than one when
> writing back dirty folios in iomap_writepage_map(), so we don't attach
> an ifs after buffer write to an entire folio until it starts writing
> back, if we partial truncate that folio, iomap_invalidate_folio() can't
> clear counterpart block's dirty bit as expected. Fix this by advance the
> ifs allocation to __iomap_write_begin().
> 
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> ---
>   fs/iomap/buffered-io.c | 17 ++++++++++++-----
>   1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 763deabe8331..79031b7517e5 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -699,6 +699,12 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
>   	size_t from = offset_in_folio(folio, pos), to = from + len;
>   	size_t poff, plen;
>   
> +	if (nr_blocks > 1) {
> +		ifs = ifs_alloc(iter->inode, folio, iter->flags);
> +		if ((iter->flags & IOMAP_NOWAIT) && !ifs)
> +			return -EAGAIN;
> +	}
> +
>   	/*
>   	 * If the write or zeroing completely overlaps the current folio, then
>   	 * entire folio will be dirtied so there is no need for

The comments upper need change too.


> @@ -710,10 +716,6 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
>   	    pos + len >= folio_pos(folio) + folio_size(folio))
>   		return 0;
>   
> -	ifs = ifs_alloc(iter->inode, folio, iter->flags);
> -	if ((iter->flags & IOMAP_NOWAIT) && !ifs && nr_blocks > 1)
> -		return -EAGAIN;
> -
>   	if (folio_test_uptodate(folio))
>   		return 0;
>   
> @@ -1928,7 +1930,12 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>   	WARN_ON_ONCE(end_pos <= pos);
>   
>   	if (i_blocks_per_folio(inode, folio) > 1) {
> -		if (!ifs) {
> +		/*
> +		 * This should not happen since we always allocate ifs in
> +		 * iomap_folio_mkwrite_iter() and there is more than one
> +		 * blocks per folio in __iomap_write_begin().
> +		 */
> +		if (WARN_ON_ONCE(!ifs)) {
>   			ifs = ifs_alloc(inode, folio, 0);
>   			iomap_set_range_dirty(folio, 0, end_pos - pos);
>   		}