linux-kernel - Re: [PATCH v1 4/5] f2fs: add 'folio_in_bio' to handle readahead folios with no BIO submission

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Message-ID: <5ca2ef6a-ce46-4d80-b2e0-ff35c628e0ba@kernel.org>
Date: Tue, 6 Jan 2026 17:31:20 +0800
From: Chao Yu <chao@...nel.org>
To: Nanzhe Zhao <nzzhao@....com>, Kim Jaegeuk <jaegeuk@...nel.org>
Cc: chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/5] f2fs: add 'folio_in_bio' to handle readahead
 folios with no BIO submission

On 1/5/2026 11:31 PM, Nanzhe Zhao wrote:
> f2fs_read_data_large_folio() can build a single read BIO across multiple
> folios during readahead. If a folio ends up having none of its subpages
> added to the BIO (e.g. all subpages are zeroed / treated as holes), it
> will never be seen by f2fs_finish_read_bio(), so folio_end_read() is
> never called. This leaves the folio locked and not marked uptodate.
> 
> Track whether the current folio has been added to a BIO via a local
> 'folio_in_bio' bool flag, and when iterating readahead folios, explicitly
> mark the folio uptodate (on success) and unlock it when nothing was added.
> 
> Signed-off-by: Nanzhe Zhao <nzzhao@....com>
> ---
>   fs/f2fs/data.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 66ab7a43a56f..ac569a396914 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2430,6 +2430,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
>   	unsigned nrpages;
>   	struct f2fs_folio_state *ffs;
>   	int ret = 0;
> +	bool folio_in_bio = false;

No need to initialize folio_in_bio?

> 
>   	if (!IS_IMMUTABLE(inode))
>   		return -EOPNOTSUPP;
> @@ -2445,6 +2446,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
>   	if (!folio)
>   		goto out;
> 
> +	folio_in_bio = false

folio_in_bio = false;

>   	index = folio->index;
>   	offset = 0;
>   	ffs = NULL;
> @@ -2530,6 +2532,7 @@ static int f2fs_read_data_large_folio(struct inode *inode,
>   					offset << PAGE_SHIFT))
>   			goto submit_and_realloc;
> 
> +		folio_in_bio = true;
>   		inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
>   		f2fs_update_iostat(F2FS_I_SB(inode), NULL, FS_DATA_READ_IO,
>   				F2FS_BLKSIZE);
> @@ -2539,6 +2542,11 @@ static int f2fs_read_data_large_folio(struct inode *inode,
>   	}
>   	trace_f2fs_read_folio(folio, DATA);
>   	if (rac) {
> +		if (!folio_in_bio) {
> +			if (!ret)
> +				folio_mark_uptodate(folio);
> +			folio_unlock(folio);
> +	}

err_out:
	/* Nothing was submitted. */
	if (!bio) {
		if (!ret)
			folio_mark_uptodate(folio);
		folio_unlock(folio);

                 ^^^^^^^^^^^^

If all folios in rac have not been mapped (hole case), will we unlock the folio twice?

Thanks,

		return ret;
	}

>   		folio = readahead_folio(rac);
>   		goto next_folio;
>   	}
> --
> 2.34.1
>