linux-kernel - Re: [PATCH v1 2/5] f2fs: Accounting large folio subpages before bio submission

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Message-ID: <553c84d8-e0b3-4d02-a417-9e810142e8d6@kernel.org>
Date: Tue, 6 Jan 2026 17:16:42 +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 2/5] f2fs: Accounting large folio subpages before bio
 submission

On 1/5/2026 11:30 PM, Nanzhe Zhao wrote:
> In f2fs_read_data_large_folio(), read_pages_pending is incremented only
> after the subpage has been added to the BIO.  With a heavily fragmented
> file, each new subpage can force submission of the previous BIO.
> 
> If the BIO completes quickly, f2fs_finish_read_bio() may decrement
> read_pages_pending to zero and call folio_end_read() while the read loop
> is still processing other subpages of the same large folio.
> 
> Fix the ordering by incrementing read_pages_pending before any possible
> BIO submission for the current subpage, matching the iomap ordering and
> preventing premature folio_end_read().
> 
> Signed-off-by: Nanzhe Zhao <nzzhao@....com>

Reviewed-by: Chao Yu <chao@...nel.org>

Thanks,