From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DC1823750CB; Wed, 17 Jun 2026 18:09:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781719777; cv=none; b=nJZkGJjdSzeBXIFkUR2/dj9zPjEoaIB0e6yguTcWyed3qOgGZq2kFDpYUA09QCGG2+fKfg4Vhh16amMEGAvOjO/8TcwCO2N2NJGjFVJK03hTFpcJ1FTtas8dURjA3MpxShtOQm6GGPzKJJDfcM2HxqsTFb9/nAeWQXAhFcXJbJM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781719777; c=relaxed/simple; bh=tPxlq0qL8ZiBrQmoi8Rx8xtOxDUmm2s8o0hFeRA4jX4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tBijIhHiuyh1luAIM6ugyFG6g2MdieUiZnyqN3Iqi8JB89Ds+1CumyXXdFLFs45GDNJWaCdm33YwEyzKxe926T9TK4ICYteN5UnCSHqH/4CRoLTQmgXdVrf2edrer/LD2CdTMYSuQCy5poYLJvG080RuT7SAWe6WZo1RQkG5Asw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FvR2WSXb; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FvR2WSXb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F19B1F000E9; Wed, 17 Jun 2026 18:09:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781719776; bh=jWEa6RP1Pi3Ycy/oGmflXx0TMIdx6fHkv2r2sAHUe5M=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=FvR2WSXb120GdkouzMt5pxNolEXMByOMorJ2qh7bQ5fpzAlqYLc4BrvcueSaoHTXa Cn1vkCsT+oHzPgJW2IWomMhsHj1FYD0FAlZURjHcNCRiqHpa11+nDYxxO95Adikfrm Sy6AdDOCZBPOeDzqGhismne1s7GGF9TG81ifMqvtfgHuZg/nMwxfIwUdlL5FyVlBTP qmMZm8/JW4us9Tpyy3+ZoJtliXwZ6/woJo0rnPBm2lTLVAeu14AcCiGWgMsSEre9je e4kcQe46sD7adaUGKfRwq0A99LjZhoUGdYz3+ICnCC19PxB91DLbZ+lL+IfKvDRsym n9s7yl3xl7NHQ== Date: Wed, 17 Jun 2026 18:09:34 +0000 From: Jaegeuk Kim To: Wenjie Qi Cc: chao@kernel.org, geoo115@gmail.com, yangyongpeng@xiaomi.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, qiwenjie@xiaomi.com Subject: Re: [f2fs-dev] [PATCH v5] f2fs: use post-decrement count for cp_wait wakeup Message-ID: References: <20260616135637.1439319-1-qiwenjie@xiaomi.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260616135637.1439319-1-qiwenjie@xiaomi.com> On 06/16, Wenjie Qi wrote: > f2fs_write_end_io() decrements the writeback page counter and then > reads it again with get_pages() to decide whether the last > F2FS_WB_CP_DATA completion should wake cp_wait. > > Use atomic_dec_return() for F2FS_WB_CP_DATA completions so the wakeup > decision is made from the value produced by the decrement itself. Keep > the existing dec_page_count() path for other writeback counters. Is there a race condition to do this? If so, can you describe? And, I think we need a wrapper function instead of calling nr_pages directly. > > Fixes: e234088758fc ("f2fs: avoid wait if IO end up when do_checkpoint for better performance") > Fixes: ce2739e482bc ("f2fs: fix to avoid UAF in f2fs_write_end_io()") > Cc: stable@vger.kernel.org > Signed-off-by: Wenjie Qi > --- > fs/f2fs/data.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index d83a21998ec2..58d23eb74ec2 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -392,15 +392,17 @@ static void f2fs_write_end_io(struct bio *bio) > if (f2fs_in_warm_node_list(folio)) > f2fs_del_fsync_node_entry(sbi, folio); > > - dec_page_count(sbi, type); > - > /* > * we should access sbi before folio_end_writeback() to > * avoid racing w/ kill_f2fs_super() > */ > - if (type == F2FS_WB_CP_DATA && !get_pages(sbi, type) && > - wq_has_sleeper(&sbi->cp_wait)) > - wake_up(&sbi->cp_wait); > + if (type == F2FS_WB_CP_DATA) { > + if (!atomic_dec_return(&sbi->nr_pages[type]) && > + wq_has_sleeper(&sbi->cp_wait)) > + wake_up(&sbi->cp_wait); > + } else { > + dec_page_count(sbi, type); > + } > > folio_clear_f2fs_gcing(folio); > folio_end_writeback(folio); > > base-commit: c0b65f6129c7fbb526e921dd60261650f1b2bef9 > -- > 2.43.0 > > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel