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 6AF6A331A53; Tue, 14 Jul 2026 17:55:29 +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=1784051731; cv=none; b=NhDgxhzfAHne+BRS5XLM4uW7bX5iic0gGeLC/91epUkXcrrtAlLwRDAUebyx4uvD4whruG+0A1gkS528ppwzApQJtFRxos1jV5kxjjhUubRRP/D1hDktsroEOxJHP4i4J/HXwboNX7J+MeeWpE+HVjcduOiab1QCoMczbj7LHTs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784051731; c=relaxed/simple; bh=hqhZ5fbL0jiyxiACcblyfKNhfoLlN2Hrs48VMQ1Q+/c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=R2WCotjRX4WeURQH1+9WrvOE0a35Wd3FCEsIapmBBjrFmEuo+/pF6hj6BEGPBSeCAob9+9LdudpCOh9vNMzh6ipoS5exjlIiC7T+525JDCK/nEGXr9aLQp3mFNycpSJ3Ez1z2TXfaD23W3RxeIUZkbTtjPwrddP7hIj6j65C2ts= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GQH+uGuf; 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="GQH+uGuf" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id D8CDB1F000E9; Tue, 14 Jul 2026 17:55:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784051728; bh=kqPa6Awexo1sZ9NAhkSiBlt6klZOADUjfwrP4NV/fLY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=GQH+uGuf7cG6jloVA22oC1BzvBnCdLn6AaVkT11e9Pl4dlrZGqhSiKh/vPEmjkhUD fF/zQxGSmJIehfWOBVrypqs9fxhp+3sTIWs8usgUkzwuvgPtVyGyiPtP4Hydrbq6OB peDtP0/8RQIj1W4l1b7eHIe/XwxTNxh2/LBPllthqzyZHWcI1GfP6HPc4IZBwGWc5v 708AyWb9OC4FTGIlsNXG1VjviLyWmvxf7+P+bISXLDRNPGX8h5NbI3IHfNXjDfWet0 tpPgF0TWMHuCOj8/oxx7kqkTGJXEK8n7ykLKBviqU9GHH0HzdA4glcbugdTEuJlBmP +vg20gZ1ZRRLg== Date: Tue, 14 Jul 2026 10:55:28 -0700 From: "Darrick J. Wong" To: "Zhou, Yun" Cc: Christoph Hellwig , cem@kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm Subject: Re: [PATCH] xfs: restore nofs context unconditionally in xfs_trans_roll Message-ID: <20260714175528.GG7380@frogsfrogsfrogs> References: <20260713035505.1635191-1-yun.zhou@windriver.com> <7a053113-f678-486e-a78b-8f5e94e73acb@windriver.com> <20260713230420.GN7195@frogsfrogsfrogs> <0792c175-6a7c-4108-966d-4afbc8c515a2@windriver.com> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0792c175-6a7c-4108-966d-4afbc8c515a2@windriver.com> [add linux-mm since we're talking about memalloc_nofs_save] On Tue, Jul 14, 2026 at 10:15:53AM +0800, Zhou, Yun wrote: > > > On 7/14/26 07:04, Darrick J. Wong wrote: > > CAUTION: This email comes from a non Wind River email account! > > Do not click links or open attachments unless you recognize the sender and know the content is safe. > > > > On Mon, Jul 13, 2026 at 06:28:38AM -0700, Christoph Hellwig wrote: > > > On Mon, Jul 13, 2026 at 06:06:38PM +0800, Zhou, Yun wrote: > > > > > > > > > > > > On 7/13/26 17:09, Christoph Hellwig wrote: > > > > > > > > > > On Mon, Jul 13, 2026 at 11:55:05AM +0800, Yun Zhou wrote: > > > > > > > > > > > > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c > > > > > > index 7bfbd9f6f0df..1b36cf12d4e3 100644 > > > > > > --- a/fs/xfs/xfs_trans.c > > > > > > +++ b/fs/xfs/xfs_trans.c > > > > > > @@ -1029,6 +1029,15 @@ xfs_trans_roll( > > > > > > * duplicate transaction that gets returned. > > > > > > */ > > > > > > error = __xfs_trans_commit(tp, true); > > > > > > + > > > > > > + tp = *tpp; > > > > > > + /* > > > > > > + * __xfs_trans_commit cleared the NOFS flag by calling into > > > > > > + * xfs_trans_free. Set it again here before doing memory > > > > > > + * allocations. > > > > > > + */ > > > > > > + xfs_trans_set_context(tp); > > > > > > > > > > The tp assignment above now returns the incorrect transaction when > > > > > __xfs_trans_commit fails, so you can't do this. > > > > > > > > > > Otherwise yes, this call should move up. I don't really see how > > > > > it fixes the syzbot report, though. > > > > > > > > > > > > > Thank you very much for your reply. The tp here is a local variable only > > > > used for convenience within the function. The caller always gets the new > > > > transaction through *tpp, which was set by xfs_trans_dup() before the commit > > > > call. Moving tp = *tpp before the error check doesn't change what the caller > > > > sees - *tpp still points to the new (dup'd) transaction regardless. > > > > > > Ah, right. Tis should be fine: > > > > > > Reviewed-by: Christoph Hellwig > > > > Why not move tp_pflags to the new transaction in xfs_trans_dup like we > > do for the deferred item list: > > > > /* move deferred ops over to the new tp */ > > xfs_defer_move(ntp, tp); > > > > ntp->t_pflags = tp->t_pflags; > > tp->t_pflags = 0; > > > > That's what the old xfs_trans_switch_context() did before a1ca658d649a > removed it. The problem is that setting tp->t_pflags = 0 means > xfs_trans_free() calls memalloc_nofs_restore(0), which relies on that being > a no-op — an mm implementation detail. A fresh memalloc_nofs_save() on the > new tp keeps the save/restore pairing correct unconditionally. So add a new helper. /** * memalloc_flags_take - move an implicit __GFP_MEMALLOC scope from one * tracking structure to another. */ static inline unsigned int memalloc_flags_take(unsigned int *old_flags) { unsigned int ret = *old_flags; *old_flags = 0; return ret; } and then: /* move deferred ops over to the new tp */ xfs_defer_move(ntp, tp); ntp->t_pflags = memalloc_flags_take(&tp->t_pflags); --D > BR, > Yun >