From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 26378224B1E for ; Tue, 17 Mar 2026 21:33:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773783231; cv=none; b=J1CACLh4WLf0e7t+uKbV/iWEAJMHOrCs9s4FIRJOeSra/Fp8X1sD5aDZO8xlw6qBaXUOltRdY0vFCUSajYTMujCIblrrcyfRBHkJ9O/3igNEvB22KCu8lGJgSogFCluWfEjV6Cibm9DQOkv1oZ4lWBLA6Qt14z/Gx22qsVq1ezk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773783231; c=relaxed/simple; bh=rSaeoSplGgpttE0wZJZypa8O0oMuVDvfE7RL3NRq+Yo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QF0Be5S4pV5VNkmZrZPBpyF73RkgHFNAwLoQP/2m+FG8JawrXkB61Eiq0gMRn0rx+Jn9xxzRgxugbDt7N7aZj9V+v+DY0xP/NFP2U2ixAFJfxVmtBBcJbDkdRYlWf2A+M+3csNSr2HzhcOcWG/2rxIpn/GLBmWmTPY9SU+mlDdc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iauhcE7y; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iauhcE7y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDCBFC4CEF7; Tue, 17 Mar 2026 21:33:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773783230; bh=rSaeoSplGgpttE0wZJZypa8O0oMuVDvfE7RL3NRq+Yo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iauhcE7y78dvK0h17v3krZ3sTDZ47QpekUxf/Yb7XxD5vJTmffZkMEcSP6WPZ41PD phT2j+MrX81koXKwvpeNP/oUXowGTafzqtJcKbFrUTYCLR401/bKMWdY72jepueLxm nsx7R8F0gFNwRf4PnYqrhakZdgerITv0s+he4qPIl9kLq1FnOW3+ULpxbc0/FfQW1l Lxp3FcaXFz5sWoyVBLLkm/U4kCb8HamRRBQfi4hZK+CF24fFHY1xhw9WoQj0uFl8o8 nmLvv0Agt1Ehdu93OboT3KmDYPXErQc2DtXYvPVr41XeUjN6T/OQmxUsB4QqkWsdlc aaK+t36uY+XnA== Date: Wed, 18 Mar 2026 08:33:30 +1100 From: Dave Chinner To: Christoph Hellwig Cc: Carlos Maiolino , Dave Chinner , Brian Foster , linux-xfs@vger.kernel.org, "Darrick J. Wong" Subject: Re: [PATCH 1/4] xfs: don't keep a reference for buffers on the LRU Message-ID: References: <20260317134110.1691097-1-hch@lst.de> <20260317134110.1691097-2-hch@lst.de> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260317134110.1691097-2-hch@lst.de> On Tue, Mar 17, 2026 at 02:40:52PM +0100, Christoph Hellwig wrote: > @@ -942,10 +887,22 @@ xfs_buf_rele( > struct xfs_buf *bp) > { > trace_xfs_buf_rele(bp, _RET_IP_); > - if (xfs_buf_is_uncached(bp)) > - xfs_buf_rele_uncached(bp); > - else > - xfs_buf_rele_cached(bp); > + > + spin_lock(&bp->b_lock); > + if (!--bp->b_hold) { > + if (xfs_buf_is_uncached(bp) || !atomic_read(&bp->b_lru_ref)) > + goto kill; > + list_lru_add_obj(&bp->b_target->bt_lru, &bp->b_lru); > + } > + spin_unlock(&bp->b_lock); > + return; > + > +kill: > + bp->b_hold = -1; > + list_lru_del_obj(&bp->b_target->bt_lru, &bp->b_lru); > + spin_unlock(&bp->b_lock); > + > + xfs_buf_destroy(bp); > } The jump with the lock held is kinda nasty. The lock scope can be straight-lined by inverting the logic like so: spin_lock(&bp->b_lock); if (--bp->b_hold) { spin_unlock(&bp->b_lock); return; } if (!xfs_buf_is_uncached(bp) && atomic_read(&bp->b_lru_ref)) { list_lru_add_obj(&bp->b_target->bt_lru, &bp->b_lru); spin_unlock(&bp->b_lock); return; } /* time to die */ bp->b_hold = -1; list_lru_del_obj(&bp->b_target->bt_lru, &bp->b_lru); spin_unlock(&bp->b_lock); xfs_buf_destroy(bp); Otherwise the change looks OK. -Dave. -- Dave Chinner dgc@kernel.org