From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D6B0E8C1E for ; Thu, 8 May 2025 06:06:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746684404; cv=none; b=b71BLNgVG66p+dzQ4E1owsROMtFkVV+pXZc6GK0zGAsvEQ99cK1SDwB9VmcNMkU/qFNTdSeVB37yyFbrMAXxyYmluCwetEQWJnXdj5PjNvpEa3k3MFl7Gvd+ILQyQWV7cBkIRluzMp0sKxcekGYXPQOoGOUFLRGq8jNm/uMoSNo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746684404; c=relaxed/simple; bh=t0MjqSYY9gKyyPZJWQQP8IE+M9Cw9afFYW2lmLnWcS8=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=gxEy/uZq4O68ULlfj8IAILpTjF4sqyEWYtwcRnKGDCBL7plQ0DmpaB5PN+fNV0DAwaIcsT3uN/R3zIjDj9859DAHZlKmEYzXeqzsIRK1LeAFZFoaPL9C6GGNN9DUvPNRIJjxlO06j/snYGI48fbOzmQ/WPh0G5A8vFcFVZLQVZI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=VV2kA55A; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="VV2kA55A" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Type:MIME-Version:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:In-Reply-To:References; bh=l4SSn4rl9nTY8u1Bl53VbD5p9y903Sc2iTntwD6tkHQ=; b=VV2kA55AUJ08ab0aPvxPBlw4NA hkRmBgCDiFOVzrpKe/2BtVQvgcJRW/G+0IecVyEpSicd5dwihCIQ/mxT7b9KeQOUyxn4V6HVBsuH3 maJN4hEYkrX3DVgtusBGfpmQDR0ZTXNGJNr0bVb/H/GkyjhPb6OKvuxivuspV5RzXEI3hstOvSYmo ZokT4Fc4o4mrpl8EsY/3YHLDLOPCz4v7j5g/1MuebuNyFsNVMuNdn531ZlFx9T5b5Oc4zv+PKlzrT QttCIVhS2v6mQ01dpSOVIOKA/L7abB88z4V+Z3j/grZmjBFlSeTRENfsToghvi7wQ97US+BBTBM2Y d2nwukDQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uCuP4-0000000HQcA-1Bzg; Thu, 08 May 2025 06:06:42 +0000 Date: Wed, 7 May 2025 23:06:42 -0700 From: Christoph Hellwig To: Chris Mason Cc: linux-btrfs@vger.kernel.org, Josef Bacik , David Sterba , linux-mm@kvack.org Subject: What is the point of the wbc->for_kupdate check in btree_writepages Message-ID: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Hi Chris, you added a wbc->for_kupdate check to btree_writepages that skips the write in this case in commit 448d640b668d ("Btrfs: Fine tune the btree writeback exclusion some more") which is not associated without any information but the subject line. Do you by any chance remember why it was doing that just for kupdate and not any other background writeback? I'm asking because it is one of only two checks for this in file system code, and the other one in nfs at least checks for all background writeback and thus makes some sense to me.