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 9F16925FA13; Tue, 15 Jul 2025 05:34:18 +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=1752557658; cv=none; b=k8tMeXSH4Vfe6a3JOCcCssia+Q4JxfBsAvxZdzHcxWaaJqnxiNLAlfDcSgJoWu2rTy9BvymYHyR3B3NS9dYYb3OdRjGg4i/pO/HnSvZ5U6WKWlas+UcHM4Vjx6aBQZA/DicYBgocgCQICzeozqZcI02Dj8VG0Tqhf75nB4OmL+0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752557658; c=relaxed/simple; bh=3qxVG0brYicTYe0lEhYy/WteBjTnpFcuTkkfe4/FAME=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bQtJH6baB/3nhN4TzE/p+8Ge7J9xocHv1TPxDm1qw/A96gB5D8KDcisfDWeNtGI6vhl6zMXpVRihl2rb5nuv7EZ6DqunhSTDf8DmFmpJAjeo7tN+iCwYKVpx0w9ypj1zPPzDkoMUId/4xKMPjSWPhV+1d17R1gCUkz7bKlJB1LY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P3tw4+WE; 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="P3tw4+WE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42DD8C4CEE3; Tue, 15 Jul 2025 05:34:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752557658; bh=3qxVG0brYicTYe0lEhYy/WteBjTnpFcuTkkfe4/FAME=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=P3tw4+WEW7mZG6qa1HvRa+XiDutd2ozlssmYfWFVFD+adFjYsLESvm+8fznAG0/rf lQCREgloSLNcKGT6c60PvZ3H+n2h0N8akKnkZsJHXfBbeWR5DYtEQsdipU3jp3PUq7 pbrX1Aj7VSsBlewO1/JKMwvoUTokBn4rWpYQtot1XNlS2/6CqJpWGjShirwB6AaLLj gI0kja6BIf6KRHbvw1gxMc8EVN7gE93d2P4mNtIIUPiOjsIvAr4AWp8BkedlnhaPEb teBh9buC3YVYTUWMhHiJDfjne0UaDJTacP6Ojcfhy0JcJqZTxsfWINdXoOriZq3q0V 3sZ0ldlhQLHKg== Date: Mon, 14 Jul 2025 22:34:17 -0700 From: "Darrick J. Wong" To: Brian Foster Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, hch@infradead.org, willy@infradead.org Subject: Re: [PATCH v3 6/7] iomap: remove old partial eof zeroing optimization Message-ID: <20250715053417.GR2672049@frogsfrogsfrogs> References: <20250714204122.349582-1-bfoster@redhat.com> <20250714204122.349582-7-bfoster@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <20250714204122.349582-7-bfoster@redhat.com> On Mon, Jul 14, 2025 at 04:41:21PM -0400, Brian Foster wrote: > iomap_zero_range() optimizes the partial eof block zeroing use case > by force zeroing if the mapping is dirty. This is to avoid frequent > flushing on file extending workloads, which hurts performance. > > Now that the folio batch mechanism provides a more generic solution > and is used by the only real zero range user (XFS), this isolated > optimization is no longer needed. Remove the unnecessary code and > let callers use the folio batch or fall back to flushing by default. > > Signed-off-by: Brian Foster > Reviewed-by: Christoph Hellwig Heh, I was staring at this last Friday chasing fuse+iomap bugs in fallocate zerorange and straining to remember what this does. Is this chunk still needed if the ->iomap_begin implementation doesn't (or forgets to) grab the folio batch for iomap? My bug turned out to be a bug in my fuse+iomap design -- with the way iomap_zero_range does things, you have to flush+unmap, punch the range and zero the range. If you punch and realloc the range and *then* try to zero the range, the new unwritten extents cause iomap to miss dirty pages that fuse should've unmapped. Ooops. --D > --- > fs/iomap/buffered-io.c | 24 ------------------------ > 1 file changed, 24 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 194e3cc0857f..d2bbed692c06 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -1484,33 +1484,9 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero, > .private = private, > }; > struct address_space *mapping = inode->i_mapping; > - unsigned int blocksize = i_blocksize(inode); > - unsigned int off = pos & (blocksize - 1); > - loff_t plen = min_t(loff_t, len, blocksize - off); > int ret; > bool range_dirty; > > - /* > - * Zero range can skip mappings that are zero on disk so long as > - * pagecache is clean. If pagecache was dirty prior to zero range, the > - * mapping converts on writeback completion and so must be zeroed. > - * > - * The simplest way to deal with this across a range is to flush > - * pagecache and process the updated mappings. To avoid excessive > - * flushing on partial eof zeroing, special case it to zero the > - * unaligned start portion if already dirty in pagecache. > - */ > - if (!iter.fbatch && off && > - filemap_range_needs_writeback(mapping, pos, pos + plen - 1)) { > - iter.len = plen; > - while ((ret = iomap_iter(&iter, ops)) > 0) > - iter.status = iomap_zero_iter(&iter, did_zero); > - > - iter.len = len - (iter.pos - pos); > - if (ret || !iter.len) > - return ret; > - } > - > /* > * To avoid an unconditional flush, check pagecache state and only flush > * if dirty and the fs returns a mapping that might convert on > -- > 2.50.0 > >