From: Ted Ts'o Subject: Re: [PATCH] Ext4: Don't normalize an falloc request if it can fit in 1 extent. Date: Mon, 31 Oct 2011 18:42:34 -0400 Message-ID: <20111031224234.GP16825@thunk.org> References: <1319824917-28345-1-git-send-email-gharm@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , linux-ext4@vger.kernel.org To: Greg Harm Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:35894 "EHLO test.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934441Ab1JaWmi (ORCPT ); Mon, 31 Oct 2011 18:42:38 -0400 Content-Disposition: inline In-Reply-To: <1319824917-28345-1-git-send-email-gharm@google.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Oct 28, 2011 at 11:01:57AM -0700, Greg Harm wrote: > If an fallocate request fits in EXT_UNINIT_MAX_LEN, then set the > EXT4_GET_BLOCKS_NO_NORMALIZE flag. For larger fallocate requests, > let mballoc.c normalize the request. > This fixes a problem where large requests were being split > into non-contiguous extents due to haldar@google.com's > "ext4: do not normalize block requests from fallocate." > > Testing: Checked that 8.x MB falloc'ed files are still laid down > next to each other (contiguously). > Checked that the maximum size extent (127.9MB) is allocated as 1 > extent. > Checked that a 1GB file is somewhat contiguous (often 5-6 > non-contiguous extents now). > Checked that a 120MB file can still be falloc'ed even if there are no > single extents large enough to hold it. > > Signed-off-by: Greg Harm Thanks, I had to tweak the patch slightly to make it apply given the current ext4 tree. - Ted commit 5f11e7c457769808bafe5048a98c5cfd624e85f3 Author: Greg Harm Date: Mon Oct 31 18:41:47 2011 -0400 ext4: Don't normalize an falloc request if it can fit in 1 extent. If an fallocate request fits in EXT_UNINIT_MAX_LEN, then set the EXT4_GET_BLOCKS_NO_NORMALIZE flag. For larger fallocate requests, let mballoc.c normalize the request. This fixes a problem where large requests were being split into non-contiguous extents due to commit 556b27abf73: ext4: do not normalize block requests from fallocate. Testing: *) Checked that 8.x MB falloc'ed files are still laid down next to each other (contiguously). *) Checked that the maximum size extent (127.9MB) is allocated as 1 extent. *) Checked that a 1GB file is somewhat contiguous (often 5-6 non-contiguous extents now). *) Checked that a 120MB file can still be falloc'ed even if there are no single extents large enough to hold it. Signed-off-by: Greg Harm Signed-off-by: "Theodore Ts'o" diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index e585caa..9dfdf8f 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4336,10 +4336,16 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len) trace_ext4_fallocate_exit(inode, offset, max_blocks, ret); return ret; } - flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT | - EXT4_GET_BLOCKS_NO_NORMALIZE; + flags = EXT4_GET_BLOCKS_CREATE_UNINIT_EXT; if (mode & FALLOC_FL_KEEP_SIZE) flags |= EXT4_GET_BLOCKS_KEEP_SIZE; + /* + * Don't normalize the request if it can fit in one extent so + * that it doesn't get unnecessarily split into multiple + * extents. + */ + if (len <= EXT_UNINIT_MAX_LEN << blkbits) + flags |= EXT4_GET_BLOCKS_NO_NORMALIZE; retry: while (ret >= 0 && ret < max_blocks) { map.m_lblk = map.m_lblk + ret;