From: Artem Bityutskiy Subject: [PATCHv5 0/4] ext4: stop using write_supers and s_dirt Date: Tue, 10 Jul 2012 15:17:49 +0300 Message-ID: <1341922673-14147-1-git-send-email-dedekind1@gmail.com> Cc: Linux FS Maling List , Linux Kernel Maling List , Ext4 Mailing List To: Theodore Tso , Jan Kara Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org This patch-set makes ext4 file-system stop using the VFS '->write_supers()' call-back and the '->s_dirt' superblock field because I plan to remove them once all users are gone. Most of the ext4 changes were done or suggested by Jan Kara (thanks!). This patch does not do anything complex - we basically notice that ext4 does not really needed the 'write_super()' functionality and we can remove it. We mark the superblock buffer as dirty directly, rather than postponing this till the next 'sync_supers()' kernel thread wake-up. However, this means that we'll end up with calculating the checksum more often, see patch 3 for more information. I've also dropped the fifth patch which removes the 'now' argument from '__ext4_handle_dirty_super()' - simply because I do not understand why we should prefer marking the buffer as dirty directly instead of calling 'ext4_commit_super()': the speed difference must be neglectable and 'ext4_commit_super()' performs some error checking. I can submit this patch later - just need some more explanation from Jan. Tested with xfstests (both journalled and non-journalled ext4 modes). Reminder: The goal is to get rid of the 'sync_supers()' kernel thread. This kernel thread wakes up every 5 seconds (by default) and calls '->write_super()' for all mounted file-systems. And the bad thing is that this is done even if all the superblocks are clean. Moreover, many file-systems do not even need this end they do not register the '->write_super()' method at all (e.g., btrfs). So 'sync_supers()' most often just generates useless wake-ups and wastes power. I am trying to make all file-systems independent of '->write_super()' and plan to remove 'sync_supers()' and '->write_super()' completely once there are no more users. ====== Overall status: 1. ext4: patches submitted, https://lkml.org/lkml/2012/7/3/210 2. exofs: patch submitted, https://lkml.org/lkml/2012/6/4/211 3. sysv: patches submitted, http://lkml.org/lkml/2012/7/3/250 4. udf: patch submitted, sits in Jan Kara's tree: https://lkml.org/lkml/2012/6/4/233 git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs for_testing 5. affs: patches submitted, sit in Al Viro's tree: https://lkml.org/lkml/2012/6/6/400 git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs for-next 6. hfs: patches submitted, sit Andrew Morton's tree http://lkml.org/lkml/2012/6/12/82 7. hfsplus: patches submitted, sit in Andrew Morton's tree: https://lkml.org/lkml/2012/6/13/195 8. ext2: done, see commit f72cf5e223a28d3b3ea7dc9e40464fd534e359e8 9. vfat: done, see commit 78491189ddb6d84d4a4abae992ed891a236d0263 10. jffs2: done, see commit 208b14e507c00ff7f108e1a388dd3d8cc805a443 11. reiserfs: done, see commit 033369d1af1264abc23bea2e174aa47cdd212f6f TODO: ufs ====== fs/ext4/ext4.h | 10 +--------- fs/ext4/ext4_jbd2.c | 2 +- fs/ext4/file.c | 14 +++++++++++++- fs/ext4/ialloc.c | 2 -- fs/ext4/mballoc.c | 2 -- fs/ext4/super.c | 15 ++------------- 6 files changed, 17 insertions(+), 28 deletions(-) Thanks, Artem.