From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga02.intel.com ([134.134.136.20]) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1SRRE7-0005jA-UA for linux-mtd@lists.infradead.org; Mon, 07 May 2012 16:56:00 +0000 From: Artem Bityutskiy To: David Woodhouse , MTD Maling List Subject: [PATCH v2 0/4] do not use s_dirt in JFFS2 Date: Mon, 7 May 2012 19:56:49 +0300 Message-Id: <1336409813-6365-1-git-send-email-dedekind1@gmail.com> Cc: Linux Kernel Maling List List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , This is the second version for the patch-set which makes JFFS2 file-system stop using the VFS '->write_supers()' call-back because I plan to remove it once all users are gone. Comparing to the previous version I gave up on using a special inode for JFFS2 because it introduces unnecessary overhead: currently JFFS2 does not register '->write_super()' at all, and if we register it for the sake of a single fake inode - it will be called for all inodes, which is unnecessary. So in this version I am using a delayed work for scheduling write-buffer flushing. v1: https://lkml.org/lkml/2012/4/11/147 The final 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, some 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. The '->write_supers()' method is mostly used by baroque file-systems like hfs, udf, etc. Modern file-systems like btrfs and xfs do not use it. This justifies removing this stuff from VFS completely and make every FS self-manage own superblock. Note: in the past I was trying to upstream patches which optimized 'sync_super()', but Al Viro wanted me to kill it completely instead, which I am trying to do now, see http://lkml.org/lkml/2010/7/22/96 fs/jffs2/jffs2_fs_sb.h | 4 +++ fs/jffs2/os-linux.h | 7 +---- fs/jffs2/super.c | 21 ------------------ fs/jffs2/wbuf.c | 55 +++++++++++++++++++++++++++++++++++++++++++++-- 4 files changed, 58 insertions(+), 29 deletions(-) Tested using fsstress on both nandsim and mtdram. ====== Overall status: 1. ext4: patches submitted, waiting for reply from Ted Ts'o: https://lkml.org/lkml/2012/4/2/111 Ted keeps silence so far WRT the fate of this patch-set. 2. ext2: patches are in the ext2 tree maintained by Jan Kara: git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next 3. Version 3 of FAT FS changes were sent to Andrew and Hirofumi: https://lkml.org/lkml/2012/5/4/183 4. JFFS2 patches version 3 are sent being sent now. TODO: affs, exofs, hfs, hfsplus, reiserfs, sysv, udf, ufs ====== Thanks, Artem.