From: Jan Kara Subject: Re: [PATCHv4 3/5] ext4: remove unnecessary superblock dirtying Date: Wed, 4 Jul 2012 15:11:24 +0200 Message-ID: <20120704131124.GA29954@quack.suse.cz> References: <1341404514-13660-1-git-send-email-dedekind1@gmail.com> <1341404514-13660-4-git-send-email-dedekind1@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Tso , Jan Kara , Linux FS Maling List , Linux Kernel Maling List , Ext4 Mailing List To: Artem Bityutskiy Return-path: Received: from cantor2.suse.de ([195.135.220.15]:36721 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751004Ab2GDNL1 (ORCPT ); Wed, 4 Jul 2012 09:11:27 -0400 Content-Disposition: inline In-Reply-To: <1341404514-13660-4-git-send-email-dedekind1@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed 04-07-12 15:21:52, Artem Bityutskiy wrote: > From: Artem Bityutskiy > > This patch changes the '__ext4_handle_dirty_super()' function which is used > by ext4 to update the superblock via the journal in the following cases: > > 1. When creating the first large file on a file system without > EXT4_FEATURE_RO_COMPAT_LARGE_FILE feature. > 2. When re-sizing the file-system. > 3. When creating an xattr on a file-system without the > EXT4_FEATURE_COMPAT_EXT_ATTR feature. > 4. When adding or deleting an orphan (because we update the 's_last_orphan' > superblock field). > > This function, however, falls back to just marking the superblock as dirty > if the file-system has no journal. This means that we delay the actual > superblock I/O submission by 5 seconds (roughly speaking). Namely, the > 'sync_supers()' kernel thread will call 'ext4_write_super()' later, where > we actually will submit the superblock down to the media. > > However: > 1. For cases 1-3 it does not add any value to delay the I/O submission. These > events are rare and we may just commit submit the superblock for > asynchronous I/O right away. > 2. For case 4 - similarly, not terribly frequent event in most of workloads. > It should be good enough to just submit asynchronous superblock write-out. Well, it happens for every inode being truncated / deleted to it can be rather frequent. That's why I wanted to have now == 1 case everywhere - i.e. just recompute the checksum and do mark_buffer_dirty(). I'd just remove the 'now' test in this patch and then in patch 5 remove the now argument from the function and callers as you did. Honza > > This patch also removes 's_dirt' condition on the unmount path because we never > set it anymore, so we should not test it. > > Tested using xfstests for both journalled and non-journalled ext4. > > Signed-off-by: Artem Bityutskiy > --- > fs/ext4/ext4.h | 1 + > fs/ext4/ext4_jbd2.c | 2 +- > fs/ext4/super.c | 5 ++--- > 3 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index 0c4042e..b2439d5 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -2041,6 +2041,7 @@ extern int ext4_superblock_csum_verify(struct super_block *sb, > struct ext4_super_block *es); > extern void ext4_superblock_csum_set(struct super_block *sb, > struct ext4_super_block *es); > +extern int ext4_commit_super(struct super_block *sb, int sync); > extern void *ext4_kvmalloc(size_t size, gfp_t flags); > extern void *ext4_kvzalloc(size_t size, gfp_t flags); > extern void ext4_kvfree(void *ptr); > diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c > index 90f7c2e..27354df 100644 > --- a/fs/ext4/ext4_jbd2.c > +++ b/fs/ext4/ext4_jbd2.c > @@ -156,6 +156,6 @@ int __ext4_handle_dirty_super(const char *where, unsigned int line, > (struct ext4_super_block *)bh->b_data); > mark_buffer_dirty(bh); > } else > - sb->s_dirt = 1; > + err = ext4_commit_super(sb, 0); > return err; > } > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index eb7aa3e..9b26ba0 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -63,7 +63,6 @@ static struct ext4_features *ext4_feat; > static int ext4_load_journal(struct super_block *, struct ext4_super_block *, > unsigned long journal_devnum); > static int ext4_show_options(struct seq_file *seq, struct dentry *root); > -static int ext4_commit_super(struct super_block *sb, int sync); > static void ext4_mark_recovery_complete(struct super_block *sb, > struct ext4_super_block *es); > static void ext4_clear_journal_err(struct super_block *sb, > @@ -896,7 +895,7 @@ static void ext4_put_super(struct super_block *sb) > EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); > es->s_state = cpu_to_le16(sbi->s_mount_state); > } > - if (sb->s_dirt || !(sb->s_flags & MS_RDONLY)) > + if (!(sb->s_flags & MS_RDONLY)) > ext4_commit_super(sb, 1); > > if (sbi->s_proc) { > @@ -4155,7 +4154,7 @@ static int ext4_load_journal(struct super_block *sb, > return 0; > } > > -static int ext4_commit_super(struct super_block *sb, int sync) > +int ext4_commit_super(struct super_block *sb, int sync) > { > struct ext4_super_block *es = EXT4_SB(sb)->s_es; > struct buffer_head *sbh = EXT4_SB(sb)->s_sbh; > -- > 1.7.7.6 > -- Jan Kara SUSE Labs, CR