From: Carlos Maiolino Subject: Re: [PATCH] fs: allow for fs-specific objects to be pruned as part of pruning inodes Date: Wed, 23 Jan 2013 08:06:35 -0500 Message-ID: <20130123130635.GB1423@localhost.localdomain> References: <20130121170937.GB15473@gmail.com> <1358921168-30921-1-git-send-email-tytso@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ext4 Developers List , gnehzuil.liu@gmail.com, linux-fsdevel@vger.kernel.org To: "Theodore Ts'o" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:28831 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755062Ab3AWNGl (ORCPT ); Wed, 23 Jan 2013 08:06:41 -0500 Content-Disposition: inline In-Reply-To: <1358921168-30921-1-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Looks good to me: Reviewed-by: Carlos Maiolino On Wed, Jan 23, 2013 at 01:06:08AM -0500, Theodore Ts'o wrote: > The VFS's prune_super() function allows for the file system to prune > file-system specific objects. Ext4 would like to use this to prune > parts of the inode's extent cache. The object lifetime rules used by > ext4 is somewhat different from the those of the dentry and inode in > the VFS. Ext4's extent cache objects can be pruned without removing > the inode; however if an inode is pruned, all of the extent cache > objects associated with the inode are immediately removed. > > To accomodate this rule, we measure the number of fs-specific objects > before the dentry and inodes are pruned, and then measure them again > afterwards. If the number of fs-specific objects have decreased, we > credit that decrease as part of the shrink operation, so that we do > not end up removing too many fs-specific objects. > > In the case where fs-specific objects are not removed when inodes are > removed, this will not change the behavior of prune_super() in any > appreciable way. (Currently the only other user of this facility is > XFS, and this change should not affect XFS's usage of this facility > for this reason.) > > Signed-off-by: "Theodore Ts'o" > Cc: linux-fsdevel@vger.kernel.org > --- > fs/super.c | 22 +++++++++++++++++++--- > 1 file changed, 19 insertions(+), 3 deletions(-) > > diff --git a/fs/super.c b/fs/super.c > index 12f1237..fb57bd2 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -80,6 +80,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) > if (sc->nr_to_scan) { > int dentries; > int inodes; > + int fs_to_scan = 0; > > /* proportion the scan between the caches */ > dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / > @@ -87,7 +88,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) > inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) / > total_objects; > if (fs_objects) > - fs_objects = (sc->nr_to_scan * fs_objects) / > + fs_to_scan = (sc->nr_to_scan * fs_objects) / > total_objects; > /* > * prune the dcache first as the icache is pinned by it, then > @@ -96,8 +97,23 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) > prune_dcache_sb(sb, dentries); > prune_icache_sb(sb, inodes); > > - if (fs_objects && sb->s_op->free_cached_objects) { > - sb->s_op->free_cached_objects(sb, fs_objects); > + /* > + * If as a result of pruning the icache, we released some > + * of the fs_objects, give credit to the fact and > + * reduce the number of fs objects that we should try > + * to release. > + */ > + if (fs_to_scan) { > + int fs_objects_now = sb->s_op->nr_cached_objects(sb); > + > + if (fs_objects_now < fs_objects) > + fs_to_scan -= fs_objects - fs_objects_now; > + if (fs_to_scan < 0) > + fs_to_scan = 0; > + } > + > + if (fs_to_scan && sb->s_op->free_cached_objects) { > + sb->s_op->free_cached_objects(sb, fs_to_scan); > fs_objects = sb->s_op->nr_cached_objects(sb); > } > total_objects = sb->s_nr_dentry_unused + > -- > 1.7.12.rc0.22.gcdd159b > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Carlos