Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932089AbWCASni (ORCPT ); Wed, 1 Mar 2006 13:43:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932094AbWCASni (ORCPT ); Wed, 1 Mar 2006 13:43:38 -0500 Received: from mx1.suse.de ([195.135.220.2]:60612 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S932089AbWCASnh (ORCPT ); Wed, 1 Mar 2006 13:43:37 -0500 Date: Wed, 1 Mar 2006 19:43:35 +0100 From: Jan Blunck To: akpm@osdl.org Cc: dev@sw.ru, linux-kernel@vger.kernel.org Subject: [PATCH,RESUBMIT] Fix shrink_dcache_parent() against shrink_dcache_memory() race Message-ID: <20060301184335.GD31712@hasse.suse.de> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="WplhKdTI2c8ulnbP" Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4213 Lines: 151 --WplhKdTI2c8ulnbP Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Kirill Korotaev discovered a race between shrink_dcache_parent() and shrink_dcache_memory() which leads to "Busy inodes after unmount". When unmounting a file system shrink_dcache_parent() is racing against a possible shrink_dcache_memory(). This might lead to the situation that shrink_dcache_parent() is returning too early. In this situation the super_block is destroyed before shrink_dcache_memory() could put the inode. This patch fixes the problem through introducing a prunes counter which is incremented when a dentry is pruned but the corresponding inoded isn't put yet.When the prunes counter is not null, shrink_dcache_parent() is waiting and restarting its work. Signed-off-by: Jan Blunck --- --WplhKdTI2c8ulnbP Content-Type: text/x-patch; charset=us-ascii Content-Disposition: attachment; filename="umount-prune_one_dentry-fix.diff" fs/dcache.c | 38 ++++++++++++++++++++++++++++++++++++++ fs/super.c | 4 +++- include/linux/fs.h | 3 +++ 3 files changed, 44 insertions(+), 1 deletion(-) Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c +++ linux-2.6/fs/dcache.c @@ -364,17 +364,21 @@ restart: */ static inline void prune_one_dentry(struct dentry * dentry) { + struct super_block *sb = dentry->d_sb; struct dentry * parent; __d_drop(dentry); list_del(&dentry->d_u.d_child); dentry_stat.nr_dentry--; /* For d_free, below */ + sb->s_prunes++; dentry_iput(dentry); parent = dentry->d_parent; d_free(dentry); if (parent != dentry) dput(parent); spin_lock(&dcache_lock); + sb->s_prunes--; + wake_up(&sb->s_wait_prunes); } /** @@ -623,6 +627,36 @@ out: return found; } +static int wait_on_prunes(struct super_block *sb) +{ + DEFINE_WAIT(wait); + + spin_lock(&dcache_lock); + if (!sb->s_prunes) { + spin_unlock(&dcache_lock); + return 0; + } + +#ifdef DCACHE_DEBUG + printk(KERN_DEBUG "%s: waiting for %d prunes\n", __FUNCTION__, + sb->s_prunes); +#endif + + while (1) { + prepare_to_wait(&sb->s_wait_prunes, &wait, + TASK_UNINTERRUPTIBLE); + if (!sb->s_prunes) + break; + spin_unlock(&dcache_lock); + schedule(); + spin_lock(&dcache_lock); + } + + finish_wait(&sb->s_wait_prunes, &wait); + spin_unlock(&dcache_lock); + return 1; +} + /** * shrink_dcache_parent - prune dcache * @parent: parent of entries to prune @@ -634,8 +668,12 @@ void shrink_dcache_parent(struct dentry { int found; + again: while ((found = select_parent(parent)) != 0) prune_dcache(found); + + if (wait_on_prunes(parent->d_sb)) + goto again; } /** Index: linux-2.6/fs/super.c =================================================================== --- linux-2.6.orig/fs/super.c +++ linux-2.6/fs/super.c @@ -80,6 +80,8 @@ static struct super_block *alloc_super(v sema_init(&s->s_dquot.dqio_sem, 1); sema_init(&s->s_dquot.dqonoff_sem, 1); init_rwsem(&s->s_dquot.dqptr_sem); + s->s_prunes = 0; + init_waitqueue_head(&s->s_wait_prunes); init_waitqueue_head(&s->s_wait_unfrozen); s->s_maxbytes = MAX_NON_LFS; s->dq_op = sb_dquot_ops; @@ -230,8 +232,8 @@ void generic_shutdown_super(struct super if (root) { sb->s_root = NULL; - shrink_dcache_parent(root); shrink_dcache_anon(&sb->s_anon); + shrink_dcache_parent(root); dput(root); fsync_super(sb); lock_super(sb); Index: linux-2.6/include/linux/fs.h =================================================================== --- linux-2.6.orig/include/linux/fs.h +++ linux-2.6/include/linux/fs.h @@ -835,6 +835,9 @@ struct super_block { struct list_head s_instances; struct quota_info s_dquot; /* Diskquota specific options */ + unsigned int s_prunes; /* protected by dcache_lock */ + wait_queue_head_t s_wait_prunes; + int s_frozen; wait_queue_head_t s_wait_unfrozen; --WplhKdTI2c8ulnbP-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/