On 02/08/2011 06:57 PM, Aneesh Kumar K. V wrote: > On Mon, 07 Feb 2011 15:14:40 +0200, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: >> On 02/05/2011 11:01 AM, Tao Ma wrote: >>> From: Tao Ma <boyu.mt@xxxxxxxxxx> >>> >>> In fa0d7e3, we use rcu free inode instead of freeing the inode >>> directly. It causes a problem when we rmmod immediately after >>> we umount the volume[1]. >>> >>> So we need to call synchronize_rcu after we kill_sb so that >>> the inode is freed before we do rmmod. The idea is inspired >>> by Chris Mason[2]. I tested with ext4 by umount+rmmod and it >>> doesn't show any error by now. >>> >>> 1. http://marc.info/?l=linux-fsdevel&m=129680863330185&w=2 >>> 2. http://marc.info/?l=linux-fsdevel&m=129684698713709&w=2 >>> >>> Cc: Nick Piggin <npiggin@xxxxxxxxx> >>> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> >>> Cc: Chris Mason <chris.mason@xxxxxxxxxx> >>> Cc: Boaz Harrosh <bharrosh@xxxxxxxxxxx> >>> Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx> >>> --- >>> fs/super.c | 7 +++++++ >>> 1 files changed, 7 insertions(+), 0 deletions(-) >>> >>> diff --git a/fs/super.c b/fs/super.c >>> index 74e149e..315bce9 100644 >>> --- a/fs/super.c >>> +++ b/fs/super.c >>> @@ -177,6 +177,13 @@ void deactivate_locked_super(struct super_block *s) >>> struct file_system_type *fs = s->s_type; >>> if (atomic_dec_and_test(&s->s_active)) { >>> fs->kill_sb(s); >>> + /* >>> + * We need to synchronize rcu here so that >>> + * the delayed rcu inode free can be executed >>> + * before we put_super. >>> + * https://bugzilla.kernel.org/show_bug.cgi?id=27652 >>> + */ >>> + synchronize_rcu(); >>> put_filesystem(fs); >>> put_super(s); >>> } else { >> >> <> > > http://lwn.net/Articles/217484/ explains how to wait for rcu callback to finish > > -aneesh Yes thanks Aneesh, rcu_barrier does the trick --- From: Boaz Harrosh <bharrosh@xxxxxxxxxxx> In fa0d7e3, we use rcu free inode instead of freeing the inode directly. It causes a problem when we rmmod immediately after we umount the volume[1]. So we need to call rcu_barrier after we kill_sb so that the inode is freed before we do rmmod. The idea is inspired by Aneesh Kumar. rcu_barrier will wait for all callbacks to end before preceding. The original patch was done by Tao Ma, but synchronize_rcu() is not enough here. 1. http://marc.info/?l=linux-fsdevel&m=129680863330185&w=2 2. http://marc.info/?l=linux-fsdevel&m=129684698713709&w=2 Cc: Nick Piggin <npiggin@xxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Chris Mason <chris.mason@xxxxxxxxxx> Cc: Tao Ma <boyu.mt@xxxxxxxxxx> Signed-off-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx> --- git diff --stat -p -M fs/super.c fs/super.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/fs/super.c b/fs/super.c index 74e149e..5fd4ec9 100644 --- a/fs/super.c +++ b/fs/super.c @@ -177,6 +177,13 @@ void deactivate_locked_super(struct super_block *s) struct file_system_type *fs = s->s_type; if (atomic_dec_and_test(&s->s_active)) { fs->kill_sb(s); + /* + * We need to synchronize rcu here so that + * the delayed rcu inode free can be executed + * before we put_super. + * https://bugzilla.kernel.org/show_bug.cgi?id=27652 + */ + rcu_barrier(); put_filesystem(fs); put_super(s); } else { -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
