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SubjectRe: busy inodes -> ext3 umount crash
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On Wed, 2010-04-21 at 17:16 +0200, Jiri Slaby wrote:
> On 04/20/2010 05:28 PM, Jan Kara wrote:
> > On Tue 20-04-10 16:12:03, Jiri Slaby wrote:
> >> On 04/19/2010 04:33 PM, Jiri Slaby wrote:
> >>> The trigger for busy inodes is as simple as (I=initialization done only
> >>> once):
> >>> I> # dd if=/dev/zero of=/dev/shm/ext3 bs=1024 count=1 seek=$((100*1024))
> >>> I> # mkfs.ext3 -m 0 /dev/shm/ext3
> >>> # mount -oloop /dev/shm/ext3 /mnt/c
> >>> # umount /mnt/c
> >>> # dmesg|tail
> >>> VFS: Busy inodes after unmount of loop0. Self-destruct in 5 seconds.
> >>> Have a nice day...
> >>>
> >>> (The printk time varies -- this sequence really suffices.)
> >>
> >> Well, this happens only after gnome-session is started and it's fuzzy --
> >> sometimes it happens, sometimes not. I didn't find 100% trigger yet.
> > Hmph - maybe something in inotify? Dunno...
>
> fsnotify...
>
> >>>> So if you can easily reproduce
> >>>> the "busy inodes" message then I'd start with debugging that one. Do you
> >>>> see it also with vanilla kernels?
> >>
> >> Vanilla seems not to be affected. It's in next/master already though
> >> (2603ecd9). I'll investigate it further later.
> > Do you mean it's in today's linux-next but not in Linus' tree?
>
> Yes, exactly.
>
> And the winner is (seemingly):
> commit 69c1182c4e5d8b7da772ddad512c6f6b67ec1bb8
> Author: Eric Paris <eparis@redhat.com>
> Date: Thu Dec 17 21:24:27 2009 -0500
>
> fsnotify: vfsmount marks generic functions
>
> Much like inode-mark.c has all of the code dealing with marks on inodes
> this patch adds a vfsmount-mark.c which has similar code but is intended
> for marks on vfsmounts.
>
> Signed-off-by: Eric Paris <eparis@redhat.com>

Surprised noone else ever hit this, it's been broken for a LONG time. In
any case I'll have this in the next time he pushes a -next.

-Eric


commit bf770d242d100882891ac60e42f2cf0096fc3f3c
Author: Eric Paris <eparis@redhat.com>
Date: Wed Apr 21 16:49:38 2010 -0400

fsnotify: add iput on inodes when no longer marked

fsnotify takes an igrab on an inode when it adds a mark. The code was
supposed to drop the reference when the mark was removed. The problem
was that what actually happened was below

void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
{
...
mark->inode = NULL;
...
}

void fsnotify_destroy_mark(struct fsnotify_mark *mark)
{
struct inode *inode = NULL;
...
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
fsnotify_destroy_inode_mark(mark);
inode = mark->i.inode;
}
...
if (inode)
iput(inode);
...
}

Obviously the intent was to capture the inode before it was set to NULL in
fsnotify_destory_inode_mark().

Signed-off-by: Eric Paris <eparis@redhat.com>

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 1e824e6..8f3b0e7 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -133,8 +133,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
spin_lock(&group->mark_lock);

if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
- fsnotify_destroy_inode_mark(mark);
inode = mark->i.inode;
+ fsnotify_destroy_inode_mark(mark);
} else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
fsnotify_destroy_vfsmount_mark(mark);
else



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