On Mon, 11 Apr 2005, Jeff Moyer wrote:
> ==> Regarding [PATCH 1/3] autofs4 - expiring filesystem from under process;
> [EMAIL PROTECTED] adds:
>
> Could also please explain how the following is handled:
>
> expire process runs and issues AUTOFS_EXPIRE_MULTI, which sets
> AUTOFS_INF_EXPIRING in flags. While the expire is in progress, another
> process access the directory in question, causing a call to
> try_to_fill_dentry. try_to_fill_dentry sees the AUTOFS_INF_EXPIRING flag
> is set, and so calls autofs4_wait with notify set to NFY_NONE. However,
> when we take the wq sem, we find that the expire has finished, and thus
> create a new wq entry. Because NFY_NONE is set, we don't tell the daemon.
>
> So how will this process ever get woken up?
>
I've thought about this for quite a while and I think all that's needed is
to recognise that we're about to expire a dentry that's not mounted
anymore.
Can you think of a case for which this patch fails?
Ian
--- linux-2.6.12-rc2-mm3/fs/autofs4/waitq.c.post-expire-race 2005-04-20
22:07:32.000000000 +0800
+++ linux-2.6.12-rc2-mm3/fs/autofs4/waitq.c 2005-04-20 22:08:29.000000000
+0800
@@ -191,6 +191,13 @@ int autofs4_wait(struct autofs_sb_info *
}
if ( !wq ) {
+ /* Can't expire if we are not mounted */
+ if (notify == NFY_EXPIRE && !d_mountpoint(dentry)) {
+ kfree(name);
+ up(&sbi->wq_sem);
+ return -ENOENT;
+ }
+
/* Create a new wait queue */
wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
if ( !wq ) {
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