Neil,
On Thursday March 9, [email protected] wrote:
Andrew,
Acked-By: Kirill Korotaev <[email protected]>
I'm afraid that I'm not convinced.
+static int wait_on_prunes(struct super_block *sb)
+{
+ DEFINE_WAIT(wait);
+ int prunes_remaining = 0;
+
+#ifdef DCACHE_DEBUG
+ printk(KERN_DEBUG "%s: waiting for %d prunes\n", __FUNCTION__,
+ sb->s_prunes);
+#endif
+
+ spin_lock(&dcache_lock);
+ for (;;) {
+ prepare_to_wait(&sb->s_wait_prunes, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (!sb->s_prunes)
+ break;
+ spin_unlock(&dcache_lock);
+ schedule();
+ prunes_remaining = 1;
+ spin_lock(&dcache_lock);
+ }
+ spin_unlock(&dcache_lock);
+ finish_wait(&sb->s_wait_prunes, &wait);
+ return prunes_remaining;
+}
I don't think that a return value from wait_on_prunes is meaningful.
All it tells us is whether a prune_one_dentry finished before or after
wait_on_prunes takes the spin_lock. This isn't very useful
information as it has no significance to upper levels.
So:
+ do {
+ shrink_dcache_parent(root);
+ } while(wait_on_prunes(sb));
+
Suppose shrink_dcache_parent misses on dentry because the inode was being
iput. This iput completes immediately that
shrink_dcache_parent completes. It decrements ->s_prunes and when
wait_on_prunes takes dcache_lock, ->s_prunes is zero so the loop
terminates, and the remaining dentries - the parents of the dentry
what was undergoing iput - don't get put.
you are right... :/
And this is actually why we originally inserted check for race
in select_parent() under dcache_lock... I just lost my memory :(
I really think that we need to stop prune_one_dentry from being called
on dentries for a filesystem that is being unmounted. With that code
currently in -git, that means passing a 'struct super_block *' into
prune_dcache so that it ignores any filesystem with ->s_root==NULL
unless that filesystem is the filesystem that was passed.
Can try...
Thanks,
Kirill
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