Re: 2.6.9-rc2-mm2

Nick Piggin
2004-09-23T03:01:12Z

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Andrew Morton wrote:
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.9-rc2/2.6.9-rc2-mm2/
>

fs/dcache.c:select_parent()
{
...
/*
* select_parent() is a performance optimization, it is
* not necessary to complete it. Abort if a reschedule is
* pending:
*/
if (need_resched())
goto out;
...
}

This one came back. It is the
VFS: Busy inodes after unmount. Self-destruct in 5 seconds. Have a nice day...
thing.

Attached is a fix.

[-- Attachment #2: sched-vfs-fix.patch --]
[-- Type: text/x-patch, Size: 1743 bytes --]

---

linux-2.6-npiggin/fs/dcache.c | 26 +++++++++++++++++---------
1 files changed, 17 insertions(+), 9 deletions(-)

diff -puN fs/dcache.c~sched-vfs-fix fs/dcache.c
--- linux-2.6/fs/dcache.c~sched-vfs-fix 2004-09-23 12:53:04.000000000 +1000
+++ linux-2.6-npiggin/fs/dcache.c 2004-09-23 12:59:25.000000000 +1000
@@ -156,7 +156,7 @@ repeat:
spin_unlock(&dcache_lock);
return;
}
-
+
/*
* AV: ->d_delete() is _NOT_ allowed to block now.
*/
@@ -540,6 +540,13 @@ positive:
* list for prune_dcache(). We descend to the next level
* whenever the d_subdirs list is non-empty and continue
* searching.
+ *
+ * It returns zero iff there are no unused children,
+ * otherwise it returns the number of children moved to
+ * the end of the unused list. This may not be the total
+ * number of unused children, because select_parent can
+ * drop the lock and return early due to latency
+ * constraints.
*/
static int select_parent(struct dentry * parent)
{
@@ -556,14 +563,6 @@ resume:
struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
next = tmp->next;

- /*
- * select_parent() is a performance optimization, it is
- * not necessary to complete it. Abort if a reschedule is
- * pending:
- */
- if (need_resched())
- goto out;
-
if (!list_empty(&dentry->d_lru)) {
dentry_stat.nr_unused--;
list_del_init(&dentry->d_lru);
@@ -577,6 +576,15 @@ resume:
dentry_stat.nr_unused++;
found++;
}
+
+ /*
+ * We can return to the caller if we have found some (this
+ * ensures forward progress). We'll be coming back to find
+ * the rest.
+ */
+ if (found && need_resched())
+ goto out;
+
/*
* Descend a level if the d_subdirs list is non-empty.
*/

_