Patch "more graceful recovery in umount_collect()" has been added to the 3.14-stable tree

Patch "more graceful recovery in umount_collect()" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    more graceful recovery in umount_collect()

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     more-graceful-recovery-in-umount_collect.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9c8c10e262e0f62cb2530f1b076de979123183dd Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Fri, 2 May 2014 20:36:10 -0400
Subject: more graceful recovery in umount_collect()

From: Al Viro <viro@zeniv.linux.org.uk>

commit 9c8c10e262e0f62cb2530f1b076de979123183dd upstream.

Start with shrink_dcache_parent(), then scan what remains.

First of all, BUG() is very much an overkill here; we are holding
->s_umount, and hitting BUG() means that a lot of interesting stuff
will be hanging after that point (sync(2), for example).  Moreover,
in cases when there had been more than one leak, we'll be better
off reporting all of them.  And more than just the last component
of pathname - %pd is there for just such uses...

That was the last user of dentry_lru_del(), so kill it off...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/dcache.c |  101 ++++++++++++++----------------------------------------------
 1 file changed, 25 insertions(+), 76 deletions(-)

--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -393,22 +393,6 @@ static void dentry_lru_add(struct dentry
 		d_lru_add(dentry);
 }
 
-/*
- * Remove a dentry with references from the LRU.
- *
- * If we are on the shrink list, then we can get to try_prune_one_dentry() and
- * lose our last reference through the parent walk. In this case, we need to
- * remove ourselves from the shrink list, not the LRU.
- */
-static void dentry_lru_del(struct dentry *dentry)
-{
-	if (dentry->d_flags & DCACHE_LRU_LIST) {
-		if (dentry->d_flags & DCACHE_SHRINK_LIST)
-			return d_shrink_del(dentry);
-		d_lru_del(dentry);
-	}
-}
-
 /**
  * d_drop - drop a dentry
  * @dentry: dentry to drop
@@ -1277,45 +1261,35 @@ void shrink_dcache_parent(struct dentry
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
 
-static enum d_walk_ret umount_collect(void *_data, struct dentry *dentry)
+static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
 {
-	struct select_data *data = _data;
-	enum d_walk_ret ret = D_WALK_CONTINUE;
+	/* it has busy descendents; complain about those instead */
+	if (!list_empty(&dentry->d_subdirs))
+		return D_WALK_CONTINUE;
+
+	/* root with refcount 1 is fine */
+	if (dentry == _data && dentry->d_lockref.count == 1)
+		return D_WALK_CONTINUE;
 
-	if (dentry->d_lockref.count) {
-		dentry_lru_del(dentry);
-		if (likely(!list_empty(&dentry->d_subdirs)))
-			goto out;
-		if (dentry == data->start && dentry->d_lockref.count == 1)
-			goto out;
-		printk(KERN_ERR
-		       "BUG: Dentry %p{i=%lx,n=%s}"
-		       " still in use (%d)"
-		       " [unmount of %s %s]\n",
+	printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
+			" still in use (%d) [unmount of %s %s]\n",
 		       dentry,
 		       dentry->d_inode ?
 		       dentry->d_inode->i_ino : 0UL,
-		       dentry->d_name.name,
+		       dentry,
 		       dentry->d_lockref.count,
 		       dentry->d_sb->s_type->name,
 		       dentry->d_sb->s_id);
-		BUG();
-	} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
-		/*
-		 * We can't use d_lru_shrink_move() because we
-		 * need to get the global LRU lock and do the
-		 * LRU accounting.
-		 */
-		if (dentry->d_flags & DCACHE_LRU_LIST)
-			d_lru_del(dentry);
-		d_shrink_add(dentry, &data->dispose);
-		data->found++;
-		ret = D_WALK_NORETRY;
-	}
-out:
-	if (data->found && need_resched())
-		ret = D_WALK_QUIT;
-	return ret;
+	WARN_ON(1);
+	return D_WALK_CONTINUE;
+}
+
+static void do_one_tree(struct dentry *dentry)
+{
+	shrink_dcache_parent(dentry);
+	d_walk(dentry, dentry, umount_check, NULL);
+	d_drop(dentry);
+	dput(dentry);
 }
 
 /*
@@ -1325,40 +1299,15 @@ void shrink_dcache_for_umount(struct sup
 {
 	struct dentry *dentry;
 
-	if (down_read_trylock(&sb->s_umount))
-		BUG();
+	WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
 
 	dentry = sb->s_root;
 	sb->s_root = NULL;
-	for (;;) {
-		struct select_data data;
-
-		INIT_LIST_HEAD(&data.dispose);
-		data.start = dentry;
-		data.found = 0;
-
-		d_walk(dentry, &data, umount_collect, NULL);
-		if (!data.found)
-			break;
-
-		shrink_dentry_list(&data.dispose);
-		cond_resched();
-	}
-	d_drop(dentry);
-	dput(dentry);
+	do_one_tree(dentry);
 
 	while (!hlist_bl_empty(&sb->s_anon)) {
-		struct select_data data;
-		dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
-
-		INIT_LIST_HEAD(&data.dispose);
-		data.start = NULL;
-		data.found = 0;
-
-		d_walk(dentry, &data, umount_collect, NULL);
-		if (data.found)
-			shrink_dentry_list(&data.dispose);
-		cond_resched();
+		dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash));
+		do_one_tree(dentry);
 	}
 }
 


Patches currently in stable-queue which might be from viro@zeniv.linux.org.uk are

queue-3.14/new-helper-dentry_free.patch
queue-3.14/don-t-remove-from-shrink-list-in-select_collect.patch
queue-3.14/fold-try_prune_one_dentry.patch
queue-3.14/more-graceful-recovery-in-umount_collect.patch
queue-3.14/expand-the-call-of-dentry_lru_del-in-dentry_kill.patch
queue-3.14/dcache-don-t-need-rcu-in-shrink_dentry_list.patch
queue-3.14/path_openat-fix-double-fput.patch
queue-3.14/fold-d_kill-and-d_free.patch
queue-3.14/ipc-modify-message-queue-accounting-to-not-take-kernel-data-structures-into-account.patch
queue-3.14/dentry_kill-don-t-try-to-remove-from-shrink-list.patch
queue-3.14/sg_start_req-make-sure-that-there-s-not-too-many-elements-in-iovec.patch