From 81be24d263dbeddaba35827036d6f6787a59c2c3 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 3 Jun 2017 07:20:09 +0100 Subject: [PATCH] Hang/soft lockup in d_invalidate with simultaneous calls It's not hard to trigger a bunch of d_invalidate() on the same dentry in parallel. They end up fighting each other - any dentry picked for removal by one will be skipped by the rest and we'll go for the next iteration through the entire subtree, even if everything is being skipped. Morevoer, we immediately go back to scanning the subtree. The only thing we really need is to dissolve all mounts in the subtree and as soon as we've nothing left to do, we can just unhash the dentry and bugger off. Signed-off-by: Al Viro --- fs/dcache.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index cddf39777835..a9f995f6859e 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1494,7 +1494,7 @@ static void check_and_drop(void *_data) { struct detach_data *data = _data; - if (!data->mountpoint && !data->select.found) + if (!data->mountpoint && list_empty(&data->select.dispose)) __d_drop(data->select.start); } @@ -1536,17 +1536,15 @@ void d_invalidate(struct dentry *dentry) d_walk(dentry, &data, detach_and_collect, check_and_drop); - if (data.select.found) + if (!list_empty(&data.select.dispose)) shrink_dentry_list(&data.select.dispose); + else if (!data.mountpoint) + return; if (data.mountpoint) { detach_mounts(data.mountpoint); dput(data.mountpoint); } - - if (!data.mountpoint && !data.select.found) - break; - cond_resched(); } }