4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Al Viro viro@ZenIV.linux.org.uk
commit 81be24d263dbeddaba35827036d6f6787a59c2c3 upstream.
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 viro@zeniv.linux.org.uk Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/dcache.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
--- a/fs/dcache.c +++ b/fs/dcache.c @@ -1510,7 +1510,7 @@ 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); }
@@ -1552,17 +1552,15 @@ 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(); } }