From: NeilBrown Date: Mon, 13 Oct 2014 22:52:14 +0000 (-0700) Subject: autofs4: allow RCU-walk to walk through autofs4 X-Git-Tag: fixes-against-v3.18-rc2~79^2~99 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=23bfc2a24ea3d993cc5cc90c9970654e7232502e;p=pandora-kernel.git autofs4: allow RCU-walk to walk through autofs4 This series teaches autofs about RCU-walk so that we don't drop straight into REF-walk when we hit an autofs directory, and so that we avoid spinlocks as much as possible when performing an RCU-walk. This is needed so that the benefits of the recent NFS support for RCU-walk are fully available when NFS filesystems are automounted. Patches have been carefully reviewed and tested both with test suites and in production - thanks a lot to Ian Kent for his support there. This patch (of 6): Any attempt to look up a pathname that passes though an autofs4 mount is currently forced out of RCU-walk into REF-walk. This can significantly hurt performance of many-thread work loads on many-core systems, especially if the automounted filesystem supports RCU-walk but doesn't get to benefit from it. So if autofs4_d_manage is called with rcu_walk set, only fail with -ECHILD if it is necessary to wait longer than a spinlock. Signed-off-by: NeilBrown Reviewed-by: Ian Kent Tested-by: Ian Kent Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed