From 209806aba9d540dde3db0a5ce72307f85f33468f Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Mon, 7 Jul 2008 10:07:28 +0100 Subject: [PATCH] [GFS2] Allow local DF locks when holding a cached EX glock We already allow local SH locks while we hold a cached EX glock, so here we allow DF locks as well. This works only because we rely on the VFS's invalidation for locally cached data, and because if we hold an EX lock, then we know that no other node can be caching data relating to this file. It dramatically speeds up initial writes to O_DIRECT files since we fall back to buffered I/O for this and would otherwise bounce between DF and EX modes on each and every write call. The lessons to be learned from that are to ensure that (for the time being anyway) O_DIRECT files are preallocated and that they are written to using reasonably large I/O sizes. Even so this change fixes that corner case nicely Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index cd0aa213fb..13391e5466 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -267,8 +267,12 @@ static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holde return 1; if (gh->gh_flags & GL_EXACT) return 0; - if (gh->gh_state == LM_ST_SHARED && gl->gl_state == LM_ST_EXCLUSIVE) - return 1; + if (gl->gl_state == LM_ST_EXCLUSIVE) { + if (gh->gh_state == LM_ST_SHARED && gh_head->gh_state == LM_ST_SHARED) + return 1; + if (gh->gh_state == LM_ST_DEFERRED && gh_head->gh_state == LM_ST_DEFERRED) + return 1; + } if (gl->gl_state != LM_ST_UNLOCKED && (gh->gh_flags & LM_FLAG_ANY)) return 1; return 0; -- 2.39.5