Commit 209806ab authored by Steven Whitehouse's avatar Steven Whitehouse

[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

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: default avatarSteven Whitehouse <>
parent 265d529c
......@@ -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;
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