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Bob Peterson 04-10-2012 06:13 PM

GFS2: Instruct DLM to avoid queue convert slowdown
 
Hi,

Here is my revised patch based on Steve's suggestion to base the
flag on the recent GLF_BLOCKING flag.

We still need to keep this on hold until the prerequisite dlm patch
is properly upstream.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
Author: Bob Peterson <rpeterso@redhat.com>
Date: Tue Apr 10 14:08:11 2012 -0500

GFS2: Instruct DLM to avoid queue convert slowdowns

This patch instructs DLM to prevent an "in place" conversion, where the
lock just stays on the granted queue, and instead forces the conversion to
the back of the convert queue. This is done on upward conversions only.

This is useful in cases where, for example, a lock is frequently needed in
PR on one node, but another node needs it temporarily in EX to update it.
This may happen, for example, when the rindex is being updated by gfs2_grow.
The gfs2_grow needs to have the lock in EX, but the other nodes need to
re-read it to retrieve the updates. The glock is already granted in PR on
the non-growing nodes, so this prevents them from continually re-granting
the lock in PR, and forces the EX from gfs2_grow to go through.

diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index f8411bd..ed9c5ca 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -200,11 +200,15 @@ static int make_mode(const unsigned int lmstate)
return -1;
}

-static u32 make_flags(const u32 lkid, const unsigned int gfs_flags,
+static u32 make_flags(struct gfs2_glock *gl, const unsigned int gfs_flags,
const int req)
{
u32 lkf = DLM_LKF_VALBLK;
+ u32 lkid = gl->gl_lksb.sb_lkid;
+ int is_upconvert = 0;

+ if (test_bit(GLF_BLOCKING, &gl->gl_flags))
+ is_upconvert = 1;
if (gfs_flags & LM_FLAG_TRY)
lkf |= DLM_LKF_NOQUEUE;

@@ -227,8 +231,11 @@ static u32 make_flags(const u32 lkid, const unsigned int gfs_flags,
BUG();
}

- if (lkid != 0)
+ if (lkid != 0) {
lkf |= DLM_LKF_CONVERT;
+ if (is_upconvert)
+ lkf |= DLM_LKF_QUECVT;
+ }

return lkf;
}
@@ -250,7 +257,7 @@ static int gdlm_lock(struct gfs2_glock *gl, unsigned int req_state,
char strname[GDLM_STRNAME_BYTES] = "";

req = make_mode(req_state);
- lkf = make_flags(gl->gl_lksb.sb_lkid, flags, req);
+ lkf = make_flags(gl, flags, req);
gfs2_glstats_inc(gl, GFS2_LKS_DCOUNT);
gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
if (gl->gl_lksb.sb_lkid) {


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