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Commit 2ddfbdd6 authored by Bob Peterson's avatar Bob Peterson Committed by Steven Whitehouse
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GFS2: Request demote when a "try" flock fails 



This patch changes the flock code so that it uses the TRY_1CB flag
instead of the TRY flag on the first attempt. That forces any holding
nodes to issue a dlm callback, which requests a demote of the glock.
Then, if the "try" failed, it sleeps a small amount of time for the
demote to occur. Then it tries again, for an increasing amount of time.
Subsequent attempts to gain the "try" lock don't use "_1CB" so that
only one callback is issued.

Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent b650738c

fs/gfs2/file.c

+12 −3
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#include <linux/dlm.h>

#include <linux/dlm_plock.h>

#include <linux/aio.h>

#include <linux/delay.h>



#include "gfs2.h"

#include "incore.h"
@@ -979,9 +980,10 @@ static int do_flock(struct file *file, int cmd, struct file_lock *fl) 
	unsigned int state;

	int flags;

	int error = 0;

	int sleeptime;



	state = (fl->fl_type == F_WRLCK) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;

	flags = (IS_SETLKW(cmd) ? 0 : LM_FLAG_TRY) | GL_EXACT;

	flags = (IS_SETLKW(cmd) ? 0 : LM_FLAG_TRY_1CB) | GL_EXACT;



	mutex_lock(&fp->f_fl_mutex);
@@ -1001,7 +1003,14 @@ static int do_flock(struct file *file, int cmd, struct file_lock *fl) 
		gfs2_holder_init(gl, state, flags, fl_gh);

		gfs2_glock_put(gl);

	}

	for (sleeptime = 1; sleeptime <= 4; sleeptime <<= 1) {

		error = gfs2_glock_nq(fl_gh);

		if (error != GLR_TRYFAILED)

			break;

		fl_gh->gh_flags = LM_FLAG_TRY | GL_EXACT;

		fl_gh->gh_error = 0;

		msleep(sleeptime);

	}

	if (error) {

		gfs2_holder_uninit(fl_gh);

		if (error == GLR_TRYFAILED)
@@ -1024,7 +1033,7 @@ static void do_unflock(struct file *file, struct file_lock *fl) 
	mutex_lock(&fp->f_fl_mutex);

	flock_lock_file_wait(file, fl);

	if (fl_gh->gh_gl) {

		gfs2_glock_dq_wait(fl_gh);

		gfs2_glock_dq(fl_gh);

		gfs2_holder_uninit(fl_gh);

	}

	mutex_unlock(&fp->f_fl_mutex);