From 26bb7505cf7db3560286be9f6384b6d3911f78b5 Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Fri, 27 Nov 2009 10:31:11 +0000 Subject: [PATCH] GFS2: Fix glock refcount issues This patch fixes some ref counting issues. Firstly by moving the point at which we drop the ref count after a dlm lock operation has completed we ensure that we never call gfs2_glock_hold() on a lock with a zero ref count. Secondly, by using atomic_dec_and_lock() in gfs2_glock_put() we ensure that at no time will a glock with zero ref count appear on the lru_list. That means that we can remove the check for this in our shrinker (which was racy). Signed-off-by: Steven Whitehouse --- fs/gfs2/glock.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index a3f90ad2af80..f455a03a09e2 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -241,15 +241,14 @@ int gfs2_glock_put(struct gfs2_glock *gl) int rv = 0; write_lock(gl_lock_addr(gl->gl_hash)); - if (atomic_dec_and_test(&gl->gl_ref)) { + if (atomic_dec_and_lock(&gl->gl_ref, &lru_lock)) { hlist_del(&gl->gl_list); - write_unlock(gl_lock_addr(gl->gl_hash)); - spin_lock(&lru_lock); if (!list_empty(&gl->gl_lru)) { list_del_init(&gl->gl_lru); atomic_dec(&lru_count); } spin_unlock(&lru_lock); + write_unlock(gl_lock_addr(gl->gl_hash)); GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders)); glock_free(gl); rv = 1; @@ -513,7 +512,6 @@ retry: GLOCK_BUG_ON(gl, 1); } spin_unlock(&gl->gl_spin); - gfs2_glock_put(gl); return; } @@ -524,8 +522,6 @@ retry: if (glops->go_xmote_bh) { spin_unlock(&gl->gl_spin); rv = glops->go_xmote_bh(gl, gh); - if (rv == -EAGAIN) - return; spin_lock(&gl->gl_spin); if (rv) { do_error(gl, rv); @@ -540,7 +536,6 @@ out: clear_bit(GLF_LOCK, &gl->gl_flags); out_locked: spin_unlock(&gl->gl_spin); - gfs2_glock_put(gl); } static unsigned int gfs2_lm_lock(struct gfs2_sbd *sdp, void *lock, @@ -600,7 +595,6 @@ __acquires(&gl->gl_spin) if (!(ret & LM_OUT_ASYNC)) { finish_xmote(gl, ret); - gfs2_glock_hold(gl); if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) gfs2_glock_put(gl); } else { @@ -712,9 +706,12 @@ static void glock_work_func(struct work_struct *work) { unsigned long delay = 0; struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_work.work); + int drop_ref = 0; - if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags)) + if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags)) { finish_xmote(gl, gl->gl_reply); + drop_ref = 1; + } down_read(&gfs2_umount_flush_sem); spin_lock(&gl->gl_spin); if (test_and_clear_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) && @@ -732,6 +729,8 @@ static void glock_work_func(struct work_struct *work) if (!delay || queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0) gfs2_glock_put(gl); + if (drop_ref) + gfs2_glock_put(gl); } /** @@ -1366,10 +1365,6 @@ static int gfs2_shrink_glock_memory(int nr, gfp_t gfp_mask) list_del_init(&gl->gl_lru); atomic_dec(&lru_count); - /* Check if glock is about to be freed */ - if (atomic_read(&gl->gl_ref) == 0) - continue; - /* Test for being demotable */ if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) { gfs2_glock_hold(gl); -- 2.30.2