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GFS2: Fix panic in glock memory shrinker 

It is possible for gfs2_shrink_glock_memory() to check a glock for
demotion
that's in the process of being freed by gfs2_glock_put().  In this case,
gfs2_shrink_glock_memory() will acquire a new reference to this glock,
and
then try to free the glock itself when it drops the refernce.  To solve
this, gfs2_shrink_glock_memory() just needs to check if the glock is in
the process of being freed, and if so skip it without ever unlocking the
lru_lock.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Acked-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
Benjamin Marzinski 2009-06-30 13:51:11 -05:00 committed by Steven Whitehouse
parent 1946f70ab5
commit a51b56fff3
1 changed files with 4 additions and 0 deletions
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4
fs/gfs2/glock.c
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@ -1314,6 +1314,10 @@ 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);