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>
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@ -1314,6 +1314,10 @@ static int gfs2_shrink_glock_memory(int nr, gfp_t gfp_mask)
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list_del_init(&gl->gl_lru);
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atomic_dec(&lru_count);
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/* Check if glock is about to be freed */
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if (atomic_read(&gl->gl_ref) == 0)
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continue;
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/* Test for being demotable */
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if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
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gfs2_glock_hold(gl);
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