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gfs2: Fix "Make glock lru list scanning safer"

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Commit 228804a35c tried to add a refcount check to
gfs2_scan_glock_lru() to make sure that glocks that are still referenced
cannot be freed.  It failed to account for the bias state_change() adds
to the refcount for held glocks, so held glocks are no longer removed
from the glock cache, which can lead to out-of-memory problems.  Fix
that.  (The inodes those glocks are associated with do get shrunk and do
get pushed out of memory.)

In addition, use the same eligibility check in gfs2_scan_glock_lru() and
gfs2_dispose_glock_lru().

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2024-03-28 19:59:45 +01:00
parent c9a0a4b028
commit acf1f42faf
1 changed files with 13 additions and 11 deletions
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24
fs/gfs2/glock.c
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@ -1987,6 +1987,14 @@ static int glock_cmp(void *priv, const struct list_head *a,
return 0;
}
static bool can_free_glock(struct gfs2_glock *gl)
{
bool held = gl->gl_state != LM_ST_UNLOCKED;
return !test_bit(GLF_LOCK, &gl->gl_flags) &&
gl->gl_lockref.count == held;
}
/**
* gfs2_dispose_glock_lru - Demote a list of glocks
* @list: The list to dispose of
@ -2020,7 +2028,7 @@ add_back_to_lru:
atomic_inc(&lru_count);
continue;
}
if (test_bit(GLF_LOCK, &gl->gl_flags)) {
if (!can_free_glock(gl)) {
spin_unlock(&gl->gl_lockref.lock);
goto add_back_to_lru;
}
@ -2052,16 +2060,10 @@ static long gfs2_scan_glock_lru(int nr)
list_for_each_entry_safe(gl, next, &lru_list, gl_lru) {
if (nr-- <= 0)
break;
/* Test for being demotable */
if (!test_bit(GLF_LOCK, &gl->gl_flags)) {
if (!spin_trylock(&gl->gl_lockref.lock))
continue;
if (!gl->gl_lockref.count) {
list_move(&gl->gl_lru, &dispose);
atomic_dec(&lru_count);
freed++;
}
spin_unlock(&gl->gl_lockref.lock);
if (can_free_glock(gl)) {
list_move(&gl->gl_lru, &dispose);
atomic_dec(&lru_count);
freed++;
}
}
if (!list_empty(&dispose))