Commit 1ebb7044 authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
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mempool: fix first round failure behavior

mempool modifies gfp_mask so that the backing allocator doesn't try too
hard or trigger warning message when there's pool to fall back on.  In
addition, for the first try, it removes __GFP_WAIT and IO, so that it
doesn't trigger reclaim or wait when allocation can be fulfilled from
pool; however, when that allocation fails and pool is empty too, it waits
for the pool to be replenished before retrying.

Allocation which could have succeeded after a bit of reclaim has to wait
on the reserved items and it's not like mempool doesn't retry with
__GFP_WAIT and IO.  It just does that *after* someone returns an element,
pointlessly delaying things.

Fix it by retrying immediately if the first round of allocation attempts
w/o __GFP_WAIT and IO fails.

[ shorten the lock hold time]
Signed-off-by: default avatarTejun Heo <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 0565d317
......@@ -221,14 +221,23 @@ repeat_alloc:
return element;
/* We must not sleep in the GFP_ATOMIC case */
* We use gfp mask w/o __GFP_WAIT or IO for the first round. If
* alloc failed with that and @pool was empty, retry immediately.
if (gfp_temp != gfp_mask) {
spin_unlock_irqrestore(&pool->lock, flags);
gfp_temp = gfp_mask;
goto repeat_alloc;
/* We must not sleep if !__GFP_WAIT */
if (!(gfp_mask & __GFP_WAIT)) {
spin_unlock_irqrestore(&pool->lock, flags);
return NULL;
/* Let's wait for someone else to return an element to @pool */
gfp_temp = gfp_mask;
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
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