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mm: hugetlb: improve the handling of hugetlb allocation failure for freed or in-use hugetlb

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alloc_and_dissolve_hugetlb_folio() preallocates a new hugetlb page before
it takes hugetlb_lock.  In 3 out of 4 cases the page is not really used
and therefore the newly allocated page is just freed right away.  This is
wasteful and it might cause pre-mature failures in those cases.

Address that by moving the allocation down to the only case (hugetlb page
is really in the free pages pool).  We need to drop hugetlb_lock to do so
and therefore need to recheck the page state after regaining it.

The patch is more of a cleanup than an actual fix to an existing problem. 
There are no known reports about pre-mature failures.

Link: https://lkml.kernel.org/r/62890fd60b1ecd5bf1cdc476c973f60fe37aa0cb.1707181934.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Baolin Wang 2024-02-06 11:08:11 +08:00 committed by Andrew Morton
parent 055267feae
commit 831bc31a5e
1 changed files with 16 additions and 16 deletions
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32
mm/hugetlb.c
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@ -3029,21 +3029,9 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h,
{
gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
int nid = folio_nid(old_folio);
struct folio *new_folio;
struct folio *new_folio = NULL;
int ret = 0;
/*
* Before dissolving the folio, we need to allocate a new one for the
* pool to remain stable. Here, we allocate the folio and 'prep' it
* by doing everything but actually updating counters and adding to
* the pool. This simplifies and let us do most of the processing
* under the lock.
*/
new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, NULL, NULL);
if (!new_folio)
return -ENOMEM;
__prep_new_hugetlb_folio(h, new_folio);
retry:
spin_lock_irq(&hugetlb_lock);
if (!folio_test_hugetlb(old_folio)) {
@ -3073,6 +3061,16 @@ retry:
cond_resched();
goto retry;
} else {
if (!new_folio) {
spin_unlock_irq(&hugetlb_lock);
new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid,
NULL, NULL);
if (!new_folio)
return -ENOMEM;
__prep_new_hugetlb_folio(h, new_folio);
goto retry;
}
/*
* Ok, old_folio is still a genuine free hugepage. Remove it from
* the freelist and decrease the counters. These will be
@ -3100,9 +3098,11 @@ retry:
free_new:
spin_unlock_irq(&hugetlb_lock);
/* Folio has a zero ref count, but needs a ref to be freed */
folio_ref_unfreeze(new_folio, 1);
update_and_free_hugetlb_folio(h, new_folio, false);
if (new_folio) {
/* Folio has a zero ref count, but needs a ref to be freed */
folio_ref_unfreeze(new_folio, 1);
update_and_free_hugetlb_folio(h, new_folio, false);
}
return ret;
}