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| author |   Peter Xu <peterx@redhat.com> | 2025-01-07 15:39:57 -0500 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2025-01-25 20:22:30 -0800 |
| commit | be8d7314b18ede1c6cdebbb982c9659020e2f1f2 (patch) | |
| tree | f4bf8c38fcc0c23fa814db5d05e12685b8236116 | |
| parent | mm/hugetlb: fix avoid_reserve to allow taking folio from subpool (diff) | |
| download | wireguard-linux-be8d7314b18ede1c6cdebbb982c9659020e2f1f2.tar.xz wireguard-linux-be8d7314b18ede1c6cdebbb982c9659020e2f1f2.zip | |
mm/hugetlb: stop using avoid_reserve flag in fork()
When fork() and stumble on top of a dma-pinned hugetlb private page, CoW
must happen during fork() to guarantee dma coherency.
In this specific path, hugetlb pages need to be allocated for the child
process. Stop using avoid_reserve=1 flag here: it's not required to be
used here, as dest_vma (which is destined to be a MAP_PRIVATE hugetlb vma)
will have no private vma resv map, and that will make sure it won't be
able to use a vma reservation later.
No functional change intended with this change. Said that, it's still
wanted to do this, so as to reduce the usage of avoid_reserve to the only
one user, which is also why this flag was introduced initially in commit
04f2cbe35699 ("hugetlb: guarantee that COW faults for a process that
called mmap(MAP_PRIVATE) on hugetlbfs will succeed"). I don't see whoever
else should set it at all.
Further patch will clean up resv accounting based on this.
Link: https://lkml.kernel.org/r/20250107204002.2683356-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Ackerley Tng <ackerleytng@google.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/hugetlb.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a10d376cb1a8..7df19b5f956c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5373,7 +5373,7 @@ again: spin_unlock(src_ptl); spin_unlock(dst_ptl); /* Do not use reserve as it's private owned */ - new_folio = alloc_hugetlb_folio(dst_vma, addr, 1); + new_folio = alloc_hugetlb_folio(dst_vma, addr, 0); if (IS_ERR(new_folio)) { folio_put(pte_folio); ret = PTR_ERR(new_folio); |