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s390/uv: Don't call folio_wait_writeback() without a folio reference

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folio_wait_writeback() requires that no spinlocks are held and that
a folio reference is held, as documented. After we dropped the PTL, the
folio could get freed concurrently. So grab a temporary reference.

Fixes: 214d9bbcd3 ("s390/mm: provide memory management functions for protected KVM guests")
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20240508182955.358628-2-david@redhat.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
David Hildenbrand 2024-05-08 20:29:46 +02:00 committed by Alexander Gordeev
parent c3f38fa61a
commit 3f29f6537f
1 changed files with 8 additions and 0 deletions
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8
arch/s390/kernel/uv.c
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@ -318,6 +318,13 @@ again:
rc = make_folio_secure(folio, uvcb); rc = make_folio_secure(folio, uvcb);
folio_unlock(folio); folio_unlock(folio);
} }
/*
* Once we drop the PTL, the folio may get unmapped and
* freed immediately. We need a temporary reference.
*/
if (rc == -EAGAIN)
folio_get(folio);
} }
unlock: unlock:
pte_unmap_unlock(ptep, ptelock); pte_unmap_unlock(ptep, ptelock);
@ -330,6 +337,7 @@ out:
* completion, this is just a useless check, but it is safe. * completion, this is just a useless check, but it is safe.
*/ */
folio_wait_writeback(folio); folio_wait_writeback(folio);
folio_put(folio);
} else if (rc == -EBUSY) { } else if (rc == -EBUSY) {
/* /*
* If we have tried a local drain and the folio refcount * If we have tried a local drain and the folio refcount