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s390/uv: Always return 0 from s390_wiggle_split_folio() if successful

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Let's consistently return 0 if the operation was successful, and just
detect ourselves whether splitting is required -- folio_test_large() is
a cheap operation.

Update the documentation.

Should we simply always return -EAGAIN instead of 0, so we don't have
to handle it in the caller? Not sure, staring at the documentation, this
way looks a bit cleaner.

Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20250516123946.1648026-3-david@redhat.com
Message-ID: <20250516123946.1648026-3-david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
This commit is contained in:
David Hildenbrand 2025-05-16 14:39:45 +02:00 committed by Claudio Imbrenda
parent 3ec8a8330a
commit bd428b8c79
1 changed files with 12 additions and 10 deletions
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22
arch/s390/kernel/uv.c
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@ -324,34 +324,36 @@ static int make_folio_secure(struct mm_struct *mm, struct folio *folio, struct u
}
/**
* s390_wiggle_split_folio() - try to drain extra references to a folio and optionally split.
* s390_wiggle_split_folio() - try to drain extra references to a folio and
* split the folio if it is large.
* @mm: the mm containing the folio to work on
* @folio: the folio
* @split: whether to split a large folio
*
* Context: Must be called while holding an extra reference to the folio;
* the mm lock should not be held.
* Return: 0 if the folio was split successfully;
* -EAGAIN if the folio was not split successfully but another attempt
* can be made, or if @split was set to false;
* -EINVAL in case of other errors. See split_folio().
* Return: 0 if the operation was successful;
* -EAGAIN if splitting the large folio was not successful,
* but another attempt can be made;
* -EINVAL in case of other folio splitting errors. See split_folio().
*/
static int s390_wiggle_split_folio(struct mm_struct *mm, struct folio *folio, bool split)
static int s390_wiggle_split_folio(struct mm_struct *mm, struct folio *folio)
{
int rc;
lockdep_assert_not_held(&mm->mmap_lock);
folio_wait_writeback(folio);
lru_add_drain_all();
if (split) {
if (folio_test_large(folio)) {
folio_lock(folio);
rc = split_folio(folio);
folio_unlock(folio);
if (rc != -EBUSY)
return rc;
return -EAGAIN;
}
return -EAGAIN;
return 0;
}
int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header *uvcb)
@ -394,7 +396,7 @@ int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header
mmap_read_unlock(mm);
if (rc == -E2BIG || rc == -EBUSY) {
rc = s390_wiggle_split_folio(mm, folio, rc == -E2BIG);
rc = s390_wiggle_split_folio(mm, folio);
if (!rc)
rc = -EAGAIN;
}