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include/linux/swapops.h: remove stub for non_swap_entry()

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The stub for non_swap_entry() may not help much, because MAX_SWAPFILES has
already contained all the information to decide whether a swap entry is
real swap entry or pesudo ones (migrations, ...).

There can be some performance influences on non_swap_entry() with below
conditions all met:

  !CONFIG_MIGRATION && !CONFIG_MEMORY_FAILURE && !CONFIG_DEVICE_PRIVATE

But that's definitely not the major config most machines will use, at the
meantime it's already in a slow path of swap entry (being parsed from a
swap pte), so IMHO it shouldn't be a major issue.  Also according to the
analysis from Alistair, somehow the stub didn't do the job right [1].

To make the code cleaner, let's drop the stub.

[1] https://lore.kernel.org/lkml/8735ihbw6g.fsf@nvdebian.thelocal/

Note: the uffd-wp shmem & hugetlbfs series will need this patch to make
sure swap entries work as expected with below config as spotted by
Alistair:

  !CONFIG_MIGRATION &&
  !CONFIG_MEMORY_FAILURE &&
  !CONFIG_DEVICE_PRIVATE &&
  CONFIG_PTE_MARKER

(PS: this config should mostly never gonna happen, though, afaict..)

Link: https://lkml.kernel.org/r/20220413191147.66645-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2022-04-28 23:16:16 -07:00 committed by akpm
parent 6fd3620b34
commit ba91fb7dd0
1 changed files with 0 additions and 8 deletions
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8
include/linux/swapops.h
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@ -387,18 +387,10 @@ static inline void num_poisoned_pages_inc(void)
}
#endif
#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION) || \
defined(CONFIG_DEVICE_PRIVATE)
static inline int non_swap_entry(swp_entry_t entry)
{
return swp_type(entry) >= MAX_SWAPFILES;
}
#else
static inline int non_swap_entry(swp_entry_t entry)
{
return 0;
}
#endif
#endif /* CONFIG_MMU */
#endif /* _LINUX_SWAPOPS_H */