mm/gup: remove the restriction on locked with FOLL_LONGTERM

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This restriction was created because FOLL_LONGTERM used to scan the vma
list, so it could not tolerate becoming unlocked.  That was fixed in
commit 52650c8b46 ("mm/gup: remove the vma allocation from
gup_longterm_locked()") and the restriction on !vma was removed.

However, the locked restriction remained, even though it isn't necessary
anymore.

Adjust __gup_longterm_locked() so it can handle the mmap_read_lock()
becoming unlocked while it is looping for migration.  Migration does not
require the mmap_read_sem because it is only handling struct pages.  If we
had to unlock then ensure the whole thing returns unlocked.

Remove __get_user_pages_remote() and __gup_longterm_unlocked().  These
cases can now just directly call other functions.

Link: https://lkml.kernel.org/r/0-v1-b9ae39aa8884+14dbb-gup_longterm_locked_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

...

This commit is contained in:

Jason Gunthorpe 2022-11-16 16:07:09 -04:00 • committed by Andrew Morton

parent eff6aa17aa

commit 53b2d09bdd

1 changed files with 27 additions and 82 deletions

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mm/gup.c

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