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| author | Logan Gunthorpe <logang@deltatee.com> | 2022-10-21 19:41:09 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-11-09 19:29:20 +0100 |
| commit | 4003f107fa2eabb0aab90e37a1ed7b74c6f0d132 (patch) | |
| tree | 07e95d5fd6b3eb4ed5ded9a51867f9706683606e /mm/hugetlb.c | |
| parent | mm: allow multiple error returns in try_grab_page() (diff) | |
| download | linux-4003f107fa2eabb0aab90e37a1ed7b74c6f0d132.tar.xz linux-4003f107fa2eabb0aab90e37a1ed7b74c6f0d132.zip | |
mm: introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages
GUP Callers that expect PCI P2PDMA pages can now set FOLL_PCI_P2PDMA to
allow obtaining P2PDMA pages. If GUP is called without the flag and a
P2PDMA page is found, it will return an error in try_grab_page() or
try_grab_folio().
The check is safe to do before taking the reference to the page in both
cases seeing the page should be protected by either the appropriate
ptl or mmap_lock; or the gup fast guarantees preventing TLB flushes.
try_grab_folio() has one call site that WARNs on failure and cannot
actually deal with the failure of this function (it seems it will
get into an infinite loop). Expand the comment there to document a
couple more conditions on why it will not fail.
FOLL_PCI_P2PDMA cannot be set if FOLL_LONGTERM is set. This is to copy
fsdax until pgmap refcounts are fixed (see the link below for more
information).
Link: https://lkml.kernel.org/r/Yy4Ot5MoOhsgYLTQ@ziepe.ca
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20221021174116.7200-3-logang@deltatee.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm/hugetlb.c')
| -rw-r--r-- | mm/hugetlb.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 67f39550520e..582ec7554927 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6361,8 +6361,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, * tables. If the huge page is present, then the tail * pages must also be present. The ptl prevents the * head page and tail pages from being rearranged in - * any way. So this page must be available at this - * point, unless the page refcount overflowed: + * any way. As this is hugetlb, the pages will never + * be p2pdma or not longterm pinable. So this page + * must be available at this point, unless the page + * refcount overflowed: */ if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs, flags))) { |