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| author |  Logan Gunthorpe <logang@deltatee.com>
| 2022-10-21 11:41:09 -0600 |
|---|---|---|
| committer |  Jens Axboe <axboe@kernel.dk>
| 2022-11-09 11:29:20 -0700 |
| commit | 4003f107fa2eabb0aab90e37a1ed7b74c6f0d132 (patch) | |
| tree | 07e95d5fd6b3eb4ed5ded9a51867f9706683606e /include | |
| parent | mm: allow multiple error returns in try_grab_page() (diff) | |
| download | linux-4003f107fa2eabb0aab90e37a1ed7b74c6f0d132.tar.gz linux-4003f107fa2eabb0aab90e37a1ed7b74c6f0d132.tar.bz2 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 'include')
| -rw-r--r-- | include/linux/mm.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 62a91dc1272b..6b081a8dcf88 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2958,6 +2958,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ #define FOLL_PIN 0x40000 /* pages must be released via unpin_user_page */ #define FOLL_FAST_ONLY 0x80000 /* gup_fast: prevent fall-back to slow gup */ +#define FOLL_PCI_P2PDMA 0x100000 /* allow returning PCI P2PDMA pages */ /* * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each |