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4003f107fa
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> |
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.