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eddb1c228f
Introduce pin_user_pages*() variations of get_user_pages*() calls, and also pin_longterm_pages*() variations. For now, these are placeholder calls, until the various call sites are converted to use the correct get_user_pages*() or pin_user_pages*() API. These variants will eventually all set FOLL_PIN, which is also introduced, and thoroughly documented. pin_user_pages() pin_user_pages_remote() pin_user_pages_fast() All pages that are pinned via the above calls, must be unpinned via put_user_page(). The underlying rules are: * FOLL_PIN is a gup-internal flag, so the call sites should not directly set it. That behavior is enforced with assertions. * Call sites that want to indicate that they are going to do DirectIO ("DIO") or something with similar characteristics, should call a get_user_pages()-like wrapper call that sets FOLL_PIN. These wrappers will: * Start with "pin_user_pages" instead of "get_user_pages". That makes it easy to find and audit the call sites. * Set FOLL_PIN * For pages that are received via FOLL_PIN, those pages must be returned via put_user_page(). Thanks to Jan Kara and Vlastimil Babka for explaining the 4 cases in this documentation. (I've reworded it and expanded upon it.) Link: http://lkml.kernel.org/r/20200107224558.2362728-12-jhubbard@nvidia.com Signed-off-by: John Hubbard <jhubbard@nvidia.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> [Documentation] Reviewed-by: Jérôme Glisse <jglisse@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Björn Töpel <bjorn.topel@intel.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: Jason Gunthorpe <jgg@mellanox.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jens Axboe <axboe@kernel.dk> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Leon Romanovsky <leonro@mellanox.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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ABI | ||
accounting | ||
admin-guide | ||
arm | ||
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bpf | ||
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core-api | ||
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x86 | ||
xtensa | ||
.gitignore | ||
asm-annotations.rst | ||
atomic_bitops.txt | ||
atomic_t.txt | ||
bus-virt-phys-mapping.txt | ||
Changes | ||
CodingStyle | ||
conf.py | ||
COPYING-logo | ||
crc32.txt | ||
debugging-modules.txt | ||
debugging-via-ohci1394.txt | ||
digsig.txt | ||
DMA-API-HOWTO.txt | ||
DMA-API.txt | ||
DMA-attributes.txt | ||
DMA-ISA-LPC.txt | ||
docutils.conf | ||
dontdiff | ||
futex-requeue-pi.txt | ||
hwspinlock.txt | ||
index.rst | ||
io-mapping.txt | ||
io_ordering.txt | ||
IPMI.txt | ||
IRQ-affinity.txt | ||
IRQ-domain.txt | ||
IRQ.txt | ||
irqflags-tracing.txt | ||
Kconfig | ||
kobject.txt | ||
kprobes.txt | ||
kref.txt | ||
logo.gif | ||
lzo.txt | ||
mailbox.txt | ||
Makefile | ||
memory-barriers.txt | ||
nommu-mmap.txt | ||
percpu-rw-semaphore.txt | ||
pi-futex.txt | ||
preempt-locking.txt | ||
rbtree.txt | ||
remoteproc.txt | ||
robust-futex-ABI.txt | ||
robust-futexes.txt | ||
rpmsg.txt | ||
speculation.txt | ||
static-keys.txt | ||
SubmittingPatches | ||
tee.txt | ||
this_cpu_ops.txt | ||
unaligned-memory-access.txt | ||
xz.txt |