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author | Jason Gunthorpe <jgg@nvidia.com> | 2020-12-14 19:05:41 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 12:13:39 -0800 |
commit | c28b1fc70390df32e29991eedd52bd86e7aba080 (patch) | |
tree | d3c3e5671bfbd3e82cf87af0cb7f0c7e7764f2da /arch/x86/kernel/tboot.c | |
parent | d0de82411864c4e1f24aaa3a653c7c08dd55c8d0 (diff) | |
download | linux-c28b1fc70390df32e29991eedd52bd86e7aba080.tar.bz2 |
mm/gup: reorganize internal_get_user_pages_fast()
Patch series "Add a seqcount between gup_fast and copy_page_range()", v4.
As discussed and suggested by Linus use a seqcount to close the small race
between gup_fast and copy_page_range().
Ahmed confirms that raw_write_seqcount_begin() is the correct API to use
in this case and it doesn't trigger any lockdeps.
I was able to test it using two threads, one forking and the other using
ibv_reg_mr() to trigger GUP fast. Modifying copy_page_range() to sleep
made the window large enough to reliably hit to test the logic.
This patch (of 2):
The next patch in this series makes the lockless flow a little more
complex, so move the entire block into a new function and remove a level
of indention. Tidy a bit of cruft:
- addr is always the same as start, so use start
- Use the modern check_add_overflow() for computing end = start + len
- nr_pinned/pages << PAGE_SHIFT needs the LHS to be unsigned long to
avoid shift overflow, make the variables unsigned long to avoid coding
casts in both places. nr_pinned was missing its cast
- The handling of ret and nr_pinned can be streamlined a bit
No functional change.
Link: https://lkml.kernel.org/r/0-v4-908497cf359a+4782-gup_fork_jgg@nvidia.com
Link: https://lkml.kernel.org/r/1-v4-908497cf359a+4782-gup_fork_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/kernel/tboot.c')
0 files changed, 0 insertions, 0 deletions