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| author | Andrea Arcangeli <aarcange@redhat.com> | 2018-03-09 15:51:06 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-03-09 16:40:01 -0800 |
| commit | 96312e61282ae3f6537a562625706498cbc75594 (patch) | |
| tree | cee11a490bf11d43696eaa577837839abd116cd6 /mm/z3fold.c | |
| parent | 1b4cfe3c0a30dde968fb43c577a8d7e262a145ee (diff) | |
| download | linux-stable-96312e61282ae3f6537a562625706498cbc75594.tar.gz linux-stable-96312e61282ae3f6537a562625706498cbc75594.tar.bz2 linux-stable-96312e61282ae3f6537a562625706498cbc75594.zip | |
mm/gup.c: teach get_user_pages_unlocked to handle FOLL_NOWAIT
KVM is hanging during postcopy live migration with userfaultfd because
get_user_pages_unlocked is not capable to handle FOLL_NOWAIT.
Earlier FOLL_NOWAIT was only ever passed to get_user_pages.
Specifically faultin_page (the callee of get_user_pages_unlocked caller)
doesn't know that if FAULT_FLAG_RETRY_NOWAIT was set in the page fault
flags, when VM_FAULT_RETRY is returned, the mmap_sem wasn't actually
released (even if nonblocking is not NULL). So it sets *nonblocking to
zero and the caller won't release the mmap_sem thinking it was already
released, but it wasn't because of FOLL_NOWAIT.
Link: http://lkml.kernel.org/r/20180302174343.5421-2-aarcange@redhat.com
Fixes: ce53053ce378c ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()")
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Tested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/z3fold.c')
0 files changed, 0 insertions, 0 deletions