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author | David Herrmann <dh.herrmann@gmail.com> | 2014-08-08 14:25:25 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-08 15:57:31 -0700 |
commit | 4bb5f5d9395bc112d93a134d8f5b05611eddc9c0 (patch) | |
tree | 68af5a8a8cc65375c51c25bff678d0f9825d86af /mm/shmem.c | |
parent | 935e9f02e798051d2923d59f6025cd74f59aa0e1 (diff) | |
download | op-kernel-dev-4bb5f5d9395bc112d93a134d8f5b05611eddc9c0.zip op-kernel-dev-4bb5f5d9395bc112d93a134d8f5b05611eddc9c0.tar.gz |
mm: allow drivers to prevent new writable mappings
This patch (of 6):
The i_mmap_writable field counts existing writable mappings of an
address_space. To allow drivers to prevent new writable mappings, make
this counter signed and prevent new writable mappings if it is negative.
This is modelled after i_writecount and DENYWRITE.
This will be required by the shmem-sealing infrastructure to prevent any
new writable mappings after the WRITE seal has been set. In case there
exists a writable mapping, this operation will fail with EBUSY.
Note that we rely on the fact that iff you already own a writable mapping,
you can increase the counter without using the helpers. This is the same
that we do for i_writecount.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ryan Lortie <desrt@desrt.ca>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Daniel Mack <zonque@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
0 files changed, 0 insertions, 0 deletions