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| author | Hugh Dickins <hughd@google.com> | 2016-07-26 15:26:15 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-07-26 16:19:19 -0700 |
| commit | c01d5b300774d130a24d787825b01eb24e6e20cb (patch) | |
| tree | e56b92aa5cf8f25ab812da30db5b36a6126e877b /ipc | |
| parent | 5a6e75f8110c97e2a5488894d4e922187e6cb343 (diff) | |
| download | lwn-c01d5b300774d130a24d787825b01eb24e6e20cb.tar.gz lwn-c01d5b300774d130a24d787825b01eb24e6e20cb.zip | |
shmem: get_unmapped_area align huge page
Provide a shmem_get_unmapped_area method in file_operations, called at
mmap time to decide the mapping address. It could be conditional on
CONFIG_TRANSPARENT_HUGEPAGE, but save #ifdefs in other places by making
it unconditional.
shmem_get_unmapped_area() first calls the usual mm->get_unmapped_area
(which we treat as a black box, highly dependent on architecture and
config and executable layout). Lots of conditions, and in most cases it
just goes with the address that chose; but when our huge stars are
rightly aligned, yet that did not provide a suitable address, go back to
ask for a larger arena, within which to align the mapping suitably.
There have to be some direct calls to shmem_get_unmapped_area(), not via
the file_operations: because of the way shmem_zero_setup() is called to
create a shmem object late in the mmap sequence, when MAP_SHARED is
requested with MAP_ANONYMOUS or /dev/zero. Though this only matters
when /proc/sys/vm/shmem_huge has been set.
Link: http://lkml.kernel.org/r/1466021202-61880-29-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
| -rw-r--r-- | ipc/shm.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index 13282510bc0d..7fa5cbebbf19 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -476,13 +476,15 @@ static const struct file_operations shm_file_operations = { .mmap = shm_mmap, .fsync = shm_fsync, .release = shm_release, -#ifndef CONFIG_MMU .get_unmapped_area = shm_get_unmapped_area, -#endif .llseek = noop_llseek, .fallocate = shm_fallocate, }; +/* + * shm_file_operations_huge is now identical to shm_file_operations, + * but we keep it distinct for the sake of is_file_shm_hugepages(). + */ static const struct file_operations shm_file_operations_huge = { .mmap = shm_mmap, .fsync = shm_fsync, |