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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 /mm/mmap.c | |
| 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 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index a41872c8f2af..86b18f334f4f 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -25,6 +25,7 @@ #include <linux/personality.h> #include <linux/security.h> #include <linux/hugetlb.h> +#include <linux/shmem_fs.h> #include <linux/profile.h> #include <linux/export.h> #include <linux/mount.h> @@ -1897,8 +1898,19 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, return -ENOMEM; get_area = current->mm->get_unmapped_area; - if (file && file->f_op->get_unmapped_area) - get_area = file->f_op->get_unmapped_area; + if (file) { + if (file->f_op->get_unmapped_area) + get_area = file->f_op->get_unmapped_area; + } else if (flags & MAP_SHARED) { + /* + * mmap_region() will call shmem_zero_setup() to create a file, + * so use shmem's get_unmapped_area in case it can be huge. + * do_mmap_pgoff() will clear pgoff, so match alignment. + */ + pgoff = 0; + get_area = shmem_get_unmapped_area; + } + addr = get_area(file, addr, len, pgoff, flags); if (IS_ERR_VALUE(addr)) return addr; |