Messages in this thread Patch in this message | | | From | Mike Kravetz <> | Subject | [patch] memfd_create.2: Add description of MFD_HUGETLB (hugetlbfs) support | Date | Fri, 15 Sep 2017 14:43:05 -0700 |
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hugetlbfs support for memfd_create was recently merged by Linus and should be in the Linux 4.14 release. To request hugetlbfs support a new memfd_create flag (MFD_HUGETLB) was added.
This patch documents the following commit:
commit 749df87bd7bee5a79cef073f5d032ddb2b211de8 Author: Mike Kravetz <mike.kravetz@oracle.com> Date: Wed Sep 6 16:24:16 2017 -0700
mm/shmem: add hugetlbfs support to memfd_create()
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> --- man2/memfd_create.2 | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)
diff --git a/man2/memfd_create.2 b/man2/memfd_create.2 index 4dfd1bb2d..b61254bb8 100644 --- a/man2/memfd_create.2 +++ b/man2/memfd_create.2 @@ -100,6 +100,33 @@ If this flag is not set, the initial set of seals will be meaning that no other seals can be set on the file. .\" FIXME Why is the MFD_ALLOW_SEALING behavior not simply the default? .\" Is it worth adding some text explaining this? +.TP +.BR MFD_HUGETLB " (since Linux 4.14)" +The anonymous file will be created in the hugetlbfs filesystem using +huge pages. See the Linux kernel source file +.I Documentation/vm/hugetlbpage.txt +for more information about hugetlbfs. The hugetlbfs filesystem does +not support file sealing operations. Therefore, specifying both +.B MFD_HUGETLB +and +.B MFD_ALLOW_SEALING +will result in an error +.RB (EINVAL) +being returned. + +.TP +.BR MFD_HUGE_2MB ", " MFD_HUGE_1GB ", " "..." +Used in conjunction with +.B MFD_HUGETLB +to select alternative hugetlb page sizes (respectively, 2 MB, 1 GB, ...) +on systems that support multiple hugetlb page sizes. Definitions for known +huge page sizes are included in the header file +.I <sys/memfd.h>. + +For details on encoding huge page sizes not included in the header file, +see the discussion of the similarly named constants in +.BR mmap (2). + .PP Unused bits in .I flags -- 2.13.5
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