[The updated changelog is here so let me comment here] On Tue 08-08-17 16:19:45, Andrew Morton wrote: > From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Subject: mm/shmem: add hugetlbfs support to memfd_create() > > This patch came out of discussions in this e-mail thread: > https://lkml.org/lkml/2017/7/6/564 Use http://lkml.kernel.org/r/1499357846-7481-1-git-send-email-mike.kravetz%40oracle.com instead please. lkml.org is broken quite often > The Oracle JVM team is developing a new garbage collection model. This > new model requires multiple mappings of the same anonymous memory. One > straightforward way to accomplish this is with memfd_create. They can use > the returned fd to create multiple mappings of the same memory. > > The JVM today has an option to use (static hugetlb) huge pages. If this > option is specified, they would like to use the same garbage collection > model requiring multiple mappings to the same memory. Using hugetlbfs, it > is possible to explicitly mount a filesystem and specify file paths in > order to get an fd that can be used for multiple mappings. However, this > introduces additional system admin work and coordination. > > Ideally they would like to get a hugetlbfs fd without requiring explicit > mounting of a filesystem. Today, mmap and shmget can make use of > hugetlbfs without explicitly mounting a filesystem. The patch adds this > functionality to hugetlbfs. > > A new flag MFD_HUGETLB is introduced to request a hugetlbfs file. Like > other system calls where hugetlb can be requested, the huge page size can > be encoded in the flags argument is the non-default huge page size is > desired. hugetlbfs does not support sealing operations, therefore > specifying MFD_ALLOW_SEALING with MFD_HUGETLB will result in EINVAL. > > Of course, the memfd_man page would need updating if this type of > functionality moves forward. > > > Add a new flag MFD_HUGETLB to memfd_create() that will specify the file to > be created resides in the hugetlbfs filesystem. This is the generic > hugetlbfs filesystem not associated with any specific mount point. As > with other system calls that request hugetlbfs backed pages, there is the > ability to encode huge page size in the flag arguments. > > hugetlbfs does not support sealing operations, therefore specifying > MFD_ALLOW_SEALING with MFD_HUGETLB will result in EINVAL. last two paragraphs are duplicated so they can be dropped > Link: http://lkml.kernel.org/r/1502149672-7759-2-git-send-email-mike.kravetz@xxxxxxxxxx > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Other than that it looks reasonably to me. Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > > include/uapi/linux/memfd.h | 24 ++++++++++++++++++++++ > mm/shmem.c | 37 +++++++++++++++++++++++++++++------ > 2 files changed, 55 insertions(+), 6 deletions(-) > > diff -puN include/uapi/linux/memfd.h~mm-shmem-add-hugetlbfs-support-to-memfd_create include/uapi/linux/memfd.h > --- a/include/uapi/linux/memfd.h~mm-shmem-add-hugetlbfs-support-to-memfd_create > +++ a/include/uapi/linux/memfd.h > @@ -1,8 +1,32 @@ > #ifndef _UAPI_LINUX_MEMFD_H > #define _UAPI_LINUX_MEMFD_H > > +#include <asm-generic/hugetlb_encode.h> > + > /* flags for memfd_create(2) (unsigned int) */ > #define MFD_CLOEXEC 0x0001U > #define MFD_ALLOW_SEALING 0x0002U > +#define MFD_HUGETLB 0x0004U > + > +/* > + * Huge page size encoding when MFD_HUGETLB is specified, and a huge page > + * size other than the default is desired. See hugetlb_encode.h. > + * All known huge page size encodings are provided here. It is the > + * responsibility of the application to know which sizes are supported on > + * the running system. See mmap(2) man page for details. > + */ > +#define MFD_HUGE_SHIFT HUGETLB_FLAG_ENCODE_SHIFT > +#define MFD_HUGE_MASK HUGETLB_FLAG_ENCODE_MASK > + > +#define MFD_HUGE_64KB HUGETLB_FLAG_ENCODE_64KB > +#define MFD_HUGE_512KB HUGETLB_FLAG_ENCODE_512KB > +#define MFD_HUGE_1MB HUGETLB_FLAG_ENCODE_1MB > +#define MFD_HUGE_2MB HUGETLB_FLAG_ENCODE_2MB > +#define MFD_HUGE_8MB HUGETLB_FLAG_ENCODE_8MB > +#define MFD_HUGE_16MB HUGETLB_FLAG_ENCODE_16MB > +#define MFD_HUGE_256MB HUGETLB_FLAG_ENCODE_256MB > +#define MFD_HUGE_1GB HUGETLB_FLAG_ENCODE_1GB > +#define MFD_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB > +#define MFD_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB > > #endif /* _UAPI_LINUX_MEMFD_H */ > diff -puN mm/shmem.c~mm-shmem-add-hugetlbfs-support-to-memfd_create mm/shmem.c > --- a/mm/shmem.c~mm-shmem-add-hugetlbfs-support-to-memfd_create > +++ a/mm/shmem.c > @@ -34,6 +34,7 @@ > #include <linux/swap.h> > #include <linux/uio.h> > #include <linux/khugepaged.h> > +#include <linux/hugetlb.h> > > #include <asm/tlbflush.h> /* for arch/microblaze update_mmu_cache() */ > > @@ -3652,7 +3653,7 @@ static int shmem_show_options(struct seq > #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1) > #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN) > > -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING) > +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB) > > SYSCALL_DEFINE2(memfd_create, > const char __user *, uname, > @@ -3664,8 +3665,18 @@ SYSCALL_DEFINE2(memfd_create, > char *name; > long len; > > - if (flags & ~(unsigned int)MFD_ALL_FLAGS) > - return -EINVAL; > + if (!(flags & MFD_HUGETLB)) { > + if (flags & ~(unsigned int)MFD_ALL_FLAGS) > + return -EINVAL; > + } else { > + /* Sealing not supported in hugetlbfs (MFD_HUGETLB) */ > + if (flags & MFD_ALLOW_SEALING) > + return -EINVAL; > + /* Allow huge page size encoding in flags. */ > + if (flags & ~(unsigned int)(MFD_ALL_FLAGS | > + (MFD_HUGE_MASK << MFD_HUGE_SHIFT))) > + return -EINVAL; > + } > > /* length includes terminating zero */ > len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1); > @@ -3696,16 +3707,30 @@ SYSCALL_DEFINE2(memfd_create, > goto err_name; > } > > - file = shmem_file_setup(name, 0, VM_NORESERVE); > + if (flags & MFD_HUGETLB) { > + struct user_struct *user = NULL; > + > + file = hugetlb_file_setup(name, 0, VM_NORESERVE, &user, > + HUGETLB_ANONHUGE_INODE, > + (flags >> MFD_HUGE_SHIFT) & > + MFD_HUGE_MASK); > + } else > + file = shmem_file_setup(name, 0, VM_NORESERVE); > if (IS_ERR(file)) { > error = PTR_ERR(file); > goto err_fd; > } > - info = SHMEM_I(file_inode(file)); > file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE; > file->f_flags |= O_RDWR | O_LARGEFILE; > - if (flags & MFD_ALLOW_SEALING) > + > + if (flags & MFD_ALLOW_SEALING) { > + /* > + * flags check at beginning of function ensures > + * this is not a hugetlbfs (MFD_HUGETLB) file. > + */ > + info = SHMEM_I(file_inode(file)); > info->seals &= ~F_SEAL_SEAL; > + } > > fd_install(fd, file); > kfree(name); > _ > > Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are > > mm-mremap-fail-map-duplication-attempts-for-private-mappings.patch > mm-hugetlb-define-system-call-hugetlb-size-encodings-in-single-file.patch > mm-arch-consolidate-mmap-hugetlb-size-encodings.patch > mm-shm-use-new-hugetlb-size-encoding-definitions.patch > mm-shmem-add-hugetlbfs-support-to-memfd_create.patch -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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