userfaultfd: hugetlbfs: allow registration of ranges containing huge pages

Expand the userfaultfd_register/unregister routines to allow VM_HUGETLB
vmas.  huge page alignment checking is performed after a VM_HUGETLB vma
is encountered.

Also, since there is no UFFDIO_ZEROPAGE support for huge pages do not
return that as a valid ioctl method for huge page ranges.

Link: http://lkml.kernel.org/r/20161216144821.5183-22-aarcange@redhat.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 50 insertions, 5 deletions

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 26e1ef00b63c..5139d05f80e6 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -27,6 +27,7 @@
 #include <linux/mempolicy.h>
 #include <linux/ioctl.h>
 #include <linux/security.h>
+#include <linux/hugetlb.h>
 
 static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
 
@@ -1058,6 +1059,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
         struct uffdio_register __user *user_uffdio_register;
         unsigned long vm_flags, new_flags;
         bool found;
+        bool huge_pages;
         unsigned long start, end, vma_end;
 
         user_uffdio_register = (struct uffdio_register __user *) arg;
@@ -1109,6 +1111,17 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
                 goto out_unlock;
 
         /*
+         * If the first vma contains huge pages, make sure start address
+         * is aligned to huge page size.
+         */
+        if (is_vm_hugetlb_page(vma)) {
+                unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
+
+                if (start & (vma_hpagesize - 1))
+                        goto out_unlock;
+        }
+
+        /*
          * Search for not compatible vmas.
          *
          * FIXME: this shall be relaxed later so that it doesn't fail
@@ -1116,6 +1129,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
          * on anonymous vmas).
          */
         found = false;
+        huge_pages = false;
         for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
                 cond_resched();
 
@@ -1124,8 +1138,21 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 
                 /* check not compatible vmas */
                 ret = -EINVAL;
-                if (!vma_is_anonymous(cur))
+                if (!vma_is_anonymous(cur) && !is_vm_hugetlb_page(cur))
                         goto out_unlock;
+                /*
+                 * If this vma contains ending address, and huge pages
+                 * check alignment.
+                 */
+                if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
+                    end > cur->vm_start) {
+                        unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
+
+                        ret = -EINVAL;
+
+                        if (end & (vma_hpagesize - 1))
+                                goto out_unlock;
+                }
 
                 /*
                  * Check that this vma isn't already owned by a
@@ -1138,6 +1165,12 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
                     cur->vm_userfaultfd_ctx.ctx != ctx)
                         goto out_unlock;
 
+                /*
+                 * Note vmas containing huge pages
+                 */
+                if (is_vm_hugetlb_page(cur))
+                        huge_pages = true;
+
                 found = true;
         }
         BUG_ON(!found);
@@ -1149,7 +1182,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
         do {
                 cond_resched();
 
-                BUG_ON(!vma_is_anonymous(vma));
+                BUG_ON(!vma_is_anonymous(vma) && !is_vm_hugetlb_page(vma));
                 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
                        vma->vm_userfaultfd_ctx.ctx != ctx);
 
@@ -1207,7 +1240,8 @@ out_unlock:
                  * userland which ioctls methods are guaranteed to
                  * succeed on this range.
                  */
-                if (put_user(UFFD_API_RANGE_IOCTLS,
+                if (put_user(huge_pages ? UFFD_API_RANGE_IOCTLS_HPAGE :
+                             UFFD_API_RANGE_IOCTLS,
                              &user_uffdio_register->ioctls))
                         ret = -EFAULT;
         }
@@ -1254,6 +1288,17 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
                 goto out_unlock;
 
         /*
+         * If the first vma contains huge pages, make sure start address
+         * is aligned to huge page size.
+         */
+        if (is_vm_hugetlb_page(vma)) {
+                unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
+
+                if (start & (vma_hpagesize - 1))
+                        goto out_unlock;
+        }
+
+        /*
          * Search for not compatible vmas.
          *
          * FIXME: this shall be relaxed later so that it doesn't fail
@@ -1275,7 +1320,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
                  * provides for more strict behavior to notice
                  * unregistration errors.
                  */
-                if (!vma_is_anonymous(cur))
+                if (!vma_is_anonymous(cur) && !is_vm_hugetlb_page(cur))
                         goto out_unlock;
 
                 found = true;
@@ -1289,7 +1334,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
         do {
                 cond_resched();
 
-                BUG_ON(!vma_is_anonymous(vma));
+                BUG_ON(!vma_is_anonymous(vma) && !is_vm_hugetlb_page(vma));
 
                 /*
                  * Nothing to do: this vma is already registered into this