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authorAxel Rasmussen <axelrasmussen@google.com>2021-06-30 18:49:20 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-30 20:47:27 -0700
commitc949b097ef2e332fa90708127c972b823fb58ec1 (patch)
tree1c8c7288f61aaf1dc64df90f8239bb73a7a4c050
parent3460f6e5c1ed94c2ab7c1ccc032a5bebd88deaa7 (diff)
userfaultfd/shmem: support minor fault registration for shmem
This patch allows shmem-backed VMAs to be registered for minor faults. Minor faults are appropriately relayed to userspace in the fault path, for VMAs with the relevant flag. This commit doesn't hook up the UFFDIO_CONTINUE ioctl for shmem-backed minor faults, though, so userspace doesn't yet have a way to resolve such faults. Because of this, we also don't yet advertise this as a supported feature. That will be done in a separate commit when the feature is fully implemented. Link: https://lkml.kernel.org/r/20210503180737.2487560-4-axelrasmussen@google.com Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> Acked-by: Peter Xu <peterx@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Brian Geffon <bgeffon@google.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Joe Perches <joe@perches.com> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Oliver Upton <oupton@google.com> Cc: Shaohua Li <shli@fb.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Wang Qing <wangqing@vivo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/userfaultfd.c3
-rw-r--r--mm/memory.c8
-rw-r--r--mm/shmem.c12
3 files changed, 17 insertions, 6 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 5dd78238cc15..82ef253d66b6 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1267,8 +1267,7 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma,
}
if (vm_flags & VM_UFFD_MINOR) {
- /* FIXME: Add minor fault interception for shmem. */
- if (!is_vm_hugetlb_page(vma))
+ if (!(is_vm_hugetlb_page(vma) || vma_is_shmem(vma)))
return false;
}
diff --git a/mm/memory.c b/mm/memory.c
index 07a71a016c18..b535a1d0317d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4026,9 +4026,11 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
* something).
*/
if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
- ret = do_fault_around(vmf);
- if (ret)
- return ret;
+ if (likely(!userfaultfd_minor(vmf->vma))) {
+ ret = do_fault_around(vmf);
+ if (ret)
+ return ret;
+ }
}
ret = __do_fault(vmf);
diff --git a/mm/shmem.c b/mm/shmem.c
index 9b66a2b2680c..0d186b91a2f9 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1797,7 +1797,7 @@ unlock:
* vm. If we swap it in we mark it dirty since we also free the swap
* entry since a page cannot live in both the swap and page cache.
*
- * vmf and fault_type are only supplied by shmem_fault:
+ * vma, vmf, and fault_type are only supplied by shmem_fault:
* otherwise they are NULL.
*/
static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
@@ -1832,6 +1832,16 @@ repeat:
page = pagecache_get_page(mapping, index,
FGP_ENTRY | FGP_HEAD | FGP_LOCK, 0);
+
+ if (page && vma && userfaultfd_minor(vma)) {
+ if (!xa_is_value(page)) {
+ unlock_page(page);
+ put_page(page);
+ }
+ *fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
+ return 0;
+ }
+
if (xa_is_value(page)) {
error = shmem_swapin_page(inode, index, &page,
sgp, gfp, vma, fault_type);