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authorMike Rapoport <rppt@linux.vnet.ibm.com>2017-02-24 14:58:22 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:55 -0800
commit897ab3e0c49e24b62e2d54d165c7afec6bbca65b (patch)
tree5fa7e09864d6c959cef33849f6cb10ed04e459e4 /fs/userfaultfd.c
parent846b1a0f1db065a8479159dd8fecddb1ebf30547 (diff)
downloadlwn-897ab3e0c49e24b62e2d54d165c7afec6bbca65b.tar.gz
lwn-897ab3e0c49e24b62e2d54d165c7afec6bbca65b.zip
userfaultfd: non-cooperative: add event for memory unmaps
When a non-cooperative userfaultfd monitor copies pages in the background, it may encounter regions that were already unmapped. Addition of UFFD_EVENT_UNMAP allows the uffd monitor to track precisely changes in the virtual memory layout. Since there might be different uffd contexts for the affected VMAs, we first should create a temporary representation for the unmap event for each uffd context and then notify them one by one to the appropriate userfault file descriptors. The event notification occurs after the mmap_sem has been released. [arnd@arndb.de: fix nommu build] Link: http://lkml.kernel.org/r/20170203165141.3665284-1-arnd@arndb.de [mhocko@suse.com: fix nommu build] Link: http://lkml.kernel.org/r/20170202091503.GA22823@dhcp22.suse.cz Link: http://lkml.kernel.org/r/1485542673-24387-3-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Pavel Emelyanov <xemul@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/userfaultfd.c')
-rw-r--r--fs/userfaultfd.c65
1 files changed, 65 insertions, 0 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 8fe601b4875e..4c78458ea78d 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -71,6 +71,13 @@ struct userfaultfd_fork_ctx {
struct list_head list;
};
+struct userfaultfd_unmap_ctx {
+ struct userfaultfd_ctx *ctx;
+ unsigned long start;
+ unsigned long end;
+ struct list_head list;
+};
+
struct userfaultfd_wait_queue {
struct uffd_msg msg;
wait_queue_t wq;
@@ -709,6 +716,64 @@ void userfaultfd_remove(struct vm_area_struct *vma,
down_read(&mm->mmap_sem);
}
+static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
+ unsigned long start, unsigned long end)
+{
+ struct userfaultfd_unmap_ctx *unmap_ctx;
+
+ list_for_each_entry(unmap_ctx, unmaps, list)
+ if (unmap_ctx->ctx == ctx && unmap_ctx->start == start &&
+ unmap_ctx->end == end)
+ return true;
+
+ return false;
+}
+
+int userfaultfd_unmap_prep(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ struct list_head *unmaps)
+{
+ for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
+ struct userfaultfd_unmap_ctx *unmap_ctx;
+ struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
+
+ if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) ||
+ has_unmap_ctx(ctx, unmaps, start, end))
+ continue;
+
+ unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL);
+ if (!unmap_ctx)
+ return -ENOMEM;
+
+ userfaultfd_ctx_get(ctx);
+ unmap_ctx->ctx = ctx;
+ unmap_ctx->start = start;
+ unmap_ctx->end = end;
+ list_add_tail(&unmap_ctx->list, unmaps);
+ }
+
+ return 0;
+}
+
+void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
+{
+ struct userfaultfd_unmap_ctx *ctx, *n;
+ struct userfaultfd_wait_queue ewq;
+
+ list_for_each_entry_safe(ctx, n, uf, list) {
+ msg_init(&ewq.msg);
+
+ ewq.msg.event = UFFD_EVENT_UNMAP;
+ ewq.msg.arg.remove.start = ctx->start;
+ ewq.msg.arg.remove.end = ctx->end;
+
+ userfaultfd_event_wait_completion(ctx->ctx, &ewq);
+
+ list_del(&ctx->list);
+ kfree(ctx);
+ }
+}
+
static int userfaultfd_release(struct inode *inode, struct file *file)
{
struct userfaultfd_ctx *ctx = file->private_data;