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| author | Pavel Emelyanov <xemul@parallels.com> | 2017-02-22 15:42:27 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-22 16:41:28 -0800 |
| commit | 893e26e61d04eac974ded0c11e1647b335c8cb7b (patch) | |
| tree | d75bbbd621a08130e8794dffcedc71f4a6ff50cc /kernel/fork.c | |
| parent | 656031445d5a855e1c13b291dedae32579d0f3f2 (diff) | |
| download | linux-893e26e61d04eac974ded0c11e1647b335c8cb7b.tar.gz | |
userfaultfd: non-cooperative: Add fork() event
When the mm with uffd-ed vmas fork()-s the respective vmas notify their uffds with the event which contains a descriptor with new uffd. This new descriptor can then be used to get events from the child and populate its mm with data. Note, that there can be different uffd-s controlling different vmas within one mm, so first we should collect all those uffds (and ctx-s) in a list and then notify them all one by one but only once per fork(). The context is created at fork() time but the descriptor, file struct and anon inode object is created at event read time. So some trickery is added to the userfaultfd_ctx_read() to handle the ctx queues' locking vs file creation. Another thing worth noticing is that the task that fork()-s waits for the uffd event to get processed WITHOUT the mmap sem. [aarcange@redhat.com: build warning fix] Link: http://lkml.kernel.org/r/20161216144821.5183-10-aarcange@redhat.com Link: http://lkml.kernel.org/r/20161216144821.5183-9-aarcange@redhat.com Signed-off-by: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.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 Kravetz <mike.kravetz@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index ff82e24573b6..d12fcc4db8a3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -55,6 +55,7 @@ #include <linux/rmap.h> #include <linux/ksm.h> #include <linux/acct.h> +#include <linux/userfaultfd_k.h> #include <linux/tsacct_kern.h> #include <linux/cn_proc.h> #include <linux/freezer.h> @@ -561,6 +562,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, struct rb_node **rb_link, *rb_parent; int retval; unsigned long charge; + LIST_HEAD(uf); uprobe_start_dup_mmap(); if (down_write_killable(&oldmm->mmap_sem)) { @@ -617,12 +619,13 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, if (retval) goto fail_nomem_policy; tmp->vm_mm = mm; + retval = dup_userfaultfd(tmp, &uf); + if (retval) + goto fail_nomem_anon_vma_fork; if (anon_vma_fork(tmp, mpnt)) goto fail_nomem_anon_vma_fork; - tmp->vm_flags &= - ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP); + tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); tmp->vm_next = tmp->vm_prev = NULL; - tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; file = tmp->vm_file; if (file) { struct inode *inode = file_inode(file); @@ -678,6 +681,7 @@ out: up_write(&mm->mmap_sem); flush_tlb_mm(oldmm); up_write(&oldmm->mmap_sem); + dup_userfaultfd_complete(&uf); fail_uprobe_end: uprobe_end_dup_mmap(); return retval; |