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userfaultfd: non-cooperative: add event for memory unmaps

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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.

[[email protected]: fix nommu build]
  Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: fix nommu build]
  Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Michal Hocko <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mike Rapoport 2017-02-24 14:58:22 -08:00 • committed by Linus Torvalds
commit 897ab3e0c4
15 changed files with 160 additions and 45 deletions
Download patch file Download diff file Expand all files Collapse all files

23
mm/mremap.c
View file

@ -252,7 +252,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
static unsigned long move_vma(struct vm_area_struct *vma,
unsigned long old_addr, unsigned long old_len,
unsigned long new_len, unsigned long new_addr,
bool *locked, struct vm_userfaultfd_ctx *uf)
bool *locked, struct vm_userfaultfd_ctx *uf,
struct list_head *uf_unmap)
{
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *new_vma;
@ -341,7 +342,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
if (unlikely(vma->vm_flags & VM_PFNMAP))
untrack_pfn_moved(vma);
if (do_munmap(mm, old_addr, old_len) < 0) {
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
/* OOM: unable to split vma, just get accounts right */
vm_unacct_memory(excess >> PAGE_SHIFT);
excess = 0;
@ -417,7 +418,8 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
unsigned long new_addr, unsigned long new_len, bool *locked,
struct vm_userfaultfd_ctx *uf)
struct vm_userfaultfd_ctx *uf,
struct list_head *uf_unmap)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
@ -435,12 +437,12 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
if (addr + old_len > new_addr && new_addr + new_len > addr)
goto out;
ret = do_munmap(mm, new_addr, new_len);
ret = do_munmap(mm, new_addr, new_len, NULL);
if (ret)
goto out;
if (old_len >= new_len) {
ret = do_munmap(mm, addr+new_len, old_len - new_len);
ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
if (ret && old_len != new_len)
goto out;
old_len = new_len;
@ -462,7 +464,8 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
if (offset_in_page(ret))
goto out1;
ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf);
ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
uf_unmap);
if (!(offset_in_page(ret)))
goto out;
out1:
@ -502,6 +505,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
unsigned long charged = 0;
bool locked = false;
struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
LIST_HEAD(uf_unmap);
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
return ret;
@ -528,7 +532,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
if (flags & MREMAP_FIXED) {
ret = mremap_to(addr, old_len, new_addr, new_len,
&locked, &uf);
&locked, &uf, &uf_unmap);
goto out;
}
@ -538,7 +542,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
* do_munmap does all the needed commit accounting
*/
if (old_len >= new_len) {
ret = do_munmap(mm, addr+new_len, old_len - new_len);
ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap);
if (ret && old_len != new_len)
goto out;
ret = addr;
@ -598,7 +602,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
}
ret = move_vma(vma, addr, old_len, new_len, new_addr,
&locked, &uf);
&locked, &uf, &uf_unmap);
}
out:
if (offset_in_page(ret)) {
@ -609,5 +613,6 @@ out:
if (locked && new_len > old_len)
mm_populate(new_addr + old_len, new_len - old_len);
mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
userfaultfd_unmap_complete(mm, &uf_unmap);
return ret;
}