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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.

[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>
This commit is contained in:
Mike Rapoport
2017-02-24 14:58:22 -08:00
committed by Linus Torvalds
parent 846b1a0f1d
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;
}