linux-hardened/mm/filemap_xip.c
Sagi Grimberg 2ec74c3ef2 mm: move all mmu notifier invocations to be done outside the PT lock
In order to allow sleeping during mmu notifier calls, we need to avoid
invoking them under the page table spinlock.  This patch solves the
problem by calling invalidate_page notification after releasing the lock
(but before freeing the page itself), or by wrapping the page invalidation
with calls to invalidate_range_begin and invalidate_range_end.

To prevent accidental changes to the invalidate_range_end arguments after
the call to invalidate_range_begin, the patch introduces a convention of
saving the arguments in consistently named locals:

	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;	/* For mmu_notifiers */

	...

	mmun_start = ...
	mmun_end = ...
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);

	...

	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);

The patch changes code to use this convention for all calls to
mmu_notifier_invalidate_range_start/end, except those where the calls are
close enough so that anyone who glances at the code can see the values
aren't changing.

This patchset is a preliminary step towards on-demand paging design to be
added to the RDMA stack.

Why do we want on-demand paging for Infiniband?

  Applications register memory with an RDMA adapter using system calls,
  and subsequently post IO operations that refer to the corresponding
  virtual addresses directly to HW.  Until now, this was achieved by
  pinning the memory during the registration calls.  The goal of on demand
  paging is to avoid pinning the pages of registered memory regions (MRs).
   This will allow users the same flexibility they get when swapping any
  other part of their processes address spaces.  Instead of requiring the
  entire MR to fit in physical memory, we can allow the MR to be larger,
  and only fit the current working set in physical memory.

Why should anyone care?  What problems are users currently experiencing?

  This can make programming with RDMA much simpler.  Today, developers
  that are working with more data than their RAM can hold need either to
  deregister and reregister memory regions throughout their process's
  life, or keep a single memory region and copy the data to it.  On demand
  paging will allow these developers to register a single MR at the
  beginning of their process's life, and let the operating system manage
  which pages needs to be fetched at a given time.  In the future, we
  might be able to provide a single memory access key for each process
  that would provide the entire process's address as one large memory
  region, and the developers wouldn't need to register memory regions at
  all.

Is there any prospect that any other subsystems will utilise these
infrastructural changes?  If so, which and how, etc?

  As for other subsystems, I understand that XPMEM wanted to sleep in
  MMU notifiers, as Christoph Lameter wrote at
  http://lkml.indiana.edu/hypermail/linux/kernel/0802.1/0460.html and
  perhaps Andrea knows about other use cases.

  Scheduling in mmu notifications is required since we need to sync the
  hardware with the secondary page tables change.  A TLB flush of an IO
  device is inherently slower than a CPU TLB flush, so our design works by
  sending the invalidation request to the device, and waiting for an
  interrupt before exiting the mmu notifier handler.

Avi said:

  kvm may be a buyer.  kvm::mmu_lock, which serializes guest page
  faults, also protects long operations such as destroying large ranges.
  It would be good to convert it into a spinlock, but as it is used inside
  mmu notifiers, this cannot be done.

  (there are alternatives, such as keeping the spinlock and using a
  generation counter to do the teardown in O(1), which is what the "may"
  is doing up there).

[akpm@linux-foundation.orgpossible speed tweak in hugetlb_cow(), cleanups]
Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Haggai Eran <haggaie@mellanox.com>
Cc: Shachar Raindel <raindel@mellanox.com>
Cc: Liran Liss <liranl@mellanox.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-09 16:22:58 +09:00

486 lines
11 KiB
C

/*
* linux/mm/filemap_xip.c
*
* Copyright (C) 2005 IBM Corporation
* Author: Carsten Otte <cotte@de.ibm.com>
*
* derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds
*
*/
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/export.h>
#include <linux/uio.h>
#include <linux/rmap.h>
#include <linux/mmu_notifier.h>
#include <linux/sched.h>
#include <linux/seqlock.h>
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <asm/tlbflush.h>
#include <asm/io.h>
/*
* We do use our own empty page to avoid interference with other users
* of ZERO_PAGE(), such as /dev/zero
*/
static DEFINE_MUTEX(xip_sparse_mutex);
static seqcount_t xip_sparse_seq = SEQCNT_ZERO;
static struct page *__xip_sparse_page;
/* called under xip_sparse_mutex */
static struct page *xip_sparse_page(void)
{
if (!__xip_sparse_page) {
struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
if (page)
__xip_sparse_page = page;
}
return __xip_sparse_page;
}
/*
* This is a file read routine for execute in place files, and uses
* the mapping->a_ops->get_xip_mem() function for the actual low-level
* stuff.
*
* Note the struct file* is not used at all. It may be NULL.
*/
static ssize_t
do_xip_mapping_read(struct address_space *mapping,
struct file_ra_state *_ra,
struct file *filp,
char __user *buf,
size_t len,
loff_t *ppos)
{
struct inode *inode = mapping->host;
pgoff_t index, end_index;
unsigned long offset;
loff_t isize, pos;
size_t copied = 0, error = 0;
BUG_ON(!mapping->a_ops->get_xip_mem);
pos = *ppos;
index = pos >> PAGE_CACHE_SHIFT;
offset = pos & ~PAGE_CACHE_MASK;
isize = i_size_read(inode);
if (!isize)
goto out;
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
do {
unsigned long nr, left;
void *xip_mem;
unsigned long xip_pfn;
int zero = 0;
/* nr is the maximum number of bytes to copy from this page */
nr = PAGE_CACHE_SIZE;
if (index >= end_index) {
if (index > end_index)
goto out;
nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
if (nr <= offset) {
goto out;
}
}
nr = nr - offset;
if (nr > len - copied)
nr = len - copied;
error = mapping->a_ops->get_xip_mem(mapping, index, 0,
&xip_mem, &xip_pfn);
if (unlikely(error)) {
if (error == -ENODATA) {
/* sparse */
zero = 1;
} else
goto out;
}
/* If users can be writing to this page using arbitrary
* virtual addresses, take care about potential aliasing
* before reading the page on the kernel side.
*/
if (mapping_writably_mapped(mapping))
/* address based flush */ ;
/*
* Ok, we have the mem, so now we can copy it to user space...
*
* The actor routine returns how many bytes were actually used..
* NOTE! This may not be the same as how much of a user buffer
* we filled up (we may be padding etc), so we can only update
* "pos" here (the actor routine has to update the user buffer
* pointers and the remaining count).
*/
if (!zero)
left = __copy_to_user(buf+copied, xip_mem+offset, nr);
else
left = __clear_user(buf + copied, nr);
if (left) {
error = -EFAULT;
goto out;
}
copied += (nr - left);
offset += (nr - left);
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;
} while (copied < len);
out:
*ppos = pos + copied;
if (filp)
file_accessed(filp);
return (copied ? copied : error);
}
ssize_t
xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
{
if (!access_ok(VERIFY_WRITE, buf, len))
return -EFAULT;
return do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
buf, len, ppos);
}
EXPORT_SYMBOL_GPL(xip_file_read);
/*
* __xip_unmap is invoked from xip_unmap and
* xip_write
*
* This function walks all vmas of the address_space and unmaps the
* __xip_sparse_page when found at pgoff.
*/
static void
__xip_unmap (struct address_space * mapping,
unsigned long pgoff)
{
struct vm_area_struct *vma;
struct mm_struct *mm;
unsigned long address;
pte_t *pte;
pte_t pteval;
spinlock_t *ptl;
struct page *page;
unsigned count;
int locked = 0;
count = read_seqcount_begin(&xip_sparse_seq);
page = __xip_sparse_page;
if (!page)
return;
retry:
mutex_lock(&mapping->i_mmap_mutex);
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
mm = vma->vm_mm;
address = vma->vm_start +
((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
pte = page_check_address(page, mm, address, &ptl, 1);
if (pte) {
/* Nuke the page table entry. */
flush_cache_page(vma, address, pte_pfn(*pte));
pteval = ptep_clear_flush(vma, address, pte);
page_remove_rmap(page);
dec_mm_counter(mm, MM_FILEPAGES);
BUG_ON(pte_dirty(pteval));
pte_unmap_unlock(pte, ptl);
/* must invalidate_page _before_ freeing the page */
mmu_notifier_invalidate_page(mm, address);
page_cache_release(page);
}
}
mutex_unlock(&mapping->i_mmap_mutex);
if (locked) {
mutex_unlock(&xip_sparse_mutex);
} else if (read_seqcount_retry(&xip_sparse_seq, count)) {
mutex_lock(&xip_sparse_mutex);
locked = 1;
goto retry;
}
}
/*
* xip_fault() is invoked via the vma operations vector for a
* mapped memory region to read in file data during a page fault.
*
* This function is derived from filemap_fault, but used for execute in place
*/
static int xip_file_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct file *file = vma->vm_file;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
pgoff_t size;
void *xip_mem;
unsigned long xip_pfn;
struct page *page;
int error;
/* XXX: are VM_FAULT_ codes OK? */
again:
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (vmf->pgoff >= size)
return VM_FAULT_SIGBUS;
error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
&xip_mem, &xip_pfn);
if (likely(!error))
goto found;
if (error != -ENODATA)
return VM_FAULT_OOM;
/* sparse block */
if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
(vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) &&
(!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
int err;
/* maybe shared writable, allocate new block */
mutex_lock(&xip_sparse_mutex);
error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
&xip_mem, &xip_pfn);
mutex_unlock(&xip_sparse_mutex);
if (error)
return VM_FAULT_SIGBUS;
/* unmap sparse mappings at pgoff from all other vmas */
__xip_unmap(mapping, vmf->pgoff);
found:
err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
xip_pfn);
if (err == -ENOMEM)
return VM_FAULT_OOM;
/*
* err == -EBUSY is fine, we've raced against another thread
* that faulted-in the same page
*/
if (err != -EBUSY)
BUG_ON(err);
return VM_FAULT_NOPAGE;
} else {
int err, ret = VM_FAULT_OOM;
mutex_lock(&xip_sparse_mutex);
write_seqcount_begin(&xip_sparse_seq);
error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
&xip_mem, &xip_pfn);
if (unlikely(!error)) {
write_seqcount_end(&xip_sparse_seq);
mutex_unlock(&xip_sparse_mutex);
goto again;
}
if (error != -ENODATA)
goto out;
/* not shared and writable, use xip_sparse_page() */
page = xip_sparse_page();
if (!page)
goto out;
err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
page);
if (err == -ENOMEM)
goto out;
ret = VM_FAULT_NOPAGE;
out:
write_seqcount_end(&xip_sparse_seq);
mutex_unlock(&xip_sparse_mutex);
return ret;
}
}
static const struct vm_operations_struct xip_file_vm_ops = {
.fault = xip_file_fault,
.page_mkwrite = filemap_page_mkwrite,
.remap_pages = generic_file_remap_pages,
};
int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
{
BUG_ON(!file->f_mapping->a_ops->get_xip_mem);
file_accessed(file);
vma->vm_ops = &xip_file_vm_ops;
vma->vm_flags |= VM_MIXEDMAP;
return 0;
}
EXPORT_SYMBOL_GPL(xip_file_mmap);
static ssize_t
__xip_file_write(struct file *filp, const char __user *buf,
size_t count, loff_t pos, loff_t *ppos)
{
struct address_space * mapping = filp->f_mapping;
const struct address_space_operations *a_ops = mapping->a_ops;
struct inode *inode = mapping->host;
long status = 0;
size_t bytes;
ssize_t written = 0;
BUG_ON(!mapping->a_ops->get_xip_mem);
do {
unsigned long index;
unsigned long offset;
size_t copied;
void *xip_mem;
unsigned long xip_pfn;
offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
index = pos >> PAGE_CACHE_SHIFT;
bytes = PAGE_CACHE_SIZE - offset;
if (bytes > count)
bytes = count;
status = a_ops->get_xip_mem(mapping, index, 0,
&xip_mem, &xip_pfn);
if (status == -ENODATA) {
/* we allocate a new page unmap it */
mutex_lock(&xip_sparse_mutex);
status = a_ops->get_xip_mem(mapping, index, 1,
&xip_mem, &xip_pfn);
mutex_unlock(&xip_sparse_mutex);
if (!status)
/* unmap page at pgoff from all other vmas */
__xip_unmap(mapping, index);
}
if (status)
break;
copied = bytes -
__copy_from_user_nocache(xip_mem + offset, buf, bytes);
if (likely(copied > 0)) {
status = copied;
if (status >= 0) {
written += status;
count -= status;
pos += status;
buf += status;
}
}
if (unlikely(copied != bytes))
if (status >= 0)
status = -EFAULT;
if (status < 0)
break;
} while (count);
*ppos = pos;
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold i_mutex.
*/
if (pos > inode->i_size) {
i_size_write(inode, pos);
mark_inode_dirty(inode);
}
return written ? written : status;
}
ssize_t
xip_file_write(struct file *filp, const char __user *buf, size_t len,
loff_t *ppos)
{
struct address_space *mapping = filp->f_mapping;
struct inode *inode = mapping->host;
size_t count;
loff_t pos;
ssize_t ret;
sb_start_write(inode->i_sb);
mutex_lock(&inode->i_mutex);
if (!access_ok(VERIFY_READ, buf, len)) {
ret=-EFAULT;
goto out_up;
}
pos = *ppos;
count = len;
/* We can write back this queue in page reclaim */
current->backing_dev_info = mapping->backing_dev_info;
ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
if (ret)
goto out_backing;
if (count == 0)
goto out_backing;
ret = file_remove_suid(filp);
if (ret)
goto out_backing;
ret = file_update_time(filp);
if (ret)
goto out_backing;
ret = __xip_file_write (filp, buf, count, pos, ppos);
out_backing:
current->backing_dev_info = NULL;
out_up:
mutex_unlock(&inode->i_mutex);
sb_end_write(inode->i_sb);
return ret;
}
EXPORT_SYMBOL_GPL(xip_file_write);
/*
* truncate a page used for execute in place
* functionality is analog to block_truncate_page but does use get_xip_mem
* to get the page instead of page cache
*/
int
xip_truncate_page(struct address_space *mapping, loff_t from)
{
pgoff_t index = from >> PAGE_CACHE_SHIFT;
unsigned offset = from & (PAGE_CACHE_SIZE-1);
unsigned blocksize;
unsigned length;
void *xip_mem;
unsigned long xip_pfn;
int err;
BUG_ON(!mapping->a_ops->get_xip_mem);
blocksize = 1 << mapping->host->i_blkbits;
length = offset & (blocksize - 1);
/* Block boundary? Nothing to do */
if (!length)
return 0;
length = blocksize - length;
err = mapping->a_ops->get_xip_mem(mapping, index, 0,
&xip_mem, &xip_pfn);
if (unlikely(err)) {
if (err == -ENODATA)
/* Hole? No need to truncate */
return 0;
else
return err;
}
memset(xip_mem + offset, 0, length);
return 0;
}
EXPORT_SYMBOL_GPL(xip_truncate_page);