Quelle remap_range.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/sched/xacct.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include <linux/dax.h>
#include <linux/overflow.h>
#include "internal.h"

#include <linux/uaccess.h>
#include <asm/unistd.h>

/*
* Performs necessary checks before doing a clone.
*
* Can adjust amount of bytes to clone via @req_count argument.
* Returns appropriate error code that caller should return or
* zero in case the clone should be allowed.
*/
static int generic_remap_checks(struct file *file_in, loff_t pos_in,
    struct file *file_out, loff_t pos_out,
    loff_t *req_count, unsigned int remap_flags)
{
struct inode *inode_in = file_in->f_mapping->host;
struct inode *inode_out = file_out->f_mapping->host;
uint64_t count = *req_count;
uint64_t bcount;
loff_t size_in, size_out;
loff_t bs = inode_out->i_sb->s_blocksize;
int ret;

/* The start of both ranges must be aligned to an fs block. */
if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_out, bs))
  return -EINVAL;

/* Ensure offsets don't wrap. */
if (pos_in + count < pos_in || pos_out + count < pos_out)
  return -EINVAL;

size_in = i_size_read(inode_in);
size_out = i_size_read(inode_out);

/* Dedupe requires both ranges to be within EOF. */
if ((remap_flags & REMAP_FILE_DEDUP) &&
     (pos_in >= size_in || pos_in + count > size_in ||
      pos_out >= size_out || pos_out + count > size_out))
  return -EINVAL;

/* Ensure the infile range is within the infile. */
if (pos_in >= size_in)
  return -EINVAL;
count = min(count, size_in - (uint64_t)pos_in);

ret = generic_write_check_limits(file_out, pos_out, &count);
if (ret)
  return ret;

/*
* If the user wanted us to link to the infile's EOF, round up to the
* next block boundary for this check.
*
* Otherwise, make sure the count is also block-aligned, having
* already confirmed the starting offsets' block alignment.
*/
if (pos_in + count == size_in &&
     (!(remap_flags & REMAP_FILE_DEDUP) || pos_out + count == size_out)) {
  bcount = ALIGN(size_in, bs) - pos_in;
} else {
  if (!IS_ALIGNED(count, bs))
   count = ALIGN_DOWN(count, bs);
  bcount = count;
}

/* Don't allow overlapped cloning within the same file. */
if (inode_in == inode_out &&
     pos_out + bcount > pos_in &&
     pos_out < pos_in + bcount)
  return -EINVAL;

/*
* We shortened the request but the caller can't deal with that, so
* bounce the request back to userspace.
*/
if (*req_count != count && !(remap_flags & REMAP_FILE_CAN_SHORTEN))
  return -EINVAL;

*req_count = count;
return 0;
}

int remap_verify_area(struct file *file, loff_t pos, loff_t len, bool write)
{
int mask = write ? MAY_WRITE : MAY_READ;
loff_t tmp;
int ret;

if (unlikely(pos < 0 || len < 0))
  return -EINVAL;

if (unlikely(check_add_overflow(pos, len, &tmp)))
  return -EINVAL;

ret = security_file_permission(file, mask);
if (ret)
  return ret;

return fsnotify_file_area_perm(file, mask, &pos, len);
}
EXPORT_SYMBOL_GPL(remap_verify_area);

/*
* Ensure that we don't remap a partial EOF block in the middle of something
* else.  Assume that the offsets have already been checked for block
* alignment.
*
* For clone we only link a partial EOF block above or at the destination file's
* EOF.  For deduplication we accept a partial EOF block only if it ends at the
* destination file's EOF (can not link it into the middle of a file).
*
* Shorten the request if possible.
*/
static int generic_remap_check_len(struct inode *inode_in,
       struct inode *inode_out,
       loff_t pos_out,
       loff_t *len,
       unsigned int remap_flags)
{
u64 blkmask = i_blocksize(inode_in) - 1;
loff_t new_len = *len;

if ((*len & blkmask) == 0)
  return 0;

if (pos_out + *len < i_size_read(inode_out))
  new_len &= ~blkmask;

if (new_len == *len)
  return 0;

if (remap_flags & REMAP_FILE_CAN_SHORTEN) {
  *len = new_len;
  return 0;
}

return (remap_flags & REMAP_FILE_DEDUP) ? -EBADE : -EINVAL;
}

/* Read a page's worth of file data into the page cache. */
static struct folio *vfs_dedupe_get_folio(struct file *file, loff_t pos)
{
return read_mapping_folio(file->f_mapping, pos >> PAGE_SHIFT, file);
}

/*
* Lock two folios, ensuring that we lock in offset order if the folios
* are from the same file.
*/
static void vfs_lock_two_folios(struct folio *folio1, struct folio *folio2)
{
/* Always lock in order of increasing index. */
if (folio1->index > folio2->index)
  swap(folio1, folio2);

folio_lock(folio1);
if (folio1 != folio2)
  folio_lock(folio2);
}

/* Unlock two folios, being careful not to unlock the same folio twice. */
static void vfs_unlock_two_folios(struct folio *folio1, struct folio *folio2)
{
folio_unlock(folio1);
if (folio1 != folio2)
  folio_unlock(folio2);
}

/*
* Compare extents of two files to see if they are the same.
* Caller must have locked both inodes to prevent write races.
*/
static int vfs_dedupe_file_range_compare(struct file *src, loff_t srcoff,
      struct file *dest, loff_t dstoff,
      loff_t len, bool *is_same)
{
bool same = true;
int error = -EINVAL;

while (len) {
  struct folio *src_folio, *dst_folio;
  void *src_addr, *dst_addr;
  loff_t cmp_len = min(PAGE_SIZE - offset_in_page(srcoff),
         PAGE_SIZE - offset_in_page(dstoff));

  cmp_len = min(cmp_len, len);
  if (cmp_len <= 0)
   goto out_error;

  src_folio = vfs_dedupe_get_folio(src, srcoff);
  if (IS_ERR(src_folio)) {
   error = PTR_ERR(src_folio);
   goto out_error;
  }
  dst_folio = vfs_dedupe_get_folio(dest, dstoff);
  if (IS_ERR(dst_folio)) {
   error = PTR_ERR(dst_folio);
   folio_put(src_folio);
   goto out_error;
  }

  vfs_lock_two_folios(src_folio, dst_folio);

  /*
* Now that we've locked both folios, make sure they're still
* mapped to the file data we're interested in.  If not,
* someone is invalidating pages on us and we lose.
*/
  if (!folio_test_uptodate(src_folio) || !folio_test_uptodate(dst_folio) ||
      src_folio->mapping != src->f_mapping ||
      dst_folio->mapping != dest->f_mapping) {
   same = false;
   goto unlock;
  }

  src_addr = kmap_local_folio(src_folio,
     offset_in_folio(src_folio, srcoff));
  dst_addr = kmap_local_folio(dst_folio,
     offset_in_folio(dst_folio, dstoff));

  flush_dcache_folio(src_folio);
  flush_dcache_folio(dst_folio);

  if (memcmp(src_addr, dst_addr, cmp_len))
   same = false;

  kunmap_local(dst_addr);
  kunmap_local(src_addr);
unlock:
  vfs_unlock_two_folios(src_folio, dst_folio);
  folio_put(dst_folio);
  folio_put(src_folio);

  if (!same)
   break;

  srcoff += cmp_len;
  dstoff += cmp_len;
  len -= cmp_len;
}

*is_same = same;
return 0;

out_error:
return error;
}

/*
* Check that the two inodes are eligible for cloning, the ranges make
* sense, and then flush all dirty data.  Caller must ensure that the
* inodes have been locked against any other modifications.
*
* If there's an error, then the usual negative error code is returned.
* Otherwise returns 0 with *len set to the request length.
*/
int
__generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
    struct file *file_out, loff_t pos_out,
    loff_t *len, unsigned int remap_flags,
    const struct iomap_ops *dax_read_ops)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);
bool same_inode = (inode_in == inode_out);
int ret;

/* Don't touch certain kinds of inodes */
if (IS_IMMUTABLE(inode_out))
  return -EPERM;

if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
  return -ETXTBSY;

/* Don't reflink dirs, pipes, sockets... */
if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
  return -EISDIR;
if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
  return -EINVAL;

/* Zero length dedupe exits immediately; reflink goes to EOF. */
if (*len == 0) {
  loff_t isize = i_size_read(inode_in);

  if ((remap_flags & REMAP_FILE_DEDUP) || pos_in == isize)
   return 0;
  if (pos_in > isize)
   return -EINVAL;
  *len = isize - pos_in;
  if (*len == 0)
   return 0;
}

/* Check that we don't violate system file offset limits. */
ret = generic_remap_checks(file_in, pos_in, file_out, pos_out, len,
   remap_flags);
if (ret || *len == 0)
  return ret;

/* Wait for the completion of any pending IOs on both files */
inode_dio_wait(inode_in);
if (!same_inode)
  inode_dio_wait(inode_out);

ret = filemap_write_and_wait_range(inode_in->i_mapping,
   pos_in, pos_in + *len - 1);
if (ret)
  return ret;

ret = filemap_write_and_wait_range(inode_out->i_mapping,
   pos_out, pos_out + *len - 1);
if (ret)
  return ret;

/*
* Check that the extents are the same.
*/
if (remap_flags & REMAP_FILE_DEDUP) {
  bool  is_same = false;

  if (!IS_DAX(inode_in))
   ret = vfs_dedupe_file_range_compare(file_in, pos_in,
     file_out, pos_out, *len, &is_same);
  else if (dax_read_ops)
   ret = dax_dedupe_file_range_compare(inode_in, pos_in,
     inode_out, pos_out, *len, &is_same,
     dax_read_ops);
  else
   return -EINVAL;
  if (ret)
   return ret;
  if (!is_same)
   return -EBADE;
}

ret = generic_remap_check_len(inode_in, inode_out, pos_out, len,
   remap_flags);
if (ret || *len == 0)
  return ret;

/* If can't alter the file contents, we're done. */
if (!(remap_flags & REMAP_FILE_DEDUP))
  ret = file_modified(file_out);

return ret;
}

int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
      struct file *file_out, loff_t pos_out,
      loff_t *len, unsigned int remap_flags)
{
return __generic_remap_file_range_prep(file_in, pos_in, file_out,
            pos_out, len, remap_flags, NULL);
}
EXPORT_SYMBOL(generic_remap_file_range_prep);

loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
       struct file *file_out, loff_t pos_out,
       loff_t len, unsigned int remap_flags)
{
loff_t ret;

WARN_ON_ONCE(remap_flags & REMAP_FILE_DEDUP);

if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
  return -EXDEV;

ret = generic_file_rw_checks(file_in, file_out);
if (ret < 0)
  return ret;

if (!file_in->f_op->remap_file_range)
  return -EOPNOTSUPP;

ret = remap_verify_area(file_in, pos_in, len, false);
if (ret)
  return ret;

ret = remap_verify_area(file_out, pos_out, len, true);
if (ret)
  return ret;

file_start_write(file_out);
ret = file_in->f_op->remap_file_range(file_in, pos_in,
   file_out, pos_out, len, remap_flags);
file_end_write(file_out);
if (ret < 0)
  return ret;

fsnotify_access(file_in);
fsnotify_modify(file_out);
return ret;
}
EXPORT_SYMBOL(vfs_clone_file_range);

/* Check whether we are allowed to dedupe the destination file */
static bool may_dedupe_file(struct file *file)
{
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct inode *inode = file_inode(file);

if (capable(CAP_SYS_ADMIN))
  return true;
if (file->f_mode & FMODE_WRITE)
  return true;
if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
  return true;
if (!inode_permission(idmap, inode, MAY_WRITE))
  return true;
return false;
}

loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
     struct file *dst_file, loff_t dst_pos,
     loff_t len, unsigned int remap_flags)
{
loff_t ret;

WARN_ON_ONCE(remap_flags & ~(REMAP_FILE_DEDUP |
         REMAP_FILE_CAN_SHORTEN));

/*
* This is redundant if called from vfs_dedupe_file_range(), but other
* callers need it and it's not performance sesitive...
*/
ret = remap_verify_area(src_file, src_pos, len, false);
if (ret)
  return ret;

ret = remap_verify_area(dst_file, dst_pos, len, true);
if (ret)
  return ret;

/*
* This needs to be called after remap_verify_area() because of
* sb_start_write() and before may_dedupe_file() because the mount's
* MAY_WRITE need to be checked with mnt_get_write_access_file() held.
*/
ret = mnt_want_write_file(dst_file);
if (ret)
  return ret;

ret = -EPERM;
if (!may_dedupe_file(dst_file))
  goto out_drop_write;

ret = -EXDEV;
if (file_inode(src_file)->i_sb != file_inode(dst_file)->i_sb)
  goto out_drop_write;

ret = -EISDIR;
if (S_ISDIR(file_inode(dst_file)->i_mode))
  goto out_drop_write;

ret = -EINVAL;
if (!dst_file->f_op->remap_file_range)
  goto out_drop_write;

if (len == 0) {
  ret = 0;
  goto out_drop_write;
}

ret = dst_file->f_op->remap_file_range(src_file, src_pos, dst_file,
   dst_pos, len, remap_flags | REMAP_FILE_DEDUP);
out_drop_write:
mnt_drop_write_file(dst_file);

return ret;
}
EXPORT_SYMBOL(vfs_dedupe_file_range_one);

int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
{
struct file_dedupe_range_info *info;
struct inode *src = file_inode(file);
u64 off;
u64 len;
int i;
int ret;
u16 count = same->dest_count;
loff_t deduped;

if (!(file->f_mode & FMODE_READ))
  return -EINVAL;

if (same->reserved1 || same->reserved2)
  return -EINVAL;

off = same->src_offset;
len = same->src_length;

if (S_ISDIR(src->i_mode))
  return -EISDIR;

if (!S_ISREG(src->i_mode))
  return -EINVAL;

if (!file->f_op->remap_file_range)
  return -EOPNOTSUPP;

ret = remap_verify_area(file, off, len, false);
if (ret < 0)
  return ret;
ret = 0;

if (off + len > i_size_read(src))
  return -EINVAL;

/* Arbitrary 1G limit on a single dedupe request, can be raised. */
len = min_t(u64, len, 1 << 30);

/* pre-format output fields to sane values */
for (i = 0; i < count; i++) {
  same->info[i].bytes_deduped = 0ULL;
  same->info[i].status = FILE_DEDUPE_RANGE_SAME;
}

for (i = 0, info = same->info; i < count; i++, info++) {
  CLASS(fd, dst_fd)(info->dest_fd);

  if (fd_empty(dst_fd)) {
   info->status = -EBADF;
   goto next_loop;
  }

  if (info->reserved) {
   info->status = -EINVAL;
   goto next_loop;
  }

  deduped = vfs_dedupe_file_range_one(file, off, fd_file(dst_fd),
          info->dest_offset, len,
          REMAP_FILE_CAN_SHORTEN);
  if (deduped == -EBADE)
   info->status = FILE_DEDUPE_RANGE_DIFFERS;
  else if (deduped < 0)
   info->status = deduped;
  else
   info->bytes_deduped = len;

next_loop:
  if (fatal_signal_pending(current))
   break;
}
return ret;
}
EXPORT_SYMBOL(vfs_dedupe_file_range);

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