Commit c4728cfb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'vfs-5.10-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux 

Pull clone/dedupe/remap code refactoring from Darrick Wong:
 "Move the generic file range remap (aka reflink and dedupe) functions
  out of mm/filemap.c and fs/read_write.c and into fs/remap_range.c to
  reduce clutter in the first two files"

* tag 'vfs-5.10-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  vfs: move the generic write and copy checks out of mm
  vfs: move the remap range helpers to remap_range.c
  vfs: move generic_remap_checks out of mm
parents f9a705ad 407e9c63

fs/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -14,7 +14,7 @@ obj-y := open.o read_write.o file_table.o super.o \ 
		pnode.o splice.o sync.o utimes.o d_path.o \

		stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \

		fs_types.o fs_context.o fs_parser.o fsopen.o init.o \

		kernel_read_file.o

		kernel_read_file.o remap_range.o



ifeq ($(CONFIG_BLOCK),y)

obj-y +=	buffer.o block_dev.o direct-io.o mpage.o

fs/read_write.c

+107 −437
Original line number Diff line number Diff line
@@ -1410,6 +1410,59 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in, 
				       flags);

}



/*

 * Performs necessary checks before doing a file copy

 *

 * Can adjust amount of bytes to copy via @req_count argument.

 * Returns appropriate error code that caller should return or

 * zero in case the copy should be allowed.

 */

static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,

				    struct file *file_out, loff_t pos_out,

				    size_t *req_count, unsigned int flags)

{

	struct inode *inode_in = file_inode(file_in);

	struct inode *inode_out = file_inode(file_out);

	uint64_t count = *req_count;

	loff_t size_in;

	int ret;



	ret = generic_file_rw_checks(file_in, file_out);

	if (ret)

		return 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;



	/* Ensure offsets don't wrap. */

	if (pos_in + count < pos_in || pos_out + count < pos_out)

		return -EOVERFLOW;



	/* Shorten the copy to EOF */

	size_in = i_size_read(inode_in);

	if (pos_in >= size_in)

		count = 0;

	else

		count = min(count, size_in - (uint64_t)pos_in);



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

	if (ret)

		return ret;



	/* Don't allow overlapped copying within the same file. */

	if (inode_in == inode_out &&

	    pos_out + count > pos_in &&

	    pos_out < pos_in + count)

		return -EINVAL;



	*req_count = count;

	return 0;

}



/*

 * copy_file_range() differs from regular file read and write in that it

 * specifically allows return partial success.  When it does so is up to
@@ -1542,475 +1595,92 @@ out2: 
	return ret;

}



static int remap_verify_area(struct file *file, loff_t pos, loff_t len,

			     bool write)

{

	struct inode *inode = file_inode(file);



	if (unlikely(pos < 0 || len < 0))

		return -EINVAL;



	 if (unlikely((loff_t) (pos + len) < 0))

		return -EINVAL;



	if (unlikely(inode->i_flctx && mandatory_lock(inode))) {

		loff_t end = len ? pos + len - 1 : OFFSET_MAX;

		int retval;



		retval = locks_mandatory_area(inode, file, pos, end,

				write ? F_WRLCK : F_RDLCK);

		if (retval < 0)

			return retval;

	}



	return security_file_permission(file, write ? MAY_WRITE : MAY_READ);

}

/*

 * 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.

 * Don't operate on ranges the page cache doesn't support, and don't exceed the

 * LFS limits.  If pos is under the limit it becomes a short access.  If it

 * exceeds the limit we return -EFBIG.

 */

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)

int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)

{

	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 page *vfs_dedupe_get_page(struct inode *inode, loff_t offset)

{

	struct page *page;



	page = read_mapping_page(inode->i_mapping, offset >> PAGE_SHIFT, NULL);

	if (IS_ERR(page))

		return page;

	if (!PageUptodate(page)) {

		put_page(page);

		return ERR_PTR(-EIO);

	}

	return page;

}



/*

 * Lock two pages, ensuring that we lock in offset order if the pages are from

 * the same file.

 */

static void vfs_lock_two_pages(struct page *page1, struct page *page2)

{

	/* Always lock in order of increasing index. */

	if (page1->index > page2->index)

		swap(page1, page2);

	struct inode *inode = file->f_mapping->host;

	loff_t max_size = inode->i_sb->s_maxbytes;

	loff_t limit = rlimit(RLIMIT_FSIZE);



	lock_page(page1);

	if (page1 != page2)

		lock_page(page2);

	if (limit != RLIM_INFINITY) {

		if (pos >= limit) {

			send_sig(SIGXFSZ, current, 0);

			return -EFBIG;

		}



/* Unlock two pages, being careful not to unlock the same page twice. */

static void vfs_unlock_two_pages(struct page *page1, struct page *page2)

{

	unlock_page(page1);

	if (page1 != page2)

		unlock_page(page2);

		*count = min(*count, limit - pos);

	}



/*

 * 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 inode *src, loff_t srcoff,

					 struct inode *dest, loff_t destoff,

					 loff_t len, bool *is_same)

{

	loff_t src_poff;

	loff_t dest_poff;

	void *src_addr;

	void *dest_addr;

	struct page *src_page;

	struct page *dest_page;

	loff_t cmp_len;

	bool same;

	int error;



	error = -EINVAL;

	same = true;

	while (len) {

		src_poff = srcoff & (PAGE_SIZE - 1);

		dest_poff = destoff & (PAGE_SIZE - 1);

		cmp_len = min(PAGE_SIZE - src_poff,

			      PAGE_SIZE - dest_poff);

		cmp_len = min(cmp_len, len);

		if (cmp_len <= 0)

			goto out_error;



		src_page = vfs_dedupe_get_page(src, srcoff);

		if (IS_ERR(src_page)) {

			error = PTR_ERR(src_page);

			goto out_error;

		}

		dest_page = vfs_dedupe_get_page(dest, destoff);

		if (IS_ERR(dest_page)) {

			error = PTR_ERR(dest_page);

			put_page(src_page);

			goto out_error;

		}



		vfs_lock_two_pages(src_page, dest_page);



		/*

		 * Now that we've locked both pages, 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 (!PageUptodate(src_page) || !PageUptodate(dest_page) ||

		    src_page->mapping != src->i_mapping ||

		    dest_page->mapping != dest->i_mapping) {

			same = false;

			goto unlock;

		}



		src_addr = kmap_atomic(src_page);

		dest_addr = kmap_atomic(dest_page);



		flush_dcache_page(src_page);

		flush_dcache_page(dest_page);

	if (!(file->f_flags & O_LARGEFILE))

		max_size = MAX_NON_LFS;



		if (memcmp(src_addr + src_poff, dest_addr + dest_poff, cmp_len))

			same = false;

	if (unlikely(pos >= max_size))

		return -EFBIG;



		kunmap_atomic(dest_addr);

		kunmap_atomic(src_addr);

unlock:

		vfs_unlock_two_pages(src_page, dest_page);

		put_page(dest_page);

		put_page(src_page);

	*count = min(*count, max_size - pos);



		if (!same)

			break;



		srcoff += cmp_len;

		destoff += 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.

 * Performs necessary checks before doing a write

 *

 * If there's an error, then the usual negative error code is returned.

 * Otherwise returns 0 with *len set to the request length.

 * Can adjust writing position or amount of bytes to write.

 * Returns appropriate error code that caller should return or

 * zero in case that write should be allowed.

 */

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)

ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)

{

	struct inode *inode_in = file_inode(file_in);

	struct inode *inode_out = file_inode(file_out);

	bool same_inode = (inode_in == inode_out);

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;

	loff_t count;

	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))

	if (IS_SWAPFILE(inode))

		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)

	if (!iov_iter_count(from))

		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)

		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);

	/* FIXME: this is for backwards compatibility with 2.4 */

	if (iocb->ki_flags & IOCB_APPEND)

		iocb->ki_pos = i_size_read(inode);



	ret = filemap_write_and_wait_range(inode_in->i_mapping,

			pos_in, pos_in + *len - 1);

	if (ret)

		return ret;

	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))

		return -EINVAL;



	ret = filemap_write_and_wait_range(inode_out->i_mapping,

			pos_out, pos_out + *len - 1);

	count = iov_iter_count(from);

	ret = generic_write_check_limits(file, iocb->ki_pos, &count);

	if (ret)

		return ret;



	/*

	 * Check that the extents are the same.

	 */

	if (remap_flags & REMAP_FILE_DEDUP) {

		bool		is_same = false;



		ret = vfs_dedupe_file_range_compare(inode_in, pos_in,

				inode_out, pos_out, *len, &is_same);

		if (ret)

			return ret;

		if (!is_same)

			return -EBADE;

	iov_iter_truncate(from, count);

	return iov_iter_count(from);

}



	ret = generic_remap_check_len(inode_in, inode_out, pos_out, len,

			remap_flags);

	if (ret)

		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;

}

EXPORT_SYMBOL(generic_remap_file_range_prep);



loff_t do_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);

EXPORT_SYMBOL(generic_write_checks);



/*

	 * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on

	 * the same mount. Practically, they only need to be on the same file

	 * system.

 * Performs common checks before doing a file copy/clone

 * from @file_in to @file_out.

 */

	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;



	ret = file_in->f_op->remap_file_range(file_in, pos_in,

			file_out, pos_out, len, remap_flags);

	if (ret < 0)

		return ret;



	fsnotify_access(file_in);

	fsnotify_modify(file_out);

	return ret;

}

EXPORT_SYMBOL(do_clone_file_range);



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)

int generic_file_rw_checks(struct file *file_in, struct file *file_out)

{

	loff_t ret;



	file_start_write(file_out);

	ret = do_clone_file_range(file_in, pos_in, file_out, pos_out, len,

				  remap_flags);

	file_end_write(file_out);



	return ret;

}

EXPORT_SYMBOL(vfs_clone_file_range);



/* Check whether we are allowed to dedupe the destination file */

static bool allow_file_dedupe(struct file *file)

{

	if (capable(CAP_SYS_ADMIN))

		return true;

	if (file->f_mode & FMODE_WRITE)

		return true;

	if (uid_eq(current_fsuid(), file_inode(file)->i_uid))

		return true;

	if (!inode_permission(file_inode(file), 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));



	ret = mnt_want_write_file(dst_file);

	if (ret)

		return ret;



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

	if (ret < 0)

		goto out_drop_write;



	ret = -EPERM;

	if (!allow_file_dedupe(dst_file))

		goto out_drop_write;



	ret = -EXDEV;

	if (src_file->f_path.mnt != dst_file->f_path.mnt)

		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;

	struct inode *inode_in = file_inode(file_in);

	struct inode *inode_out = file_inode(file_out);



	if (S_ISDIR(src->i_mode))

	/* Don't copy dirs, pipes, sockets... */

	if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->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))

	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))

		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++) {

		struct fd dst_fd = fdget(info->dest_fd);

		struct file *dst_file = dst_fd.file;



		if (!dst_file) {

			info->status = -EBADF;

			goto next_loop;

		}



		if (info->reserved) {

			info->status = -EINVAL;

			goto next_fdput;

		}



		deduped = vfs_dedupe_file_range_one(file, off, dst_file,

						    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;

	if (!(file_in->f_mode & FMODE_READ) ||

	    !(file_out->f_mode & FMODE_WRITE) ||

	    (file_out->f_flags & O_APPEND))

		return -EBADF;



next_fdput:

		fdput(dst_fd);

next_loop:

		if (fatal_signal_pending(current))

			break;

	}

	return ret;

	return 0;

}
 
EXPORT_SYMBOL(vfs_dedupe_file_range);

fs/remap_range.c

0 → 100644
+571 −0

File added.

Preview size limit exceeded, changes collapsed.

include/linux/fs.h

+2 −6
Original line number Diff line number Diff line
@@ -2946,13 +2946,9 @@ extern int sb_min_blocksize(struct super_block *, int); 
extern int generic_file_mmap(struct file *, struct vm_area_struct *);

extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);

extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);

extern int generic_remap_checks(struct file *file_in, loff_t pos_in,

				struct file *file_out, loff_t pos_out,

				loff_t *count, unsigned int remap_flags);

extern int generic_write_check_limits(struct file *file, loff_t pos,

		loff_t *count);

extern int generic_file_rw_checks(struct file *file_in, struct file *file_out);

extern int generic_copy_file_checks(struct file *file_in, loff_t pos_in,

				    struct file *file_out, loff_t pos_out,

				    size_t *count, unsigned int flags);

extern ssize_t generic_file_buffered_read(struct kiocb *iocb,

		struct iov_iter *to, ssize_t already_read);

extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);

mm/filemap.c

+0 −222
Original line number Diff line number Diff line
@@ -3121,228 +3121,6 @@ struct page *read_cache_page_gfp(struct address_space *mapping, 
}

EXPORT_SYMBOL(read_cache_page_gfp);



/*

 * Don't operate on ranges the page cache doesn't support, and don't exceed the

 * LFS limits.  If pos is under the limit it becomes a short access.  If it

 * exceeds the limit we return -EFBIG.

 */

static int generic_write_check_limits(struct file *file, loff_t pos,

				      loff_t *count)

{

	struct inode *inode = file->f_mapping->host;

	loff_t max_size = inode->i_sb->s_maxbytes;

	loff_t limit = rlimit(RLIMIT_FSIZE);



	if (limit != RLIM_INFINITY) {

		if (pos >= limit) {

			send_sig(SIGXFSZ, current, 0);

			return -EFBIG;

		}

		*count = min(*count, limit - pos);

	}



	if (!(file->f_flags & O_LARGEFILE))

		max_size = MAX_NON_LFS;



	if (unlikely(pos >= max_size))

		return -EFBIG;



	*count = min(*count, max_size - pos);



	return 0;

}



/*

 * Performs necessary checks before doing a write

 *

 * Can adjust writing position or amount of bytes to write.

 * Returns appropriate error code that caller should return or

 * zero in case that write should be allowed.

 */

inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;

	loff_t count;

	int ret;



	if (IS_SWAPFILE(inode))

		return -ETXTBSY;



	if (!iov_iter_count(from))

		return 0;



	/* FIXME: this is for backwards compatibility with 2.4 */

	if (iocb->ki_flags & IOCB_APPEND)

		iocb->ki_pos = i_size_read(inode);



	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))

		return -EINVAL;



	count = iov_iter_count(from);

	ret = generic_write_check_limits(file, iocb->ki_pos, &count);

	if (ret)

		return ret;



	iov_iter_truncate(from, count);

	return iov_iter_count(from);

}

EXPORT_SYMBOL(generic_write_checks);



/*

 * 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.

 */

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) {

		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;

}





/*

 * Performs common checks before doing a file copy/clone

 * from @file_in to @file_out.

 */

int generic_file_rw_checks(struct file *file_in, struct file *file_out)

{

	struct inode *inode_in = file_inode(file_in);

	struct inode *inode_out = file_inode(file_out);



	/* Don't copy 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;



	if (!(file_in->f_mode & FMODE_READ) ||

	    !(file_out->f_mode & FMODE_WRITE) ||

	    (file_out->f_flags & O_APPEND))

		return -EBADF;



	return 0;

}



/*

 * Performs necessary checks before doing a file copy

 *

 * Can adjust amount of bytes to copy via @req_count argument.

 * Returns appropriate error code that caller should return or

 * zero in case the copy should be allowed.

 */

int generic_copy_file_checks(struct file *file_in, loff_t pos_in,

			     struct file *file_out, loff_t pos_out,

			     size_t *req_count, unsigned int flags)

{

	struct inode *inode_in = file_inode(file_in);

	struct inode *inode_out = file_inode(file_out);

	uint64_t count = *req_count;

	loff_t size_in;

	int ret;



	ret = generic_file_rw_checks(file_in, file_out);

	if (ret)

		return 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;



	/* Ensure offsets don't wrap. */

	if (pos_in + count < pos_in || pos_out + count < pos_out)

		return -EOVERFLOW;



	/* Shorten the copy to EOF */

	size_in = i_size_read(inode_in);

	if (pos_in >= size_in)

		count = 0;

	else

		count = min(count, size_in - (uint64_t)pos_in);



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

	if (ret)

		return ret;



	/* Don't allow overlapped copying within the same file. */

	if (inode_in == inode_out &&

	    pos_out + count > pos_in &&

	    pos_out < pos_in + count)

		return -EINVAL;



	*req_count = count;

	return 0;

}



int pagecache_write_begin(struct file *file, struct address_space *mapping,

				loff_t pos, unsigned len, unsigned flags,

				struct page **pagep, void **fsdata)

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