1#include <linux/module.h>
 2#include <linux/fs.h>
 3#include <linux/fs_stack.h>
 4
 5/* does _NOT_ require i_mutex to be held.
 6 *
 7 * This function cannot be inlined since i_size_{read,write} is rather
 8 * heavy-weight on 32-bit systems
 9 */
10void fsstack_copy_inode_size(struct inode *dst, struct inode *src)
11{
12	loff_t i_size;
13	blkcnt_t i_blocks;
14
15	/*
16	 * i_size_read() includes its own seqlocking and protection from
17	 * preemption (see include/linux/fs.h): we need nothing extra for
18	 * that here, and prefer to avoid nesting locks than attempt to keep
19	 * i_size and i_blocks in sync together.
20	 */
21	i_size = i_size_read(src);
22
23	/*
24	 * But if CONFIG_LBDAF (on 32-bit), we ought to make an effort to
25	 * keep the two halves of i_blocks in sync despite SMP or PREEMPT -
26	 * though stat's generic_fillattr() doesn't bother, and we won't be
27	 * applying quotas (where i_blocks does become important) at the
28	 * upper level.
29	 *
30	 * We don't actually know what locking is used at the lower level;
31	 * but if it's a filesystem that supports quotas, it will be using
32	 * i_lock as in inode_add_bytes().
33	 */
34	if (sizeof(i_blocks) > sizeof(long))
35		spin_lock(&src->i_lock);
36	i_blocks = src->i_blocks;
37	if (sizeof(i_blocks) > sizeof(long))
38		spin_unlock(&src->i_lock);
39
40	/*
41	 * If CONFIG_SMP or CONFIG_PREEMPT on 32-bit, it's vital for
42	 * fsstack_copy_inode_size() to hold some lock around
43	 * i_size_write(), otherwise i_size_read() may spin forever (see
44	 * include/linux/fs.h).  We don't necessarily hold i_mutex when this
45	 * is called, so take i_lock for that case.
46	 *
47	 * And if CONFIG_LBADF (on 32-bit), continue our effort to keep the
48	 * two halves of i_blocks in sync despite SMP or PREEMPT: use i_lock
49	 * for that case too, and do both at once by combining the tests.
50	 *
51	 * There is none of this locking overhead in the 64-bit case.
52	 */
53	if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
54		spin_lock(&dst->i_lock);
55	i_size_write(dst, i_size);
56	dst->i_blocks = i_blocks;
57	if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
58		spin_unlock(&dst->i_lock);
59}
60EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
61
62/* copy all attributes */
63void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
64{
65	dest->i_mode = src->i_mode;
66	dest->i_uid = src->i_uid;
67	dest->i_gid = src->i_gid;
68	dest->i_rdev = src->i_rdev;
69	dest->i_atime = src->i_atime;
70	dest->i_mtime = src->i_mtime;
71	dest->i_ctime = src->i_ctime;
72	dest->i_blkbits = src->i_blkbits;
73	dest->i_flags = src->i_flags;
74	dest->i_nlink = src->i_nlink;
75}
76EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);