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().  tmpfs uses other locking, and
33	 * its 32-bit is (just) able to exceed 2TB i_size with the aid of
34	 * holes; but its i_blocks cannot carry into the upper long without
35	 * almost 2TB swap - let's ignore that case.
36	 */
37	if (sizeof(i_blocks) > sizeof(long))
38		spin_lock(&src->i_lock);
39	i_blocks = src->i_blocks;
40	if (sizeof(i_blocks) > sizeof(long))
41		spin_unlock(&src->i_lock);
42
43	/*
44	 * If CONFIG_SMP or CONFIG_PREEMPT on 32-bit, it's vital for
45	 * fsstack_copy_inode_size() to hold some lock around
46	 * i_size_write(), otherwise i_size_read() may spin forever (see
47	 * include/linux/fs.h).  We don't necessarily hold i_mutex when this
48	 * is called, so take i_lock for that case.
49	 *
50	 * And if CONFIG_LBADF (on 32-bit), continue our effort to keep the
51	 * two halves of i_blocks in sync despite SMP or PREEMPT: use i_lock
52	 * for that case too, and do both at once by combining the tests.
53	 *
54	 * There is none of this locking overhead in the 64-bit case.
55	 */
56	if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
57		spin_lock(&dst->i_lock);
58	i_size_write(dst, i_size);
59	dst->i_blocks = i_blocks;
60	if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
61		spin_unlock(&dst->i_lock);
62}
63EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
64
65/* copy all attributes */
66void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
67{
68	dest->i_mode = src->i_mode;
69	dest->i_uid = src->i_uid;
70	dest->i_gid = src->i_gid;
71	dest->i_rdev = src->i_rdev;
72	dest->i_atime = src->i_atime;
73	dest->i_mtime = src->i_mtime;
74	dest->i_ctime = src->i_ctime;
75	dest->i_blkbits = src->i_blkbits;
76	dest->i_flags = src->i_flags;
77	dest->i_nlink = src->i_nlink;
78}
79EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);
80