Branch data Line data Source code
1 : : #include <linux/export.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 : : */
10 : 0 : void 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 : 0 : 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 : 0 : dst->i_blocks = i_blocks;
57 : : if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
58 : : spin_unlock(&dst->i_lock);
59 : 0 : }
60 : : EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
61 : :
62 : : /* copy all attributes */
63 : 0 : void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
64 : : {
65 : 0 : dest->i_mode = src->i_mode;
66 : 0 : dest->i_uid = src->i_uid;
67 : 0 : dest->i_gid = src->i_gid;
68 : 0 : dest->i_rdev = src->i_rdev;
69 : 0 : dest->i_atime = src->i_atime;
70 : 0 : dest->i_mtime = src->i_mtime;
71 : 0 : dest->i_ctime = src->i_ctime;
72 : 0 : dest->i_blkbits = src->i_blkbits;
73 : 0 : dest->i_flags = src->i_flags;
74 : 0 : set_nlink(dest, src->i_nlink);
75 : 0 : }
76 : : EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);
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