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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 | 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 | 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 | } |
60 | EXPORT_SYMBOL_GPL(fsstack_copy_inode_size); |
61 | |
62 | /* copy all attributes */ |
63 | void 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 | set_nlink(dest, src->i_nlink); |
75 | } |
76 | EXPORT_SYMBOL_GPL(fsstack_copy_attr_all); |
77 |
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