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_LBDAF (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