1 // SPDX-License-Identifier: GPL-2.0-only 2 #include <linux/export.h> 3 #include <linux/fs.h> 4 #include <linux/fs_stack.h> 5 6 /* does _NOT_ require i_mutex to be held. 7 * 8 * This function cannot be inlined since i_size_{read,write} is rather 9 * heavy-weight on 32-bit systems 10 */ 11 void fsstack_copy_inode_size(struct inode *dst, struct inode *src) 12 { 13 loff_t i_size; 14 blkcnt_t i_blocks; 15 16 /* 17 * i_size_read() includes its own seqlocking and protection from 18 * preemption (see include/linux/fs.h): we need nothing extra for 19 * that here, and prefer to avoid nesting locks than attempt to keep 20 * i_size and i_blocks in sync together. 21 */ 22 i_size = i_size_read(src); 23 24 /* 25 * But on 32-bit, we ought to make an effort to keep the two halves of 26 * i_blocks in sync despite SMP or PREEMPT - though stat's 27 * generic_fillattr() doesn't bother, and we won't be applying quotas 28 * (where i_blocks does become important) at the 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 on 32-bit, continue our effort to keep the two halves of 48 * i_blocks in sync despite SMP or PREEMPT: use i_lock for that case 49 * 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