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/*
* Copyright (c) 2006-2009 Erez Zadok
* Copyright (c) 2006-2007 Josef 'Jeff' Sipek
* Copyright (c) 2006-2009 Stony Brook University
* Copyright (c) 2006-2009 The Research Foundation of SUNY
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/fs_stack.h>
/*
* does _NOT_ require i_mutex to be held.
*
* This function cannot be inlined since i_size_{read,write} is rather
* heavy-weight on 32-bit systems
*/
void fsstack_copy_inode_size(struct inode *dst, struct inode *src)
{
loff_t i_size;
blkcnt_t i_blocks;
/*
* i_size_read() includes its own seqlocking and protection from
* preemption (see include/linux/fs.h): we need nothing extra for
* that here, and prefer to avoid nesting locks than attempt to
* keep i_size and i_blocks in synch together.
*/
i_size = i_size_read(src);
/*
* But if CONFIG_LSF (on 32-bit), we ought to make an effort to keep
* the two halves of i_blocks in synch despite SMP or PREEMPT - though
* stat's generic_fillattr() doesn't bother, and we won't be applying
* quotas (where i_blocks does become important) at the upper level.
*
* We don't actually know what locking is used at the lower level; but
* if it's a filesystem that supports quotas, it will be using i_lock
* as in inode_add_bytes(). tmpfs uses other locking, and its 32-bit
* is (just) able to exceed 2TB i_size with the aid of holes; but its
* i_blocks cannot carry into the upper long without almost 2TB swap -
* let's ignore that case.
*/
if (sizeof(i_blocks) > sizeof(long))
spin_lock(&src->i_lock);
i_blocks = src->i_blocks;
if (sizeof(i_blocks) > sizeof(long))
spin_unlock(&src->i_lock);
/*
* If CONFIG_SMP on 32-bit, it's vital for fsstack_copy_inode_size()
* to hold some lock around i_size_write(), otherwise i_size_read()
* may spin forever (see include/linux/fs.h). We don't necessarily
* hold i_mutex when this is called, so take i_lock for that case.
*
* And if CONFIG_LSF (on 32-bit), continue our effort to keep the
* two halves of i_blocks in synch despite SMP or PREEMPT: use i_lock
* for that case too, and do both at once by combining the tests.
*
* There is none of this locking overhead in the 64-bit case.
*/
if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
spin_lock(&dst->i_lock);
i_size_write(dst, i_size);
dst->i_blocks = i_blocks;
if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
spin_unlock(&dst->i_lock);
}
EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
/*
* copy all attributes; get_nlinks is optional way to override the i_nlink
* copying
*/
void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
{
dest->i_mode = src->i_mode;
dest->i_uid = src->i_uid;
dest->i_gid = src->i_gid;
dest->i_rdev = src->i_rdev;
dest->i_atime = src->i_atime;
dest->i_mtime = src->i_mtime;
dest->i_ctime = src->i_ctime;
dest->i_blkbits = src->i_blkbits;
dest->i_flags = src->i_flags;
dest->i_nlink = src->i_nlink;
}
EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);
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