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