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fs/stack.c
2.52 KB
81f7e3824
Initial Release, ...
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#include <linux/export.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 sync together.
*/
i_size = i_size_read(src);
/*
* But if CONFIG_LBDAF (on 32-bit), we ought to make an effort to
* keep the two halves of i_blocks in sync 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().
*/
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 or CONFIG_PREEMPT 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_LBDAF (on 32-bit), continue our effort to keep the
* two halves of i_blocks in sync 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 */
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;
set_nlink(dest, src->i_nlink);
}
EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);
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