Quelle stack.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/fs_stack.h>

/* does _NOT_ require i_rwsem 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 on 32-bit, we ought to make an effort to keep the two halves of
* i_blocks in sync despite SMP or PREEMPTION - 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_PREEMPTION 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_rwsem when this
* is called, so take i_lock for that case.
*
* And if on 32-bit, continue our effort to keep the two halves of
* i_blocks in sync despite SMP or PREEMPTION: 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;
inode_set_atime_to_ts(dest, inode_get_atime(src));
inode_set_mtime_to_ts(dest, inode_get_mtime(src));
inode_set_ctime_to_ts(dest, inode_get_ctime(src));
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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