LXR linux/fs/stack.c

   1#include <linux/export.h>
   2#include <linux/fs.h>
   3#include <linux/fs_stack.h>
   4
   5/* does _NOT_ require i_mutex to be held.
   6 *
   7 * This function cannot be inlined since i_size_{read,write} is rather
   8 * heavy-weight on 32-bit systems
   9 */
  10void fsstack_copy_inode_size(struct inode *dst, struct inode *src)
  11{
  12        loff_t i_size;
  13        blkcnt_t i_blocks;
  14
  15        /*
  16         * i_size_read() includes its own seqlocking and protection from
  17         * preemption (see include/linux/fs.h): we need nothing extra for
  18         * that here, and prefer to avoid nesting locks than attempt to keep
  19         * i_size and i_blocks in sync together.
  20         */
  21        i_size = i_size_read(src);
  22
  23        /*
  24         * But on 32-bit, we ought to make an effort to keep the two halves of
  25         * i_blocks in sync despite SMP or PREEMPT - though stat's
  26         * generic_fillattr() doesn't bother, and we won't be applying quotas
  27         * (where i_blocks does become important) at the upper level.
  28         *
  29         * We don't actually know what locking is used at the lower level;
  30         * but if it's a filesystem that supports quotas, it will be using
  31         * i_lock as in inode_add_bytes().
  32         */
  33        if (sizeof(i_blocks) > sizeof(long))
  34                spin_lock(&src->i_lock);
  35        i_blocks = src->i_blocks;
  36        if (sizeof(i_blocks) > sizeof(long))
  37                spin_unlock(&src->i_lock);
  38
  39        /*
  40         * If CONFIG_SMP or CONFIG_PREEMPT on 32-bit, it's vital for
  41         * fsstack_copy_inode_size() to hold some lock around
  42         * i_size_write(), otherwise i_size_read() may spin forever (see
  43         * include/linux/fs.h).  We don't necessarily hold i_mutex when this
  44         * is called, so take i_lock for that case.
  45         *
  46         * And if on 32-bit, continue our effort to keep the two halves of
  47         * i_blocks in sync despite SMP or PREEMPT: use i_lock  for that case
  48         * too, and do both at once by combining the tests.
  49         *
  50         * There is none of this locking overhead in the 64-bit case.
  51         */
  52        if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
  53                spin_lock(&dst->i_lock);
  54        i_size_write(dst, i_size);
  55        dst->i_blocks = i_blocks;
  56        if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
  57                spin_unlock(&dst->i_lock);
  58}
  59EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
  60
  61/* copy all attributes */
  62void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
  63{
  64        dest->i_mode = src->i_mode;
  65        dest->i_uid = src->i_uid;
  66        dest->i_gid = src->i_gid;
  67        dest->i_rdev = src->i_rdev;
  68        dest->i_atime = src->i_atime;
  69        dest->i_mtime = src->i_mtime;
  70        dest->i_ctime = src->i_ctime;
  71        dest->i_blkbits = src->i_blkbits;
  72        dest->i_flags = src->i_flags;
  73        set_nlink(dest, src->i_nlink);
  74}
  75EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);
  76