Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0-only
       2             : #include <linux/export.h>
       3             : #include <linux/fs.h>
       4             : #include <linux/fs_stack.h>
       5             : 
       6             : /* does _NOT_ require i_mutex to be held.
       7             :  *
       8             :  * This function cannot be inlined since i_size_{read,write} is rather
       9             :  * heavy-weight on 32-bit systems
      10             :  */
      11           0 : void fsstack_copy_inode_size(struct inode *dst, struct inode *src)
      12             : {
      13             :         loff_t i_size;
      14             :         blkcnt_t i_blocks;
      15             : 
      16             :         /*
      17             :          * i_size_read() includes its own seqlocking and protection from
      18             :          * preemption (see include/linux/fs.h): we need nothing extra for
      19             :          * that here, and prefer to avoid nesting locks than attempt to keep
      20             :          * i_size and i_blocks in sync together.
      21             :          */
      22           0 :         i_size = i_size_read(src);
      23             : 
      24             :         /*
      25             :          * But on 32-bit, we ought to make an effort to keep the two halves of
      26             :          * i_blocks in sync despite SMP or PREEMPTION - though stat's
      27             :          * generic_fillattr() doesn't bother, and we won't be applying quotas
      28             :          * (where i_blocks does become important) at the upper level.
      29             :          *
      30             :          * We don't actually know what locking is used at the lower level;
      31             :          * but if it's a filesystem that supports quotas, it will be using
      32             :          * i_lock as in inode_add_bytes().
      33             :          */
      34             :         if (sizeof(i_blocks) > sizeof(long))
      35             :                 spin_lock(&src->i_lock);
      36           0 :         i_blocks = src->i_blocks;
      37             :         if (sizeof(i_blocks) > sizeof(long))
      38             :                 spin_unlock(&src->i_lock);
      39             : 
      40             :         /*
      41             :          * If CONFIG_SMP or CONFIG_PREEMPTION on 32-bit, it's vital for
      42             :          * fsstack_copy_inode_size() to hold some lock around
      43             :          * i_size_write(), otherwise i_size_read() may spin forever (see
      44             :          * include/linux/fs.h).  We don't necessarily hold i_mutex when this
      45             :          * is called, so take i_lock for that case.
      46             :          *
      47             :          * And if on 32-bit, continue our effort to keep the two halves of
      48             :          * i_blocks in sync despite SMP or PREEMPTION: use i_lock for that case
      49             :          * too, and do both at once by combining the tests.
      50             :          *
      51             :          * There is none of this locking overhead in the 64-bit case.
      52             :          */
      53             :         if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
      54             :                 spin_lock(&dst->i_lock);
      55           0 :         i_size_write(dst, i_size);
      56           0 :         dst->i_blocks = i_blocks;
      57             :         if (sizeof(i_size) > sizeof(long) || sizeof(i_blocks) > sizeof(long))
      58             :                 spin_unlock(&dst->i_lock);
      59           0 : }
      60             : EXPORT_SYMBOL_GPL(fsstack_copy_inode_size);
      61             : 
      62             : /* copy all attributes */
      63           0 : void fsstack_copy_attr_all(struct inode *dest, const struct inode *src)
      64             : {
      65           0 :         dest->i_mode = src->i_mode;
      66           0 :         dest->i_uid = src->i_uid;
      67           0 :         dest->i_gid = src->i_gid;
      68           0 :         dest->i_rdev = src->i_rdev;
      69           0 :         dest->i_atime = src->i_atime;
      70           0 :         dest->i_mtime = src->i_mtime;
      71           0 :         dest->i_ctime = src->i_ctime;
      72           0 :         dest->i_blkbits = src->i_blkbits;
      73           0 :         dest->i_flags = src->i_flags;
      74           0 :         set_nlink(dest, src->i_nlink);
      75           0 : }
      76             : EXPORT_SYMBOL_GPL(fsstack_copy_attr_all);