Branch data     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                 :          0 :         loff_t i_size;
      14                 :          0 :         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                 :          0 :         if (sizeof(i_blocks) > sizeof(long))
      35                 :            :                 spin_lock(&src->i_lock);
      36                 :          0 :         i_blocks = src->i_blocks;
      37                 :          0 :         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                 :          0 :         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                 :          0 :         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);