On Fri, 2006-04-07 at 21:51 -0700, UZAIR LAKHANI wrote:
> I want to find out the purpose of a part of Wrapfs
> code.
>
> The function name is wrapfs_interpose
>
> The code is
>
> /* check that the lower file system didn't cross a
> mount point */
> if (lower_inode->i_sb != SUPERBLOCK_TO_LOWER(sb)) {
> err = -EXDEV;
> goto out;
> }
>
> I want to find out what is the purpose of the above
> check.
Exactly what the comment says - it checks to make sure that we didn't
cross a mount point. It does this by making sure that the lower-level
superblock of this lower-level inode is the same as the lower-level
superblock that we expect (the one used at mount-time). So basically,
if we see a superblock that is different from the one we usually use, we
crossed a mount point and so we return an error.
Avishay Traeger
http://www.fsl.cs.sunysb.edu/~avishay/
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