Re: Reg file system hash function

Russell King (rmk@arm.linux.org.uk)
Fri, 15 Jun 2001 11:30:38 +0100


On Fri, Jun 15, 2001 at 03:52:52PM +0530, SATHISH.J wrote:
> In the vfs layer when we see the lookup_dentry() function code we see that
> a part of the code checks whether low level filesystem wants to use its
> own hash. the part odf the code that calls the filesystem dependant
> hashing is "error = base->d_op->d_hash->(base,&this);". Why should it
> callfilesystem dependant hashing. What is the main purpose of hashing
> here.
> Please help me with these details.

It is used in two cases. If a filesystem has:

1. case-insensitive filenames (its much better to have the names 'FOO' and
'foo' refer to the same dentry, since they refer to the same file)

2. a limited filename length and your filesystem truncates names (on a
non-vfat filesystem 'dosfilen.ame' and 'dosfilename.ame' would be the
same file and the same dentry structure).

--
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/