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SubjectRe: Reg file system hash function
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 ( The developer of ARM Linux

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