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Re: [PATCH 2/4] XFS: Return case-insensitive match for dentry cache

To: "Christoph Hellwig" <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 2/4] XFS: Return case-insensitive match for dentry cache
From: "Barry Naujok" <bnaujok@xxxxxxx>
Date: Tue, 22 Apr 2008 13:54:28 +1000
Cc: xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx
In-reply-to: <20080421094641.GA5191@xxxxxxxxxxxxx>
Organization: SGI
References: <20080421083103.433280025@xxxxxxxxxxxxxxxxxxxxxxx> <20080421083644.809426871@xxxxxxxxxxxxxxxxxxxxxxx> <20080421085947.GA10399@xxxxxxxxxxxxx> <20080421094641.GA5191@xxxxxxxxxxxxx>
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On Mon, 21 Apr 2008 19:46:41 +1000, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

> +kmem_zone_t       *xfs_name_zone;

What about just using kmalloc here?  We know the length of the name
anyway, so there is no point of allocating the maximum possible size.

>    error = xfs_iget(dp->i_mount, NULL, inum, 0, 0, ipp, 0);
> -  if (error)
> +  if (error) {
> +          if (ci_match && *ci_match)
> +                  xfs_name_free(name->name);
>            goto out;
> +  }

All the allocation and freeing for ci_match looks odd and error prone
to me.  I think the low-level directory code should never allocate
args->value unless it's explicitly asked for a CI match.  That way
there's only one place in xfs_ci_lookup to free it either.

Also the low-level name duplication code could be factored out a little
more ala:

 * If a case-insensitive match, allocate a buffer and copy the actual
 * name into the buffer. Return it via args->value.
void xfs_copy_ci_name(struct xfs_da_args *args, const char *name, int namelen)
        if (args->return_ci_name && args->cmpresult == XFS_CMP_CASE) {
                args->valuelen = namelen;
                args->value = kmemdup(name, namelen, GFP_NOFS);
                /* error handled in higher layers */

Instead of adding args->return_ci_name it might make sense to just
replace the last four chars there with an unsigned short lookup_flags
and just set bits in it.

There's already a "flags" field in xfs_da_args and only the low 16 bits
are currently used for attr operations.

We could use 5 of the high bits for these flags, or just add another
flags field (which are used for things other than lookup).

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