Re: [PATCH][FAT] FAT dirent scan with hin take #3

[Pekka Enberg <penberg@cs.helsinki.fi>]

On 8/31/05, Machida, Hiroyuki <machida@sm.sony.co.jp> wrote:
> How about this ?
> 
>         if (!MSDOS_I(dir)->scan_hints) {
>                 hints  = kcalllo(....);
> 
>                 down
>                 if (MSDOS_I(dir)->scan_hints) {
>                         up
>                         goto already_allocated;
>                 }
>                 if (hints)
>                         MSDOS_I(dir)->scan_hints = hints;
>                 up
>         }
>         return (hints == 0) ? -ENOMEM : 0;
> 
> already_allocated:
>         kfree(hints); /* kfree accepts NULL */
>         return 0;

After finally understanding what you're doing, how about:

static inline int hint_allocate(struct inode *dir)
{
        loff_t *hints;
        int err = 0;

        if (!MSDOS_I(dir)->scan_hints)
                return 0;

        hints = kcalloc(FAT_SCAN_NWAY, sizeof(loff_t), GFP_KERNEL);
        if (!hints)
                err = -ENOMEM;

        down(&MSDOS_I(dir)->scan_lock);
        /*
         * We allocated memory without scan_lock so lets make sure
         * no other thread completed hint_allocate() before us.
         */
        if (!MSDOS_I(dir)->scan_hints) {
                MSDOS_I(dir)->scan_hints = hints;
                hints = NULL;
        }
        up(&MSDOS_I(dir)->scan_lock);

        kfree(hints);
        return err;
}

                                    Pekka