Re: [PATCH] Added CONFIG_VFAT_FS_DUALNAMES option

> This is a new patch for VFAT long filename support, replacing the one
> that I posted last month. It retains a lot more functionality then the
> previous patch.
>
> A FAQ will be posted immediately after this patch to answer the
> questions that were raised from the previous discussion.
>
> Cheers, Tridge
>
>
> ------------
>
> When VFAT_FS_DUALNAMES is disabled we avoid the creation of 8.3 short
> filenames for files on VFAT filesystems that require a long name. The
> patch uses a pattern of 11 bytes in the directory entry which contains
> invalid characters such that it cannot be considered to be a valid short
> filename.
>
> Signed-off-by: Andrew Tridgell <tridge@...>
> Acked-by: Dave Kleikamp <shaggy@...>
> Acked-by: Paul E. McKenney <paulmck@...>
> ---
>  fs/fat/Kconfig      |   20 +++++++++++++++++
>  fs/fat/dir.c        |   15 ++++++-------
>  fs/fat/namei_vfat.c |   59 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 86 insertions(+), 8 deletions(-)
>
> diff --git a/fs/fat/Kconfig b/fs/fat/Kconfig
> index 182f9ff..907a5de 100644
> --- a/fs/fat/Kconfig
> +++ b/fs/fat/Kconfig
> @@ -74,6 +74,26 @@ config VFAT_FS
>    To compile this as a module, choose M here: the module will be called
>    vfat.
>  
> +config VFAT_FS_DUALNAMES
> + bool "VFAT dual names support"
> + depends on VFAT_FS
> + help
> +  This option provides support for dual filenames on VFAT filesystems.
> +  If this option is disabled then file creation will either put
> +  a short (8.3) name or a long name on the file, but never both.
> +  The field where a shortname would normally go is filled with
> +  invalid characters such that it cannot be considered a valid
> +  short filename.
> +
> +  That means that long filenames created with this option
> +  disabled will not be accessible at all to operating systems
> +  that do not understand the VFAT extensions.
> +
> +  Users considering enabling this option should consider the implications
> +  of any patents that may exist on dual filenames in VFAT.
> +
> +  If unsure, say N
> +
>  config FAT_DEFAULT_CODEPAGE
>   int "Default codepage for FAT"
>   depends on MSDOS_FS || VFAT_FS
> diff --git a/fs/fat/dir.c b/fs/fat/dir.c
> index 38ff75a..cd5d3ec 100644
> --- a/fs/fat/dir.c
> +++ b/fs/fat/dir.c
> @@ -420,14 +420,13 @@ parse_record:
>   }
>   i += chl;
>   }
> - if (!last_u)
> - continue;
> -
> - /* Compare shortname */
> - bufuname[last_u] = 0x0000;
> - len = fat_uni_to_x8(sbi, bufuname, bufname, sizeof(bufname));
> - if (fat_name_match(sbi, name, name_len, bufname, len))
> - goto found;
> + if (last_u) {
> + /* Compare shortname */
> + bufuname[last_u] = 0x0000;
> + len = fat_uni_to_x8(sbi, bufuname, bufname, sizeof(bufname));
> + if (fat_name_match(sbi, name, name_len, bufname, len))
> + goto found;
> + }
>  
>   if (nr_slots) {
>   void *longname = unicode + FAT_MAX_UNI_CHARS;