On Mon 16-08-10 12:13:19, Joel Becker wrote:
> On Mon, Aug 16, 2010 at 09:44:35AM -0500, Eric Sandeen wrote:
> > Joel Becker wrote:
> > > How about:
> > >
> > > u64 last_fs_page = last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
> > >
> > > ... ||
> > > (last_fs_page > (pgoff_t)(~0ULL))) {
> > >
> > > Is that more readable?
> >
> > To me, yes. Maybe do similar for last_fs_sector.
>
> last_fs_sector would be shifting up, which could wrap a really
> large last_fs_blocks. So I'm going to keep the sector_t check as-is.
> How's this:
>
> >From 8de5cb9164cdc179ba84a07b282a895d0eb794b0 Mon Sep 17 00:00:00 2001
> >From: Joel Becker <joel.becker@xxxxxxxxxx>
> Date: Mon, 16 Aug 2010 12:10:17 -0700
> Subject: [PATCH] libfs: Fix shift bug in generic_check_addressable()
>
> generic_check_addressable() erroneously shifts pages down by a block
> factor when it should be shifting up. To prevent overflow, we shift
> blocks down to pages.
>
> Signed-off-by: Joel Becker <joel.becker@xxxxxxxxxx>
Looks good.
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/libfs.c | 8 ++++----
> 1 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 8debe7b..62baa03 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -925,6 +925,8 @@ EXPORT_SYMBOL(generic_file_fsync);
> int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
> {
> u64 last_fs_block = num_blocks - 1;
> + u64 last_fs_page =
> + last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
>
> if (unlikely(num_blocks == 0))
> return 0;
> @@ -932,10 +934,8 @@ int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
> if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
> return -EINVAL;
>
> - if ((last_fs_block >
> - (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
> - (last_fs_block >
> - (pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - blocksize_bits))) {
> + if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
> + (last_fs_page > (pgoff_t)(~0ULL))) {
> return -EFBIG;
> }
> return 0;
> --
> 1.7.1
>
> --
>
> Life's Little Instruction Book #267
>
> "Lie on your back and look at the stars."
>
> Joel Becker
> Consulting Software Developer
> Oracle
> E-mail: joel.becker@xxxxxxxxxx
> Phone: (650) 506-8127
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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