From: Joel Becker Subject: Re: [PATCH 1/3] ext3/ext4: Factor out disk addressability check Date: Mon, 16 Aug 2010 12:13:19 -0700 Message-ID: <20100816191319.GC5786@mail.oracle.com> References: <1F3EDC08-AC93-4D4D-8F83-A13C418DFC88@dilger.ca> <20100812201534.GA22777@mail.oracle.com> <209AEA97-E284-4ADB-8774-50C2630606B9@dilger.ca> <20100812222949.GC22777@mail.oracle.com> <20100813163006.GB4329@quack.suse.cz> <4C6821A8.5080805@redhat.com> <20100816025436.GA9061@mail.oracle.com> <4C68B244.6080406@redhat.com> <20100816092114.GB9061@mail.oracle.com> <4C694ED3.5070500@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Andreas Dilger , "Ted Ts'o" , linux-fsdevel@vger.kernel.org, Jan Kara , linux-ext4@vger.kernel.org, ocfs2-devel@oss.oracle.com To: Eric Sandeen Return-path: Content-Disposition: inline In-Reply-To: <4C694ED3.5070500@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com List-Id: linux-ext4.vger.kernel.org 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 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 --- 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@oracle.com Phone: (650) 506-8127