From: Jan Kara Subject: Re: [Ocfs2-devel] [PATCH 1/3] ext3/ext4: Factor out disk addressability check Date: Fri, 13 Aug 2010 18:30:07 +0200 Message-ID: <20100813163006.GB4329@quack.suse.cz> References: <874ofr2myq.fsf@patl.com> <20100812174215.GC6561@mail.oracle.com> <1F3EDC08-AC93-4D4D-8F83-A13C418DFC88@dilger.ca> <20100812201534.GA22777@mail.oracle.com> <209AEA97-E284-4ADB-8774-50C2630606B9@dilger.ca> <20100812222949.GC22777@mail.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , Ted Ts'o , Jan Kara , ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, "linux-kernel@vger.kernel.org Patrick J. LoPresti" To: Joel Becker Return-path: Content-Disposition: inline In-Reply-To: <20100812222949.GC22777@mail.oracle.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu 12-08-10 15:29:49, Joel Becker wrote: > diff --git a/fs/libfs.c b/fs/libfs.c > index dcaf972..f099566 100644 > --- a/fs/libfs.c > +++ b/fs/libfs.c > @@ -955,6 +955,35 @@ int generic_file_fsync(struct file *file, int datasync) > } > EXPORT_SYMBOL(generic_file_fsync); > > +/** > + * generic_check_addressable - Check addressability of file system > + * @blocksize_bits: log of file system block size > + * @num_blocks: number of blocks in file system > + * > + * Determine whether a file system with @num_blocks blocks (and a > + * block size of 2**@blocksize_bits) is addressable by the sector_t > + * and page cache of the system. Return 0 if so and -EFBIG otherwise. > + */ > +int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks) > +{ > + u64 last_fs_block = num_blocks - 1; > + > + if (unlikely(num_blocks == 0)) > + return 0; > + > + 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))) { ^^^ I don't get the pgoff_t check. Shouldn't it rather be (u64)(pgoff_t)(~0ULL) << (PAGE_CACHE_SHIFT - blocksize_bits)? Because on 32-bit arch we are able to address 16TB device, which is for 1KB blocksize 1<<34 blocks. But your math gives 1<<30 blocks... Honza -- Jan Kara SUSE Labs, CR