linux-ext4 - Re: [Ocfs2-devel] [PATCH 1/3] ext3/ext4: Factor out disk addressability check

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Date:	Thu, 12 Aug 2010 12:45:41 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Joel Becker <Joel.Becker@...cle.com>
Cc:	"Ted Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
	ocfs2-devel@....oracle.com, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	"linux-kernel@...r.kernel.org Patrick J. LoPresti" 
	<lopresti@...il.com>
Subject: Re: [Ocfs2-devel] [PATCH 1/3] ext3/ext4: Factor out disk addressability check

On 2010-08-12, at 11:42, Joel Becker wrote:
>> +/**
>> + * 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**@...cksize_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;
>> +
>> +	BUG_ON(blocksize_bits < 9);
>> +	BUG_ON(blocksize_bits > PAGE_CACHE_SHIFT);

I'd rather not have a BUG_ON() for a "check" function that may be called with on-disk values by some filesystem.  Some filesystems (AFAIR) also handle blocksize > PAGE_SIZE internally, so this helper would not be useful for them.

Cheers, Andreas



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