linux-ext4 - Re: [RFC][PATCH V3 1/4] ext4: add EXT4_IOC_CONTROL

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Message-Id: <62E660B4-8AF6-4B94-B3C0-1557ACA136DB@dilger.ca>
Date:	Wed, 1 Dec 2010 03:14:20 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	Kazuya Mio <k-mio@...jp.nec.com>
Cc:	ext4 <linux-ext4@...r.kernel.org>, Theodore Tso <tytso@....edu>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [RFC][PATCH V3 1/4] ext4: add EXT4_IOC_CONTROL_PA to create/discard inode PA

On 2010-11-30, at 23:06, Kazuya Mio wrote:
> EXT4_IOC_CONTROL_PA allows to create new inode PA based on the specified
> range, or to discard all inode PAs in the target inode.
> 
> INTERFACE
> -----------
> 
> #define EXT4_IOC_CONTROL_PA	_IOWR('f', 16, struct ext4_prealloc_info)
> 
> struct ext4_prealloc_info {
> 	__u64 pi_pstart; /* physical offset for the start of the PA from
> 			  * the beginning of the file (in/out) */
> 	__u32 pi_lstart; /* logical offset for the start of the PA from
> 			  * the beginning of the disk (in/out) */

Is the comment here wrong, or do I misunderstand that there is a 64-bit offset for the file, and only a 32-bit offset for the disk?  It doesn't make sense to create a new API that only has a 32-bit offset for the disk, since ext4 is nearly supporting 64-bit filesystem blocks.

Looking at the patch, it seems that pi_pstart is indeed the physical offset, so it should be 64-bit, and it just appears that the comment is incorrect.

Cheers, Andreas





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