On Sat, Dec 20, 2008 at 8:25 PM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote:
> On Sat, Dec 20, 2008 at 11:43 PM, Rohit Sharma <imreckless@xxxxxxxxx> wrote:
>> A little confusion.
>>
>> Just refer this structure in linux/ext2_fs_sb.h
>>
>> struct ext2_block_alloc_info {
>> 46 /* information about reservation window */
>> 47 struct ext2_reserve_window_node rsv_window_node;
>> 48 /*
>> 49 * was i_next_alloc_block in ext2_inode_info
>> 50 * is the logical (file-relative) number of the
>> 51 * most-recently-allocated block in this file.
>> 52 * We use this for detecting linearly ascending allocation requests.
>> 53 */
>> 54 __u32 last_alloc_logical_block;
>
> if i interpret the meaning of "file-relative logical number"
> correctly, and since one-file-one-inode concept, then it means that it
> should mean inode-relative logical block number.
>
>> 55 /*
>> 56 * Was i_next_alloc_goal in ext2_inode_info
>> 57 * is the *physical* companion to i_next_alloc_block.
>> 58 * it the the physical block number of the block which was
>
>> inode1 has logical blocks 0 1 2 , physical 22 23 24
>> inode2 has logical blocks 0 1 2 , physical 34 35 50
>>
>
> as per comment above, the sequence above looks likely, but then this
> is my guess again.
You are correct. last_alloc_logical_block is used to detect if the
write workload against a given inode is sequential (the current
logical block is last_alloc_logical_block+1).
Mike
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