On 2018年03月02日 16:21, Misono, Tomohiro wrote:
> On 2018/03/02 14:22, Qu Wenruo wrote:
>> Btrfs shows max_inline option into kernel message, but for
>> max_inline=4096, btrfs won't really inline 4096 bytes inline data if
>> it's not compressed.
> Hello,
> I have a question.
> man mount(8) says: 
>    max_inline=bytes
>           Specify  the  maximum  amount  of space, in bytes, that can be
>           inlined in a metadata B-tree leaf.  The value is specified  in
>           bytes,  optionally with a K, M, or G suffix, case insensitive.
>           In practice, this value is limited by the  root  sector  size,
>           with  some  space  unavailable  due to leaf headers.  For a 4k
>           sectorsize, max inline data is ~3900 bytes.
> So, is the size of 4k-(size of leaf header) actually the maximum value
> of max_inline instead of 4095 for 4k sectorsize?

Not exactly.

For 4K nodesize, max_inline would be 3960 bytes.
As leaf header and EXTENT_ITEM header takes extra bytes.

For 16K nodesize (default), we can go up to 4095 bytes then.

And that man page needs updated, as it should be 4K *nodesize*.


> Thanks,
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