[PATCH v4 0/5] Write-placement hints and FDP

[Kanchan Joshi]

Hi Amir,


On 8/26/2024 10:36 PM, Kanchan Joshi wrote:
> Current write-hint infrastructure supports 6 temperature-based data life
> hints.
> The series extends the infrastructure with a new temperature-agnostic
> placement-type hint. New fcntl codes F_{SET/GET}_RW_HINT_EX allow to
> send the hint type/value on file. See patch #3 commit description for
> the details.
> 
> Overall this creates 128 placement hint values [*] that users can pass.
> Patch #5 adds the ability to map these new hint values to nvme-specific
> placement-identifiers.
> Patch #4 restricts SCSI to use only life hint values.
> Patch #1 and #2 are simple prep patches.
> 
> [*] While the user-interface can support more, this limit is due to the
> in-kernel plumbing consideration of the inode size. Pahole showed 32-bit
> hole in the inode, but the code had this comment too:
> 
> /* 32-bit hole reserved for expanding i_fsnotify_mask */
> 
> Not must, but it will be good to know if a byte (or two) can be used
> here.

Since having one extra byte will simplify things, I can't help but ask - 
do you still have the plans to use this space (in entirety) within inode?