Re: [PATCH v3 7/7] fs/ext4,jbd2: add support for passing write-hint with journal

[Martin K. Petersen]

Kanchan,

> For NAND based SSDs, mixing of data with different life-time reduces
> efficiency of internal garbage-collection. During FS operations,
> series of journal updates will follow/precede series of data/meta
> updates, causing intermixing inside SSD. By passing a write-hint with
> journal, its write can be isolated from other data/meta writes,
> leading to endurance/performance benefit on SSD.

Why not just introduce REQ_JOURNAL and let the device driver decide how
to turn that into something appropriate for the device?

That's what I'll need for SCSI. Existing SCSI streams are not a good
fit.

-- 
Martin K. Petersen	Oracle Linux Engineering