Hi Martin, > Why not just introduce REQ_JOURNAL and let the device driver decide how to turn that into something appropriate for the device? It began with that kind of thought/goal i.e. introduce something just for FS journal. But it seems to have evolved for good. Current approach extends write-hint infra so that whole thing becomes extensible for other kind of use-cases (than FS journal) as well. Also in this approach, driver will do little, while block-layer will do majority of the work. > That's what I'll need for SCSI. Existing SCSI streams are not a good fit. Do you see that it's difficult for SCSI to use write-hint infrastructure for streams? -----Original Message----- From: Martin K. Petersen [mailto:martin.petersen@xxxxxxxxxx] Sent: Wednesday, April 03, 2019 8:28 AM To: Kanchan Joshi <joshi.k@xxxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; linux-nvme@xxxxxxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx; linux-ext4@xxxxxxxxxxxxxxx; axboe@xxxxxx; prakash.v@xxxxxxxxxxx; anshul@xxxxxxxxxxx; joshiiitr@xxxxxxxxx Subject: Re: [PATCH v3 7/7] fs/ext4,jbd2: add support for passing write-hint with journal 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
