"Last month, at the kernel summit, there was discussion of putting a Reviewed-by: tag onto patches to document the oversight they had received on their way into the mainline," began Jonathan Corbet in an effort to define the meaning of the recently introduced reviewed-by tag. He continued, "that tag has made an occasional appearance since then, but there has not yet been a discussion of what it really means. So it has not yet brought a whole lot of value to the process."

In the continued discussion, it was requested that all commit tags be defined, prompting Jonathan to update his documentation to include Signed-off-by, Acked-by, Cc, and Tested-by along with his documentation for Reviewed-by. He offered the following definition for the new Reviewed-by tag:

"The patch has been reviewed and found acceptible according to the Reviewer's Statement as found at the bottom of this file. A Reviewed-by tag is a statement of opinion that the patch is an appropriate modification of the kernel without any remaining serious technical issues. Any interested reviewer (who has done the work) can offer a Reviewed-by tag for a patch."

"With 2.6.24 probably opening in the not-too-distant future, it's probably a good time to review what my plans are for when the merge window opens," began Roland Dreier on the Linux Kernel mailing list. He reflected on the recent decision to phase in usage of reviewed-by tags noting that he was a little behind on reviews, "unfortunately, due to the length of the backlog and the fact that 2.6.23 seems fairly close, some of the things listed below are going to miss the 2.6.24 merge window." Roland continued, stressing the importance of getting in-depth reviews:

"Although the plan is to phase in requiring 'Reviewed-by:' gently, for this merge, if you can get someone other than me to review your work, then the chances of it being merged increase dramatically. I'm talking about a real review -- ideally, someone independent (from another company would be good) who is willing to provide a 'Reviewed-by:' line that means the reviewer has really looked at and thought about the patch. There should be a mailing list thread you can point me at where the reviewer comments on the patch and a new version of that patch addressing all comments is posted (or in exceptional cases, where the patch is perfect to start with, where the reviewer says the patch is great)."

"Some people seem to be using 'Acked-by' to mean, 'seems good to me', without necessarily doing a full review of the patch, and instead of trying to change the meaning of 'Acked-by', [the plan is] to have a new sign off which is a bit more explicitly about what it means," Theodore Tso explained in a recent thread on the Linux Kernel mailing list. He continued:

"This was proposed by Andrew and discussed at the Kernel Summit; the basic idea is that it is a formal indication that the person has done a *full* review of the patch (a few random comments from the local whitespace police don't count), and is willing to vouch that the patch is correct, safe, extremely unlikely to cause regressions, etc. If the patch does need to be reverted or fixed because it was buggy, then both the original submitter and the reviewer would bear responsibility and subsystem maintainers might take that into account when assessing the reputations of the submitter and reviewer in the future when deciding whether or not to accept a patch."

Andrew Morton noted that the idea isn't fully fleshed out yet, "we will start introducing Reviewed-by: (I haven't yet quite worked out how yet) but it will be a quite formal thing and it would be something which the reviewer explicitly provided. For now, let's please stick with acked-by". Theodore added, "there was also some discussion about whether or not patches would not be accepted at all without a Reviewed-by, but that probably won't happen initially. The general consensus was to gently ease into it and see how well it works first."