A patch is a file that describes a change to another file (or set of files). For example,

    NFSD/SUNRPC: Fix the automatic selection of RPCSEC_GSS
    
    Bruce's patch broke the ability to compile RPCSEC_GSS as a module.
    
    Signed-off-by: Trond Myklebust 

diff --git a/fs/Kconfig b/fs/Kconfig
index 6a64990..58a0650 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -1674,7 +1674,7 @@ config NFSD_V3_ACL
 
 config NFSD_V4
        bool "Provide NFSv4 server support (EXPERIMENTAL)"
-       depends on NFSD_V3 && EXPERIMENTAL
+       depends on NFSD && NFSD_V3 && EXPERIMENTAL
        select RPCSEC_GSS_KRB5
        help
          If you would like to include the NFSv4 server as well as the NFSv2

This is a patch my friend and coworker Trond made to correct a mistake of mine; it tells you to modify the file fs/Kconfig by deleting one line (the one preceded by a minus sign) and adding a slightly modified version (the one preceded by a plus sign).

The nice thing about a patch is that it's precise enough that a computer can apply the described change automatically, but it's still readable by people, once they get used to the format.

That means you can send a patch to a mailing list and it's easy for people to read it, argue about whether it's a good idea or not, quote parts of it as necessary, and so on.

So as a Linux kernel developer, what I do all day is write patches, to fix problems or add new features, and review them, to decide which are worth applying and which aren't.

And that's the way all changes to the kernel happen--we accumulate patches on top of patches. Linus takes the patches we agree are good and applies them to his version of the kernel, and the rest of us mostly use his versions as the basis for further work. Not because he has any special power--the code is licensed in such a way that anyone can do the same thing--but because over the years he's shown consistently pretty good taste about which patches to apply and which not to.

But the kernel is a big project at this point--a single major revision of the kernel, which takes 2 or 3 months, will include several thousand new patches, and Linus can't keep up with that pace on his own--so the review decisions end up requiring the input of hundreds of developers.

The review process is completely open--anyone with an email address may observe and contribute, and patch authors are expected to deal with any legitimate criticism regardless of the source. That also means that the community is too large and ill-defined to achieve complete consensus. And we can't really just take a vote either.

So in practice we depend on a sort of web of trust, relying on the opinions of developers with proven track records in their areas of expertise. This is formalized by recognizing some developers as "maintainers" of certain subsystems. Maintainers are responsible for filtering the good patches from the bad, giving feedback, working with people to resolved problems, and hopefully providing some overall direction.

I've been working on the kernel's NFS server for a while now, and as of recently it started looking like we might agree that I should be an official maintainer for that code.

That's just attaching a name to something that I've already been starting to do. But it's somewhat of a big deal to me anyway. And it potentially makes some difference to the people I work with and for. So I spent some of day at work figuring out how to explain some of the above. We'll see where it goes.

Anyway, that all sort of started Friday. Saturday I spent mostly with juggling friends. A guy and his daughter visited from Japan--they have roots in the area, and she's starting college in a year, so they're looking around at campuses. I passed clubs with her for a while, which was fun. Afterwards we had some noodles and then went back to our friend (and new neighbor) Ajit's place to play some Wii games. Also fun, though a little tiring in the end--maybe we should have called a quits a little earlier.

Sunday I went to a "Cinema Guild" event. It was in a classroom in the basement of Angell Hall. There were four of us altogether, so we chatted in between a little.

They were showing two short movies, one, "La Fin Du Monde", an unfinished French movie that had been cut up into pieces and had plan-9-worthy subitles, narration, and more, complete with a scientist's overly stiff and earnest introduction. It was a collage on so many levels--sound, text, video, all thrown together to give the vague impression of a plot. It was fun to guess what the original movie might have been about.

The second movie was Pabt's 1933 "Don Quixote", which was wonderful. They captured the spirit of the character really well, and I liked the songs. I'd see it again.

Last night and tonight we watched Miyazaki's "Laputa" which is typically touching and full of unexpected and delightful details.

Also, the unsolved mystery of the little bundles of sticks that we saw at Park Lyndon with my parents in April appears to be solved by this boing-boing post; they were probably caddis fly larvae!

The annual Ann Arbor Art Fairs are several fairs under different management (with, no doubt, all sorts of fascinating politics) that all run at the same time, but despite the occasional pedantic reminder, everybody refers to whole as "Art Fair".

Anyway, it ran Wednesday through Saturday. It's hard to miss, as it fills down large swaths of the downtown core with rows and rows of a little tents each filled with wares for sale and an artist in a director's chair.

Sara and I walked around for an hour or so after work on Thursday, but that's all I could take. I'm not sure why. It's the kind of thing I think I should like, but it always just depresses me. Maybe it's the quantity. An otherwise interesting painting might lose its impact in a tent with a bunch of its kin, in the middle of this huge artists' cubical farm, where there's probably somebody doing similar work two blocks over.

Maybe there's great stuff I'd like if I just had the patience to look for it.

Sara and I got married in Rocky Mountain National Park five years ago today. Our friend Ajit was also moving in Saturday. So we figured it was a good day for a combined welcome-(back-)to-ann-arbor / anniversary party. We had brunch with bagels from the nice bagel place next door, sticky orange muffins (from a Fanny Farmer recipe), fruit salad, and omelets. It was possibly as many as 12 or 13 people (turned out to be 9 and a baby, I think), and we're not used to doing that sort of thing, so the preparation was a little hectic at the last minute. It seemed to work out fine, though. We played a game that Fred and Deanna brought, and Ajit stayed on a little while longer while we cleaned up. I thought it turned out to be pretty pleasant overall.

It came a little out of the blue--my friend Bill, who was a year behind me in the math PhD program, and who still lives in Ann Arbor, but who I don't see that often--emailed me to let me know a bunch of mutual friends from grad school were all getting together this weekend.

So, Saturday morning he picked me up at my place and we drove the 45 minutes to Monroe, Michigan, where our David, who was in my cohort but left after a couple years, and who I had no idea was even in the area any more, has a house and a family. We were early. He and his wife and three kids all seemed to be doing pretty well. She (and the two elder kids, from a previous marriage I assume) are from England. While offering us drinks she noted that squash and ribena were available.

Eric and his girlfriend had arrived Friday and stayed there overnight. Chris S. and his wife and two kids showed up a little later, as did Scott. There were vegetable skewers, hot dogs, hamburgers, a couple salads, various drinks and snacks, and ice cream and cookies for desert. We sat around talking till probably 7 or so, then headed back to Ann Arbor to pick up Sara for dinner, which we had at Grizzly Peak.

It was good to catch up with that particular group of people. But I'm reminded of why I didn't continue in academics. Everybody was doing fine, it's not that--despite a certain amount of griping and self-deprecation the two that had gone on as professors sounded like they were doing well--but it just didn't sound like what I'd want to be doing.

I had a bad stomache ache when I got home, for some reason. It lingered on through Sunday, which I mostly spent laying around reading, but nothing really bad came of it in the end. Today I'm fine.

Saturday Dave and Paul met at our place and we carpooled together to Millford, where we were offered free canoe rental in the morning in return for juggling at an event that afternoon. Ajit, Micah, and Gene met us there. The rest of them each got Kayaks, and Sara and I paddled a canoe with Ajit as a passenger, since he was having a problem with his hands.

Sara wasn't sure about the steering, so I figured I'd stop paddling for a while so she could figure out how it worked without my interference. She did too good a job, and I got lazy, and by the end she was complaining about having to do all the work, so I took over more of the paddling again.

There were a fair number of other people on the river, but we did still get to see a few interesting things, including a lot of turtles, and one bird's nest complete with baby birds and a couple of extremely agitated parents. We heard a lot of frogs, but never managed to see one.

The event was the first stop in someone's swim down the Huron River, intended to raise awareness of the Huron watershed, I guess. There were some tents set up in a park, and we juggled and interacted with the other people, including the swimmer herself, who we tried teaching to juggle.

It was a pretty good time overall, but by early afternoon I already felt like I'd been up and outside for a little too long.

So we got back home in time to nap a little before someone else gave us a lift to a party for Trond and Laura (who were married in an extremely small ceremony earlier in the year), at my coworker Andy's house. It was quite an affair--fireworks, two bands (Andy and his friends are great musicians), lots of food and drink, a bonfire, and some silly Viking hats (a tribute to Trond's Norwegian-ness). We got back around midnight.

We took it pretty easy the next day. I got in to my office late in the afternoon and did a little git housekeeping, then met Sara and some other friends at Top of the Park for the final event of the year, featuring (as always) George Bedard and the Kingpins. As it happened the "Kingpins" (Bedard's drummer and bassist) were both jamming at the party the night before, so Sara and I were feeling pretty cool. It was a good end to the series. We went home to get to bed at a reasonable hour instead of staying for the final movie ("Night at the Museum", which didn't sound that good anyway).

Sara suggested Russel Hoban's "Riddley Walker" for our science-fiction book group this year, and that's what we're discussing tommorow night. It's tough going--entirely written in a dialect of the author's invention--and though I got an early start on it I'd set it aside more recently thinking I'd leave it mainly to Sara to defend the family honor at the book group. Which she'll do quite handily--our copy is bristling with her notes now identifying all sorts of little puns and such. But she convinced me I should finish, so I did that last night and this morning. I'm glad she did. It's absolutely fascinating, and the moment I finished it I turned back to the first page and started reading again. I've never read anything quite like it.

The last day of OLS went fine. The keynote was mildly entertaining, but didn't tell me anything I hadn't heard before. I had dinner with filesystem people, Jeff S. and Steven W., then poked around Chapters a few minutes before the night's party.

They take over a local pub, the Black Thorn, for the traditional party. The place is still never quite large enough. By the end of the night I was losing my voice trying to talk over the crowd. But I got to talk to a few interesting people, including an ex-NFS person, now at Google, who regaled us with stories of the bizarre hardware and software bugs you can find when you have thousands of machines running full-tilt all the time. Google has a reputation for scooping up open-source developers who are never heard from again by the outside world. Unfortunately that seems to apply to him and to the students we've sent there. I also talked to a local entrepreneur who'd also spent time working in Paris and Quebec City. He claims Europe and francophone Canada are ahead of the US in terms of open source adoption.

The next morning was Canada day, but I got a little bit of a slow start on it--I'm not much of a drinker, and didn't really have that much at the party, but it was enough more than my usual to make me a little queasy the next day.

The crowds were impressive--standing in the middle of it gave the impression of wall-to-wall people as far as you could see. I saw a couple street performers and some nice acrobatics and freestyle bike tricks, but spent most of the time camped out on Parliament Hill with the mob for the big events. It was pretty fun, though I wasn't nearly so excited by the performers as some of the teenagers around me were--Feist in particular didn't do much for me. Gregory Charles did some fun gospel-y stuff, though to my ears it all seemed a little uniform. My favorites were a band named "Delhi 2 Dublin" and a couple performances by the national circus school. Tanya Tagaq also did some really interesting stuff, but it seemed a little out of place--her performance was a little more avant-garde and didn't have the sort of larger-than-life showmanship it needed to reach such a huge crowd.

This turned out not to really be the ideal place to see the fireworks--the stage and the parliament building were both in the way. I weaved back through the crowd a bit, but the lowest explosions were still just out of view.

Getting out afterwards was a little nuts--the main exit from Parliament Hill opened to a bit of Wellington that for some reason seemed to be totally gridlocked. After a few minutes of inching towards the exit shoulder-to-shoulder with my neighbors, I gave up and followed a different flow to an farther exit which let me loop back towards Rideau and my locked-up bicycle.

Riding down Colonel By afterwards was an interesting experience--the road was lined with other cyclists doing the same. I was tired of sitting still and ready to fly, so I spent most of the first part of the ride passing them.

The next morning I got up, had a lovely breakfast, turned in my bike, and caught the bus back to the airport. I got there maybe 2 and a half hours early, so there wasn't even anyone to check me in yet--next year I should take my time a little more. But I got to read a bit and chat with some other kernel hackers while waiting.

The shuttle from DTW dropped me off at work, and I puttered around in my office a little before heading home.

Tuesday I was still a little tired, and went straight home after work.

Wednesday was the 4th, but I felt like working, so I spent most of the day in my office, then met Sara and Paul at Top of the Park to see my coworker's band FUBAR. There were other coworkers and friends there as well, and we also ran into Po and Igor, who we hadn't seen in a few years. They were also leading around a 1-year old that we hadn't heard about before. It was a great evening, and we stayed for "Young Frankenstein".

Thursday and Friday we also met after work for pizza and music.

Thursday there was a power outage in the afternoon, so I worked a couple hours at the public library.

Tomorrow we're up early to go canoeing and then teach people to juggle, and then in the evening there's a party at Andy's (probably featuring FUBAR again), in honor of Trond and Andy's sister Laura, who were married earlier this year.

Our every-other-monthly chance to merge new stuff into the kernel is coming up any day now, so I'm getting a lot of little projects tied up and ready to submit. It's a busy time, but fun.

What a week!

For some reason I woke up around 5:30 this morning and had trouble getting to sleep again, so I felt like I was sleep-walking through most of the day.

But I still managed to make it to three talks in the morning (on lguest, Zumastor, and SMB2), and get some long-delayed work done in the afternoon.

Afterwards I spent some time browsing at Chapters and Librarie du Soleil, where I picked up Trondheim's "La Couleur de l'Enfer", and Rabagliati's "Paul à la Pêche". The bookstore clerk was extremely enthusiastic about the latter, which follows a couple others ("Paul en Appartement", and "Paul a un Travail d'Été") that are wonderful. The first time I came out to OLS, the day after it ended, I picked up "Paul en Appartement" on a whim and took it down to the park overlooking the locks, just where the canal empties into the river, and had an extremely pleasant afternoon sitting on a park bench not believing my luck at having come across the book.

I stopped by a laundry near my B&B on my way back, but saw that it was about to close in a half hour, so decided to leave it tomorrow, and headed to the Thai restaurant a block away instead, where I had a good green curry and some mango ice cream before heading back "home" and turning in.

Breakfast was good, and my ride in went well. There'd been some brief overnight rain, and the temperature was down to something more comfortable.

The first talk was a bunch of statistics about kernel development--rate of change (high!) number of developers (lots, and increasing!). The data was kind of fun to look at, but didn't seem very well thought-out to me; for one thing, it wasn't entirely clear what they were trying to figure out, or how the numbers might help. And for another, I felt like it fell into the usual quantity-over-quality trap: if they'd spent more time carefully examining a few randomly chosen examples, instead of trying to collect huge gobs of (probably inaccurate) aggregate statistics, they might have had more interesting results.

There was a giant chart on the back wall of the room with a bubble for each kernel developer and lines connecting any two kernel developers that had consecutive sign-offs on some patch. They were collecting autographs next to each developer's name. I found mine, but couldn't follow any of the lines--the chart wasn't really printed with sufficient resolution.

After that there was an interesting talk by someone who'd examined performance of some big "enterprise" (I think that means Oracle) workloads on a machine with a lot of processors--four quad cores. The problem here is that access to the computer's RAM is really slow, so each processor has to have a cache of recently used memory. But then those caches have to be kept consistent--if a write to memory on one processor is followed by a read of the same address on another processor, then you have to make sure the read sees the new value stored at that address. This is slow, so if it happens a lot, performance can decrease dramatically. So you try to make sure that different processors are mostly working on different parts of memory, instead of bouncing around the same piece of memory from one cache to another. The speaker seemed to have some quite nice tools that would show exactly which pieces of which data structures were getting bounced around to much, and which code was responsible.

I didn't really pay as close attention to anything else that day.

Dinner was at a nearby pseudo-Irish pub, with a few selinux ("security enhanced linux") and NFS people. There's some interesting work to be done to make the two systems play well together. By the end of dinner I felt like I understood at least a few basic things about selinux.

I couldn't get my laptop to work with the conference wireless network, but found some ethernet ports and managed to get some routine work done in gaps during the day.

I was idly hoping to make it to one of the Ottawa Jazz Festival events in the evening, but by the end I was tired and ready to go back.

And the ride home was fine again. I'm feeling a little more comfortable on the rental bike.

Monday we met at Top of the Park to see a couple songs before heading home. I was up fairly late packing for the next morning's trip to Ottawa for the Ottawa Linux Symposium.

The trip was routine: my ride to the airport picked me up at 8, the flight left at 10:15, and once in Ottawa I hopped on the bus downtown; by 12:30 I was sitting down for lunch in the Byward Café. The conference wasn't starting till the next day, but I registered and spend a little time book-shopping. Is it my imagination, or has the Francophone bookstore in downtown Ottawa (Librarie Du Soleil) just gotten a comic-book buyer with taste closer to my own?; this year they have a zillion things I'd love to read. Some restraint will be required to stay within the limits of my backpack (my only luggage on this trip) and my budget.

I'm staying at a B&B that's maybe a couple miles south of downtown--thanks perhaps to Canada day on Sunday, most closer places were filling up by the time I looked. So I figured it'd be fun to rent a bike for my commute. I wonder what the university will say when I give them the bill for that? I know they'd cover a car in the same situation. The bike is a so-called "comfort" bike, which I'm finding a little uncomfortable. But it works. I was surprised that they didn't include lights (or even reflectors)--that seems like a dumb omission if they're renting out bikes overnight--but they had some cute LED headlights and taillights for very cheap.

I rode down the canal a little ways, found a tree to sit under, and read a new acquisition, "Inventaire avant Travaux", the sixth in Dupuy and Berberian's "Monsier Jean" series. I really love the previous albums in the series, so though this one was well done, it wasn't really up to my expectations. I felt like it revisited a lot of ideas they'd covered before without advancing the story much.

I had a beer and some pizza at the pre-event pub night, then headed to the B&B around 9:30. They had a key waiting for me in a box outside, and I found my room without any trouble.

Today was the first day of the conference; my short bike ride in was fine, though the weather's been very hot and humid, and I arrived a little sweaty.

My limited patience for talks ran out by the afternoon, but I managed to learn a couple interesting things on the way. I got both lunch and dinner in the food court of the mall attached to the conference center, so I basically spent the whole day in the mall.

I left for the B&B a little earlier than last night, so got a chance to catch up on a little work (and on this blog!). But now it's almost midnight and well past time I put myself to bed with a comic and read myself to sleep....

Sara's come down with my cold, now that I'm almost over it. Thursday night we both went straight home. We tried watching the beginning of "The Prestige". The beginning introduces a bunch of characters all at once, with scenes that are wildly out of chronological order, coming from at least 4 different points in the story. The dialog's a little hard to follow at points too. So it wasn't the best thing to watch over dinner. Sara said she was too tired after about 20 minutes. I ended up watching the rest on my own, finishing it last night after we got home from Top of the Park.

Top of the Park last night featured "Strange Fruit", an Australian group that doing a sort of mime show to music on top of tall swaying polls. It was visually very striking, though I don't know how long it would stay interesting. The choice of name seems a little odd, since the first thing it makes me think of is the Billy Holiday song.

We also saw a bluegrass band and the first set of two by Bugs Beddow before we left.