Re: must-fix, version 6
From: Andrew Morton (akpm@digeo.com)
Date: Fri May 30 2003 - 18:47:31 EST
The should-fix list, version 6.
Not-ready features and speedups
===============================
Legend:
PRI1: We're totally lame if this doesn't get in
PRI2: Would be nice
PRI3: Not very important
drivers/block/
~~~~~~~~~~~~~~
o Framework for selecting IO schedulers. This is the main one really.
Once this is in place we can drop in new schedulers any old time, no risk.
PRI1
o Anticipatory scheduler. Working OK now, still has problems with seeky
OLTP-style loads.
PRI1
o CFQ scheduler. Seems to work but Jens planning significant rework.
PRI2
o cryptoloop: jmorris: There's no cryptoloop in the 2.4 mainline kernel,
but I think every distro ships some version. It would probably be useful
to have crypto natively supported in 2.6, with backward compatibility for
the majority of 2.4 users.
problem: lack of a loop maintainer
PRI2
o viro: paride drivers need a big cleanup
PRI2
drivers/char/rtc/
~~~~~~~~~~~~~~~~~
o rmk, trini: add support for alarms to the existing generic rtc driver.
PRI2
device mapper
~~~~~~~~~~~~~
o ioctl interface cleanup patch is ready (redo the structure layouts)
PRI1
o A port of the 2.4 snapshot target is in progress
PRI1
o the fs interface to dm needs to be redone. gregkh was going to work on
this. viro is interested in seeing work thus-far.
PRI2
drivers/net/wireless/
~~~~~~~~~~~~~~~~~~~~~
(Jean Tourrilhes <jt@xxxxxxxxxxxxxxxxxx>)
o get latest orinoco changes from David.
PRI1
o get the latest airo.c fixes from CVS. This will hopefully fix problems
people have reported on the LKML.
PRI1
o get HostAP driver in the kernel. No consolidation of the 802.11
management across driver can happen until this one is in (which is probably
2.7.X material). I think Jouni is mostly ready but didn't find time for
it.
PRI2
o get more wireless drivers into the kernel. The most "integrable" drivers
at this point seem the NWN driver, Pavel's Spectrum driver and the Atmel
driver.
PRI1
o The last two drivers mentioned above are held up by firmware issues (see
flamewar on LKML a few days ago). So maybe fixing those firmware issues
should be a requirement for 2.6.X, because we can expect more wireless
devices to need firmware upload at startup coming to market.
(in progress?)
PRI1
drivers/usb/gadget/
~~~~~~~~~~~~~~~~~~~
o rmk: SA11xx USB client/gadget code (David B has been doing some work on
this, and keeps trying to prod me, but unfortunately I haven't had the time
to look at his work, sorry David.)
PRI3
fs/
~~~
o ext3 lock_kernel() removal: that part works OK and is mergeable. But
we'll also need to make lock_journal() a spinlock, and that's deep surgery.
Patches exist in -mm.
PRI1
o ext3 and ext2 block allocators have serious failure modes - interleaved
allocations.
PRI3
o 32bit quota needs a lot more testing but may work now
PRI2
o Integrate Chris Mason's 2.4 reiserfs ordered data and data journaling
patches. They make reiserfs a lot safer.
Ordered: PRI2
data journalled: PRI3
o (Trond:) Yes: I'm still working on an atomic "open()", i.e. one
where we short-circuit the usual VFS path_walk() + lookup() +
permission() + create() + .... bullsh*t...
I have several reasons for wanting to do this (all of
them related to NFS of course, but much of the reasoning applies
to *all* networked file systems).
1) The above sequence is simply not atomic on *any* networked
filesystem.
2) It introduces a sh*tload of completely unnecessary RPC calls (why
do a 'permission' RPC call when the server is in *any* case going to
tell you whether or not this operations is allowed. Why do a
'lookup()' when the 'create()' call can be made to tell you whether or
not a file already exists).
3) It is incompatible with some operations: the current create()
doesn't pass an 'EXCLUSIVE' flag down to the filesystems.
4) (NFS specific?) open() has very different cache consistency
requirements when compared to most other VFS operations.
I'd very much like for something like Peter Braam's 'lookup with
intent' or (better yet) for a proper dentry->open() to be integrated with
path_walk()/open_namei(). I'm still working on the latter (Peter has
already completed the lookup with intent stuff).
PRI2 (?)
o (Chuck Lever <cel@xxxxxxxxxxxxxx>): NFS O_DIRECT support must be
completed. The best approach is to fall back to something like the 2.4 NFS
O_DIRECT support, which issues RPCs synchronously and uses the RPC
completion mechanism to wait for I/O completion.
PRI2
o rmk: update acorn partition parsing code - making all acorn schemes
appear in check.c so we don't have to duplicate the scanning of multiple
types, and adding support for eesox partitions.
PRI2
o atomic i_size patches
PRI1
o viro: cleaning up options-parsers in filesystems. (patch exists, needs
porting).
PRI2
o aio: fs IO isn't async at present. suparna has restart patches, they're
in -mm. Need to get Ben to review/comment.
PRI1.
kernel/
~~~~~~~
o rusty: Zippel's Reference count simplification. Tricky code, but cuts
about 120 lines from module.c. Patch exists, needs stressing.
PRI3
o rusty: /proc/kallsyms. What most people really wanted from /proc/ksyms.
Patch exists.
PRI3
o rusty: Fix module-failed-init races by starting module "disabled". Patch
exists, requires some subsystems (ie. add_partition) to explicitly say
"make module live now". Without patch we are no worse off than 2.4 etc.
PRI1
o Integrate userspace irq balancing daemon.
PRI2
o kexec. Seems to work, was in -mm.
PRI3
o rmk: modules / /proc/kcore / vmalloc This needs sorting and testing to
ensure that stuff like gdb vmlinux /proc/kcore works as expected. I
believe this is the only show stopper preventing any ARM platform being
built in Linus' kernel.
Patch exists in -mm, nobody has tested it for the above afaik.
PRI1
o kcore is a problem for ia64 (Tony Luck)
Patch exists in -mm.
PRI1
o rmk: lib/inflate.c must not use static variables (causes these to be
referenced via GOTOFF relocations in PIC decompressor. We have a PIC
decompressor to avoid having to hard code a per platform zImage link
address into the makefiles.)
PRI2
o klibc merge?
PRI2
mm/
~~~
o objrmap: concerns over page reclaim performance at high sharing levels,
and interoperation with nonlinear mappings is hairy.
o Reintroduce and make /proc/sys/vm/freepages writable again so that boxes
can be tuned for heavy interrupt load.
Patch exists in -mm.
PRI1
o oxymoron's async write-error-handling patch
PRI1
o dropbehind for large files
PRI2
net/
~~~~
(davem)
o Real serious use of IPSEC is hampered by lack of MPLS support. MPLS is a
switching technology that works by switching based upon fixed length labels
prepended to packets. Many people use this and IPSEC to implement VPNs
over public networks, it is also used for things like traffic engineering.
A good reference site is:
http://www.mplsrc.com/
Anyways, an existing (crappy) implementation exists. I've almost
completed a rewrite, I should have something in the tree next week.
PRI1
o Sometimes we generate IP fragments when it truly isn't necessary.
The way IP fragmentation is specified, each fragment must be modulo 8
bytes in length. So suppose the device has an MTU that is not 0 modulo 8,
ethernet even classifies in this way. 1500 == (8 * 187) + 4
Our IP fragmenting engine can fragment on packets that are sized within
the last modulo 8 bytes of the MTU. This happens in obscure cases, but it
does happen.
I've proposed a fix to Alexey, whereby very late in the output path we
check the packet, if we fragmented but the data length would fit into the
MTU we unfragment the packet.
This is low priority, because technically it creates suboptimal behavior
rather than mis-operation.
PRI1
net/*/netfilter/
~~~~~~~~~~~~~~~~
o Lots of misc. cleanups, which are happening slowly.
PRI2
o davem: Netfilter needs to stop linearizing packets as much as possible.
Zerocopy output packets are basically undone by netfilter becuase all of
it assumed it was working with linear socket buffers.
Rusty is fixing this piece by piece. He is nearly done with this work.
PRI1
power management
~~~~~~~~~~~~~~~~
(Pat) There is some preliminary work at bk://ldm.bkbits.net/linux-2.5-power,
though I'm currently in the process of reworking it.
It includes:
o New device power management core code, both for individual devices,
and for global state transitions.
PRI1
o A generic user interface for triggering system power state transitions.
PRI1
o Arch-independent code for performing state transitions, that calls
platform-specific methods along the way.
PRI1
o A better suspend-to-disk mechanism than swsusp.
There are various other details to be worked out, which are the real fun
part. And of course, driver support, but that is something that can happen
at any time.
(Alan)
PRI2
o Frame buffer restore codepaths (that requires some deep PCI magic)
PRI2
o XFree86 hooks
PRI2
o AGP restoration
PRI2
o DRI restoration
(davej/Alan: not super-critical, can crash laptop on restore. davej
looking into it.)
PRI2
o IDE suspend/resume without races (Ben is looking at this a little)
PRI2
o Pat: There are already CPU device structures; MTRRs should be a
dynamically registered interface of CPUs, which implies there needs
to be some other glue to know that there are MTRRs that need to be
saved/restored.
PRI1
global
~~~~~~
o 64-bit dev_t. Seems almost ready, but it's not really known how much
work is still to do. Patches exist in -mm but with the recent rise of the
neo-viro I'm not sure where things are at.
PRI1
o We need a kernel side API for reporting error events to userspace (could
be async to 2.6 itself)
(Prototype core based on netlink exists)
PRI2
o Kai: Introduce a sane, easy and standard way to build external modules
PRI2
o Kai: Allow separate src/objdir
PRI2
o general confusion over firmware policy:
o do we mandate that it be uploaded from userspace?
o Is binary-blob-in-kernel-image OK?
o Each driver (wireless, scsi, etc) seems to do it in a different,
private manner.
gregkh: patch exists, drivers can be ported to use new infrastructure at
any time.
PRI1
o larger cpumask_t - supporting more than BITS_PER_LONG CPUs.
wli: patch exists. ia32, ppc are done. ppc64 in progress. Needs work
for other architectures.
PRI1
o pavel: ioctl32 emulation should be shared across architectures. (patch
exists).
PRI2
drivers
~~~~~~~
o Alan: Cardbus/PCMCIA requires all Russell's stuff is merged to do
multiheader right and so on
PRI1
drivers/acpi/
~~~~~~~~~~~~~
o alan: VIA APIC stuff is one bit of this, there are also some other
reports that were caused by ACPI not setting level v edge trigger some
times
PRI1
o mochel: it seems the acpi irq routing code could use a serious rewrite.
grover: The problem is the ACPI irq routing code is trying to piggyback
on the existing MPS-specific data structures, and it's generally a hack.
So yes mochel is right, but it is also purging MPS-ities from common code
as well. I've done some preliminary work in this area and it doesn't seem
to break anything (yet) but a rewrite in this area imho should not be
rushed out the door. And, I think the above bugs can be fixed w/o the
rewrite.
PRI2
o mochel: ACPI suspend doesn't work. Important, not cricital. Pat is
working it.
PRI2
drivers/block/
~~~~~~~~~~~~~~
o Floppy is almost unusably buggy still
akpm: we need more people to test & report.
alan: "Floppy has worked for me since the patches that went in 2.5.69-ac
and I think -bk somewhere"
PRI1
drivers/char/
~~~~~~~~~~~~~
o Alan: Multiple serious bugs in the DRI drivers (most now with patches
thankfully). "The badness I know about is almost entirely IRQ mishandling.
DRI failing to mask PCI irqs on exit paths."
(This is understood and fixed in DRI CVS)
PRI1
o Various suspect things in AGP.
PRI1
drivers/ide/
~~~~~~~~~~~~
(Alan)
o IDE requires bio walking
"Bartlomiej has IDE multisector working" (does that mean it's fixed?)
PRI1
o IDE PIO has occasional unexplained PIO disk eating reports
PRI1
o IDE has multiple zillions of races/hangs in 2.5 still
PRI1
o IDE scsi needs rewriting
PRI2
o IDE needs significant reworking to handle Simplex right
PRI2
o IDE hotplug handling for 2.5 is completely broken still
PRI2
o There are lots of other IDE bugs that wont go away until the taskfile
stuff is included, the locking bugs that allow any user to hang the IDE
layer in 2.5, and some other updates are forward ported. (esp. HPT372N).
PRI1
drivers/isdn/
~~~~~~~~~~~~~
(Kai, rmk)
o isdn_tty locking is completely broken (cli() and friends)
PRI2
o fix lots of remaining bugs in the isdn link layer / hisax protocol layer
/ hisax subdrivers, so that at least 99% of the users have a usable ISDN
subsystem
PRI1
o fix other drivers
PRI2
o lots more cleanups, adaption to recent APIs etc
PRI3
o fixup tty-based ISDN drivers which provide TIOCM* ioctls (see my recent
3-set patch for serial stuff)
Alternatively, we could re-introduce the fallback to driver ioctl parsing
for these if not enough drivers get updated.
PRI3
drivers/net/
~~~~~~~~~~~~
o davej: Either Wireless network drivers or PCMCIA broke somewhen. A
configuration that worked fine under 2.4 doesn't receive any packets. Need
to look into this more to make sure I don't have any misconfiguration that
just 'happened to work' under 2.4
PRI1
drivers/scsi/
~~~~~~~~~~~~~
o qlogic follies:
- jejb: Merge the feral driver. It covers all qlogic chips: 1020 all
the way up to 23xxx. mjacob is promising a "major" rewrite which
eliminates this as a candidate for immediate inclusion. Panics on my
parisc hardware, works on my ia64. BK tree is
http://linux-scsi.bkbits.net/scsi-isp-2.5
- qla2xxx: only for FC chips. Has significant build issues. hch
promises to send me a "must fix" list for this. I plan not to merge this
until I at least see how Qlogic responds to the issues. Can't currently
build this for my only fibre card (a qla2100). BK tree is at
http://linux-scsi.bkbits.net/scsi-qla2xxx-2.5
- I think the best plan currently is not to merge either of these, but
keep shadow BK trees for them (thus holding out the possibility of
merger) to see how they evolve. I agree with hch that feral seems to be
in the better shape but, barring directions to the contrary, I can't see
why both shouldn't be included eventually.
PRI2
arch/i386/
~~~~~~~~~~
o Also PC9800 merge needs finishing to the point we want for 2.6 (not all).
PRI3
o ES7000 wants merging (now we are all happy with it). That shouldn't be a
big problem.
PRI2
o davej: PAT support (for mtrr exhaustion w/ AGP)
PRI2
o 2.5.x won't boot on some 440GX
alan: Problem understood now, feasible fix in 2.4/2.4-ac. (440GX has two
IRQ routers, we use the $PIR table with the PIIX, but the 440GX doesnt use
the PIIX for its IRQ routing). Fall back to BIOS for 440GX works and Intel
concurs.
PRI1
o 2.5.x doesn't handle VIA APIC right yet.
1. We must write the PCI_INTERRUPT_LINE
2. We have quirk handlers that seem to trash it.
PRI1
o ACPI needs the relax patches merging to work on lots of laptops
alan: ACPI relax stuff is in 2.4-ac, compaq workaround is in next -ac
coming. These seem to deliver the goods - toshibas now work a treat. Some
other relax bits are being discussed (assume local0 starts 0 etc) and
progress looks great. This can occur before 2.6 or during.
PRI1
o ECC driver questions are not yet sorted (DaveJ is working on this) (Dan
Hollis)
alan: ECC - I have some test bits from Dan's stuff - they need no kernel
core changes for most platforms. That means we can treat it as a random
driver merge.
PRI3
o alan: 2.4 has some fixes for tsc handling bugs. One where some bioses in
SMM mode mess up our toggle on the time high/low or mangle the counter and
one where a few chips need religious use of _p for timer access and we
don't do that. This is forward porting little bits of fixup.
ACPI HZ stuff we can't trap - a lot of ACPI is implemented as outb's
triggering SMM traps
PRI1
arch/x86_64/
~~~~~~~~~~~~
(Andi)
o time handling is broken. Need to move up 2.4 time.c code.
PRI1
o Another report of a crash at shutdown on Simics with no iommu when all
memory was used. Could be related to the one above.
PRI1
o NMI watchdog seems to tick too fast
PRI2
o not very well tested. probably more bugs lurking.
PRI1
o need to coredump 64bit vsyscall code with dwarf2
PRI2
o move 64bit signal trampolines into vsyscall code and add dwarf2 for it.
PRI1
o describe kernel assembly with dwarf2 annotations for kgdb (currently
waiting on some binutils changes for this)
PRI3
arch/alpha/
~~~~~~~~~~~
o rth: Ptrace writes are broken. This means we can't (reliably) set
breakpoints or modify variables from gdb.
PRI1
arch/arm/
~~~~~~~~~
o rmk: missing raw keyboard translation tables for all ARM machines.
Haven't even looked into this at all. This could be messy since there
isn't an ARM architecture standard. I'm presently hoping that it won't be
an issue. If it does, I guess we'll see drivers/char/keyboard.c explode.
PRI2
arch/others/
~~~~~~~~~~~~
o SH/SH-64 need resyncing, as do some other ports. No impact on
mainstream platforms hopefully.
PRI2
o IA64 needs merging, has impact on core code
PRI1
arch/s390/
~~~~~~~~~
o A nastly memory management problem causes random crashes. These appear
to be fixed/hidden by the objrmap patch, more investigation is needed.
PRI1
drivers/s390/
~~~~~~~~~~~~~
o Early userspace and 64 bit dev_t will allow the removal of most of
dasd_devmap.c and dasd_genhd.c.
PRI2
o The 3270 console driver needs to be replaced with a working one
(prototype is there, needs to be finished).
PRI2
o Minor interface changes are pending in cio/ when the z990 machines are
out.
There are some more things being worked on that are either post-2.6.0 or
are likely to remain outside of the official kernel (i.e. not for your
list):
PRI3
o Jan Glauber is working on a fix for the timer issues related to running
on virtualized CPUs (wall-clock vs. cpu time).
PRI1
o new zfcp fibre channel driver
PRI3
o the qeth driver will become GPL soon
PRI3
o a block device driver for ramdisks shared among virtual machines
PRI3
o driver for crypto hardware
PRI2
o 'claw' network device driver
PRI3
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