The previous fix worked, but it opened a window where mounts could have
disappeared from mountlist while the caller was traversing it using
vfs_trybusy(). Fix that.
The symptom was that sometimes file systems would occasionally not appear
in output from 'df' or 'mount' if the system was busy. Resolution:
- Make mount locks work somewhat like vm_map locks.
- vfs_trybusy() now only fails if the mount is gone, or if someone is
unmounting the file system. Simple contention on mnt_lock doesn't
cause it to fail.
- vfs_busy() will wait even if the file system is being unmounted.
proclist_mutex and proclist_lock into a single adaptive mutex (proc_lock).
Implications:
- Inspecting process state requires thread context, so signals can no longer
be sent from a hardware interrupt handler. Signal activity must be
deferred to a soft interrupt or kthread.
- As the proc state locking is simplified, it's now safe to take exit()
and wait() out from under kernel_lock.
- The system spends less time at IPL_SCHED, and there is less lock activity.
- Add a lot of missing selinit() and seldestroy() calls.
- Merge selwakeup() and selnotify() calls into a single selnotify().
- Add an additional 'events' argument to selnotify() call. It will
indicate which event (POLL_IN, POLL_OUT, etc) happen. If unknown,
zero may be used.
Note: please pass appropriate value of 'events' where possible.
Proposed on: <tech-kern>
- Do reference counting for 'struct mount'. Each vnode associated with a
mount takes a reference, and in turn the mount takes a reference to the
vfsops.
- Now that mounts are reference counted, replace the overcomplicated mount
locking inherited from 4.4BSD with a recursable rwlock.
Introduce a per-FS rename lock and new vfsops to manipulate it.
Get this lock while renaming. Also add another relookup() in do_sys_rename,
which is a hack to kludge around some of the worst deficiencies of
ufs_rename.
reviewed-by: pooka (and an earlier rev by ad)
posted on tech-kern with no objections.
shutdown). There are still problems with device access and a PR will be
filed.
- Kill checkalias(). Allow multiple vnodes to reference a single device.
- Don't play dangerous tricks with block vnodes to ensure that only one
vnode can describe a block device. Instead, prohibit concurrent opens of
block devices. As a bonus remove the unreliable code that prevents
multiple file system mounts on the same device. It's no longer needed.
- Track opens by vnode and by device. Issue cdev_close() when the last open
goes away, instead of abusing vnode::v_usecount to tell if the device is
open.
zero - our implementation can't handle it (how sensible handling
a case like that would be is a whole other debate).
fixes panic reported by Jukka Salmi on current-users
the newly added space first. This significantly speeds up write speed for
msdosfs and making it at par with ffs wich already had this patched.
Speed increase measured on my IDE disc from 2Mb/sec to 32 Mb/sec
The general trend is to remove it from all kernel interfaces and
this is a start. In case the calling lwp is desired, curlwp should
be used.
quick consensus on tech-kern
a bug: the homegrown version neglected to unlock vp
* don't reimplement eopnotsupp()
* init genfs_node earlier vget, protects against error paths in vget
from attempting to destroy a non-inited node
same file were renamed simultaneously, there was a window where
directory entry cached in the vnode during lookup would be replaced
before calling rename. This lead to one directory entry getting
renamed twice and the other one getting zero renames. Do a relookup
in rename to make sure we have the correct directory entry.
Thanks go to Greg Oster for reporting the problem, helping with
debugging and thoroughly testing the patch.
called with NOWAIT.
XXX: this is just a quick fix to stop the diagnostic panic. I
think ENOSPC should be treated elsewhere depending on how much
memory tmpfs claims.
thing and release locks before the userspace wait for operations
which release the lock before exit from the method in any case.
However, releasing the lock after inserting the request on the
operation queue gives us proper ordering possibilities in userspace
(at least if that bit were implemented, but I don't think there
any file system in userspace that depends on kernel locking and
probably there never should be one).
inspired by a conversation with Nacho Navarro
with the file server happen through puffs_msg_enqueue() and
puffs_msg_wait() instead of having a billion different routines.
Build the existing system upon these two. Most importantly though,
decouple insertation into the op queue from the actual wait. This
is useful for a number of reasons coming soon to a cvs repo near you.
unlocked vnode when trying to rename a directory. The fix was to
shuffle some bits around and #pray.
The rename routine actually needs a very very major wide-angle whopping:
* it takes locks out-of-order
* it deals with references from SAVESTART lookups in interesting ways
* I doubt there is any guarantee for correct operation if there
are multiple concurrent accesses
* the error branches might just as well call panic() directly
Rip the transport code completely out of puffs and generalize it
into an independent module which will be used for multiple purposes
in the future. This module is called the Pass-to-Userspace
Transporter (known as "putter" among friends).
This is very much work-in-progress and one dependency with puffs
remains: the request framing format.
The device name is still /dev/puffs, but that will change soon.
Users of puffs need the following in their kernel configs now:
pseudo-device putter
when vclean()ing. Pending an adventure to the genfs/vm labyrinth
to fix this properly, compensate here by not allowing unstrategic
(no pun) return values. They are always due to the userspace server
crashing anyway, so it's no big deal if we lie about the final
resting place of the pages.
userspace, since it doesn't contain any information yet. I should
still rework this more so this is just a quickie to get the read/write
style interface more up to speed with the ioctl version.
interacts with the userspace file server:
* since the kernel-user communication is not purely request-response
anymore (hasn't been since 2006), try to rename some "request" to
"message". more similar mangling will take place in the future.
* completely rework how messages are allocated. previously most of
them were borrowed from the stack (originally *all* of them),
but now always allocate dynamically. this makes the structure
of the code much cleaner. also makes it possible to fix a
locking order violation. it enables plenty of future enhancements.
* start generalizing the transport interface to be independent of puffs
* move transport interface to read/write instead of ioctl. the
old one had legacy design problems, and besides, ioctl's suck.
implement a very generic version for now; this will be
worked on later hopefully some day reaching "highly optimized".
* implement libpuffs support behind existing library request
interfaces. this will change eventually (I hate those interfaces)
userspace call, namely our private mount structure, in the activation
record. This avoids problems in situations where the userspace
file server happens to die during our upcall and the vnode is
forcibly reclaimed before we roll back to the current stack frame.
committed something, issue an abort. The abort is done through
the regular op channel, e.g. failed mkdir leads to regular rmdir,
inactive and reclaim. No internal interface is planned currently
for the one file system out of a million which would implement it
to benefit from the one case in a billion where kernel resource
allocation actually does fail and out of that one case in a trillion
where internal vs. external would make a difference.
to be vaild errno values
* include string describing error in PUFFS_ERR
* get rid of union in puffs_req, it's nothing but trouble
* pass pmp to async i/o callbacks
locked. Ideally the function should be rewritten to do things in
a different order, but this tries to keep changes minimal aiming
for a possible netbsd-4 pullup.
fixes PR kern/37034
kernel to the file server for silly things the file server did,
e.g. attempting to create a file with size VSIZENOTSET. The file
server can handle these as it chooses, but the default action is
for it to throw its hands in the air and sing "goodbye, cruel world,
it's over, walk on by".
was done separate of inserting the cookie into the lookup structure
and without any form of interlock. This could lead to the same
cookie pointing to two different nodes. Remedy the race by creating
a separate "checked and ready to be inserted" cookie list which
serves as an interlock without having to hold a fs-global creation
lock.
before copying them out, rather just use a single one. Further, follow
the example of tmpfs and others by simply allocating on the stack.
This should have the side-effect of silencing false Coverity reports like
CID 4559 and 4554.
VOP_LOOKUP ignores LOCKPARENT completely, so make this ignore it also.
XXX: tested only with rump, but I can't really see how this worked
at all before
knew what it was supposed to be used for and wrstuden gave a go-ahead
* while rototilling, convert file systems which went easily to
use VFS_PROTOS() instead of manually prototyping the methods
need to understand the locking around that field. Instead of setting
B_ERROR, set b_error instead. b_error is 'owned' by whoever completes
the I/O request.
need to understand the locking around that field. Instead of setting
B_ERROR, set b_error instead. b_error is 'owned' by whoever completes
the I/O request.
ad