from under us while waiting for syncer_lock and before we got to vfs_busy.
This happens easily e.g. when the userspace server loses its will to
live in VOP_RECLAIM, which is called from vflush() in VFS_UNMOUNT. We
get two competing unmounters. When the first one finishes, it releases
syncer_lock. Now the second one tries to vfs_busy(), but is greeted
with garbage in *mp.
XXX: Technically this is a more general issue and should be fixed
elsewhere, but it's hard to trigger it with normal file systems
unless they are unmounted "simultaneously" twice and are dirty
enough for flushing to take a while. So make a note about it in
the little black book next to the poems and postpone the crusade
for now.
mmap and therefore execution of binaries starting to work, some
speed improvements with large file I/O also. caching semantics
and error case handling most likely need revisiting.
predictable. This solves a problem that may appear when serving a tmpfs
over NFS: if the server reboots, newly allocated files should have
different file handles; otherwise the remote clients could access files
they were not supposed to touch.
not persistent across reboots but neither are those of MFS, which we are
trying to replace. We should probably warn the user somehow, but not
prevent him doing this if he really wants to.
While here add a "reply" to the code-style change item.
binaries which cast the returned values to 64-bits and fail due to sign
expansion. More details are provided in the big comment in tmpfs.h that
describes how the new tmpfs_dircookie works.
This is a rather ugly hack that shall be fixed with a cleaner solution,
but this resolves the problem in an effective way.
Fixes kern PR/32034.
reference to the parent directory's vnode instead of its smbnode to
avoid a use-after-free bug causing a panic when a smbfs mount is
forcefully unmounted.
Keep trying to flush the vnode list for the mount while some are still
busy and we are making progress towards making them not busy. This
stops attempts to unmount idle smbfs mounts failing with EBUSY.
The easiest way to reproduce the above problem, from what I have seen is:
1) Assume /s is a smbfs mount point.
2) mount /s
3) stat /s/foo/1
4) umount /s
Returns error because the file system is busy.
5) Shutdown the machine: panic in smbfs_reclaim because vrele
accesses already-released memory.
array's contents and returning all the requested pages. Otherwise there
are problems (accessing invalid memory) when the a_m vector is passed
uninitialized as the NFS server code does. Fixes PR kern/34959.
Note that this is not a "real" fix. While this makes tmpfs's getpages
operation consistent with the behavior of other file systems, it does
not resolve the different semantics between uvn_get and uao_get as
described in PR kern/32166. I'm adding a comment in the code mentioning
exactly this so that it can be reviewed when this last problem is
addressed.
it, not the mtime of the file itself. This fixes the problems exposed when
unpacking software under a tmpfs and trying to build it because dependencies
were not calculated properly (e.g. autoconf 2.60 as reported by tls@).
loops where vnodes can get removed or added during the loops. This could
lead to panic's on unmount since nodes are skipped or otherwise
TAILQ_NEXT(0xdeadbeef, ...) was dereferenced.
all waiters *before* trying to get the syncer lock necessary for
dounmount(). This prevents a deadlock if the userspace server dies
while the syncer is running.
getnewvnode() while holding on to any vnode lock deadlocks the
system if the file system is being forcibly unmounted.
Normal file systems don't trigger this problem because of two reaons:
1) they don't hold on to vnode locks while idling who-knows-where, so
the race doesn't trigger
2) they aren't usually unmounted with FORCE; puffs is, in case "someone"
manages to make a crashy userspace server
Nevertheless, a real solution is slowly being braised.
It contains the VFS attachment and userspace message-passing interface.
This work was initially started and completed for Google SoC 2005
and tweaked to work a bit better in the past few weeks. While
being far from complete, it is functional enough to be able and
stable to host a fairly general-purpose in-memory file system in
userspace. Even so, puffs should be considered experimental and
no binary compatibility for interfaces or crash-freedom or zero
security implications should be relied upon just yet.
The GSoC project was mentored by William Studenmund and the final
review for the code was done by Christos.
christos