case functionality of namei in a simple package with only a couple flags.
A substantial majority of the namei call sites in the kernel can use
this interface; this will isolate those areas from the changes arising
as the internals of namei are fumigated.
- NOCHROOT flag must be assigned to different bit from TRYEMULROOT
since the code expected to be executed is in the else clase of
if (flags & TRYEMULROOT).
- Necessary variables aren't set.
Add Wasabi System's WAPBL (Write Ahead Physical Block Logging)
journaling code. Originally written by Darrin B. Jewell while
at Wasabi and updated to -current by Antti Kantee, Andy Doran,
Greg Oster and Simon Burge.
OK'd by core@, releng@.
Simplify the mount locking. Remove all the crud to deal with recursion on
the mount lock, and crud to deal with unmount as another weirdo lock.
Hopefully this will once and for all fix the deadlocks with this. With this
commit there are two locks on each mount:
- krwlock_t mnt_unmounting. This is used to prevent unmount across critical
sections like getnewvnode(). It's only ever read locked with rw_tryenter(),
and is only ever write locked in dounmount(). A write hold can't be taken
on this lock if the current LWP could hold a vnode lock.
- kmutex_t mnt_updating. This is taken by threads updating the mount, for
example when going r/o -> r/w, and is only present to serialize updates.
In order to take this lock, a read hold must first be taken on
mnt_unmounting, and the two need to be held across the operation.
One effect of this change: previously if an unmount failed, we would make a
half hearted attempt to back out of it gracefully, but that was unlikely to
work in a lot of cases. Now while an unmount that will be aborted is in
progress, new file operations within the mount will fail instead of being
delayed. That is unlikely to be a problem though, because if the admin
requests unmount of a file system then s(he) has made a decision to deny
access to the resource.
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.
- 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.
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
checking for a readonly lookup. This shouldn't make a difference
now, though, as the only RDONLY lookup is done by getcwd(), and
that a) doesn't create files b) calls LOOKUP directly anyway.
Also, fix comment I managed to miss in the previous commit (I didn't
expect the same comment to be there twice).
- use macros to deal with pathnames in userspace, when veriexec is used.
- reorder the veriexec_ call arguments for consistency.
With help from elad@ finding the last bug.
to the real root. Rather that do the check inside lookup() - where it
applies to to every ".." in a pathname, explicitly check the start of
the caller-supplied buffers and any absolute symbolic links.
Note that in the latter case the re-search from the real root is supressed.
Should fix PR kern/36225
emulation lookups.
If doing a lookup relative to the emulation root, prepend the emulation root
to the traced filename.
While here pass the filename length through to the ktrace code since namei()
knows the length and ktr_namei() would have to call strlen().
Note: that if namei() is being called during execve processing, the emulation
root name isn't available and "/emul/???" is used. Also namei() has to use
strlen() to get the lenght on the emulatoon root - even though it is a
compile-time constant string.
avoid having to allocate space in the 'stackgap'
- which is very LWP unfriendly.
The additional code for non-emulation namei() is trivial, the reduction for
the emulations is massive.
The vnode for a processes emulation root is saved in the cwdi structure
during process exec.
If the emulation root the TRYEMULROOT flag are set, namei() will do an initial
search for absolute pathnames in the emulation root, if that fails it will
retry from the normal root.
".." at the emulation root will always go to the real root, even in the middle
of paths and when expanding symlinks.
Absolute symlinks found using absolute paths in the emulation root will be
relative to the emulation root (so /usr/lib/xxx.so -> /lib/xxx.so links
inside the emulation root don't need changing).
If the root of the emulation would be returned (for an emulation lookup), then
the real root is returned instead (matching the behaviour of emul_lookup,
but being a cheap comparison here) so that programs that scan "../.."
looking for the root dircetory don't loop forever.
The target for symbolic links is no longer mangled (it used to get the
CHECK_ALT_xxx() treatment, so could get /emul/xxx prepended).
CHECK_ALT_xxx() are no more. Most of the change is deleting them, and adding
TRYEMULROOT to the flags to NDINIT().
A lot of the emulation system call stubs could now be deleted.
P_*/L_* naming convention, and rename the in-kernel flags to avoid
conflict. (P_ -> PK_, L_ -> LW_ ). Add back the (now unused) LSDEAD
constant.
Restores source compatibility with pre-newlock2 tools like ps or top.
Reviewed by Andrew Doran.
- don't use SAVESTART in calls to relookup() from unionfs,
just vref() the desired vnode when we need to.
- fix locking and refcounting in the unionfs EEXIST error cases.
- release any vnode locks before calling VFS_ROOT(), vfs_busy() is enough.
this allows us to simplify union_root() and fix PR 3006.
- union_lock() doesn't handle shared lock requests correctly,
so convert them to exclusive instead. fixes PR 34775.
- in relookup(), avoid reusing "dp" for different purposes,
the error handling wasn't right. (actually just get rid of dp.)
also, change relookup() to ignore LOCKLEAF and always return the
vnode locked since the callers already expect this.
variation suggested by yamt on tech-kern.
XXX: The exception is that this doesn't any longer prevent caching
of RENAME, which was implied in a weird weird way previously. But
that's handled by the callers currently.
- don't hold the parent directory vnode locked while traversing mount points.
the fs that's mounted might be an NFS served by a userland process
like the automounter, which might need to traverse the parent directory
in order to complete the lookup.
- in the ENAMETOOLONG case fixed in rev. 1.75, set ni_dvp to dp
since we've logically moved on to using "dp" as the parent.
the caller will then handle vput()ing it as normal.
this fixes PR 35279.
Introduce the (intentionally undocumented) pathname_get(), pathname_path(),
and pathname_put(), to deal with allocating and copying of pathnames from
either kernel- or user-space.
- LOCKPARENT is no longer relevant for lookup(), relookup() or VOP_LOOKUP().
these now always return the parent vnode locked. namei() works as before.
lookup() and various other paths no longer acquire vnode locks in the
wrong order via vrele(). fixes PR 32535.
as a nice side effect, path lookup is also up to 25% faster.
- the above allows us to get rid of PDIRUNLOCK.
- also get rid of WANTPARENT (just use LOCKPARENT and unlock it).
- remove an assumption in layer_node_find() that all file systems implement
a recursive VOP_LOCK() (unionfs doesn't).
- require that all file systems supply vfs_vptofh and vfs_fhtovp routines.
fill in eopnotsupp() for file systems that don't support being exported
and remove the checks for NULL. (layerfs calls these without checking.)
- in union_lookup1(), don't change refcounts in the ISDOTDOT case, just
adjust which vnode is locked. fixes PR 33374.
- apply fixes for ufs_rename() from ufs_vnops.c rev. 1.61 to ext2fs_rename().
