entries on one client when a directory was renamed on another client. The
root cause for the stale entry being trusted is that each per-vnode nfsnode
structure has a single 'n_ctime' timestamp used to validate positive name
cache entries. However, if there are multiple entries for a single vnode,
they all share a single timestamp. To fix this, extend the name cache
to allow filesystems to optionally store a timestamp value in each name
cache entry. The NFS clients now fetch the timestamp associated with
each name cache entry and use that to validate cache hits instead of the
timestamps previously stored in the nfsnode. Another part of the fix is
that the NFS clients now use timestamps from the post-op attributes of
RPCs when adding name cache entries rather than pulling the timestamps out
of the file's attribute cache. The latter is subject to races with other
lookups updating the attribute cache concurrently. Some more details:
- Add a variant of nfsm_postop_attr() to the old NFS client that can return
a vattr structure with a copy of the post-op attributes.
- Handle lookups of "." as a special case in the NFS clients since the name
cache does not store name cache entries for ".", so we cannot get a
useful timestamp. It didn't really make much sense to recheck the
attributes on the the directory to validate the namecache hit for "."
anyway.
- ABI compat shims for the name cache routines are present in this commit
so that it is safe to MFC.
MFC after: 2 weeks
This was reported to the mailing list freebsd-net@freebsd.org
on July 21, 2011 under the subject "LOR with nfsclient sillyrename".
The LOR occurred when nfs_inactive() called vrele(sp->s_dvp)
while holding the vnode lock on the file in s_dvp. This patch
modifies the client so that it performs the vrele(sp->s_dvp)
as a separate task to avoid the LOR. This fix was discussed
with jhb@ and kib@, who both proposed variations of it.
Tested by: pho, jlott at averesystems.com
Submitted by: jhb (earlier version)
Reviewed by: kib
Approved by: re (kib)
MFC after: 2 weeks
by both clients. Since the NLM uses various fields of the
nfsmount structure, those fields were extracted and put in a
separate nfs_mountcommon structure stored in sys/nfs/nfs_mountcommon.h.
This structure also has a function pointer for a function that
extracts the required information from the mount point and nfs vnode
for that particular client, for information stored differently by the
clients.
Reviewed by: jhb
MFC after: 2 weeks
fixed the issues with file descriptor locks, but the same problems are
present for vnode lock/user map lock.
If the nfs_asyncio() cannot find the free nfsiod, schedule task to
create new nfsiod and return error. This causes fall back to the
synchronous i/o for nfs_strategy(), or does not start read at all in
the case of readahead. The caller that holds vnode and potentially
user map lock does not wait for kproc_create() to finish, preventing
the LORs.
The change effectively reverts r203072, because we never hand off the
request to newly created nfsiod thread anymore.
Reviewed by: jhb
Tested by: jhb, pluknet
MFC after: 3 weeks
directories for purposes of validating name cache entries. This
closes races where two updates to a file or directory within the same
second could result in stale entries in the name cache. While here,
remove the 'n_expiry' field as it is no longer used.
Reviewed by: rmacklem
MFC after: 1 week
to avoid sending multiple ACCESS/GETATTR RPCs during a single open()
between VOP_LOOKUP() and VOP_OPEN(). Now we always send the RPC in
VOP_LOOKUP() and not VOP_OPEN() in the cases that multiple RPCs could be
sent.
MFC after: 2 weeks
Without this patch it was possible for a different thread that calls
nfs_asyncio() to snitch a newly created nfsiod thread that was
intended for another caller of nfs_asyncio(), because the nfs_iod_mtx
mutex was unlocked while the new nfsiod thread was created. This patch
labels the newly created nfsiod, so that it is not taken by another
caller of nfs_asyncio(). This is believed to fix the problem reported
on the freebsd-stable email list under the subject:
FreeBSD NFS client/Linux NFS server issue.
Tested by: to DOT my DOT trociny AT gmail DOT com
Reviewed by: jhb
MFC after: 2 weeks
This avoids a bogus negative name cache entry from persisting forever
when another client creates an entry with the same name within the
same NFS server time of day clock tick. The mount option negnametimeo
can be used to override the default timeout interval on a
per-mount-point basis. Setting negnametimeo to 0 disables negative
name caching for the mount point.
I also fixed one obvious typo where args.timeo should be
args.maxgrouplist.
Submitted by: jhb (earlier version)
Reviewed by: jhb
MFC after: 2 weeks
The number of entries in the cache defaults to 8 but is easily changed in
nfsclient/nfs.h. When the cache is filled, the oldest cache entry is
evicted when space is needed.
I mirrored the changes to the NFSv[23] client in the NFSv4 client to fix
compile breakage. However, the NFSv4 client doesn't actually use the
access cache currently.
Submitted by: rmacklem
stale entries, we save a copy of the directory's modification time when
the first negative cache entry was added in the directory's NFS node.
When a negative cache entry is hit during a pathname lookup, the parent
directory's modification time is checked. If it has changed, all of the
negative cache entries for that parent are purged and the lookup falls
back to using the RPC. This required adding a new cache_purge_negative()
method to the name cache to purge only negative cache entries for a given
directory.
Submitted by: mohans, Rick Macklem, Ricardo Labiaga @ NetApp
Reviewed by: mohans
provides the correct semantics for flock(2) style locks which are used by the
lockf(1) command line tool and the pidfile(3) library. It also implements
recovery from server restarts and ensures that dirty cache blocks are written
to the server before obtaining locks (allowing multiple clients to use file
locking to safely share data).
Sponsored by: Isilon Systems
PR: 94256
MFC after: 2 weeks
filesystem-specific vnode data to the struct vnode. Provide the
default implementation for the vop_advlock and vop_advlockasync.
Purge the locks on the vnode reclaim by using the lf_purgelocks().
The default implementation is augmented for the nfs and smbfs.
In the nfs_advlock, push the Giant inside the nfs_dolock.
Before the change, the vop_advlock and vop_advlockasync have taken the
unlocked vnode and dereferenced the fs-private inode data, racing with
with the vnode reclamation due to forced unmount. Now, the vop_getattr
under the shared vnode lock is used to obtain the inode size, and
later, in the lf_advlockasync, after locking the vnode interlock, the
VI_DOOMED flag is checked to prevent an operation on the doomed vnode.
The implementation of the lf_purgelocks() is submitted by dfr.
Reported by: kris
Tested by: kris, pho
Discussed with: jeff, dfr
MFC after: 2 weeks
owned by a NULL owner. This will lead consequent VOP_ISLOCKED() present
into nfs_upgrade_vnlock() to panic as it only acquire curthread now.
Fix nfs_upgrade_vnlock() and nfs_downgrade_vnlock() in order to not use
more the struct thread pointer passed as argument (as it is really nomore
required there as vn_lock() and VOP_UNLOCK doesn't get the lock more).
Using curthread, in place, doesn't get ambiguity as LK_EXCLOTHER should
be handled as a "not locked" request by both functions.
Reported by: kris
Tested by: kris
Reviewed by: ups
GETATTRs being generated - one from lookup()/namei() and the other
from nfs_open() (for cto consistency). This change eliminates the
GETATTR in nfs_open() if an otw GETATTR was done from the namei()
path. Instead of extending the vop interface, we timestamp each attr
load, and use this to detect whether a GETATTR was done from namei()
for this syscall. Introduces a thread-local variable that counts the
syscalls made by the thread and uses <pid, tid, thread syscalls> as
the attrload timestamp. Thanks to jhb@ and peter@ for a discussion on
thread state that could be used as the timestamp with minimal overhead.
adds a FS type specific flag indicating that the FS supports shared
vnode lock lookups, adds some logic in vfs_lookup.c to test this flag
and set lock flags appropriately.
- amd on 6.x is a non-starter (without this change). Using amd under
heavy load results in a deadlock (with cascading vnode locks all the
way to the root) very quickly.
- This change should also fix the more general problem of cascading
vnode deadlocks when an NFS server goes down.
Ideally, we wouldn't need these changes, as enabling shared vnode lock
lookups globally would work. Unfortunately, UFS, for example isn't
ready for shared vnode lock lookups, crashing pretty quickly.
This change is the result of discussions with Stephan Uphoff (ups@).
Reviewed by: ups@
writers that want to extend the file. It was also used to serialize
readers that might want to read the last block of the file (with a
writer extending the file). Now that we support vnode locking for
NFS, the rslock is unnecessary. Writers grab the exclusive vnode
lock before writing and readers grab the shared (or in some cases
the exclusive) lock.
Submitted by: Mohan Srinivasan
of sillyrenames (which were limited to 58 per pid per directory,
for no good reason). The new format of sillyrenames looks like
.nfs.0000b31a.00d24.4
^^^^^^^^ ^^^^^
ticks pid
Submitted by: Mohan Srinivasan mohans at yahoo-inc dot com
Obtained from: Yahoo!
- NFS direct IO completely bypasses the buffer and page caches.
If a file is open for direct IO all caching is disabled.
- Direct IO for Directories will be addressed later.
- 2 new NFS directio related sysctls are added. One is a knob to
disable NFS direct IO completely (direct IO is enabled by default).
The other is to disallow mmaped IO on a file that has at least one
O_DIRECT open (see the comment in nfs_vnops.c for more details).
The default is to allow mmaps on a file that has O_DIRECT opens.
Submitted by: Mohan Srinivasan mohans at yahoo-inc dot com
Obtained from: Yahoo!
Kick off a readahead only when sequential access is detected. This
eliminates wasteful readaheads in random file access.
Submitted by: Mohan Srinivasan mohans at yahoo-inc dot com
Obtained from: Yahoo!
- Change the cached mtime to a 'struct timespec' from a
time_t. Improving the precision of the cached mtime tightens up
NFS' "close-to-open" consistency considerably.
- Always force an over-the-wire consistency check from nfs_open()
(unless the file is marked modified). This further improves
NFS' "close-to-open" consistency.
Submitted by: Mohan Srinivasan mohans at yahoo-inc dot com
vnode EXCLUSIVE lock. This prevents threads from adding pages to
the vnode while an invalidation is in progress, closing potential
races. In the bioread() path, callers acquire the SHARED vnode lock
- so while an invalidate was in progress, it was possible to fault
in new pages onto the vnode causing the invalidation to take a while
or fail. We saw these races at Yahoo! with very large files+heavy
concurrent access. Forcing an upgrade to EXCLUSIVE lock before doing
the invalidation closes all these races.
Submitted by: Mohan Srinivasan mohans at yahoo-inc dot com
initializations but we did have lofty goals and big ideals.
Adjust to more contemporary circumstances and gain type checking.
Replace the entire vop_t frobbing thing with properly typed
structures. The only casualty is that we can not add a new
VOP_ method with a loadable module. History has not given
us reason to belive this would ever be feasible in the the
first place.
Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc.
Give coda correct prototypes and function definitions for
all vop_()s.
Generate a bit more data from the vnode_if.src file: a
struct vop_vector and protype typedefs for all vop methods.
Add a new vop_bypass() and make vop_default be a pointer
to another struct vop_vector.
Remove a lot of vfs_init since vop_vector is ready to use
from the compiler.
Cast various vop_mumble() to void * with uppercase name,
for instance VOP_PANIC, VOP_NULL etc.
Implement VCALL() by making vdesc_offset the offsetof() the
relevant function pointer in vop_vector. This is disgusting
but since the code is generated by a script comparatively
safe. The alternative for nullfs etc. would be much worse.
Fix up all vnode method vectors to remove casts so they
become typesafe. (The bulk of this is generated by scripts)
Extend it with a strategy method.
Add bufstrategy() which do the usual VOP_SPECSTRATEGY/VOP_STRATEGY
song and dance.
Rename ibwrite to bufwrite().
Move the two NFS buf_ops to more sensible places, add bufstrategy
to them.
Add inlines for bwrite() and bstrategy() which calls through
buf->b_bufobj->b_ops->b_{write,strategy}().
Replace almost all VOP_STRATEGY()/VOP_SPECSTRATEGY() calls with bstrategy().
on anything but DEVFS and in this case it was not even used (see below).
Put the NFS4 vop method for fifo's behind "#if 0" because it is unused.
Add a XXX comment to say that I think the unusedness is a bug.
This avoids presenting invalid data to the client's applications
when the file is modified, and then extended within the window of
the resolution of the modifcation timestamp.
Reviewed By: iedowse
PR: kern/64091
and the nfs3 client. Also fix some bugs that happen to be causing crashes
in both v3 and v4 introduced by the v4 import.
Submitted by: Jim Rees <rees@umich.edu>
Approved by: re
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.
Sorry john! (your next MFC will be a doosie!)
Reviewed by: peter@freebsd.org, dillon@freebsd.org
X-MFC after: ha ha ha ha
is an application space macro and the applications are supposed to be free
to use it as they please (but cannot). This is consistant with the other
BSD's who made this change quite some time ago. More commits to come.
occur due to np->n_size potentially changing if nfs_getcacheblk()
blocks in nfs_write().
Second, under -current we must supply the proper bufsize when obtaining
buffers that straddle the EOF, but due to the fact that np->n_size can
change out from under us it is possible that we may specify the wrong
buffer size and wind up truncating dirty data written by another
process.
Both problems are solved by implementing nfs_rslock(), which allows us
to lock around sensitive buffer cache operations such as those that
occur when appending to a file.
It is believed that this race is responsible for causing dirtyoff/dirtyend
and (in stable) validoff/validend to exceed the buffer size. Therefore
we have now added a warning printf for the dirtyoff/end case in current.
However, we have introduced a new problem which we need to fix at some
point, and that is that soft or intr NFS mounts may become
uninterruptable from the point of view of process A which is stuck waiting
on rslock while process B is stuck doing the rpc. To unstick process A,
process B would have to be interrupted first.
Reviewed by: Alfred Perlstein <bright@wintelcom.net>
cache. If the cached result lets us say "yes", then go with that. If
we're not sure, or we think the answer might be "no", go to the wire to be
certain. This avoids all of the possible false veto cases, and allows us
to key the cached value with just the UID for which the cached value holds,
reducing the bloat of the nfsnode structure from 104 bytes to just 12 bytes.
Since the "yes" case is by far the most common, this should still provide
a substantial performance improvement. Also default the cache to on, with
a conservative timeout (2 seconds). This improves performance if NFS is
loaded as a KLD module, as there's not (yet) code to parse an option out
of the module arguments to set it, and sysctl doesn't work (yet) for OIDs
in modules.
The 'accelerator' mode was suggested by Bjoern Groenvall (bg@sics.se)
Feedback on this would be appreciated as testing has been necessarily
limited by Comdex, and it would be valuable to have this in 2.2.8.
This yields startling performance increases for NFS clients for many
access profiles, due to the fact that ACCESS results are persistently
cached in the namecache in many cases.
Note that the code is somewhat conservative in that it requires an
exact credential match for a cache hit. This bloats the nfsnode
structure by sizeof(struct ucred) (96 bytes). Any less conservative
approach opens the possibility for a false veto in eg. setuid
applications. Alternative suggestions would be welcomed.
The cache is normally disabled, to activate set the sysctl variable
vfs.nfs.access_cache_timeout to a nonzero value. This is the time in
seconds that a cached entry will be considered valid; useful values appear
to be 2-10 seconds. Performance of the cache can be monitored with the
vfs.nfs.access_cache_hits and vfs.nfs.access_cache_hits variables.
